Abstract: Sunlight is the most abundant and inexhaustible energy source on earth. However, its low energy density, dispersibility and intermittent nature make its direct utilization with industrial relevance challenging, suggesting that converting sunlight into chemical energy and storing it is a valuable measure to achieve global sustainable development. Carbon–neutral, clean and secondary pollution-free solar-driven water splitting to produce hydrogen is one of the most attractive avenues among all the current options and is expected to realize the transformation from dependence on fossil fuels to zero-pollution hydrogen. Artificial photosynthetic systems (APSs) based on photoelectrochemical (PEC) devices appear to be an ideal avenue to efficiently achieve solar-to-hydrogen conversion. In this review, we comprehensively highlight the recent developments in photocathodes, including architectures, semiconductor photoabsorbers and performance optimization strategies. In particular, frontier research cases of organic semiconductors, dye sensitization and surface grafted molecular catalysts applied to APSs based on frontier (molecular) orbital theory and semiconductor energy band theory are discussed. Moreover, research advances in typical photoelectrodes with the metal–insulator–semiconductor (MIS) architecture based on quantum tunnelling are also introduced. Finally, we discuss the benchmarks and protocols for designing integrated tandem photoelectrodes and PEC systems that conform to the solar spectrum to achieve high-efficiency and cost-effective solar-to-hydrogen conversion at an industrial scale in the near future.

Key words: Photoelectrochemical (PEC) cells, Solar water splitting, Photocathodes, Semiconductors, Metal-insulator-semiconductor (MIS) heterostructure, Tandem photoelectrodes