Activity and Regeneration of Electrodeposited Fe–Ni–Co-Based Electrocatalysts for the Alkaline Oxygen Evolution Reaction

Abstract A methodology to recover the oxygen evolution reaction (OER) kinetics of aged, electrodeposited Fe–Ni–Co thin films is presented. The electrodeposits were fabricated galvanostatically onto rotating copper electrodes and contained a small amount of Co. The OER characterized in 1 M KOH was a function of the deposit composition. The Tafel slope and the overpotential at 10 mA/cm2 observed with ohmically corrected linear sweep voltammetry were both a function of the deposit metal ratio, Fe/(Ni + Co), with the lowest values occurring at a ratio of 1.2. An Fe-rich deposit was purposely altered upon aging to degrade the OER kinetics. The Tafel slope and overpotential were largely recovered when the aged electrocatalyst was treated with a cathodic current density of −100 mA/cm2 for 10 min. Soft X-ray absorption spectroscopy provided insight into the changes of the electron density distribution upon aging and regenerating the electrocatalyst. Through X-ray absorption near-edge structure (XANES), the L-edge spectra of Fe, Ni, Co, and K-edge spectra of O, suggested that the recovery is due to the redistribution of the electron density from the oxygen to Fe and Ni.