Ni/Fe Codoped In 2 S 3 Nanosheet Arrays Boost Photo‐Electrochemical Performance of Planar Si Photocathodes

The photo‐electrochemical performance of the Si photocathode is seriously restricted by the severe charge recombination at the Si/electrolyte interface and sluggish hydrogen evolution reaction (HER) kinetics. Herein, a facile hydrothermal process is reported to integrate Ni/Fe codoped In 2 S 3 nanosheet arrays onto the surface of unmodified a p‐Si photocathode for water reduction. The experimental results and density functional theory calculations indicate that the Ni and Fe codoping of In 2 S 3 contributes to small surface transfer impedance, prolonged carrier lifetime, increased charge carrier concentration, and reduced overpotential for HER. Moreover, a p–n junction formed at the interface of Si and Ni/Fe:In 2 S 3 promotes the photogenerated electron–hole separation and reduces the recombination in the bulk. As a result, the Si–Ni/Fe:In 2 S 3 photocathode exhibits high performance with significantly enhanced photocurrent of −80.9 mA cm −2 at −1.3 V RHE and positive onset potential of 0.44 V RHE .