Silicon Photoanodes Partially Covered by Ni@Ni(OH) 2 Core–Shell Particles for Photoelectrochemical Water Oxidation

Two obstacles hindering solar energy conversion by photoelectrochemical (PEC) water‐splitting devices are the charge separation and the transport efficiency at the photoanode–electrolyte interface region. Herein, core–shell‐structured Ni@Ni(OH) 2 nanoparticles were electrodeposited on the surface of an n‐type Si photoanode. The Schottky barrier between Ni and Si is sensitive to the thickness of the Ni(OH) 2 shell. The photovoltage output of the photoanode increases with increasing thickness of the Ni(OH) 2 shell, and is influenced by interactions between Ni and Ni(OH) 2 , the electrolyte screening effect, and the p‐type nature of the Ni(OH) 2 layer. Ni@Ni(OH) 2 core–shell nanoparticles with appropriate shell thicknesses coupled to n‐type Si photoanodes promote the separation of photogenerated carriers and improve the charge‐injection efficiency to nearly 100 %. An onset potential of 1.03 V versus reversible hydrogen electrode (RHE) and a saturated current density of 36.4 mA cm −2 was obtained for the assembly.