A Si Photocathode Protected and Activated with a Ti and Ni Composite Film for Solar Hydrogen Production

An efficient, stable and scalable hybrid photoelectrode for visible‐light‐driven H2 generation in an aqueous pH 9.2 electrolyte solution is reported. The photocathode consists of a p‐type Si substrate layered with a Ti and Ni‐containing composite film, which acts as both a protection and electrocatalyst layer on the Si substrate. The film is prepared by the simple drop casting of the molecular single‐source precursor, [{Ti2(OEt)9(NiCl)}2] (TiNipre), onto the p‐Si surface at room temperature, followed by cathodic in situ activation to form the catalytically active TiNi film (TiNicat). The p‐Si|TiNicat photocathode exhibits prolonged hydrogen generation with a stable photocurrent of approximately −5 mA cm−2 at 0 V vs. RHE in an aqueous pH 9.2 borate solution for several hours, and serves as a benchmark non‐noble photocathode for solar H2 evolution that operates efficiently under neutral–alkaline conditions. A benchmark non‐noble photocathode: An efficient, stable, and scalable photocathode containing solely earth‐abundant materials effects solar H2 evolution under near neutral pH. Figure (a) shows a p‐type silicon electrode modified with a Ti and Ni composite film with high activity under solar light illumination. Figure (b) shows the stable photocurrent generated with this hybrid photocathode.