Highly dispersive bimetallic sulfides afforded by crystalline polyoxometalate-based coordination polymer precursors for efficient hydrogen evolution reaction

Abstract

Molybdenum disulfide (MoS2) is viewed as one of the most promising hydrogen evolution reaction (HER) electrocatalyst thanking to its graphene-like layered structure and suitable hydrogen chemisorption free energy. However, its application is still hindered by some obstacles, such as less exposed active sites and poor inherent conductivity. Herein, two new crystalline polyoxometalate-based metal-organic polymers with Co/Ni and Mo, {(C2H2N3)3Co2·6H2O}[H3SiMo12O40]·9H2O (1) and {(C2H2N3)3Ni2·6H2O}[H3SiMo12O40]·5H2O (2) (1,2,4-triazole = C2H2N3) are firstly designed and fabricated, and characterized by sufficient technologies including single-crystal X-ray diffraction and so on. And they are directly utilized as ‘preassembly platform’ reacting with thiourea to synthesize highly dispersive CoS2–MoS2 and Ni3S2–MoS2 bimetallic sulfides with mesoporous structure. In virtue of the synergistic effects, and high dispersiveness and porosity of CoS2/Ni3S2 and MoS2 in carbon cloth (CC), 50%CoS2–MoS2@CC and 50%Ni3S2–MoS2@CC composites display a low overpotential of 222 and 224 mV at 10 mA cm−2, and a small Tafel slope of 64.2 and 65.7 mV·dec−1 in H2SO4 solution, respectively. Such superior electrocatalytic HER performances outperform most of both POM-based and MoS2-based non-noble metal catalysts. Hence, this work presents a facile tactic for engineering highly dispersive bimetallic sulfides with excellent electrocatalytic HER performance.