Ni(II) complex based on imidazole dicarboxylic acid as a promising electrocatalyst for hydrogen evolution reaction and H2O2-sensing  

A new mononuclear Ni(II) complex, [Ni( p -MOPhH 2 IDC) 2 (H 2 O) 2 ], was synthesized by the reaction of p -MOPhH 3 IDC (2-(4-methoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid) and Ni(NO 3 ) 2 ·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. For electrocatalytic HER (hydrogen evolution reaction), linear sweep voltammetry curves at different temperatures were determined. The polarization curve shows that the η 10 298K (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 H 2 O 2 were found to have a linear response from 0.5 μM to 4.0 mM with a detection limit of 0.036 μM. The information obtained from this study will help to expand the application of Ni(II) complex in the field of electrochemistry.