Electrocatalytic Water Oxidation by a Heterogenized Co (III)-Aminophenol Complex: Structure-Activity Relationship and...

The advancement of efficient and cost-effective molecular electrocatalysts is essential in the quest for sustainable energy solutions. The design and synthesis of a new mononuclear cobalt (III) complex with a redox-active aminophenol ligand have been presented in this work. The formation of an anionic Co (III) complex 1 with triethylammonium acting as the counterion was confirmed using the crystallographic technique. Cyclic voltammetry studies were performed to assess the redox behavior of complex 1 in both the solid and solution states, demonstrating that quasi-reversible oxidation events during the anodic sweep are crucially enabled by ligand-centered sites. The synthesized cobalt complex displays strong catalytic aptitude for OER in 1 M KOH, requiring an overpotential of 410 mV to reach a current density of 10 mA cm^-2 and exhibiting a low Tafel slope of 54.3 mV dec^-1, indicative of faster reaction kinetics. The retention of structural and morphological features following extended OER operation was assessed through post-operation characterization using a variety of spectroscopic techniques. The plausible mechanism is proposed based on the combination of DFT analysis and experimental observations. The preferred pathway for water oxidation was identified by performing DFT calculations to determine oxidation potentials and the free energies of plausible intermediates.