Strategies for Photoelectrochemical Splitting of Water

The photoelectrochemical splitting (PEC) of water provides a direct route to converting solar energy into storable chemical fuels. When illuminated, a semiconductor photoelectrode can absorb light and generate electron-hole pairs, which participate in interfacial redox reactions at the semiconductor-electrolyte junction. Therefore, to achieve high-performance PEC, photoelectrodes with optimized optical absorption and charge have been explored. This review analyzes recent fabrication strategies used to design photoelectrodes for the PEC dissociation of water. Physical fabrication techniques, including pulsed laser deposition, magnetron sputtering, and physical vapor deposition, allow for precise control of film thickness, crystallinity, and defect density, critical parameters for efficient charge transport. Typically, in physical methods, reported photocurrent densities span from ~10^-2 to 10¹ mAcm^-2, depending on the semiconductor material, nanostructure design, and interfacial engineering strategies. Chemical synthesis methods, such as hydrothermal growth, successive ion layer adsorption and reaction, and microemulsion techniques, provide greater compositional flexibility and enable controlled doping, surface functionalization, and the formation of nanostructured morphologies. Finally, hybrid fabrication strategies integrate physical and chemical processes within a single synthesis framework to combine structural precision with compositional tuning capabilities. These approaches enable the development of advanced architecture such as heterojunctions, core-shell nanostructures, and catalyst-modified interfaces, which enhance light absorption and optimize interfacial transfer. Furthermore, theoretical and computational tools are here analyzed as complementary approaches that guide the rational design and optimization of photoelectrochemical materials and devices.