Highly Efficient Photoelectrochemical Hydrogen Generation Reaction Using Tungsten Phosphosulfide Nanosheets

The initiation of hydrogen energy production from sunlight through photoelectrochemical (PEC) system is an important strategy for resolving contemporary issues in energy requirement. Although precious Pt and other noble metals offer a desirable catalytic activity for this method, earth-abundant nonprecious metal catalysts must be developed for wide-scale application. In this regard, P-type silicon (P-Si) micropyramids (Si MPs) are a favorable photocathode because of their effective light-conversion properties and appropriate band gap position. In this study, we developed amorphous tungsten phosphosulfide nanosheets (WS_{2- x}P _x NSs) on Si MPs through a simple thermal annealing process for solar-driven hydrogen evolution reaction. The P substitution in the nanostructure effectively produced many defective sites at the edges. The product exhibited an efficient photocurrent density of 19.11 mA cm^-2 at 0 V and a low onset potential of 0.21 V_RHE compared with tungsten disulfide (WS₂; 13.43 mA cm^-2). The fabricated catalyst also showed desirable stability for up to 8 h for the WS_0.60P_1.40@Si MPs photocathode. The extraordinary activity could be due to numerous active sites provided by heteroatoms (sulfur and phosphorus) in the edges, resulting in dwindling reaction kinetics barrier and enhanced PEC activity.