Partial crystallization of Co-Fe oxyhydroxides towards enhanced oxygen evolution activity

Developing high-performance noble-metal-free electrocatalysts for the oxygen evolution reaction (OER) is of great significance for the large-scale implement of electrochemical water splitting. Here, we demonstrate that cobalt-iron oxyhydroxide (CoFe0.8(OH)(x)) with appropriate crystallization exhibits excellent OER activity with a low overpotential of only 246 mV, which is much lower than that achieved on amorphous one. Kinetic experiments indicate that the OER active sites should be di-mu-oxo bridged Fe-Co, on which lower energy barrier is attained than that on Fe-O and Co-O sites. Partial crystallization is beneficial to the lattice contraction, the formation of Co-O-Fe sites, and the decrease of charge transfer resistance, thus accelerating OER process. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.