Sage Journals: Discover world-class research

Abstract

Polyvinyl alcohol has the potential to be used in fuel cell membranes due to its chemical, mechanical, and membrane-forming capabilities, as well as its higher hydrophilicity and low methanol permeability. However, the pure PVA membrane has a lower proton conductivity than the Nafion^TM membrane. With the addition of some ceramic fillers, PVA can be a possible alternative to Nafion^TM membranes. Therefore, we used the solution method to prepare three polyvinyl alcohol-based composite membranes with the following compositions: a) 5 wt% PVA (polyvinyl alcohol), b) 5 wt% PVA/2 wt % PEG (polyethylene glycol)/wt.1% silicon dioxide (SiO₂) nanoparticles, and c) 5 wt% PVA/2 wt% PEG/wt.1% clay powder. The membranes were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX), oxidative stability, ion exchange capacity, water absorption characteristics, conductivity, and permeability. FITR, EDX, and SEM confirmed the successful fabrication of the composite membrane, while TGA demonstrated membrane thermal stability and other parameters relevant to fuel cell membranes. The methanol permeability of the membrane is pure 5 wt % PVA, 5 wt%PVA/2 wt%/1 wt% SiO₂, and 5 wt% PVA/2 wt% PEG/wt.1% Clay measured 2.37 × 10⁻⁶ cm²/s, 2.89 × 10⁻⁶ cm²/s, and 1.57 × 10⁻⁶ cm²/s, respectively. The methanol permeability of 5 wt% PVA/2 wt% PEG/wt.1% Clay is better than of Nafion117 (5.16 × 10⁻⁶ cm²/s as reported). The membrane 5 wt% PVA/2 wt% PEG/1% Clay exhibits satisfactory levels of oxidative stability (RW% = 94.09 at 1.32 h), IEC (0.232 meq/g), conductivity (0.00432 S/cm), methanol permeability (1.57 × 10⁻⁶ cm²/s), selectivity (3.63 × 10⁻⁴ Ss/cm³), and better water uptake properties at fuel cell operating temperature. As a result, it is reasonable to expect that PVA-based modified membranes will outperform Nafion^TM membranes in the future.

Keywords

Poly (vinyl alcohol)polyethylene glycol clay powder composite membranes

Introduction

Fuel Cells are an attractive alternative energy source to fossil energy and have the potential to generate eco-friendly energy for portable electronics and vehicles.^1–3 The fuel cell is the electrochemical device that directly converts fuel chemical energy to electrical energy. Among the fuel cells, direct methanol fuel cells (DMFCs) are attractive power sources for a wide range of applications, from vehicles to portable electrical devices like laptop computers, radios, mobile phones, personal digital assistants (PDA), and other devices.^4–7 Fuel cells consist of two major parts: one is two electrodes, and the other one is a Polymeric membrane with other auxiliary components. In the two electrodes, the electrochemical combustion of the fuel is performed; on the other hand, the membrane separates the two electrodes with the sustained concentration gradient to transport ionic species between the two electrodes to complete the half-cell reactions. The polymeric composite membrane in a fuel cell gets attention in applications toward stationary and portable for their high efficiency, power density, and low-temperature operating conditions.

The working principle of the fuel cells is to generate electrical energy by converting the chemical energy. Figure 1 shows the mechanism of operation of direct methanol cells, which shows a polymer-electrolyte membrane with diffusion and catalyst sides. The fuel or reactants are forced to enter the cell and penetrate the diffusion side to reach the anode section catalyst side, where the fuel is oxidized.

Figure 1.

Schematic diagram of the direct methanol fuel cells (DMFC) working principle.

The diffusion side provides an electrical bridge between the catalyst and current collectors. The oxidation reaction also occurred on both sides of the membrane by the catalyst side. The catalyst side also works to transport protons, electrons, and reactants.⁸ The carbon dioxide then passes backward to exit via the diffusion side. The protons are transported through the membrane to the cathode, and a reduction reaction of O₂ and H₂O (water) is formed.

The detailed chemical reactions that occurred at the anode as oxidation, cathode as reduction, and overall reaction as redox are given below:

Oxidation: CH₃OH + H₂O → CO₂ + 6H+ + 6e⁻

Reduction: 6H+ + 6e⁻ + 1.5 O₂ → 3H₂O

Redox: 1.5O₂ + CH₃OH → CO₂ + 2H₂O

Until now, the Nation® membrane is the predominating membrane used as a polymeric electrolyte membrane in fuel cells. The reason is that only Nafion exhibits expected physiochemical characteristics, including higher conductivity at a normal thermal condition, and can perform better in a maximum humidity environment. However, Nation® membranes have limitations in the commercialization market of fuel cells, such as high cost, lower thermal stability, and methanol crossover issues.⁹ Methanol crossover in DMFC produces oxidation of fuel at the cathode and results-in (1) depolarization of the electrode, (2) lowering in the open-circuit voltage, (3) high consumption of O₂, (4) CO poisoning, and (5) accumulation of water. These parameters directly affect the efficiency of the DMFCs with high fuel crossover.¹⁰ The fuel crossover in DMFCs may controlled by providing more thickness of the membrane, which also increases the flow resistance of the fuel cells.¹¹ So, it is better to find alternative proton electrolyte membranes.

Recently, the research has focused on finding an alternative polymer electrolyte membrane that focuses on organic-inorganic composite membranes.^12–17 Current research to find alternative fuel research area is inspired by the enthusiastic promotion of hydrogen energy as the next-generation energy source.¹⁸ Among the many options available to use fuel in an operative fuel cell, methanol is one of the best other than hydrogen. So, Direct Methanol Fuel Cells (DMFCs) have a unique opportunity to be a choice and suitable option in the future.¹⁹ Many commercial polymers with sufficient data are available in the DMFC applications. Commercial polymeric membranes such as perflurosulphonic acid-based membranes (like Nafion), various kinds of membranes like modified sulfonated polymers, acid-base polymers, polymers based on aromatic hydrocarbons, as well as organic and inorganic composite membranes have been developed, and many of these polymeric membranes have limitations to use in fuel cells.²⁰ Addressing these issues, Viswanathan and Helen, in the publication question, is Nafion the only choice? ²¹

There are many works of literature have already been reported for organic-inorganic composite membranes such as PEO (polyethylene oxide)- SiO₂,^22,23 PEG (polyethylene glycol)- SiO₂,²⁴ PPG (polypropylene glycol)- SiO₂,²⁴ PTMO (polytetraethylene oxide)- SiO₂,²⁵ PVA-graphene,²⁶ PVA-Oxalic acid,²⁷ PVA-fumaric acid cross-linked biodegradable films²⁸ and much more. These membranes showed better proton conductivity and were thermally stable up to 150⁰C. However, many of the hybrid membranes have lower conductivities than commercial Nafion membranes.²⁹

So, it has become a big challenge for researchers to find a suitable membrane that is cost-effective for DMFCs, has a good balance in conductivity, and reduces fuel crossover. Among the polymeric membrane, small molecules such as Polyethylene glycol (PEG) help reduce the membrane’s crystallinity by increasing proton conductivity. The small molecules assist in increasing the polymeric membrane conductivity by (1) improving the amorphous part of the polymeric membrane, (2) preventing ion aggregation in the polymer electrolytes membrane, and (3) decreasing the Tg temperature.³⁰ The scientists noted that incorporating the inorganic matrix significantly improved the physiochemical properties of the polymer electrolyte membrane.³¹ There are several inorganic matrices, but silica nanoparticles may be better for applying polymer electrolytes to the membrane.³¹ The silica nanoparticles have a large specific surface area, unfolded channels of large dimensions, and a comprehensive structural lack of consistency.³¹ The clay powder and nano clay^32–34 have been widely used as fillers integrated into polymeric membranes.

According to some research, PVA/SiO₂^35,36 and PVA/polyrotaxane³⁷ are two examples of inorganic fillers that can be added to PVA polymers to enhance their barrier qualities. A well-known layered silicate called montmorillonite (MMT) was introduced as filler to the Nafion polymer membrane.^38,39 The methanol permeability should be reduced by the layered structure and high aspect ratio of the MMT clays since methanol has a convoluted diffusion path. The hydrophilic MMT fillers enhanced the PVA polymer matrix’s ionic conductivity and, as a result, decreased the glass transition temperature (Tg), increased the amorphous phases of the matrix, and reduced the polymer’s crystallinity. We know that the swelling ratio of the PVA/MMT composite polymer membrane is effectively decreased when the hydrophilic MMT (clay) filler, which is a stiffer material, is injected into the PVA matrix. The composite polymer membranes showed improvements in both swelling ratio and dimensional stability. Adding an appropriate quantity of MMT fillers to the solid polymer electrolytes (SPEs) has significantly improved the composite polymer membranes’ ionic conductivity, thermal characteristics, and dimensional stability.^33,40,41 The MMT clays in the polymer matrix play a crucial role in increasing the ionic conductivity of the composite polymer electrolyte by forming certain imperfections or amorphous domains at the interface between the ceramic particle and the polymer chain. These findings open new possibilities for developing advanced polymer membranes with enhanced properties. Additionally, clay is an inexpensive, conventional, and environmentally friendly material. The clay structure is shown in Figure 1, and the compositions are summarized in Table 1.

Table 1.

Chemical composition of Clay powder (Particle size 1.0–1.4 µm).

Chemical	Wt (%) in composition
Silicon dioxide	44–46
Aluminum oxide	37–40
Magnesium oxide	0.2–0.4
Calcium oxide	0.03–0.06
Ferric oxide	0.2–0.4
Titanium dioxide	1.5–2.0

Among the many potential alternative polymers, poly (vinyl alcohol) (PVA) is the one that meets all the requirements to be a possible candidate for use as a membrane host material in the application of DMFC. It is much cheaper than Nafion, has better chemical stability, has the membrane-forming capacity, and most importantly, has high hydrophilicity and cross-linking sites ability to create good mechanical properties based on stable membrane and is very selective in the permeability to the water.^9,42–44 Since it is highly selectivity for water to alcohol, it can reduce the methanol crossover using as a membrane in direct methanol fuel cells (DMFCs). Moreover, PVA membranes are also used as alcohol-dehydrating agents, especially in alcohol-water azeotrope. Therefore, properly optimizing PVA-based composite membranes can perform as potential alternative electrolyte membranes for DMFC operation.

Considering the above points, polyvinyl alcohol-based composite membranes were prepared to overcome cost, conductivity, thermal stability, and fuel crossover issues. Therefore, the three electrolyte membranes were prepared using the solution method and cast onto glass^9,⁴⁵ using polyvinyl alcohol as the host polymer. The composition of the three polymeric electrolyte membranes was a) 5 wt % PVA, b) 5 wt % PVA/2 wt % PEG/1 wt% SiO₂ nanoparticles, and c) 5 wt% PVA/2 wt% PEG/1 wt % Clay powder. The polyvinyl alcohol and other composite materials used to make the three membranes are much cheaper than Nafion or Nafion-based composite membranes. The membranes were characterized through functional group analysis by Fourier transforms infrared spectrum, thermal stability by TGA and DSC, oxidative stability, Ion exchange capacity, proton conductivity, H₂O uptake, surface morphology (SEM/EDX), and methanol crossover phenomenon of these polymeric electrolyte membranes. Among the three membranes, we are trying to find which one has better and more balanced properties and a possible alternative of Nafion to use in direct methanol fuel cells.

Experimental section

Chemicals: PVA (Sigma Aldrich), clay (Alfa chemistry), Polyethylene glycol (Merck), and SiO₂ nanoparticles (Sigma Aldrich), NaOH (Sigma Aldrich) were used as it. The clay structure is shown in Figure 2, and the chemical composition (provided by Alfa chemistry) is in Table 1.

Figure 2.

Structure of the clay.

Membrane Preparations: Deionized water was used as a membrane preparation solvent. The PVA (5 wt%) and deionized water (as solvent) were homogeneously mixed by continuous stirring at 650 r/min for 120 min using a hot plate with a magnetic stirrer. The mixture was heated at a constant temperature 70– 80°C. After that, the PEG, SiO₂ nanoparticles, and Clay powder were added according to the polymeric electrolyte membranes composition required and stirred for 120 min at a constant temperature of 70–80 C. Then the concentrated mixture was cast onto a tempered glass plate (ASTM C1048-18). The doctor blade technique was used to make a uniform membrane thickness. The solvent of all polymeric electrolyte membranes was evaporated by keeping all membranes in a vacuum oven for 60 min at a constant temperature of 100°C. These dried polymeric electrolyte membranes are now ready to be characterized. The membrane fabrication process is shown in Figure 3. The Fourier transform infrared spectrum (Bruker-Tensor) was applied to analyze and confirm the structural composition of membranes. The sample and the potassium bromide (KBr) pellet were pressed, and the pellet was used to measure FT-IR.

Figure 3.

Experimental procedure to produce PVA-based composite membranes.

Scanning electron microscopy (SEM), TGA (NETZSCH STA 449F5 STA449F5B-0167-M), and (EDX) energy dispersive X-ray spectroscopy [JEOL (FESEM JSM-6700F) along with INCA (EDX)] were used to analyze the membrane surface morphology and the presence of metals in the composition as well.

The water uptake investigations were measured from a temperature range of 30 to 90°C with 20°C intervals. The electrolyte membranes were immersed in distilled H₂O at a temperature of 30°C for 60 min under 1 atm pressure. The immersed electrolyte membranes were subjected to drying by wiping using filter paper and taking the weight. Similarly, by increasing the temperature to 10°C, the weights of the samples were measured as before. The experiment was carried out up to 90°C with a 10°C temperature interval. The water uptake (Wu) was mathematically calculated as below:

W_{u} = \frac{W_{s} - W_{d}}{W_{d}}

(1)

In the equation, Ws represents the weights of the swollen membranes, and Wd is the weight of the dry membranes.

Thermochemical Stability: The TGA-DTA (TGA-DTA, NETZSCH STA 449F5 STA449F5B-0167-M) was used to test the membranes’ thermochemical stability. The previously dried sample was thermally scanned at a heat flow rate from 30 to 820°C at 10°C/min under an inert atmosphere.

Oxidative stability: The antioxidation of the membrane was studied by immersing it in Fenton’s reagent at 80°C. It was measured by changing the weight after 1 hour of treatment in Fenton’s reagent (2 ppm FeSO4 in 3 wt % H₂O₂ solution), and the time when membranes started to dissolve was also noted. After that, the membrane was taken out and washed several times. After drying at 80°C, the residual weight percentage (RW) was determined using the equation below:⁴⁷

% R W = \frac{m_{a}}{m_{b}} \times 100

(2)

Here, m_a = weight of the membranes before treatment, m_b = weight after treatment.

Ion Exchange Capacity (IEC): The titration method was used to measure the experimental IEC of the membranes. According to the procedure,^47,48 membranes were soaked 24 h under saturation NaCl. The soaked solution was collected. The solution was titrated using 0.1 M NaOH with a phenolphthalein indicator; the experimental IEC was determined from the equation below:⁴⁸

I E C (m e q / g) = \frac{V_{N a O H} \times M_{N a O H}}{W}

(3)

Here, V_NaOH = the NaOH volume consumed by the membrane, and M_NaOH = the normality of NaOH.

The impedance spectroscopy (AC) with a 1260 gain phase analyzer was used to determine the conductivity properties of the prepared membranes. The experiment was done in the frequency range from 0.1 Hz to 10 MHz. The cell (four-probe) was used and placed in a sealed vessel with controlled temperature and 100% RH environmental condition. The membrane conductivity was mathematically calculated as below:

σ = \frac{L}{R W D}

(4)

Here, R is the membrane’s resistance from the impedance zero phase angle, the distance between the two electrodes is L, the membrane width is W, and the membrane thickness is D, respectively.

The permeability of fuel methanol was determined using a laboratory manufacturing cell with two chambers. One chamber marked by A was full [150 mL 20% (v/v)] with methanol solution in de-ionized the other chamber marked by B was totally full with deionized water (volume 150 mL). The sample of the membrane was placed between chambers A and B, and the diameter of the diffusion area was approximately 3.0 cm. A hotplate magnetic stirrer was used to stir the chamber liquids with a magnetic bar. The methanol concentration in chamber B was measured by a refractive index detector (RI BT600, Young Lin Instrument Co., Korea), and a pump was used to maintain a constant flow, as shown in Figure 4. The permeability (P) of fuel methanol was calculated from the equation (4) as given below:⁴⁹

C_{B} (t) = \frac{A P}{V_{B} L} C_{A} (t - t_{0})

(5)

P = \frac{1}{A} \frac{C_{B} (t)}{C_{A} (t - t_{0})} V_{B} L

(6)

Here, the initial concentration of methanol fuel in chamber A is denoted by C_A; after a time, t, the concentration of methanol fuel in chamber B was denoted by C_B(t); the deionized water volume in chamber B was indicated by V_B; the membrane thickness was symbolized by symbol L; and symbol A represents the effective diffusion area/the effective permeating area.

Figure 4.

Schematic diagram of methanol permeability measurement apparatus.

Membrane efficiency or Selectivity: To evaluate the efficacy of PVA-based composite membranes in DMFCs, the methanol permeability and ionic conductivity were expressed using equation (5).

E = \frac{σ}{ρ}

(7)

Here, E is the membrane’s effectiveness as a function of the relationship between methanol permeability (P) and ionic conductivity (σ).⁵⁰

Results and discussion

The fabrication methods of the PVA-based composite membrane structural analyses of the three electrolyte membranes are shown in Figure 5. PVA peaks around 1036 cm⁻¹ because of C-O stretching, 1384-1643 cm⁻¹ due to C-H stretching, and the bond peaks at 2924-3440 cm⁻¹ for O-H accordingly.⁵¹ The ether groups peaks in regions 1051 to 1112 cm⁻¹, and the optimum peak at 1112 cm⁻¹. The alkyl groups (R– CH₂) stretching was observed from 2851 to 2920 cm⁻¹. The hydroxyl functional groups’ contribution appeared broadly from 3301 to 3502 cm⁻¹.⁵² Moreover, 5 wt % PVA, as well as 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ FTIR wavenumber was observed a slight shift of peak position and the respective intensity of all blends –OH stretching is referring the H-bonding formation between PVA and 5 wt%PVA/2 wt%PEG/1 wt%SiO₂.⁵³ The SiO₂ in 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ show up in the electrolyte membrane at 843 cm⁻¹ (Si-O-Si) and 982 cm⁻¹ (Si-OH). In the 5 wt%PVA/2 wt% PEG/1 wt % Clay composite electrolyte membrane, the clay appeared at 3436 cm⁻¹ for amine (–NH), 1640 cm⁻¹ for alkene, 843 cm⁻¹ for (–CH₂), stretching peak of Si-O at 965 cm⁻¹, stretching peak of Al-O at 532 cm⁻¹ and stretching peak of Mg–O 470 at cm⁻¹, respectively.⁵⁴

Figure 5.

FTIR Spectrum of 5 wt%PVA, 5 wt%PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay membranes.

Thermal and oxidation stability: Thermal stability is an important prerequisite for DMFCs. The thermal properties were measured by a previously dried sample at a scanned heat flow rate from 30 to 820°C at 10°C/min under an inert atmosphere, as shown in Figure 6. The degradation properties of the PVA membrane, 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ composite membrane, and 5 wt% PVA/2 wt % PEG/1 wt % Clay membranes were investigated by TGA. The PVA membrane shows three weight loss steps: (i) at around 57–122°C, the evaporation of water (ii) at around 234–420°C, the decomposition of the polymer chain functional groups; (iii) at around 620–811°C, the polymer backbones became degraded. The 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay composite membranes started to lose weight from 72–111⁰C, and weight loss was about 5 wt%. The second transitional region at around 427-451⁰C was for degradation of the polymer chain, and total weight loss in this region was about 17-22 %. The third region, at around 625-648°C to 800°C, due to the breakdown of the chemical bond, is called carbonation, and it has a total weight loss of almost 90%. Since polymer chains have restricted motion when adjacent to an impervious surface, the configurational entropy theory of the glass transition indicates that T_g should increase. On the other hand, low T_g could result from a drop in the density of polymer chains close to the clay-polymer interface, which would be caused by an increase in local free volume, according to free volume theories of the glass transition.⁵⁵ Due to adsorbed water and leftover solvent, the composite membranes have a more noticeable mass loss between 100 and 165°C. However, we observe that the mass loss for the composite membranes is shifted to a higher temperature value, indicating their superior water retention.⁵⁶ Compared to pure PVA, the composite membranes showed superior water retention, and they are thermally stable down to 250°C, which is greater than the operating temperature of the DMFC.^56,57 However, 5% weight loss was improved in 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay composite membranes, as shown in Figure 6.

Figure 6.

Thermogravimetric analysis of the prepared membranes.

SEM images of pure PVA and PVA-based blend membranes are shown in Figure 7. The pure PVA membrane has a smooth surface morphology, indicating a homogeneous and compatible polymer matrix. Adding SiO₂ and Clay to the matrix modified the membrane’s surface morphology, resulting in a rougher and irregular structure. The white dots in the photos may be attributed to air-borne dust, as found in SEM images of membranes in some studies as in references.^58,59 The micrographs demonstrate that the 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt % PEG/1 wt % Clay membranes have less surface homogeneity and more roughness than pure PVA membranes. It’s worth noting that membrane roughness promotes liquid permeability and water retention. However, the presence of clay in polymeric electrolyte membranes forms a multidimensional array and is resistant to methanol’s permeability, thereby significantly reducing fuel crossover. This practical implication of the research is a key finding.⁵⁰ From the polymer membrane morphology shown in Figure 7, we can say that the right proportion of mixing elements and sulfonation may prevent aggregation of the ceramic filler particles and give the electrolyte membrane a uniform surface morphology.

Figure 7.

SEM image of (a) PVA, (b) 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ and (c) 5 wt% PVA/2 wt % PEG/1 wt % Clay membranes.

Figure 8 depicts the EDX spectrums for 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay. Figure 8(a) and 8(b) show the EDX spectra of 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay, respectively. PVA’s silicon structural properties ensure that organic PVA yields carbon and oxygen. However, the peak of the silicon element indicates an inorganic component in the membranes,⁶⁰ which we used in 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay. The EDX spectrum of 5 wt% PVA/2 wt% PEG/1 wt% Clay has much sharper silicon peaks than that of 5 wt%PVA/2 wt% PEG/1 wt% Clay indicates a significantly large amount of silicon. Table 2 summarizes the elements’ weights and atomic ratios in the EDX spectrum. Figure 8 and Table 2 indicate the different amounts of silicon components found in 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay, respectively. This is because the silicon in the two membranes comes from different sources. As a result of Figure 8 and Table 2, we may deduce that the element silicon is dispersed evenly in the membranes. Figure 8(b) shows an equal distribution of silicon components in the electrolyte membrane composed of 5 wt% PVA/2 wt% PEG/1 wt% clay.

Figure 8.

EDX image of (a) 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ and (b) 5 wt% PVA/2 wt % PEG/1 wt % Clay membranes.

Table 2.

The presence of elements in atomic and weight percentage in 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ in Figure 8(a) and 5 wt% PVA/2 wt % PEG/1 wt % Clay in Figure 8(b) in EDX analysis.

Figure	Carbon		Oxygen		Silicon		Total
Figure	At %	Wt .%	At %	Wt %	At %	Wt %	At %	Wt %
Figure 8(a)	67.58	60.96	32.33	38.85	0.09	0.20	100	100
Figure 8(b)	63.95	56.44	34.72	40.82	1.33	2.74	100	100

In fuel cell operation, the degradation usually occurs in the polymer backbone due to free radicals like HO* and H₂O*.⁴⁷ The membrane proton conductivity usually increases with an increasing degree of sulfonation but lowers the oxidative stability. Therefore, it is important to measure the oxidative stability of the membrane. The oxidative stability test of every sample was measured and compared accordingly, as shown in Table 3. The PVA membrane started to dissolve within 1.30 h and dissolved completely within 2 h, similarly, 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay membranes also began to dissolve at 1.30-1.32 and 2–2.5 h, respectively. The completely dissolved time of the 5 wt% PVA/2 wt% PEG/1 wt% Clay membrane is also higher than other membranes. Moreover, the residual weight percentage (RW) was also higher in the 5 wt%PVA/2 wt%PEG/Clay membrane.

Table 3.

The conductivity (σ), fuel permeability (P), and selectivity (S) values of the prepared four membranes at 30⁰C temperature.

Membrane	Conductivity (S/cm)	Fuel permeability (cm²s⁻¹)	Selectivity (sscm⁻³)	Oxidative stability		IEC (meq/g)
Membrane	Conductivity (S/cm)	Fuel permeability (cm²s⁻¹)	Selectivity (sscm⁻³)	RW(%)a	T (h)b	IEC (meq/g)
PVA	0.00338	2.89 × 10⁻⁶	8.55 × 10⁻⁴	88.4	1.30	0.024
5 wt% PVA/2 wt % PEG/1 wt %SiO₂	0.00413	2.37 × 10⁻⁶	5.74 × 10⁻⁴	71.12	1.30	0.017
5 wt% PVA/2 wt % PEG/1 wt % clay	0.00432	1.57 × 10⁻⁶	3.63 × 10⁻⁴	94.09	1.32	0.232

^aRetained weight of membranes after immersing in Fenton's reagent.

^bThe time for membranes began to dissolve.

Water uptake is crucial to DMFC performance. Water intake is critical for proton conductivity and proton transport. Higher water uptake values result in a shorter membrane lifetime, yet correct water uptake can preserve the performance of DMFCs. Figure 9 shows the membrane’s water uptake properties. Because of its hydrophilic nature, increasing temperature improves the capacity of the PVA membrane to absorb water. Incorporating ceramic elements with PVA increased the composite’s water absorption properties. The water intake in the membrane 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ declines significantly at 50°C but progressively increases. At 70°C, the 5 wt% PVA/2 wt% PEG/1 wt % Clay membrane water uptake decreases considerably as shown in Figure 9(a). PVA-based composite membranes with high hydrophilic characteristics result in dissolving at higher temperatures. Figure 9 shows that combining ceramic materials with PVA in composite membranes can manage the water uptake properties of PVA-based composite membranes, resulting in the predicted performance. The 5 wt% PVA/2 wt % PEG/1 wt % Clay membrane performed better than the other membranes. Figure 9(b) represents the water uptake properties of the three membranes using standard derivation and there are no remarkable differences from Figure 9(a).

Figure 9.

(a)Water uptake of 5 wt%PVA, 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay membranes and (b) water uptake of the three membranes with standard derivation.

The ion exchange capacity (IEC) is used to investigate the effect of a polymer or polymer composite on proton conductivity. The quantity of ions determines it in the consumable sites scattered throughout the polymer chain. Table 3 summarizes the IEC features of all three membranes. Due to its hydrophilic functional group, the PVA membrane is a poor proton conductor and cannot achieve high conductivity. Pure 5 wt% PVA, 5 wt% PVA/2 wt% PEG/1 wt% SiO₂, and 5 wt% PVA/2 wt% PEG/1 wt% Clay had IEC values of 0.024, 0.017, and 0.232 meq/g, respectively. The IEC data in Table 3 show that the membrane with 5 wt% PVA/2 wt% PEG/1 wt% Clay has improved IEC characteristics.

Figure 10 presents the membranes proton conductivity. The conductivity property of electrolyte membranes is the main issue because proton conductivity contributes an important part of cell operation. The impedance spectroscopy was used to analyze the proton conductivity of the membranes with relative humidity from 90% to 100% at ambient temperature. The proton conductivity of 5 wt%PVA, 5 wt%PVA/2 wt%PEG/1 wt%SiO₂, and 5 wt% PVA/2 wt % PEG/1 wt % Clay electrolyte membranes at 30⁰C were 0.0.00,338, 0.00,413 and 0.00,432 S/cm respectively. In the proton conductivity study, we can say that 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay shows comparatively higher proton conductivity than PVA. In the same way, we investigated the experimental procedure of maintaining a 5⁰C interval in temperature. In this condition, the proton conductivity increases with increasing temperature in the case of every membrane, as shown in Figure 10. At 60⁰ C, the 5 wt% PVA/2 wt % PEG/1 wt % SiO₂ and 5 wt% PVA/2 wt % PEG/1 wt % Clay was shown proton conductivity of 0.00,448 S/cm and 0.00,478 S/cm, respectively which were higher than compared to PVA. The composite membrane ionic mobility increased with its clay content. At 60°C, the composite membrane with a clay component yielded the highest conductivity value of 0.00,478 S/cm. Since the clay dispersion inside the polymer matrix, the increase in ionic conductivity as a function of clay content could result from well-dispersed clay in the PVA matrix. Research has shown that silane-induced membrane functionalization can interact with water molecules to form a hydration layer that encourages proton hopping for proton conductivity.^61,62 The IEC values strongly influence membrane conductivity. While greater IEC speeds up proton conduction by reducing the distance between anionic groups, larger water intake encourages proton transport. The 5 wt% PVA/2 wt% PEG/1 wt% Clay has higher IEC and water uptake values than the membrane 5 wt% PVA/2 wt % PEG/1 wt % SiO₂. Figure 10(a) shows that the proton conductivity of the electrolyte membranes did not remarkably increase in every electrolyte membrane. This can be seen in the hydrophobic-hydrophilic interaction nature of PVA polymers in electrolyte membranes. Figure 10(b) represents the conductivity of the three membranes using standard derivation and there were no significant differences from Figure 10(a).

Figure 10.

(a) Proton conductivity of 5 wt%PVA, 5 wt% PVA/2 wt% PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay membranes and (b) proton conductivity of the three membranes with standard derivation.

The permeability property of methanol in the membranes has been mathematically calculated using the equation (4). The methanol fuel permeability of 5 wt%PVA, 5 wt%PVA/2 wt%PEG/1 wt%SiO₂, and 5 wt% PVA/2 wt % PEG/1 wt % Clay electrolyte membranes are 2.89 × 10⁻⁶ cm²/s, 2.37 × 10⁻⁶ cm²/s, and 1.57 × 10⁻⁶ cm²/s respectively. The hydrophilic ionic channels were used for methanol penetration in methanol fuel transportation. On the other hand, the hopping ionic sites were used to pass through released water molecules and protons due to hydrogen bonding. As a result, the permeability of methanol is significantly reduced due to the methanol permeation barrier nature of the SiO₂ and clay particles, and it is better than Nafion 117.^62,63 This barrier nature of silicon dioxide and clay particles was also lowered to release water. This property was achieved due to the irregular surface condition of the electrolyte membrane of 5 wt% PVA/2 wt % PEG/1 wt% SiO₂ and 5 wt% PVA/2 wt% PEG/1 wt% Clay. Table 3 summarizes the proton conductivity, permeability, and selectivity of the membranes we used in this investigation. Selectivity, defined as the ratio of methanol permeability to proton conductivity, is frequently used to assess the overall effectiveness of membranes. The selectivity of the 5 wt% PVA/2 wt% PEG/1 wt% Clay membrane (3.63 × 10⁻⁴ Sscm⁻³) is better than other membranes.

Table 4 compares the data analysis in this work with the summarized articles from other reference articles. From the information in Table 4, we can conclude that the 5 wt%PVA/2 wt% PEG/1 wt%Clay membrane, with its good balance in proton conductivity, permeability, and selectivity, holds great promise for application in direct methanol fuel cells.^62–64 In the future, the literature will provide information on the cell’s performance, which may ensure the potential application of Clay composite PVA membrane in DMFCs, bringing us closer to practical solutions in fuel cell technology.

Table 4.

Comparison of some reported literatures with the present research article.

Membrane	Conductivity (S/cm) (At 30°C)	Methanol permeability (cm²/s) (At 30°C)	Selectivity (sscm⁻³)	Ref. No.
5 wt% PVA/2 wt % PEG/1 wt % clay	0.00432	1.57 × 10⁻⁶	3.63 × 10⁻⁴	This work
5 wt% PVA/2 wt % PEG/1 wt %SiO₂	0.00413	2.37 × 10⁻⁶	5.74 × 10⁻⁴	This work
PVA/10 wt%MMT	0.0368	3.67 × 10⁻⁶	1.00 × 10⁴	[63]
Nafion 117	0.0029412	5.16 × 10⁻⁶	……	[62,63]
PVA/PSSA_MA/Clay 15A (4 wt.%)	0.023	2.19 ×10⁻⁷	…	[64]
PVA/Phosphoric acid treated modified kaolinite	0.062 (at 80°C)	2.87 × 10⁻⁶ (at 80°C)		[62]

Conclusions

We prepared PVA-based three electrolyte membranes to use in DMFCs. The three membranes’ composition was a) 5 wt%PVA itself, b) 5 wt%PVA/2 wt%PEG/1 wt%SiO₂, and c) 5 wt% PVA/2 wt%PEG/1 wt%Clay. We used the solution casting method, and the membrane was characterized. The three-electrolyte membrane was compared and tried to find the better one for DMFCs application. The investigation of the membranes suggested that the performances of PVA composite electrolyte membranes have a balanced property, similar to polymer electrolyte membranes for DMFC applications. This balance in properties reassures us of the reliability of these membranes. Among the three electrolyte membranes, the 5 wt% PVA/2 wt % PEG/1 wt % Clay composite membrane showed a better balance in proton conductivity and methanol permeability (0.00,432 Scm⁻¹, and 1.57 × 10⁻⁶ cm²s⁻¹), and lower selectivity value meant a silent increase in its performance. Compared to the other reported articles, the clay-incorporated membrane in the present work has a low methanol permeability, even better than Nafion 117 (5.16 × 10⁻⁶ cm²/s). For the trading position, this membrane can be a good alternative candidate for future DMFCs in commercialization and can replace lithium-ion batteries because DMFC batteries do not need charging time-fill methanol and charge the battery.

Footnotes

Acknowledgments

Department of Applied Chemistry and Chemical Engineering, Dr Muhammad Qudrat-I-Khuda Academic Building, University of Rajshahi. Motihar, Rajshahi 6205, University of Rajshahi, Bangladesh.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest concerning the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Compliance for publication

All the authors have read and approved the final manuscript to publish.

ORCID iDs

Md. Anwarul Karim

Mohammad Mahfuz Enam Elahi

Data Availability Statement

The data acquired or analyzed during this investigation are incorporated in this article.

References

Winter

Brodd

. What are batteries, fuel cells, and supercapacitors? Chem Rev 2004; 104(10): 4245–4270. DOI: 10.1021/cr020730k.

Alberti

Casciola

. Solid state protonic conductors, present main applications and future prospects. Solid State Ionics 2001; 145: 3–16. DOI: 10.1016/S0167-2738(01)00911-0.

Wang

. Fundamental models for fuel cell engineering. Chem Rev 2004; 104(10): 4727–4765. DOI: 10.1021/cr020718s.

Chen

Yang

. Performance of an air-breathing direct methanol fuel cell. J Power Sources 2003; 123: 37–42. DOI: 10.1016/S0378-7753(03)00434-8.

Dyer

. Fuel cells for portable applications. J Power Sources 2002; 106: 31–34. DOI: 10.1016/S0378-7753(01)01069-2.

Lue

Wang

Mahesh

, et al. Enhanced performance of a direct methanol alkaline fuel cell (DMAFC) using a polyvinyl alcohol/fumed silica/KOH electrolyte. J Power Sources 2010; 195: 7991–7999. DOI: 10.1016/j.jpowsour.2010.06.049.

Ahmed

Dincer

. A review on methanol crossover in direct methanol fuel cells: challenges and achievements. Int J Energy Res 2011; 35: 1213–1228. DOI: 10.1002/er.1889.

Deluca

Elabd

. Polymer electrolyte membranes for the direct methanol fuel cell: a review. J Polym Sci B Polym Phys 2006; 44: 2201–2225, DOI: 10.1002/polb.20861.

Chang

Lin

. Proton conducting membranes based on PEG/SiO₂ nanocomposites for direct methanol fuel cells. J Memb Sci 2003; 218: 295–306. DOI: 10.1016/S0376-7388(03)00187-X.

10.

Zhao

Chen

, et al. Mass transport phenomena in direct methanol fuel cells. Prog Energy Combust Sci 2009; 35: 275–292. DOI: 10.1016/j.pecs.2009.01.001.

11.

Maiti

Kakati

Lee

, et al. PVA nano composite membranefor DMFC application. Solid State Ion 2011; 201(1): 21–26. DOI: 10.1016/j.ssi.2011.07.013.

12.

Liu

Xiong

Shi

, et al. Halloysite ionogels enabling poly(2,5-benzimidazole)-based proton-exchange membranes for wide-temperature-range applications. J Membr Sci 2023; 668(15): 121192–121207. DOI: 10.1016/j.memsci.2022.121192.

13.

Liu

Sun

, et al. Novel octopus shaped organic–inorganic composite membranes for PEMFCs. Int J Hydrogen Energy 2016; 41(36): 16160–16166. DOI: 10.1016/j.ijhydene.2016.05.078.

14.

Zhang

Liu

Xia

, et al. Poly(2,5-benzimidazole)/sulfonated sepiolite composite membranes with low phosphoric acid doping levels for PEMFC applications in a wide temperature range. J Membr Sci 2019; 574: 282–298. DOI: 10.1016/j.memsci.2018.12.085.

15.

Zhang

Yang

, et al. Design of sepiolite-supported ionogel-embedded composite membranes without proton carrier wastage for wide-temperature-range operation of proton exchange membrane fuel cells. J Mater Chem A 2019; 7: 15288–15301. DOI: 10.1039/C9TA03666K.

16.

Liu

Wang

Zhang

, et al. Polyethyleneimine-filled sepiolite nanorods-embedded poly(2,5-benzimidazole) composite membranes for wide-temperature PEMFCs. J Clean Prod 2022; 359: 131977. DOI: 10.1016/j.jclepro.2022.131977.

17.

Zhou

Wang

Ling

, et al. Advances in ionogels for proton-exchange membranes. Sci Total Environ 2024; 921: 171099. DOI: 10.1016/j.scitotenv.2024.171099.

18.

Haffner

Klett

Lehman

. Japan’s open future: an agenda for global citizenship. London: Anthem Press, 2009.

19.

Divisek

Fuhrmann

Gartner

, et al. Performance modeling of a direct methanol fuel cell. J Electrochem Soc 2003; 150: A811–A825. DOI: 10.1149/1.1572150.

20.

Maiti

Kakati

Lee

, et al.

Where do poly(vinyl alcohol) based membranes stand in relation to Nafion^® for direct methanol fuel cell applications?

J Power Sources 2012; 216: 48–66. DOI: 10.1016/j.jpowsour.2012.05.057.

21.

Viswanathan

Helen

. Is Nafion^®, the only choice? Bulletin of the Catalysis Society of India 2007; 6: 50–66.

22.

Honma

Takeda

Bae

. Protonic conducting properties of sol-gel derived organic/inorganic nanocomposite membranes doped with acidic functional molecules. Solid State Ionics 1999; 120(1-4): 255–264. DOI: 10.1016/S0167-2738(98)00562-1.

23.

Qiao

Okada

Ono

. High molecular weight PVA-modified PVA/PAMPS proton-conducting membranes with increased stability and their application in DMFCs. Solid State Ionics 2009; 180(23-25): 1318–1323. DOI: 10.1016/j.ssi.2009.08.010.

24.

Honma

Nakajima

Nomura

. High temperature proton conducting hybrid polymer electrolyte membranes. Solid State Ion 2002; 154-155: 707–712. DOI: 10.1016/S0167-2738(02)00431-9.

25.

Lavrenčič Štangar

Grošelj

Orel

, et al. Proton-conducting sol–gel hybrids containing heteropoly acids. Solid State Ionics 2001; 145(1-4): 109–118. DOI: 10.1016/S0167-2738(01)00920-1.

26.

Sati

Verma

Zindal

, et al. PVA biopolymer-acidic functionalized graphene hybrid nanocomposite for vibration isolation application: an experimental approach with variable reflux and vacuum timings. Chemical Physics Impact 2023; 6: 100212. DOI: 10.1016/j.chphi.2023.100212.

27.

Jain

Sharma

Verma

, et al. Enhancement of thermo-mechanical, creep-recovery, and anti-microbial properties in PVA-based biodegradable films through cross-linking with oxalic acid: implications for packaging application. Biomass Conv. Bioref. 2023; 18: 1–10. DOI: 10.1007/s13399-023-04748-y.

28.

Sharma

Agrawal

Singh

, et al. Experimental synthesis and characterization of PVA-fumaric acid cross-linked biodegradable films: implications as a sustainable matrix for composites. Polymer Engineering Sci 2024; 64(4): 1467–1481. DOI: 10.1002/pen.26636.

29.

Kim

Lim

Shul

, et al. Mesoporous silica: polymer composite membrane for direct methanol fuel cell. Stud Surf Sci Catal 2004; 154(Part C): 3036–3043. DOI: 10.1016/S0167-2991(04)80589-5.

30.

Anis

Banthia

Bandyopadhyay

. Synthesis and characterization of polyvinyl alcohol copolymer/phosphomolybdic acid-based crosslinked composite polymer electrolyte membranes. J Power Sources 2008; 179(1): 69–80. DOI: 10.1016/j.jpowsour.2007.12.041.

31.

Krishnakumar

Shanmugam

. Electrical and optical properties of pure and Pb²⁺ iondoped PVA − PEG polymer composite electrolyte membranes. Ionics 2012; 18: 403–411. DOI: 10.1007/s11581-011-0643-2.

32.

Halla

Mamak

Williams

, et al. Meso-SiO₂–C₁₂EO₁₀OH–CF₃SO₃H A novel proton‐conducting solid electrolyte. Adv Funct Mater 2003; 13(2): 133–138. DOI: 10.1002/adfm.200390019.

33.

Yang

Lee

Yang

. Direct methanol fuel cell (DMFC) based on PVA/MMT composite polymer membranes. J Power Sources 2009; 188(1): 30–37. DOI: 10.1016/j.jpowsour.2008.11.098.

34.

Duangkaew

Wootthikanokkhan

. Methanol permeability and proton conductivity of direct methanol fuel cell membranes based on sulfonated poly (vinyl alcohol)–layered silicate nanocomposites. J Appl Polym Sci 2008; 109(1): 452–458. DOI: 10.1002/app.28072.

35.

Kim

Park

Rhim

, et al. Preparation and characterization of crosslinked PVA/SiO2 hybrid membranes containing sulfonic acid groups for direct methanol fuel cell applications. J Memb Sci 2004; 240: 37–48. DOI: 10.1016/j.memsci.2004.04.010.

36.

Panero

Fiorenza

Navarra

, et al. Silica-added, composite poly(vinyl alcohol) membranes for fuel cell application. J Electrochem Soc 2005; 152(12): A2400. DOI: 10.1149/1.2104207.

37.

Son

Kang

Won

. Poly(vinyl alcohol)-based polymer electrolyte membranes containing polyrotaxane. J Memb Sci 2006; 281: 345–350. DOI: 10.1016/j.memsci.2006.04.001.

38.

Gaowen

Zhentao

. Organic/inorganic composite membranes for application in DMFC. J Memb Sci 2005; 261(1-2): 107–113. DOI: 10.1016/j.memsci.2005.03.036.

39.

Chuang

Hsu

SLC

Hsu

. Synthesis and properties of fluorine-containing polybenzimidazole/montmorillonite nanocomposite membranes for direct methanol fuel cell applications. J Power Sources 2007; 168(1): 172–177. DOI: 10.1016/j.jpowsour.2007.03.021.

40.

Aiswarya

Joseph

. Green synthesis of polyvinyl-alcohol-montmorillonite clay cation exchange membrane for alkaline direct methanol fuel cellInt. Int J Hydrogen Energy 2023; 48(99): 39658–39672. DOI: 10.1016/j.ijhydene.2022.11.344.

41.

Vaia

Ishii

Giannelis

. Synthesis and properties of two-dimensional nanostructures by direct intercalation of polymer melts in layered silicates. Chem Mater 1993; 5(12): 1694–1696. DOI: 10.1021/cm00036a004.

42.

Krumova

López

Benavente

, et al. Effect of crosslinking on the mechanical and thermal properties of poly(vinyl alcohol). Polymer 2000; 41(26): 9265–9272. DOI: 10.1016/S0032-3861(00)00287-1.

43.

Jin

Diniz da Costa

. Proton conductive composite membrane of phosphosilicate and polyvinyl alcohol. Solid State Ionics 2007; 178(13-14): 937–942. DOI: 10.1016/j.ssi.2007.04.005.

44.

Martinelli

Matic

Jacobsson

, et al. Structural analysis of PVA-based proton conducting membranes. Solid State Ionics 2006; 177(26-32): 2431–2435. DOI: 10.1016/j.ssi.2006.01.035.

45.

Dodda

Bělský

Chmelaŕ

, et al. Comparative study of PVA/SiO2 and PVA/SiO₂/glutaraldehyde (GA) nanocomposite membranes prepared by single-step solution casting method. J Mater Sci 2015; 50(19): 6477–6490. DOI: 10.1007/s10853-015-9206-7.

46.

Karim

. Titanium dioxide nanoparticle incorporated PVDF-HFP based composite membrane for direct methanol fuel cells application. Bangladesh J Sci Ind Res 2021; 56(2): 125–132. DOI: 10.3329/bjsir.v56i2.54319.

47.

Yang

Lyu

, et al. A graphene oxide polymer brush-based crosslinked nanocomposite proton exchange membrane for direct methanol fuel cells. RSC Adv 2018; 8: 15740–15753. DOI: 10.1039/C8RA01731J.

48.

Sharma

Tinh

VDC

Kim

. Improved oxidative stability by embedded cerium into graphene oxide nanosheets for proton exchange membrane fuel cell application. Membranes 2021; 11: 238. DOI: 10.3390/membranes11040238.

49.

Woo

Seo

, et al. Covalent organic/inorganic hybrid proton-conductive membrane with semi-interpenetrating polymer network: preparation and characterizations. Power Sources 2008; 179(2): 458–466. DOI: 10.1016/j.jpowsour.2007.12.118.

50.

Elerian

Mohamed

Elnaggar

, et al. Development of novel proton exchange membranes based on cross linked polyvinyl alcohol (PVA)/5 sulfosalicylic acid (SSCA) for fuel cell applications. Discov Appl Sci 2024; 6: 341. DOI: 10.1007/s42452-024-05940-z.

51.

Yang

Liou

. Preparation of novel poly (vinyl alcohol)/SiO₂ nanocomposite membranes by a sol–gel process and their application on alkaline DMFCs. Desalination 2011; 276(1-3): 366–372. DOI: 10.1016/j.desal.2011.03.079.

52.

Mansur

Oréfice

Mansur

. Characterization of poly (vinylalcohol)/poly(ethylene glycol) hydrogels and PVA-derived hybrids by small-angle X-ray scattering and FTIR spectroscopy. Polymer 2004; 45(21): 7193–7202. DOI: 10.1016/j.polymer.2004.08.036.

53.

Falqi

Osamah

ABD

Hussain

, et al. Preparation of miscible PVA/PEG blends and effect of graphene concentration on thermal, crystallization, morphological, and mechanical properties of PVA/PEG (10 wt.%) blend. Int. J. Polym. Sci 2018; 2018(ID 8527693): 1–10. DOI: 10.1155/2018/8527693.

54.

Lin

Yeh

, et al. Preparation and properties of poly (vinyl alcohol)–clay nanocomposite materials. Polymer 2003; 44(12): 3553–3560. DOI: 10.1016/S0032-3861(03)00062-4.

55.

Bandi

Schiraldi

. Glass transition behavior of clay aerogel/poly(vinyl alcohol) composites. Macromolecules 2006; 39: 6537–6545. DOI: 10.1021/ma0611826.

56.

Charradi

Ahmed

Aranda

, et al. Silica/montmorillonite nanoarchitectures and layered double hydroxideSPEEK based composite membranes for fuel cells applications. Appl Clay Sci 2019; 174: 77–85. DOI: 10.1016/j.clay.2019.03.027.

57.

Dohle

Mergel

Stolten

. Heat and power management of a direct-methanol-fuel- cell (DMFC) system. J Power Sources 2002; 111(2): 268–282. DOI: 10.1016/S0378-7753(02)00339-7.

58.

Mansur

AAP

Rodrigues

Capanema

NSV

, et al. Functionalized bio adhesion-enhanced carboxymethyl cellulose/polyvinyl alcohol hybrid hydrogels for chronic wound dressing applications. RSC Adv 2023; 13: 13156–13168. DOI: 10.1039/D3RA01519J.

59.

Mansor

Abdallah

Shaban

. Fabrication of high selectivity blend membranes based on poly vinyl alcohol for crystal violet dye removal. J Environ Chem Eng 2020; 8: 103706. DOI: 10.1016/j.jece.2020.103706.

60.

Imaan

Mir

Ahmad

. Synthesis and characterization of a novel poly (vinyl alcohol)-based zinc oxide (PVA-ZnO) composite proton exchange membrane for DMFC. J. Hydrog. Energy 2021; 46(22): 12230–12241. DOI: 10.1016/j.ijhydene.2020.05.008.

61.

Salarizadeh

Javanbakht

Pourmahdian

, et al. Surface modification of Fe₂ TiO ₅ nanoparticles by silane coupling agent: synthesis and application in proton exchange composite membranes. J Colloid Interface Sci 2016; 472: 135–144. DOI: 10.1016/j.jcis.2016.03.036.

62.

Altaf

Gill

Batool

, et al. Proton conductivity and methanol permeability study of polymer electrolyte membranes with range of functionalized clay content for fuel cell application. Eur Polym J 2019; 110: 155–167. DOI: 10.1016/j.eurpolymj.2018.11.027.

63.

Yang

Lee

. Preparation of the acidic PVA/MMT nanocomposite polymer membrane for the direct methanol fuel cell (DMFC). Thin Solid Films 2009; 517: 4735–4740. DOI: 10.1016/j.tsf.2009.03.138.

64.

Kim

Park

Cho

, et al. Effect of organoclay content on proton conductivity and methanol transport through crosslinked PVA hybrid membrane for direct methanol fuel cell. J Ind Eng Chem 2009; 15: 265–269. DOI: 10.1016/j.jiec.2008.10.002.

Clay powder in polymer composite membranes enhanced the performance of direct methanol fuel cells

Abstract

Keywords

Introduction

Experimental section

Results and discussion

Conclusions

Footnotes

Acknowledgments

Declaration of conflicting interests

Funding

Compliance for publication

ORCID iDs

Data Availability Statement

References