Phase-engineered nickel selenide cocatalyst on CdS for enhanced visible-light photocatalytic H2 production

Abstract

To improve the efficiency of photocatalytic H₂ generation, cocatalysts are commonly utilized to suppress the recombination of photogenerated charge carriers and provide reaction active sites. Herein, four different crystalline phases of nickel selenide were controllably prepared via a simple one-pot approach. The nickel selenide underwent multiple phase transformations at reaction temperatures of 180, 240, 280, and 300 ℃, resulting in orthorhombic, orthorhombic-cubic, cubic, and cubic-hexagonal phases, respectively. Nickel selenides were combined with CdS using an in-situ precipitation method for photocatalytic H₂ generation reactions. All four crystalline phases of nickel selenide were found to be effective cocatalysts that boosted the photocatalytic H₂ production performance of CdS under visible light. Among these phases, the orthorhombic-cubic NiSe₂ demonstrated a superior H₂ generation rate of 3039 µmol h⁻¹ g⁻¹, 6.5 times higher than CdS. The effective charge transfer between CdS and nickel selenide was revealed through photoluminescence (PL), electrochemical, and photoelectrochemical analyses. This work introduces a practical approach to designing cost-effectiveness NiSe_x cocatalysts on metal sulfide semiconductors, leveraging phase control to optimize photocatalytic solar-to-H₂ conversion.