O-2p Hybridization Enhanced Transformation of Active γ-NiOOH by Chromium Doping for Efficient Urea Oxidation Reaction

The electrooxidation of urea holds great potential for converting urea from wastewater into hydrogen, contributing to environmental protection and sustainable energy production. This necessitates the development of highly efficient and stable catalysts for the urea oxidation reaction (UOR). In this study, a NiCoCr-LDH/NF (nickel-cobalt-chromium layered double hydroxide/nickel foam) electrode is successfully synthesized via a simple hydrothermal method, demonstrating excellent electrocatalytic performance with a low work potential of 1.38 V at a high current density of 100 mA cm⁻². In situ, Raman spectra analysis revealed that the incorporation of chromium (Cr) facilitated the generation of active γ-NiOOH species and catalyst reconstruction. Density functional theory (DFT) simulations confirmed that the lower formation energy of γ-NiOOH is due to the weakened interaction of O─H bonds because of a narrow energy range of hybridization between O-2p_z orbitals and H-1s orbitals. The introduction of Cr also improved the adsorption energy of urea molecules and its intermediates, thereby enhancing the overall activity of UOR. With its excellent electrocatalytic performance, unique electronic states, and coordination structures, the NiCoCr-LDH/NF electrode showcases great potential for practical applications in the field of energy catalysis. © 2024 Wiley-VCH GmbH.