5f Covalency Synergistically Boosting Oxygen Evolution of UCoO4 Catalyst

Electronic structure modulation among multiple metal sites is key to the design of efficient catalysts. Most studies have focused on regulating 3d transition-metal active ions through other d-block metals, while few have utilized f-block metals. Herein, we report a new class of catalyst, namely, UCoO 4 with alternative CoO 6 and 5f-related UO 6 octahedra, as a unique example of a 5f-covalent compound that exhibits enhanced electrocatalytic oxygen evolution reaction (OER) activity because of the presence of the U 5f-O 2p-Co 3d network. UCoO 4 exhibits a low overpotential of 250 mV at 10 mA cm -2 , surpassing other unitary cobalt-based catalysts ever reported. X-ray absorption spectroscopy revealed that the Co 2+ ion in pristine UCoO 4 was converted to high-valence Co 3+/4+ , while U 6+ remained unchanged during the OER, indicating that only Co was the active site. Density functional theory calculations demonstrated that the OER activity of Co 3+/4+ was synergistically enhanced by the covalent bonding of U 6+ -5f in the U 5f-O 2p-Co 3d network. This study opens new avenues for the realization of electronic structure manipulation via unique 5f involvement.