Stability of Photocathodes: A Review on Principles, Design, and Strategies

Photoelectrochemical devices based on semiconductor photoelectrode can directly convert and store solar energy into chemical fuels. Although the efficient photoelectrodes with commercially valuable solar-to-fuel energy conversion efficiency have been reported over past decades, one of the most enormous challenges is the stability of the photoelectrode due to corrosion during operation. Thus, it is of paramount importance for developing a stable photoelectrode to deploy solar-fuel production. This Review commences with a fundamental understanding of thermodynamics for photoelectrochemical reactions and the fundamentals of photocathodes. Then, the commercial application of photoelectrochemical technology is prospected. We specifically focus on recent strategies for designing photocathodes with long-term stability, including energy band alignment, hole transport/storage/blocking layer, spatial decoupling, grafting molecular catalysts, protective/passivation layer, surface element reconstruction, and solvent effects. Based on the insights gained from these effective strategies, we propose an outlook of key aspects that address the challenges for development of stable photoelectrodes in future work.