Polyoxometalate-based coordination polymers enhance electrocatalytic hydrogen evolution in trimetallic sulfides†

Electrocatalytic water splitting is a promising, efficient and environmentally friendly method for sustainable hydrogen production, but the development of highly effective electrocatalysts is crucial to enhance its efficiency. In this study, we design and synthesize a novel crystalline polyoxometalate-based metal–organic compound, [H₃(C₅H₅N)₄(PMo₁₂O₄₀)·H₂O], via a simple one-step hydrothermal process. Next, this polymer serves as the molybdenum source for fabricating MoS₂/Ag₂S/NiS@NF electrodes, with AgNO₃ providing silver, thiourea as the sulfur source, and nickel foam (NF) as both the conductive substrate and nickel source. The results reveal stable and homogeneous growth of trimetallic sulfide nanoflakes on the NF surface. The MoS₂/Ag₂S/NiS@NF electrodes exhibit superior electrocatalytic performance compared to many polyoxometalate-based and sulfide-based catalysts, demonstrating a low overpotential of 82 mV and a Tafel slope of 94 mV dec⁻¹ at a current density of 10 mA cm⁻². The enhanced hydrogen evolution reaction activity is primarily attributed to the synergistic interactions and efficient electron transfer across the heterostructured sulfide interfaces, which significantly boost the availability of active sites. The Faraday efficiency of the composite can reach 94%. This work provides a promising approach for the design and fabrication of highly efficient trimetallic sulfide electrocatalysts.