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Assignment sample solution of CHEM652 - Sustainable Chemistry and Energy

Photocatalytic Water Splitting for Hydrogen Production: Mechanisms and Material Innovations

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Chemistry Assignment Sample

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Photocatalytic water splitting is a promising approach for producing clean hydrogen fuel using solar energy. The process involves splitting water into hydrogen and oxygen using a semiconductor photocatalyst under light irradiation. The fundamental mechanism includes light absorption, charge separation, and redox reactions.

The first step is photon absorption by the photocatalyst, which generates electron-hole pairs. The excited electrons reduce water to hydrogen at the cathode, while the holes oxidize water to oxygen at the anode. Key parameters influencing this process include the bandgap energy of the photocatalyst, charge carrier mobility, and surface reaction kinetics.
Material innovation is crucial for improving photocatalytic efficiency. TiO2 has been widely studied due to its stability, non-toxicity, and suitable bandgap for UV light absorption. However, its efficiency under visible light is limited. To address this, doping with elements like nitrogen or metals enhances its visible light activity. Similarly, materials like g-C3N4 and perovskite oxides have shown promise for visible light-driven water splitting.

 

Heterojunction photocatalysts, which combine two or more semiconductors, improve charge separation and light absorption. For instance, TiO2 coupled with CdS quantum dots forms an efficient heterojunction for hydrogen production. Plasmonic photocatalysts, incorporating noble metals like gold or silver, further enhance light absorption via localized surface plasmon resonance (LSPR).
Despite these advancements, challenges remain, including photocatalyst stability, scalability, and cost. Research efforts are directed toward developing earth-abundant materials, optimizing reactor designs, and integrating photocatalytic systems with renewable energy sources. The successful implementation of photocatalytic water splitting will play a pivotal role in transitioning to a hydrogen-based economy.