Abstract
The direct transformation of seawater into hydrogen fuel offers a sustainable pathway toward clean energy generation, yet it remains hindered by competing ionic reactions and photocathode instability. Here, we report a tellurium dioxide-decorated polypyrrole (TeO2–PPy/PPy) nanostructured photocathode that overcomes these barriers by combining broad optical absorption, efficient charge separation, and structural robustness within a single hybrid design. The composite exhibits strong light absorption with an optical band gap of 2.25 eV and a well-defined crystalline framework, enabling efficient photocarrier generation. Electrochemical evaluation was performed in both natural seawater collected from the Red Sea and a laboratory-prepared artificial seawater analog. Under dark conditions, both electrolytes yielded a negligible current density of approximately −0.05 mA cm−2, whereas illumination produced enhanced photocurrent densities of −0.072 and −0.08 mA cm−2 for artificial and natural seawater, respectively. These photocurrents translate into hydrogen evolution rates of 20.0 and 19.5 µmol h−1 for a 10 cm2 photocathode, in excellent agreement with theoretical predictions derived from Faraday's law. Optical-filter-dependent measurements confirm the broadband photoresponse of the electrode, while repeated operational cycles demonstrate remarkable durability and resistance against chloride-induced corrosion—a critical challenge in seawater electrolysis. Collectively, these results establish TeO₂–PPy/PPy as a robust and scalable photocathode platform for direct seawater-driven hydrogen generation. Beyond the immediate application, this molecular design approach provides a versatile blueprint for engineering polymer–oxide heterostructures with tailored interfacial energetics, paving the way for the development of next-generation solar-to-hydrogen energy conversion systems.
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