Activation of oxygen reduction reaction on carbon supported Ni-based complexes

There are unremitting efforts towards developing an effective oxygen reduction reaction (ORR) catalyst as it is seminal for the commercially viable energy conversion and storage devices such
as fuel cell and metal-air batteries. In this study, three carbon-supported Ni-based coordination complexes; Ni-phen/AC, Ni-bpy/AC and Ni-bimz/AC (where phen=1,10- Phenanthroline,
bpy= 2, 2'-bipyridine and bimz= Benzimidazole) were explored for ORR. Among these, Nibimz forms a 1D-polymer chain via a succinate bridge, and these chains are stacked by the ππ interactions and hydrogen bonding. The ORR potentials of these catalysts were studied using cyclic voltammetry technique with a rotating ring disk electrode system, and oxygen adsorption
energies (Ead) onto these complexes were calculated using density functional theory (DFT) analysis. The highest onset potential of 0.89 V vs. RHE was observed for Ni-bimz/AC, whereas 0.88 V and 0.86 V vs. RHE for Ni-phen/AC and Ni-bpy/AC catalysts, respectively. The Ead value for O2 via side-on and end-on mode over Ni-phen, Ni-bpy, and Ni-bimz complexes, were calculated. The highest negative Ead value of -25.53 eV via side-on mode was observed for Ni-bimz complex.