Loading Amorphous NiMoO_4–<i>x</i>S_<i>x</i> Nanosheet Cocatalyst to Improve Performance of <i>p</i>‑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 NiMoO_4–<i>x</i>S_<i>x</i> 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