A new tetranuclear N-heterocyclic silver(I) complex as electrocatalyst for hydrogen evolution reaction

A new Ag(I) complex with the chemical composition, [Ag4(BBP)2(H2ebidc)]·4H2O (BBP = 1,3-bis(1H-benzimidazol-2-yl)propane, H6ebidc = 2,2’-(ethane-1,2-diyl)bis(1H-imidazole-4,5-dicarboxylic acid), was successfully synthesized by hydrothermal method and characterized by X-ray single crystal diffraction, elemental analysis, and infrared and ultraviolet spectroscopy. Crystallographic analysis revealed that the Ag(I) complex has a tetranuclear ring cluster structure, which are connected by π…π (d = 3.641 Å) interactions to form a one-dimensional supramolecular structure. The performance of electrocatalytic hydrogen evolution reaction (HER) of Ag(I) complex-modified carbon paste electrode (1-CPE) and bare electrode (sCPE) were investigated. In 0.5 M H2SO4 with current density of 10 mA·cm−2, compared to sCPE, 1-CPE exhibited excellent electrocatalytic performance, with a positive shift of the overpotential (η10) by 478 mV and a reduction of the Tafel slope (b) by 95 mV·dec−1. The Nyquist plot of 1-CPE at −0.65 V has significantly smaller semicircle diameter in the high frequency region than sCPE, which indicated that it possessed less charge transfer resistance at the electrode surface as HER catalyst. The 1-CPE exhibited better electrocatalytic performance than the sCPE, presumably because the presence of Ag(I) complex improved the electrocatalytic performance of HER. This further confirms the potential value of Ag(I) complex as electrochemical materials.