Experimental and Theoretical Investigations on Hydrogen Evolution Reaction (HER) Abilities of Some Salphen and Salen Complexes

Metal complexes based on salen and salphen ligands have been extensively studied in chemical and biological sciences for several applications. However, their utility in producing renewable energy is relatively less studied. In the present work, we report the synthesis, characterization, and hydrogen evolution reaction (HER) abilities of Cu(II), Fe(II) and Mn(II) complexes based on salphen and salen ligands. The ligands and their corresponding complexes were synthesized in good yields. The electrochemical properties of the complexes were studied in dimethyl formamide (DMF) containing [NBu₄][BF₄] electrolyte. The reported complexes were studied for homogenous electrocatalytic performance towards HER. All catalysts studied here showed respectable HER activity as the reduction of acetic acid took place at a lower overpotential (-1.30 to -1.63 V vs. Ag/AgCl) and shifted the reduction potential by 220–550 mV. While the ligand had a negligible impact, the potential shift was found to be the function of metal center (size). Density functional theory (DFT) calculations also complement the experimental findings.