Hydrogen evolution reaction on silver(I) complex modified electrode materials as electrocatalysts

Two new silver(I) complexes, [Ag2(BDC)(Et-BBA)2] (1) and {[Ag3(BTC)(Et-BBA)3]·(C2H5OH)6·(H2O)3}2 (2) (Et-BBA = N,N-bis[(1-ethyl-1H-benzo[d]imidazol-2-yl)methyl]aniline, H2BDC = 1,4-benzendicarboxylic acid, H3BTC = 1,3,5-benzenetricarboxylic acid), were prepared and structurally characterized. Complex 1 is binuclear, whereas 2 forms a trinuclear structure. The carbon paste composite electrodes (CPCEs 1 and 2) prepared from graphite powder and 1 and 2 were used as molecular electrocatalysts to investigate their catalytic hydrogen evolution reaction (HER) performance by variable temperature linear sweep voltammetry (VT-LSV) and electrochemical impedance spectroscopy (EIS). The results indicated that the overpotentials η10293K of CPCEs 1 and 2 in 0.5 M H2SO4 electrolyte undergo a significant positive shift (–915 mV for CPCE 1, −600 mV for CPCE 2) with respect to sCPCE (–966 mV). The Tafel slope, activation energy and EIS were used to further verify that the modified electrodes CPCEs 1 and 2 could effectively catalyze the HER behavior. Based on the identified structures, the catalytic mechanisms of 1 and 2 toward HER were hypothesized. The active intermediate (triangular bipyramidal configuration) formed upon addition of 2 is more reactive, which may be the reason for the higher HER activity of CPCE 2 than CPCE 1.