Crystal Facet-Controlled Efficient SnS Photocathodes for High Performance Bias-Free Solar Water Splitting

To achieve a high solar-to-hydrogen (STH) conversion efficiency, delicate strategies toward high photocurrent together with sufficient onset potential should be developed. Herein, an SnS semiconductor is reported as a high-performance photocathode. Use of proper sulfur precursor having weak dipole moment allows to obtain high-quality dense SnS nanoplates with enlarged favorable crystallographic facet, while suppressing inevitable anisotropic growth. Furthermore, the introducing Ga₂ O₃ layer between SnS and TiO₂ in SnS photocathodes efficiently improves the charge transport kinetics without charge trapping. The SnS photocathode reveals the highest photocurrent density of 28 mA cm^-2 at 0 V versus the reversible hydrogen electrode. Overall solar water splitting is demonstrated for the first time by combining the optimized SnS photocathode with a Mo:BiVO₄ photoanode, achieving a STH efficiency of 1.7% and long-term stability of 24 h. High performance and low-cost SnS photocathode represent a promising new material in the field of photoelectrochemical solar water splitting.