Ni(II) Complex Based on Imidazole Dicarboxylic Acid as a Promising Electrocatalyst for Hydrogen Evolution Reaction and H2O2-Sensing

The determination of complex structure helps to explore its reaction mechanism and provides design strategies for guiding synthesis of high-performance hydrogen evolution reaction (HER) electrocatalysts. A new mononuclear Ni(II) complex, [Ni(p-MOPhH2IDC)(2)(H2O)(2)], was synthesized by the reaction of p-MOPhH3IDC (2-(4-methoxyphenyl)(-1) H-imidazole-4,5-dicarboxylic acid) and Ni(NO3)(2)center dot 6H(2)O under solvothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV-vis spectroscopy. The structure analysis revealed that the nickel center was six-coordinated octahedron coordination geometry. The electrochemical properties of the Ni(II) complex-doped carbon paste electrode (Ni-CPE) were investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 0.5 M H(2)SO(4 )electrolyte. The HER measurements show that the eta(298K)(10) (overpotential, 10 mA cm(-2)) of the Ni-CPE was positively shifted by 265 mv compared with the bare-CPE (without complex). The Tafel slope of the Ni-CPE was 187 mV dec(-1). These indicated that the Ni-CPE was effective for HER electrocatalytic reaction. In addition, the electrochemical sensing performances of the Ni-CPE towards H2O2 were found to have a linear response from 0.5 mu M to 4.0 mM with a detection limit of 0.036 mu M. The above studies prove that the Ni(II) complex can be used as an effective bi-functional molecular electrocatalyst for HER and H2O2 sensing, and provide a new approach for designing efficient, non-precious metal electrochemical catalysts.