Supercritical Fluid-Assisted Synthesis of Metal Selenide/TiO₂ Nanocomposites for Photocatalytic Hydrogen Production

Photocatalytic hydrogen generation from water is one of the promising approaches for direct solar-to-fuel conversion to address the energy crisis. Developing an efficient, cost-effective, durable photocatalyst for sustainable hydrogen production is a great challenge in this technology. Metal chalcogenides are widely used potential materials in the photocatalysis field; however, metal sulfides are photocorrosive in nature compared to metal selenides, which limits their application. Herein, supercritical fluid becomes completely compatible with photocatalyst preparation, as it controls the morphology of materials. The synthesis of CoSe and NiSe using a homogeneous, one-pot synthesis of supercritical fluid processing with a very short reaction time of 30 min has been demonstrated, and then they are coupled with a TiO2 photocatalyst to improve the hydrogen production rate. Due to the conductive nature of metal selenides (CoSe and NiSe), fast electron transfer and charge separation are highly feasible, which help to improve the hydrogen production rate. Various weight percentages of the metal selenide (CoSe or NiSe)/TiO2 nanocomposite were prepared, and photocatalytic activity was examined using glycerol and lactic acid as hole scavengers. The CoSe/TiO2 and NiSe/TiO2 nanocomposites showed maximum hydrogen evolution rates of 202.2 and 169 mmol/h/gcat, respectively, which are very close to that of 1 wt % Pt/TiO2. In this context, metal selenides (CoSe/NiSe) are promising cocatalysts for TiO2 toward viable hydrogen production.