High-valence metal doping on cobalt-iron (oxy) hydroxide to activate the lattice oxygen for boosting oxygen evolution performance

The precise modulation of the electronic structure of cobalt-iron (oxy) hydroxides to facilitate the lattice oxygen mechanism (LOM) activation is essential for lowering the energy barriers of the alkaline oxygen evolution reaction (OER), and promoting the energy-saving water electrolysis technology. In this study, we propose the introduction of high-valence heterometal (Mo, V, W) to regulate the orbital hybridization state of the asymmetric Co-O-Fe coupling configuration. Through systematic characterization and theoretical calculations, we demonstrate that the high-valence metal sites act as electron acceptors, which tailor the 2p orbitals state of the adjacent lattice oxygen, enhancing the covalency of the metal-oxygen bond to help activate the lattice oxygen sites. Undergoing the LOM pathway, the optimized candidate of Mo-CoFeOxHy exhibits the best OER performance, with an overpotential of 240/340 mV at 10/400 mA cm(-2), which is significantly lower than that of pristine CoFeOxHy and commercial RuO2. Encouragingly, a self-constructed alkaline flow-type water electrolyze with the catalyst pair of Pt/C and Mo-CoFeOxHy shows promising performance of 2.03 V at 100 mA cm(-2), and also possesses long-term durability, with almost no activity decay after 100 hours of operation. We validate that this universal modification strategy can provide general guidance for rational design of OER catalysts.