5f Covalency Synergistically Boosting Oxygen Evolution of UCoO(4) Catalyst

[Image: see text] 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.