Rare-Earth-Element-Doped NiCo Layered Double Hydroxides for High-Efficiency Oxygen Evolution

The development of low-cost and high-efficiency oxygen evolution reaction (OER) catalysts is essential to enhance the practicality of electrochemical water splitting for green hydrogen production. Layered double hydroxides (LDHs), especially those based on nickel and cobalt, have attracted attention due to their tunable composition, abundant redox-active sites, and earth-abundant constituents. However, their application is hindered by their limited conductivity and sluggish reaction kinetics. In this study, rare-earth-element-doped NiCo LDHs were synthesized directly on nickel foam through a one-step hydrothermal approach to improve the OER activity by modulating the electronic structure and optimizing the surface morphology. Among the representative catalysts, the incorporation of Sm significantly influenced the microstructure and electronic configuration of the catalyst, as confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Electrochemical tests showed that the optimized Sm-NiCo LDH achieved a low overpotential of 172 mV at 10 mA cm−2 and a small Tafel slope of 84 mV dec−1 in 1 M KOH, indicating an expanded electrochemically active surface and improved charge transport. Long-term stability tests further showed its durability. These findings suggest that Sm doping enhances the OER performance by increasing active site exposure and promoting efficient charge transfer, offering a promising strategy for designing rare-earth-modified, non-precious-metal-based OER catalysts.