Loading Amorphous NiMoO_4–xS_x Nanosheet Cocatalyst to Improve Performance of p-Silicon Wafer Photocathode

Considering its small band gap and appropriate conduction band level, Si is a suitable semiconductor for photocathodes in a photoelectrochemical (PEC) cell. Unfortunately, its PEC activity is far from desirable because of inferior stability, high recombination of photogenerated electron–hole pairs, and sluggish hydrogen evolution kinetics at the Si/electrolyte interface. The introduction of low-cost and earth-abundant non-noble metal cocatalysts onto the Si photocathode is a promising route to improve its PEC performance. Herein, we fabricate efficient and stable photocathodes by integrating non-noble metal NiMoO4–xSx nanosheets with planar p-Si wafers, along with ultrathin TiO2 as a protective and passivating film at the intermediate and outermost layer. An onset potential of 0.3 V (vs RHE) and a photocurrent density of 5.1 mA cm–2 at −0.5 V (vs RHE) are obtained for the optimal photocathode, representing significant enhancement compared to the pristine Si wafers. Moreover, long-term measurement demonstrates that the TiO2 layer can effectively protect the photocathode from degradation of electrolyte and photocorrosion.