Lanthanide-Tuned Electronic Modulation in Rare Earth-Doped NiCo₂O₄/CP (RE=La, Ce, Pr, Gd) Nanosheets for Enhanced Oxygen Evolution Reaction

Oxygen evolution reaction (OER) is a critical challenge in electrochemical water splitting, necessitating the development of efficient catalysts. In this study, a room-temperature gas–liquid diffusion strategy is presented to synthesize rare earth-doped NiCo₂O₄ nanosheets on carbon paper (RE-NiCo₂O₄/CP, RE = La, Ce, Pr, Gd) as alkaline OER electrocatalysts. Among them, Ce-NiCo₂O₄/CP demonstrates catalytic activity, requiring an overpotential of only 265 mV to achieve a current density of 20 mA cm⁻² in 1 M KOH, which is lower than that of undoped NiCo₂O₄/CP (348 mV). Comprehensive characterization reveals that RE doping modulates the electronic structure of NiCo₂O₄, increasing the Co 3+ /Co 2+ ratio and optimizing intermediate adsorption. Notably, Ce doping facilitates the formation of highly active Ni(Co)OOH species during OER, further enhancing catalytic performance. Combination experiments and in-situ analysis confirmed that the increase in activity was due to the incorporation of rare earths, which enhanced the charge transfer of reaction intermediates and promoted the formation of highly active phases. This work not only presents a synthesis method for high-performance OER catalysts, but also elucidates the electronic modulation effect into the role of rare-earth elements in tuning electrocatalytic properties.