Development of polyoxometalate-based Ag-H₂biim inorganic-organic hybrid compounds functionalized for the acid...

The electrocatalytic hydrogen evolution reaction (HER) is an ideal method for hydrogen production. Transition metal complex electrocatalysts exhibit poor HER activity due to excessive or weak adsorption of H during the electrochemical reduction of water to molecular hydrogen in acidic environments. Developing specific functional complex materials as desired catalysts is challenging. Here, an electrochemical surface restructuring strategy of polyoxometalate (POM)-modified Ag materials toward the HER with a dramatically decreased overpotential under acidic aqueous conditions is established. We prepared two POM [SiW₁₂O₄₀]^4- (SiW₁₂)/[P₂W₁₈O₆₂]^6- (P₂W₁₈)-based Ag-2,2'-biimidazole (H₂biim) inorganic-organic hybrid compounds (1 and 2) via the hydrothermal method and these two compounds undergo an electrochemical restructuring process in 0.5 M H₂SO₄ during the HER, in which Ag nanoparticles are in situ formed with the basic structures of SiW₁₂ and P₂W₁₈ being maintained. The activated catalysts (1-AC-RDE and 2-AC-RDE) exhibit good electrocatalytic activity for the HER with good long-term stability, and the required overpotentials at a current density of 10 mA cm^-2 are 112 mV (1-AC-RDE) and 91 mV (2-AC-RDE) with Tafel slopes of 77 mV dec^-1 and 65 mV dec^-1, respectively. The excellent electron-proton storage and transferability of SiW₁₂ and P₂W₁₈ may provide a solution for the insufficient capture of H by Ag, leading to an effective self-optimizing behavior and superior acidic HER activity.