Single-crystal silicon-based electrodes for unbiased solar water splitting: current status and prospects

Water splitting for hydrogen production by harvesting sunlight is widely accepted as one of the most promising routes to relieve the energy crisis and environmental issues caused by excessive use of fossil fuels. Earth-abundant silicon (Si) is emerging as a suitable candidate for a photoelectrode material for efficient solar water splitting. This review describes the current status and prospects of single-crystal Si-based photoelectrodes in photoelectrochemical (PEC) water splitting for hydrogen production. We start with highlighting the recent achievements in single-crystal Si-based photocathodes and photoanodes for PEC water reduction and oxidation. We then discuss the recent progress in the design and fabrication of unbiased solar water splitting cells with single-crystal Si-based photoelectrodes. Finally, we provide an overview from the optimization of a single-crystal Si-based electrode (both a photocathode and a photoanode) to the integration of a full cell for unassisted overall solar water splitting. This review describes recent developments of single-crystal silicon (Si) as the photoelectrode material for solar water splitting, including the promising strategies to obtain highly efficient and stable single-crystal Si-based photoelectrodes for hydrogen evolution and water oxidation, as well as the future development of spontaneous solar water splitting with single-crystal Si-based tandem cells.