Effective electrocatalytic hydrogen evolution of carbon paste electrode modified by Fe (II) and Ni (II) phenylimidazole‐dicarboxylate complexes

Abstract

The structure determined is helpful to explore the reaction mechanism and provide a design strategy for the synthesis of high‐performance hydrogen evolution reaction (HER) electricity catalysts. Therefore, two structurally tunable and deterministic metal complexes, [Fe(m‐H2MOPhIDC)2(H2O)2]·2H2O (1) and [Ni(m‐HMOPhIDC)(H2O)2)]n (2) (m‐H3MOPhIDC = 2‐[3‐methoxyphenyl]‐1H‐imidazole‐4,5‐dicarboxylic acid), were synthesized under solvothermal conditions and used to assemble modified carbon paste electrodes (CPE 1–2) to explore the relationship between structure and catalytic performance. Structural analysis revealed that complexes 1 and 2 had a mononuclear structure and 1D linear structure, respectively, and that the central ions of the two complexes had the same coordination environment of the octahedral spatial configuration. In 0.5 M H2SO4 and 293 K, linear sweep voltammetry and Tafel curve indicate that the η10 (overpotential, 10 mA cm−2) of two modified carbon paste electrodes are −574 and −539 mV and Tafel slopes are 161 and 128 mV dec−1. Comparing the overpotential of CPE 1–2 with that of unmodified solid carbon paste electrode (sCPE, −976 mV), it was found that the overpotential of CPE1–2 shifted positively and the Tafel slopes are obviously reduced compared to sCPE (221 mV dec−1), which proves that the CPE 1–2 has effective electrocatalytic hydrogen evolution activity. The controlled potential electrolysis and impedance spectroscopy further validated the above conclusions. The higher HER activity of the CPE 2 than CPE 1 can be attributed to the fact that complex 2 is a one‐dimensional polymer, which can efficiently disperse the catalytic active site. The use of metal complexes as HER electrocatalysts provides a new idea for an effective method for converting electric energy into hydrogen energy and is beneficial to the development of the HER research field.