Marine-derived photocatalysts for building envelopes: A review of materials,passive strategies,and physical implementation challenges

Abstract

This review explores the innovative potential of integrating marine-based photocatalysts in the built environment, aiming to bridge the gap between sustainable material synthesis and performance-based envelope design. By analyzing 108 studies, the research addresses 10 primary questions concerning synthesis pathways, characterization techniques, and the transition from laboratory chemistry to building-relevant implementation. The analysis reveals that algae (41.7%) and seashells (38%), often combined with TiO₂, ZnO, and Ag, serve as effective carriers (53.7%), reducing agents (36.1%), or photocatalysts themselves (10.2%). While these bio-composites demonstrate significant chemical potential, a critical disparity is identified: over 77% of current research targets wastewater treatment. This review critically evaluates the transferability of these liquid-phase findings to building physics applications, highlighting challenges in gas-phase pollutant diffusion and surface boundary layer interactions. Despite this gap, key positive findings demonstrate that marine-derived composites can achieve complete degradation of indoor pollutants, such as formaldehyde and toluene. Furthermore, bio-doping was shown to effectively reduce bandgap energies, enabling passive air purification under indoor light sources. The review concludes that future research must prioritize standardized gas-phase testing and long-term hygrothermal durability assessments to validate these materials for high-performance building envelopes.

Keywords

photocatalysis built environment marine-derived building envelope indoor air quality

Introduction

Climate change is one of the most pressing global challenges, with the United Nations’ Sustainable Development Goal 13 (SDG 13), Climate Action, still far from being achieved by 2030 (United Nations, 2023). The building sector is a significant contributor to greenhouse gases, accounting for over 36% of global energy-related emissions (European Union, 2021). The foreseen climatic conditions are expected to affect the long-term performance of construction materials and building envelope systems exposed to environmental loads (Lacasse et al., 2020). However, sustainable construction practices have the potential to support multiple SDGs (Scrucca et al., 2023), including SDG 11 on Sustainable Cities and Communities, by fostering resilience and reducing environmental impact through improved building physics–based design strategies.

One promising approach involves enhancing building envelopes with photocatalytic materials, which can actively reduce air pollution (Sapiña et al., 2013) while providing self-cleaning and antimicrobial surface properties (European Union, 2021), both of which are beneficial in urban environments and for maintaining façade and roof performance over time. Photocatalysis occurs when semiconductors, upon activation by light, generate electron-hole pairs that interact with ambient air and produce reactive species capable of degrading pollutants through redox reactions (Hot et al., 2020). Such processes are of increasing interest in building physics due to their potential interaction with surface heat, air, and moisture transfer phenomena, as the photocatalytic efficiency is intrinsically linked to the boundary layer conditions at the building’s surface.

Titanium dioxide (TiO₂) and zinc oxide (ZnO) are the most widely studied photocatalysts (Alshandoudi et al., 2023; Nath et al., 2016; Tjardts et al., 2023), effective, among others, in decomposing volatile organic compounds (VOCs) into less harmful byproducts, such as carbon dioxide (CO₂) and water molecules (H₂O; Nath et al., 2016). This is particularly relevant for indoor environmental quality and occupant exposure reduction in buildings. Despite their efficacy, conventional photocatalyst production methods often involve the use of toxic chemicals and high costs (Malik et al., 2023). The considerable bandgap energy of materials like TiO₂ restricts their activation mainly to ultraviolet (UV) light (Gonçalves et al., 2024), which comprises less than 7% of the solar spectrum (Ameta and Ameta, 2016). Rapid electron-hole recombination (Ling et al., 2022) and concerns over the ecotoxicity of nanomaterials pose additional challenges (Cassar, 2004; Ferreira et al., 2023), especially when considering large-scale deployment in building materials and construction products.

To overcome these limitations, green synthesis methods have emerged, using biological organisms such as bacteria, fungi, and plant extracts (Malik et al., 2023). This approach not only reduces hazardous chemical use but also aligns with circular economy principles by converting waste into valuable, functional materials, which is fundamental for the construction sector and for sustainable material cycles in the built environment (Ferreira et al., 2023; The European Parliament and The Council of the European Union, 2020).

Targeting a blue economy (Hossain et al., 2024), marine-based materials, particularly algae and mollusk shells, offer unique advantages: they are renewable, abundant byproducts of aquaculture, and often discarded as waste, contributing to pollution (Li et al., 2020; Saikia et al., 2023). The use of materials coming from the sea to face environmental pollution can represent the “control of waste by waste.” As photocatalysts, they can enhance performance due to their intrinsic trace metals and increased surface area for pollutant adsorption (Li et al., 2020; Wang et al., 2020b), making them promising candidates for circular building envelope coatings and components.

This study introduces an innovative connection between marine-based photocatalysts and the built environment. By focusing on marine-derived green synthesis of photocatalysts, the research promotes a sustainable, circular alternative to conventional photocatalysts, integrating environmental remediation with low-impact construction practices and supporting performance-based approaches to building envelope design and operation, in support of blue economy goals and SDGs, particularly in urban settings.

Ten primary questions were addressed through a comprehensive literature review: (1) What are the general applications of marine-based photocatalysts so far? (2) What are the passive environmental control strategies and applications of marine-derived photocatalysts in the built environment? (3) Which materials are used in the synthesis of marine-based photocatalysts? (4) How are the marine-based photocatalysts synthesized? (5) What characterization techniques are employed regarding the marine-based photocatalysts? (6) How is the performance of the novel marine-based synthesized materials experimentally evaluated? (7) How are the reaction mechanisms and kinetics experimentally characterized? (8) Are environmental and toxicity assessments conducted, and what are the implications for occupant safety? (9) Is research progressing from material synthesis to building envelope implementation and performance-based evaluation? (10) What are some key findings on the photocatalytic performance of the novel marine-based materials? By answering these questions, this review maps the state of the art and identifies scientific gaps, aiming to guide future research toward the development of sustainable and resilient building technologies with measurable impacts on indoor air quality, envelope durability, and building performance under changing climatic conditions.

Methods

The rationale guiding this research is derived from the growing interest in sustainable and bio-inspired materials for environmental protection and sustainable construction within the context of building physics and performance-based envelope design. A systematic literature review was conducted, drawing on combined guidelines and methodologies from Bersch et al. (2023), Saade et al. (2020), and Page et al. (2021a).

The following query string was defined within the search strategy for the literature review, intentionally broad: “(bio* OR natur* OR green OR waste OR sustainab* OR organic) AND (synthes* OR produc* OR compos* OR fabric*) AND (fish OR shell OR *algae OR marine OR maritime OR sea*) AND (photocatal* OR photoact*).” Journal papers in English published from 2020 to the first half of 2025 were assessed, with the Scopus database serving as the information source, accessed on June 25, 2025. This approach ensured coverage of both environmental remediation studies and emerging building-related applications, such as indoor air purification and envelope surface treatments, focusing on the identification of physical properties and boundary conditions relevant to building performance.

The selection process was divided into filtering rounds carried out by the authors, beginning with title screening, followed by abstracts and full-text reading, depending on the appropriateness of the works at each step. As eligibility criteria for inclusion, the works had to answer at least a primary question: “How to synthesize (and evaluate) an effective marine-based photocatalyst?” with potential relevance to building materials, indoor environmental quality, or building envelope performance. Regarding exclusion criteria, studies were discarded straightforwardly if the photocatalysts were not effectively produced with marine materials; to be selected for full-paper reading, the synthesis with biological materials needed to be clearly stated in the title or abstract.

The selection of full papers focused on those that explicitly presented the extraction procedure of sea raw materials within the text; experiments using purchased chitosan, alginate, or algae powder, for instance, were excluded. Since the objective of this paper was to trace the current situation of marine-based materials related to buildings and their close environments within a macro-context of their entire applications, papers were not discarded if their focus was on another topic, such as wastewater treatment, for instance; indeed, their approaches were quantified because of the review to identify transferable knowledge toward building-scale implementation, particularly regarding mass transport, pollutant adsorption kinetics, and material durability. Literature reviews were disqualified in the final selection. Chapter 3 provides a general overview of the final sample, examining the relationships between the selected full papers and the highlights identified through their keywords.

The authors proposed 10 questions to guide the investigation and structure the “Results section,” inspired by Blocken (2015) and van Hoof et al. (2025). The questions began by asking whether the construction sector already uses marine-based photocatalysts and, if not, what their main applications are. Afterward, the inquiries delved into the materials and methods needed to foster the potential implementation of these bio-photocatalysts in building envelopes, façade coatings, and passive indoor environmental control technologies, emphasizing the transition from laboratory synthesis to functional building components.

Data were collected from the full documents concerning the type of sea species reported and their role in the photocatalyst synthesis process, the chemicals used with the biomaterials for photoactivation, synthesis details, environmental and toxicity evaluations, characterization procedures, and photoactive performance under conditions relevant to the built environment (e.g. air pollutant degradation and surface functionality). The discussions were developed to compile and connect the main findings with their implications and recommendations for future building physics research, including performance assessment, durability, and field-scale validation.

Overview

A total of 2993 papers were initially retrieved from Scopus. After title and abstract analysis, 217 documents were selected, 109 of which were discarded after full-paper reading. After all screening and reading, the final sample consisted of 108 papers. Figure 1 summarizes the main steps taken to consolidate this overview, based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) flow diagram for new systematic reviews (Page et al., 2021b).

Figure 1.

Flow diagram of the literature review.

The inclusion and exclusion of papers were carried out based on the eligibility criteria presented in Chapter 2, keeping the review limited to those explicitly addressing the primary question. To illustrate title and abstract filtering rounds, examining the search query, several papers were initially retrieved due to the word “shell.” At the same time, some referred to fruits (Liu et al., 2025c; Zhang et al., 2024), eggshells (Munir et al., 2025), nuts (Junior et al., 2025), or core-shell structures (Xiong et al., 2025), being disregarded. The term “sea” led to the initial selection of papers regarding seawater splitting (Zhang et al., 2025); freshwater (Kar and Chakraborty, 2024) and terrestrial (Khandelwal et al., 2024) species were the focus of some studies, which were excluded. This screening ensured that the final sample remained specific to marine-derived resources with possible transferability to sustainable construction and envelope-related materials, specifically concerning their potential as porous functional substrates for gas-phase pollutant removal.

The ResearchRabbit platform was searched for citation relationships among the papers of the final sample. The strongest group, comprising six of the 108 papers, revealed the interconnection among the papers by Cao et al. (2023), Li et al. (2020), Wang et al. (2020b, 2021a, 2021b), and Qiu et al. (2022). Regarding this connection, for instance, while two documents (Wang et al., 2021a, 2021b) cite Wang et al. (2020b) to justify the amount of seashell waste produced in China since 2002 (over 10 million tons), Cao et al. (2023) and Li et al. (2020) reference the study (Wang et al., 2020b) to explain the potential improvement in photocatalytic activity of their own prepared catalyst due to the presence of transition metal elements on the used mussel shells. This chemical-physical synergy is a key factor for building physics, as it suggests that bio-based carriers not only provide structural support but also influence the surface reaction kinetics.

Figures 2 and 3 provide a panorama of the final sample from this review. Figure 2 is based on the author keywords (intentionally assigned to the documents by their authors), organized using the Word Cloud tool in Power BI Desktop, with a minimum of two repetitions to display. In Figure 3, a bibliometric network is depicted based on all the keywords (author keywords and indexed vocabulary terms assigned to the documents) from the 108 selected papers. VOSviewer v1.6.1 was chosen to create Figure 3, as it is a widely used open-source software for bibliometric analysis, enabling the visualization of similarities (Wang et al., 2025b). A co-occurrence map was developed, clustering keywords in communities of terms (Wang et al., 2025b) using the full counting method, with a minimum of five keyword occurrences. With the thesaurus files, near-synonyms such as ZnO and zinc oxide, or dyes and dye, were grouped to find their true representation in the final chart.

Figure 2.

Recurrence of the author keywords from the 108 selected papers.

Figure 3.

Network visualization of all the keywords from the 108 selected papers.

There are several terms in common between Figures 2 and 3, such as degradation and nanoparticles. Both figures suggest that dye degradation is an important parameter when studying green-synthesized photocatalysts, also mentioning the biological species used in their study. However, fewer keywords directly address indoor air purification, building envelope durability, or field-scale performance, highlighting an important research gap for building physics applications.

In Figure 2, the most recurrent author keywords refer to the materials used in the production of the bio-photocatalysts and their photoactivity, as exemplified by composite (keyword in 16 papers), degradation (25 papers), hydroxyapatite (14 papers), nanoparticles (22 papers), shells (21 papers), TiO₂ (18 papers), and ZnO (16 papers), which is well aligned with the blue and red clusters from Figure 3. In Figure 3, the upper green section integrates characterization techniques employed by the research, such as ultraviolet-visible (UV-Vis) spectroscopy and Scanning Electron Microscopy (SEM). Overall, the overview confirms that while marine-based photocatalysts are widely studied for environmental remediation, further research is needed to evaluate their hygrothermal durability, field performance, and integration into building envelope systems, as well as their long-term stability under fluctuating temperature and relative humidity cycles typical of the built environment.

Results

This section is structured to answer the 10 primary questions posed about marine-based photocatalysts in the context of the built environment.

What are the general applications of marine-based photocatalysts so far?

Regarding the general landscape of research, four papers (3.7%) addressed indoor air purification as the primary reason for the synthesis of marine-based photocatalysts, and three other studies (2.7%) (Joseph et al., 2025; Karthik et al., 2025; Matei et al., 2024) investigated applications in glass. Nevertheless, at least 77.2% of the documents had wastewater or water treatment as their underlying application goal.

The well-recognized presence of organic dyes in industrial effluents (Bhole et al., 2024), the accumulation of herbicides (Zhang et al., 2023), and the acknowledged existence of antibiotics (Alshandoudi et al., 2023; Xiao et al., 2023) in aquatic environments are among the justifications for the search for alternatives to mitigate environmental impacts. Although at least 20.4% of the studies mentioned more than one potential purpose, all of them evaluated the degradation of dyes or organic molecules in liquid media to discuss performance. While these liquid-phase studies provide valuable mechanistic insights, their direct translation to building physics requires fundamental shifts toward gas-phase kinetics, surface-to-air exposure, and the assessment of how building envelope porous structures influence pollutant capture.

Antibacterial (Adhitiyan et al., 2024; Alprol et al., 2024; Aouadi et al., 2024; Balaraman et al., 2020, 2022; Bhatti et al., 2023; Borah et al., 2023; Dhanaraj et al., 2024; Fatimah et al., 2024a; Fouda et al., 2022; Geethamala et al., 2024; Joseph et al., 2025; Karthik et al., 2025; Kumar et al., 2022; López-Miranda et al., 2025; Manoj et al., 2021; Serrà et al., 2020a; Sudhakar et al., 2025; Sundar et al., 2024; Tejaswi and Devi, 2025; Thankachan et al., 2024), antiprotozoal (Amina et al., 2023), larvicidal (Balaraman et al., 2020, 2022), and anticancer (Amina et al., 2023; Balaraman et al., 2020; Janani et al., 2024; Lavanya et al., 2023; Rajivgandhi et al., 2022; Sudhakar et al., 2025; Sundar et al., 2024) activities are among other identified applications. However, from a building performance perspective, the antibacterial potential is particularly relevant for mitigating bio-deterioration on façade surfaces.

Concerning the built environment, although self-cleaning ability is well known (Diamanti et al., 2021; Lapidus et al., 2022; Padmanabhan and John, 2020), it has been limited to glass applications in the reviewed sample (Karthik et al., 2025; Matei et al., 2024), since self-cleaning glazing is an advanced technology (Li and Wu, 2025). This reveals a significant research gap: the lack of studies investigating the interaction between these photocatalysts and high-mass envelope materials, such as cementitious renders or masonry. Figure 4 summarizes the main trends identified.

Figure 4.

Main applications explored in research for marine-based photocatalysts.

What are the passive environmental control strategies and applications of marine-derived photocatalysts in the built environment?

Considering the built environment elements, the most explored direct application was indoor air purification as a passive indoor environmental quality strategy. 3.7% of the documents (Qiu et al., 2022; Wang et al., 2021a, 2021b, 2025b) identified this issue as their primary goal, aiming to transform building surfaces into active filters to tackle sick-house pollution (Wang et al., 2025b) and incomplete photodegradation (Wang et al., 2021a, 2021b).

Qiu et al. (2022) and Wang et al. (2021a) investigated the ability of novel photocatalysts derived from sea resources to degrade formaldehyde, which is commonly found in furniture, paint, and adhesives, thereby raising concerns for occupant health and exposure in indoor environments. Several factors influence the emission of volatile organic compounds from materials such as PVC flooring, including pH and moisture (Leivo et al., 2026), justifying the need for enhancing surface protection through building physics–informed design. Wang et al. (2021b, 2025b) evaluated the mineralization of toluene, another common indoor air pollutant that poses health risks to humans and is relevant to ventilation and source-control strategies in buildings.

Self-cleaning windows were mentioned by Joseph et al. (2025) among the applications of chitosan-cellulose nanocrystal composites, for which water contact angles were measured, regarding the potential of the resulting hydrophilic surfaces to attract and spread water. Glass slides were coated by Karthik et al. (2025) with marine-actinobacteria-mediated TiO₂ to observe, in contrast, the self-cleaning performance due to water-repellent behavior. Matei et al. (2024) also evaluated photodegradation by incorporating their novel photocatalyst within a paint applied to glass slides.

A critical finding is that no papers have tested these bio-photocatalysts directly in building envelopes or façades under real climatic boundary conditions or long-term durability requirements. Although previously explored in the work of Saeli et al. (2018), where Atlantic codfish bone waste was used to produce photocatalysts incorporated into mortars for low-maintenance building façades, it has not been sustained over time, according to the papers assessed in this review. This indicates a major opportunity: the growth of algae on façades can be addressed by integrating chemical (photocatalysis) and hygrothermal strategies (creating hostile environments through moisture control; von Werder et al., 2015). This demonstrates the urgent need for integrated Heat-Air-Moisture (HAM) and surface chemistry approaches in future building physics research.

Which materials are used in the synthesis of marine-based photocatalysts?

Based on the function of the marine materials in the synthesis of photocatalysts, three main groups were identified from the literature review. The sea resources were used as (i) primary carriers or supports for well-known photocatalysts (53.7%); (ii) reducing and capping agents (36.1); (iii) catalysts used without additional photoactive materials (10.2%). Understanding these functional roles is crucial for evaluating their integration into building envelope systems, as the choice of carrier directly influences the specific surface area available for gas-phase pollutant adsorption and the moisture buffering capacity of the final composite.

In most cases, additional chemical substances and doping agents were required. Regarding the first group, since nanoparticles tend to agglomerate, using marine substrates with high adsorption abilities and hydrophilic surfaces reduces aggregation (Tang et al., 2018). This property is particularly relevant for façade and glazing surfaces, where uniform dispersion governs the self-cleaning behavior and the optical properties of the coating. For the second group, phytochemicals such as proteins, saponins, and quinines may reduce metallic ions, prevent aggregation, and provide stability (Maduraimuthu et al., 2023).

Concerning the exploited marine resources, algae were used to synthesize photocatalysts in 41.7% of the papers, including seaweed and microalgae. 42.2% of the studies on seaweed worked with Sargassum (Balaraman et al., 2020, 2022; Kishore et al., 2025; Liu et al., 2025b; López-Miranda et al., 2023, 2025; Rabie et al., 2020; Soroush et al., 2025) and Ulva (Arulsoosairaj et al., 2024; Borah et al., 2023, 2024; Chen et al., 2024; Dumbrava et al., 2023; Fouda et al., 2022; Maduraimuthu et al., 2023; Saikia et al., 2023; Soroush et al., 2025; Sudhakar et al., 2025; Wang et al., 2025a) species. For microalgae, among 10 studies, the Scenedesmus species was chosen by two (Wu et al., 2021; Zamani et al., 2023), whereas Spirulina platensis was the adopted sea resource in three papers (Serrà et al., 2020a, 2020b, 2021).

33.3% of the papers working with algae employed them as supports or carriers for other photocatalytic products, and 64.4% of the studies used the materials as reducing or complexing agents. The exception was Wu et al. (2021), who studied the removal of estrogen through algal extracellular organic matter, fitting in the category of catalysts produced without combining additional photoactive materials. Such functional versatility suggests potential for algae-derived composites in building envelopes where multifunctional properties (adsorption, photodegradation, self-cleaning) are desired.

Shells were studied in 38% of the articles, including those of abalones (Wang et al., 2020b, 2021a, 2021b, 2025b), clams (Chen et al., 2025; Ling et al., 2022; Matei et al., 2024; Qu et al., 2022; Wang et al., 2020b), cockles (Dhanaraj et al., 2024; Fatimah et al., 2024a, 2024b), crabs (El-Ella et al., 2020), crawfish (Xiao et al., 2023), mussels (Cai et al., 2023; Cao et al., 2023; Chen et al., 2025; Li et al., 2020; Mohammad et al., 2022; Nejatpour et al., 2025; Qiu et al., 2022; Sheng et al., 2022; Wang et al., 2020b, 2020c), oysters (Chen et al., 2025; Chinnaswamy et al., 2024; Eddy et al., 2023a, 2023b, 2024a; Maravilla et al., 2024; Ogoko et al., 2024; Wang et al., 2020b; Zamani et al., 2024; Zhang et al., 2023), scallops (Adhitiyan et al., 2024; Alshandoudi et al., 2023; Chen et al., 2025; Manoj et al., 2021; Wang et al., 2020b), snails (Eddy et al., 2024b; Elemike et al., 2021), shrimps (Aadnan et al., 2020; Aouadi et al., 2024; Joseph et al., 2025; Li et al., 2025), and seashells in general (Bhole et al., 2024; Castro et al., 2025; Zamani et al., 2023). The predominance of calcium carbonate (CaCO₃) in seashells makes them highly compatible with cementitious, lime-based, and gypsum-based building materials due to their chemical affinity.

Calcium oxide (CaO) or chitosan obtained from shells was investigated as an independent photocatalyst in eight papers (Eddy et al., 2023a, 2023b, 2024a, 2024b; Joseph et al., 2025; Maravilla et al., 2024; Ogoko et al., 2024; Qu et al., 2022). In 90.5% of the studies involving shells, they were supported or combined with other materials.

Although algae and shells were the most frequently used bio-sources, other marine species were addressed in a smaller number of papers: single studies used marine oyster extract (Safat et al., 2021), sand (Kamali et al., 2022), sponge (Bhatti et al., 2023), and tunicates (Wang et al., 2020a); two studies each examined fungi (Ameen et al., 2021; Kumar et al., 2022) and coral (Janani et al., 2024; Prajaputra et al., 2025); three papers worked with bacteria (Karthik et al., 2025; Tejaswi and Devi, 2025; Zhang et al., 2020), fish scales (Campalani et al., 2021; García-Gutierrez et al., 2025; Yadav et al., 2025) and plants (Morjène et al., 2021; Rajivgandhi et al., 2022; Sundar et al., 2024); five papers investigated fish bones (Ahamed et al., 2023; Liu et al., 2025a; Prosad Moulick et al., 2023; Roy et al., 2024a, 2024b). Among these sea resources, Otolithoides Pama fish bones were explored as catalysts themselves after their transformation into hydroxyapatite (calcium phosphate hydroxide; Prosad Moulick et al., 2023). These diverse marine sources offer multiple chemical and structural functionalities that could be exploited in building materials to impart photocatalytic, antimicrobial, or self-cleaning properties.

93.5% of the marine-based photocatalysts synthesized did not rely solely on the sea resources as the photoactive material but instead were combined with one or more chemicals. In this context, a wide variety of compositions was explored, but the most recurrent combinations involved marine materials associated with Zn/ZnO (24 cases), TiO₂ (22 cases), and silver (Ag) (18 cases), followed by copper, iron, and others. The doping of marine-supported photocatalysts with metals is critical for building applications to reduce the band-gap energy, allowing the envelope to be photo-activated not only by UV light but also by the visible spectrum of solar radiation. Figure 5 compiles the primary materials investigated to compose the marine-based photocatalysts.

Figure 5.

Main materials investigated to compose marine-based photocatalysts.

How are the marine-based photocatalysts synthesized?

Several synthesis methods have been presented in the literature, varying according to the marine material employed and its specific function. In research addressing marine materials primarily as carriers or supports, solid-state reactions were implemented, involving the reactive grinding of CaO, previously prepared via the calcination of seashells, together with a second chemical component expected to enhance its photoactivity (Bhole et al., 2024; Koladia et al., 2024). Solid-state methods would be advantageous for the mass production required in the construction industry.

Other reported approaches included the sol-gel mixing (Alshandoudi et al., 2023) and the solvothermal method. For example, Cai et al. (2023) used a solvothermal protocol starting with the immersion of mussel shells in hydrochloric acid (HCl), calcination at 900°C, and grinding. A microwave-assisted synthesis was employed by Dhanaraj et al. (2024) to produce Ag- and Zn-doped hydroxyapatite from Anadora granosa seashells. Ahamed et al. (2023) produced chitosan-impregnated hydroxyapatite/manganese dioxide composite using co-precipitation. Hydrothermal protocols were used by Zhang et al. (2023) and Bhatti et al. (2023). In Serrà et al. (2021), electroless Cu deposition and soft thermal treatment were used to fabricate a Cu@Cu₂O@CuO–microalgae hybrid. Wang et al. (2020c) synthesized a SiO₂-doped photocatalyst from waste mussel shells through acidification, by immersing crushed shells in HCl until bubbles ceased, indicating decarbonation. These synthesis techniques demonstrate the flexibility to produce tailored particle morphologies, which could influence light absorption, pollutant interaction, and surface durability in building applications.

In the second group, Borah et al. (2023) extracted bioactive compounds from marine algae, which had been washed, dried, ground into powder, and suspended in water. Nickel(II) nitrate hexahydrate ((Ni(NO₃)₂⋅6H₂O, ≥97.0% purity) solution was added dropwise to the extract with constant stirring at 100°C. Sodium hydroxide (NaOH) was used to control the pH, and the resulting NiO nanoparticles were obtained through centrifugation, washing, drying, and annealing at 500°C for 2 hours (Borah et al., 2023). Garcia-Bedoya et al. (2021) used an algal extract in methanol as a complexing agent.

In the third group, which explored photocatalysts composed entirely of sea-based materials, Eddy et al. (2023b) applied a sol-gel method to synthesize CaO nanoparticles from oyster shells. The shells were washed, dried, and crushed into powder. Treatment with HCl converted calcium carbonate (CaCO₃) to calcium chloride (CaCl₂), which was then hydrolyzed with NaOH to form calcium hydroxide (Ca(OH)₂). After filtering, drying, and calcinating at 700°C, CaO nanoparticles were obtained (Eddy et al., 2023b). In another study, Prosad Moulick et al. (2023) used calcination to transform fish bones into hydroxyapatite, which served directly as a photocatalyst. The bones were de-fleshed, washed to remove organic impurities, dried, crushed, calcined at 900°C, and pulverized into a fine powder (Prosad Moulick et al., 2023). Figure 6 summarizes the main synthesis techniques retrieved from the literature review to produce marine-based photocatalysts.

Figure 6.

Methods to produce marine-based photocatalysts.

What characterization techniques are employed regarding the marine-based photocatalysts?

Considering the characterization of novel materials, which does not directly assess their photocatalytic performance, 93.5% of the papers reported UV-Vis (including diffuse reflectance spectroscopy (DRS)) or UV-Vis/NIR spectroscopies. The spectrophotometers were used to determine the optical properties of the photocatalysts, revealing the ranges in which they exhibited stronger absorptions. This information is critical when evaluating potential applications in building envelopes or coatings, as light absorption properties directly influence photocatalytic efficiency under solar or indoor illumination. Tauc plot studies were frequently conducted to estimate the bandgap for the synthesized photocatalysts and their corresponding band potential (Bhole et al., 2024).

In 39.8% of the papers, X-ray photoelectron spectroscopy (XPS) was also discussed, allowing the measurement of the chemical states of the photocatalysts and their electron transfers (Wang et al., 2023). 19.4% of the papers relied on photoluminescence spectra (PL) to monitor the recombination rate of electrons and holes (Cai et al., 2023).

81.5% of the papers presented SEM or field emission scanning electron microscopy (FE-SEM) images for morphological and surface studies (Pachiyappan et al., 2022; Saikia et al., 2023), and 50.9% of the documents showed transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) results. 52.8% of the papers associated image analysis with an energy-dispersive spectrometer (EDAX/EDX/EDS), identifying the significant elements in the composition of the bio-photocatalysts (Pachiyappan et al., 2022).

X-ray diffraction (XRD) was also a key factor, as was reported in 84.3% of the studies. A diversity of mineralogical and crystallographic information can be obtained from marine-based photocatalysts through XRD, including phase purity, crystal grain size, degree of crystallinity, dislocation density, microstrain, crystallinity index, and changes (Prosad Moulick et al., 2023). Al-Enazi (2022), for example, applied the Scherrer formula to calculate the average crystalline size of nanoparticles synthesized with mediation by unicellular algae.

Fourier-transform infrared spectroscopy (FTIR), used by 71.3% of researchers, was essential for identifying functional groups in the novel composites by analyzing transmittance bands (Ling et al., 2022). Nitrogen adsorption/desorption isotherms and the Brunauer–Emmett–Teller (BET) technique, used in 18.5% of the papers, were employed to assess surface characteristics and porosity. This low percentage represents a notable gap for building physics applications, as specific surface area and pore size distribution are the primary governors of gas-phase diffusion and pollutant adsorption capacity in porous building materials.

Thermogravimetric analyses (TGA) appeared in 14.8% of studies, while Raman spectroscopy was employed in 13.9%. Dynamic light scattering (DLS) was developed to determine the average diameter of the nanoparticles (Eddy et al., 2024a) in 10.2% of the studies, and zeta potential measurements to analyze chemical surface charge and pH (Alshandoudi et al., 2023) for 9.3% of the novel photocatalysts. The remaining characterization techniques, such as X-ray fluorescence (XRF) and inductively coupled plasma (ICP), were less common. Figure 7 compiles the main tests used to characterize the synthesized marine-based photocatalysts, developed using the Bubble Chart feature in the Akvelon 2.2.2 tool from Power BI Desktop.

Figure 7.

Main characterization tests for the marine-based photocatalysts.

How is the performance of the novel marine-based synthesized materials experimentally evaluated?

71.3% of the studies performed at least dye degradation to evaluate photocatalytic performance. Methylene blue (MB), rhodamine B (RhB), methyl orange (MO), and Congo red (CR) were the most frequently used dyes considered as reference pollutants. Although dye degradation is primarily a model test, the methodology provides insights into pollutant removal potential, which can be translated to the degradation of volatile organic compounds (VOCs) and other contaminants in building environments. From a building physics perspective, it is a useful screening tool for chemical activity, with dyes commonly used to assess self-cleaning capacity.

In summary, the protocols involved mixing the photocatalysts in a solution with the compound to be degraded and kept in the dark for variable times (30 minutes (Amina et al., 2023; Bhatti et al., 2023; Bhole et al., 2024; Lavanya et al., 2023; Maduraimuthu et al., 2023), 1 hour (Mohammad et al., 2022), 2 hours (Qu et al., 2022, etc.), until reaching adsorption-desorption equilibrium (Wang et al., 2020c), and under stirring to achieve good dispersion (Amina et al., 2023). Then, the prepared suspensions were exposed to light sources, such as visible light (Fouda et al., 2022; Manoj et al., 2021; Sundar et al., 2024; Wang et al., 2023), sunlight (Bhatti et al., 2023; Eddy et al., 2023b; Maduraimuthu et al., 2023), LED light (Kamali et al., 2022; Pinna et al., 2021), xenon (Amereh et al., 2023; Amina et al., 2023; Cai et al., 2023), UV (Aadnan et al., 2020; Al-Enazi, 2022; Pachiyappan et al., 2022), and fluorescent lamps (Aadnan et al., 2020), generally under continuous agitation. This illumination simulates conditions relevant for façade surfaces or indoor coatings, highlighting the potential efficiency under sunlight or artificial lighting in buildings.

At given intervals (3 minutes (Saikia et al., 2023), 10 minutes (Lavanya et al., 2023), 30 minutes (Maduraimuthu et al., 2023, etc.), aliquots (in some cases with fixed volumes, such as 1 ml (Li et al., 2025)) were collected from the solutions for UV-Vis or UV-Vis/NIR spectroscopy. Supernatants were usually collected and centrifuged for sampling (Bhole et al., 2024). In the study of Matei et al. (2024), where the photocatalyst was applied to glass slides within a paint of styrene-acrylic film-forming material and apatitic material, the slides were immersed in vessels containing the dye in solution for further UV-Vis assessment. In general, for the degradation studies developed in liquid solutions with several origins of pollutants, reusability tests for the marine-based photocatalysts were carried out by submitting the photoactive materials to several consecutive degradation runs, like three (Ling et al., 2022), four (Sundar et al., 2024), five (Saikia et al., 2023), six (Alshandoudi et al., 2023), or ten (Serrà et al., 2021).

In 20.4% of the papers, pollutants other than dyes were assessed, including 2,4-dichloro phenoxy acetic acid (García-Gutierrez et al., 2025), 2,4,6-trinitrophenol (Yadav et al., 2025), 4-nitrophenol (Aadnan et al., 2020; Kishore et al., 2025; Pritha et al., 2025; Wang et al., 2023, 2025a), atrazine (Li et al., 2025), chromium (de Bittencourt et al., 2020; Yadav et al., 2025), ethidium bromide (El-Ella et al., 2020), formaldehyde (Qiu et al., 2022; Wang et al., 2021a, 2021b), glyphosate (Zhang et al., 2023), lead (Liu et al., 2025a), naphthalene (Chen et al., 2024), palm oil mill effluent (Putri et al., 2022), perfluorocarboxylic acids (Nejatpour et al., 2025), phenol (Morjène et al., 2021), and toluene (Wang et al., 2021b, 2025b). Except for the gases, the degradation of these pollutants (Aadnan et al., 2020; de Bittencourt et al., 2020; El-Ella et al., 2020; Morjène et al., 2021; Putri et al., 2022; Wang et al., 2023; Zhang et al., 2023) was also carried out in aqueous solution.

However, specific studies on formaldehyde (Qiu et al., 2022; Wang et al., 2021a) and toluene (Wang et al., 2021b) represent the state-of-the-art for building applications. Pollutants like formaldehyde and toluene are directly relevant to indoor air quality in buildings. These setups are the most aligned with building physics standards (such as ISO 22197), as they model the kinetic degradation of Indoor Air Quality (IAQ) pollutants under dynamic flow conditions. Qiu et al. (2022) used photoacoustic spectroscopy to measure CO₂ generation, allowing for the assessment of mineralization rates, ensuring that the pollutant is not merely adsorbed but chemically converted.

Several studies analyzed the total organic carbon (TOC) of the reactions before and after pollutant degradation by photocatalysis, allowing for a discussion of the extent of organic molecule mineralization (Serrà et al., 2020b). TOC analysis is a vital proxy for “complete oxidation,” preventing the accumulation of potentially toxic intermediate byproducts on indoor surfaces. While these tests indicate chemical stability, they do not simulate the mechanical abrasion or weathering (rain/wind) that a coating would endure on a building façade.

Regarding biological tests, the antimicrobial potential was evaluated against bacteria and microalgae (Balaraman et al., 2022; Kumar et al., 2022; Manoj et al., 2021; Sundar et al., 2024; Zhang et al., 2020). In summary, antibacterial studies can be based on growing bacteria in a nutrient-rich environment, inoculating them with photocatalysts, and, after incubation, measuring the zones of bacterial inhibition (Bhatti et al., 2023; Borah et al., 2023).

While medical applications (anticancer, larvicidal) are outside the scope of the built environment, the protocols for antibiofilm assessment are transferable to the study of biological colonization (greening) on building façades. The inhibition of biofilm formation on glass or stone substrates is a key parameter for reducing maintenance costs and preserving the esthetic and thermal properties of the envelope. The antibiofilm performance of marine-based materials was assessed by growing bacteria in glass test tubes, incubating them with photocatalysts, and staining the surface with a dye to document the amount of biofilm adhered to the glass (Balaraman et al., 2020, 2022; Kumar et al., 2022).

How are the reaction mechanisms and kinetics experimentally characterized?

Reactive species trapping tests were presented by at least 28% of the papers to explore the photocatalytic mechanism of the novel synthesized materials. These tests were based on the dependency of the photodegradation efficiency of the catalysts on the presence of free radicals at their surface (Qu et al., 2022). From a building physics perspective, identifying the dominant active species is fundamental for predicting the material’s dependence on environmental boundary conditions, specifically relative humidity.

For example, Koladia et al. (2024) conducted MB discoloration runs using benzoquinone (BQ), isopropanol (IPA), and ethylene-diamine tetraacetic acid (EDTA) as electrons (e⁻), hydroxyl radical (·OH), and hole (h⁺) radical scavengers. Saikia et al. (2023) also used BQ (≥98% purity) and IPA (≥99% purity), but for h⁺, ammonium oxalate monohydrate (99% purity) was used. Aadnan et al. (2020) used potassium peroxydisulfate (K₂S₂O₈), potassium iodide (KI), and IPA as e⁻, h⁺, and ·OH radical scavengers.

Nearly half of the studies evaluated the kinetics of the reactions. The experimental results were fitted into various kinetic models (Bhole et al., 2024), including the Modified Freundlich, Langmuir-Hinshelwood, and zero-order to second-order kinetics. If the differences between experimental and calculated values were small (Dumbrava et al., 2023), the models were deemed appropriate. Reaction kinetics are particularly important for building-related implementation, as they allow the estimation of pollutant removal rates under time-dependent exposure scenarios, such as VOC degradation in indoor environments or contaminant breakdown on exterior surfaces. Future implementation in building simulation tools requires deriving reaction rate constants and adsorption coefficients specifically for the solid-gas interface.

Are environmental and toxicity assessments conducted, and what are the implications for occupant safety?

Although the studies are directed toward the green synthesis of photocatalysts, it is through a life cycle assessment (LCA) that the flows exchanged with the environment can be analyzed throughout their life cycle to support circularity (Saade et al., 2020). A critical finding of this review is that no LCA was retrieved within the 108 full papers. This represents a major gap for the construction sector, as the net environmental benefit of these materials remains unquantified. Future research must determine if the operational benefits outweigh the embodied energy required for the calcination and processing of marine waste.

In terms of toxicity, evaluations have been carried out within the study of marine-based photocatalysts’ antimicrobial, larvicidal, and anticancer activities, thereby examining this issue as potentially advantageous. Primarily due to the widespread use of nanoparticles, the ecotoxicity evaluation regarding potential hazardous effects is crucial (Matějová et al., 2023).

Safat et al. (2021) evaluated the cytotoxic effect and biocompatibility of CeO₂ nanoparticles prepared using marine oyster extract against fibroblast cells. Since no cytotoxicity was identified, the nanoparticles demonstrated biosafety. Fatimah et al. (2024b) also verified insignificant cytotoxicity for their Zr-doped hydroxyapatite. These results suggest that marine-based additives may be safer alternatives for indoor coatings.

In Chinnaswamy et al. (2024), the methylene blue aqueous solution, after treatment with oyster-shell-derived composites, was tested on seeds (green gram, black gram) for germination. The normal growth demonstrated the nontoxic nature of the nanocomposite. This finding is particularly relevant for exterior applications, indicating that the leaching or runoff water from a photocatalytic façade would likely not be harmful to the surrounding urban green infrastructure.

Despite not being included in the final sample, the study of Vijayakumar et al. (2021) presented an ecotoxicity assessment for marine polysaccharide-formulated gold nanoparticles using brine shrimp (Artemia salina). No significant ecotoxicity was verified up to 400 μg/mL. However, for building envelope implementation, future research must go beyond acute toxicity and address the long-term release of nano-objects due to weathering and abrasion, ensuring that the “circular” solution does not introduce persistent contaminants into the urban ecosystem.

Is research progressing from material synthesis to building envelope implementation and performance-based evaluation?

Most papers focused strictly on synthesis, revealing a disconnect between chemical engineering and building physics. Wang et al. (2020b) investigated the cost of TiO₂/seashell composites compared with commercial P25 TiO₂, concluding that introducing shell waste can reduce production costs. This economic factor is crucial for the scalability of photocatalytic technologies in the construction sector, where large surface areas (façades and roofs) demand cost-effective solutions. Although Karthik et al. (2025) mentioned antifouling paints, experimentally incorporating bio-photocatalysts in construction materials, functional coatings, or indoor finishes remains virtually unexplored in the sampled literature.

However, specific studies offer technical pathways for this implementation. Garcia-Bedoya et al. (2021) reported a need for encapsulation in a sol-gel matrix (using tetraethyl orthosilicate) to separate nanoparticles from organisms. Encapsulation strategies such as these are directly relevant for building physics, as they provide a method to immobilize photocatalysts within a coating.

Not only the photocatalysts but also their immobilization media can benefit from sea resources when applied. The immobilization contributes to the photoactivity and reusability (Chanani et al., 2023). El-Ella et al. (2020) extracted chitosan from crab shell wastes to support and immobilize TiO₂ and TiO₂-Au photocatalysts in thin films (0.1 mm), together with a biopolymer polyvinylidene chloride (PVDC). Such thin-film approaches are transferable to indoor surface finishes or glazing membranes. From a physics perspective, determining the vapor permeability and thermal resistance of these bio-based films is the next step to ensure they do not disrupt the moisture balance of the envelope assembly.

Li et al. (2025) immobilized their co-doped g-C₃N₄/shrimp shell biochar onto a polylactic acid-degradable mulching film. Wang et al. (2020a) dispersed and immobilized β-FeOOH photocatalysts in hydrogels produced through the isolation of tunicate cellulose. Similarly, Joseph et al. (2025) made a green nanocomposite chitosan film derived from shrimp shells and incorporated with synthesized cellulose nanocrystals. Future research could evaluate how these hydrophilic matrices behave in building surfaces.

What are some key findings on the photocatalytic performance of the novel marine-based materials?

Regarding the built environment and indoor air quality, the TiO₂/C/CaCO₃ heterojunctions produced by Qiu et al. (2022) with mussel shell extract could wholly degrade formaldehyde in 80 minutes under light. This finding is significant for “sick building syndrome” mitigation, as complete degradation prevents the desorption of captured pollutants. The TiO₂/C/MnO₂ produced with abalone shells by Wang et al. (2021b) had electrons transferred from the conduction band (CB) of the TiO₂ and MnO₂ to the carbon (C), enhancing electron-hole separation. In Wang et al. (2021a), pure TiO₂ had a bandgap energy of 3.3 eV, which was decreased from 3.1 to 2.9 eV through the addition of insoluble matrix proteins from abalone shell waste ranging from 0.2 to 0.8 g. Bandgap reduction is especially relevant for indoor environments, where visible-light-driven photocatalysis is needed due to the limited availability of UV radiation.

Wang et al. (2025b) observed complete degradation of toluene over a periostracum-modified TiO₂ photocatalyst with an initial RH of 45%, which was enhanced by trace elements such as C, N, P, Fe, and Cu in PAL serving as doping agents. Humidity-dependent performance is important to consider in building enclosures, where relative humidity strongly influences surface chemistry and pollutant adsorption.

Abstracting from indoor air, coherent results were identified regarding the enhancement of optical properties. Prajaputra et al. (2025) and Chen et al. (2024) attributed performance improvements to a synergistic effect between marine carriers and photocatalysts, where the biocomposite outperformed pure oxides. This is physically explained by the optimization of energy bands: Rabie et al. (2020) reported bandgaps of 2.45 and 2.32 eV for algae-supported composites, significantly lower than pure ZnO. For building envelopes, this bandgap reduction implies a higher potential for harvesting solar energy in the visible spectrum, extending the active period of self-cleaning façades beyond peak UV-hours.

Similarly, Yan et al. (2025) achieved nearly complete degradation of tetracycline using biochar-based composites due to improved electrical properties. Although tetracycline is a pharmaceutical pollutant, its degradation demonstrates the material’s capacity to break down complex organic structures, suggesting efficacy against organic pollutants found in urban environments. Lavanya et al. (2024) and Alprol et al. (2024) also confirmed high efficiencies (>89%) for algae-mediated nanoparticles under sunlight, validating the stabilization role of marine extracts.

Finally, the role of adsorption capacity, a critical parameter for porous building materials, was highlighted in the third group (shells). Qu et al. (2022) found that clam shells calcined at 1000°C removed 70.55% of pollutants in the dark (adsorption) and over 90% under light. Eddy et al. (2024b) and Maravilla et al. (2024) corroborated that CaO derived from shells offers a dual mechanism of high adsorption followed by photodegradation.

Following the discussions on this topic, Table 1 summarizes five selected well-performing marine-based photocatalysts.

Table 1.

Summary of five well-performing marine-based photocatalysts.

Study	Marine-based photocatalyst	Contaminant degraded	Degradation
Qiu et al. (2022)	TiO₂/C/MnO₂ with abalone shells	Formaldehyde	100% after 80 minutes under xenon light
Prajaputra et al. (2025)	CaO-ZnO with marine coral fragments	Chloramphenicol	66.99% after 240 minutes under UV light
Chen et al. (2024)	TiO₂-decorated carbon quantum dots with Sargassum horneri	Naphthalene	86.63% after 240 minutes under visible light
Lavanya et al. (2024)	Au nanoparticles with Halimeda macroloba	Methylene blue and methyl orange	97.23% and 89.91% after 90 minutes under sunlight
Maravilla et al. (2024)	CaO with oyster shells	Methyl orange	93.7% after 120 minutes under UVC light

Considering mineralization rates, testing a Bi₂WO₆/calcined mussel shell composite, 52.3% TOC removal from RhB occurred after 150 minutes of reaction, suggesting a gradual mineralization (Li et al., 2020). Wang et al. (2020c) found lower mineralization rates of dyes (33.5% and 16.5% for MB and RhB) in the presence of a SiO₂-doped photocatalyst derived from a waste mussel shell, indicating that the dyes were decomposed and only partially mineralized under visible light.

Concerning the mechanism, Cai et al. (2023) produced calcined mussel shell powder supports doped with Y-Bi₂MoO₆ through a solvothermal method. ·O₂⁻ and h⁺ represented the primary active species, with a crucial role played by ·OH. Regarding stability and reusability, after four cycles, a decrease in RhB degradation from 99.7% to 83.3% occurred, likely due to the loss of catalyst during centrifugation and the adsorption of intermediates onto the catalyst surface (Cai et al., 2023).

As for kinetics, Zhang et al. (2020) identified zero-order constant values. Defining these kinetic constants is the first step toward integrating marine-based materials into simulations for performance-based building design. Overall, marine-based photocatalysts demonstrate significant potential. However, Building Physics challenges remain: ensuring long-term performance under hygrothermal cycles, immobilization within construction materials to prevent leaching, and verification of safe indoor exposure pathways (preventing nanoparticle inhalation).

Discussion

The findings highlight a clear underutilization of marine-based photocatalysts in the built environment, which is particularly noteworthy since integrating seafood and aquaculture waste into construction presents an opportunity within the circular and blue economy. However, regarding building envelopes, the large exposed surface areas offer a platform not just for passive depollution, but for active surface engineering. The step-by-step approach of this review yields practical implications primarily related to future research in the building sector.

Regarding theoretical implications, the reviewed literature showed that marine-derived materials from algae, shells, and fish bones may function not only as structural supports but also as active components in photocatalytic systems. While the traditional photocatalysts are still materials like TiO₂ and ZnO (Navidpour et al., 2024), marine-based composites demonstrate that green-synthesized alternatives can outperform the conventional ones. The synergies can lead to improved visible-light response, electron–hole separation, and pollutant degradation. Bandgap tuning must be enhanced for indoor environments, where UV irradiation is limited, and visible-light activation is needed.

Innovative materials and technologies are key to trends toward nearly zero-energy buildings (nZEB) and positive-energy buildings (Magrini et al., 2020). In urban environments, nitrogen oxides (NOx) lead to environmental problems, such as acid rain, and threaten human health. Therefore, marine-based materials capable of degrading formaldehyde and toluene present opportunities for building-integrated passive air purification without additional operational energy demand.

The potential of marine-based photocatalysts should be exploited for self-cleaning behavior. As passive design strategies, their advantages may include easy maintenance in façades (Ma et al., 2024). Smits et al. (2013) demonstrated this with TiO₂ on cementitious materials, observing 60% soot mineralization, while Pozo-Antonio and Dionísio (2017) noted limitations with mortars. This reinforces the potential benefit of exploiting the synergistic effect of marine-based photocatalysts to overcome these efficiency limits and maintain the solar reflectance of the envelope.

Dyes such as RhB and MB are often used as surrogates for pollutants and applied to mortar renderings to understand the self-cleaning activity (Bersch et al., 2023). However, a critical theoretical gap remains regarding mass transport limitations. Unlike the reactors used in most reviewed studies, a building façade relies on the diffusion of gas-phase pollutants into the solid porous matrix.

In this review, despite promising laboratory results, no studies have tested marine-based photocatalysts in full-scale façade systems. This highlights a significant gap in translating these materials into real applications. As supported by the previous discussion, key challenges include ensuring durability under weathering and UV exposure, as well as validating performance through standardized gas-phase testing. Future research implies moving beyond characterization to integrate reaction kinetics into Heat, Air, and Moisture (HAM) simulation tools, enabling performance prediction under dynamic climatic conditions.

Conclusions

This review offers a novel perspective on sustainable construction by systematically linking marine-based photocatalysts with the built environment. Rather than viewing these materials solely as chemical agents, this work frames them as functional components for high-performance building envelopes. The research was motivated by the potential of photocatalysis to provide passive depollution and self-cleaning capabilities, addressing the environmental concerns of conventional synthesis through the valorization of marine waste.

By addressing 10 key research questions across 108 selected studies, this work provides a structured overview of how marine-derived materials, particularly seashells (used in 38% of studies) and algae (41.7%), can function as carriers, reducing agents, or active photocatalysts either alone or in combination with conventional compounds like TiO₂, ZnO, and Ag. In many cases, these materials demonstrated enhanced photocatalytic performance compared with photolysis alone. From a physics perspective, the use of calcined shells and algae extracts was shown to optimize surface area and bandgap energy, allowing for broader solar spectrum utilization, a critical factor for façade activation under varying daylight conditions.

A critical finding is the disconnect between current testing methods and building reality. Although 77% of the studies focused on wastewater and dye degradation, only a limited number addressed built environment applications. Standardization is also lacking: while chemical characterization (UV-Vis, SEM, XRD) is consistent, the lack of Life Cycle Assessments (LCA) prevents a definitive conclusion on the operational benefits.

To advance from laboratory synthesis to technological readiness, this study proposes a technical roadmap. For material scientists, the priority is to optimize the efficiency and compatibility of marine-based photocatalysts within cementitious, lime-based, or paint matrices. For building physicists, the challenge is to validate these composites through standardized gas-phase testing, dirt degradation, and long-term durability assessments. Ultimately, successful implementation depends on bridging the gap between chemical synthesis and hygrothermal performance, ensuring these circular materials can withstand the rigorous demands of the built environment.

Footnotes

Acknowledgements

The authors acknowledge the support of FCT, CERIS, CERENA, IST, PPGCI, UFRGS, CAPES, and CNPq. The authors appreciate the incentive received following the second place in the Call for Projects for PhD and Researchers Category at the H2O & Sustainability Summit 2024.

ORCID iD

Jéssica Deise Bersch

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was funded by the Fundação para a Ciência Tecnologia, I.P. (FCT, https://ror.org/00snfqn58) under Grant UID/6438/2025 (https://doi.org/10.54499/UID/06438/2025) of the research unit CERIS, CERENA (UIDB/04028/2020, https://doi.org/10.54499/UIDB/04028/2020), the PhD grant number 2023.05316.BD (DOI: https://doi.org/10.54499/2023.05316.BD), and the ReCoveRing project (2023.17249.ICDT-16277, ).

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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