Molecular Co-Catalysts of Molybdenum Sulfide Clusters on Antimony Selenide Photocathodes for Hydrogen Generation

Molybdenum sulfide is a highly effective non-precious metal catalyst for hydrogen evolution, mainly active at edge sites with unsaturated molybdenum or terminal disulphide and possesses a catalytically inert basal plane. To enhance activity at low loading density, two molybdenum sulfide clusters, [Mo₃S₄(H₂O)₉]Cl₄ ([Mo₃S₄]⁴⁺) and (NH₄)₂[Mo₃S₁₃] x 2H₂O ([Mo₃S₁₃]^2–), were investigated. These molybdenum sulfide molecular catalysts were deposited on Sb₂Se₃ photocathodes using a simple soaking method, forming a thin catalyst layer. When paired with Sb₂Se₃ both [Mo₃S₄]⁴⁺ and [Mo₃S₁₃]^2– displayed excellent catalytic activity and can achieve up to 20 mA cm^–2 under one sun illumination. [Mo₃S₁₃]^2– proved to excel catalytically and demonstrated improved photovoltage and an average faradaic efficiency of 100% for hydrogen evolution. This superiority is due to the effective loading and higher catalytic activity of [Mo₃S₁₃]^2– on the Sb₂Se₃ surface.