Scaling photoelectrochemical water splitting for a commercial future of clean hydrogen: A review of photoelectrode advances

The generation of solar H₂ is seen to be a potentially effective means of utilizing the sunlight and combating climate change caused by the burning of fossil fuels. Photoelectrochemical water splitting (PECWS) produces hydrogen with one of the least negative environmental effects of all the methods presently in use. However, its manufacturing costs remain expensive when compared to more established methods like steam reforming of methane. Furthermore, there is an immediate need for practical solutions for scaling up the essential parts of PEC devices, particularly photoelectrodes (PEs). However, the effective scaling up of energy-effective PEs that is, reaching the standard values of the three-pillar rules for commercialization that is, an active area of 100 cm², 2920 h of consistent operation, and a current density of 10 mA cm⁻² is a critical component of the commercial feasibility of PEC-H₂ generation. This review begins with an explanation of the fundamental PECWS mechanism and PEC device configuration. A summary of the latest developments in solar H₂ generation is provided after a discussion of the issues with PECWS. In conclusion, we discuss pertinent approaches to efficiently prepare large-area PEs and PEC device layouts that can be scaled up.