The alarming depletion rate of reserved fossil fuel associated with rapid increase in environmental pollution has caused an urgent need to develop efficient clean and renewable energy resources. In this regard, many different approaches have been followed up. The sun is a free, clean, sustainable and easy access energy source, and the solar produced hydrogen, which can be used in fuel cells to generate electricity or changed directly in combustion engines, makes no pollution except water. Hence, to obtain hydrogen as a clean energy carrier, the scenario of a renewable hydrogen economy has attracted much attention from researchers recently. Because of low operation temperature and strong synergies with contemporary researches in the field of photovoltaic and nanomaterials, photoelectrochemical (PEC) water splitting is an emerging technology for the future world hydrogen generation. The concept of this method is based on a semiconductor photoelectrode device which excites with sunlight irradiation, oxidizes/reduces H₂O molecules by generated h+/e− pair and finally converted them to chemical energy (H₂ gas). For efficient PEC reaction, the selected semiconductor photoanodes should exhibit chemical stability, suitable band edge positions for absorbing sunlight and also participating in water oxidation/reduction, high charge carrier mobility and also variety of low cost synthesis methods.

Photoelectrodes based on transition metal oxides, TMDCs or other emerging 2D materials have been extensively investigated in aqueous solution. Different approaches have been followed to prohibit charge recombination and improve visible response of these photoanodes.  Many interesting reports and reviews are available in this context which present recent strategies and trends to improve solar hydrogen production systems in PEC, EC or PC approaches.

1- Faraji et al. Two-dimensional materials in semiconductor photoelectrocatalytic systems for water splitting, Energy & Environmental Science, 2019.

2- Abouelela et al. Metal chalcogenide-based photoelectrodes for photoelectrochemical water splitting, Journal of Energy Chemistry, 2022.

3- Chen et al. Metal–organic frameworks and derived materials as photocatalysts for water splitting and carbon dioxide reduction, Coordination Chemistry Reviews, 2022.

4- Sharma et al. Key Strategies to Advance the Photoelectrochemical Water Splitting Performance of α‐Fe₂O₃ Photoanode, 2018. 

5- Viory et al. Low-dimensional catalysts for hydrogen evolution and CO₂ reduction, 2018.

e