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.