Synergistic Sm,Fe Co‐Doping in NiO Nanoparticles on Carbon Nanofibers Boosts Electrocatalytic Oxygen Evolution Reaction

Nickel oxide (NiO) electrocatalysts suffer from inevitable oxidative degradation during alkaline oxygen evolution reaction (OER), where irreversible phase transitions compromise structural integrity and long-term stability. Herein, the Sm,Fe co-doped NiO nanoparticles anchored on interconnected carbon nanofibers (denoted as Sm,Fe-NiO/CNFs) was proposed as highly efficient and stable OER catalyst. By employing rare earth (RE) Sm doping to stabilize low-valence Ni sites and generate oxygen vacancies (V_O) through charge compensation, the Sm,Fe-NiO/CNFs exhibits exceptional OER activity, with a low overpotential of only 274 mV at 10 mA cm^-2, which is superior to that of Fe-NiO/CNFs (280 mV) and RuO₂ (333 mV). Besides, Sm,Fe-NiO/CNFs also has robust long-term stability and satisfying selectivity (nearly 100% Faradic efficiency). Using Sm,Fe-NiO/CNFs as the anode in a water-splitting electrolyzer, it operates at a low potential of just 1.51 V to achieve 10 mA cm^-2, making it a promising candidate for water splitting applications. It was discovered that Sm doping offers electron donation to Ni active sites in Fe-NiO to stabilize the Ni─O bonds, preventing over-oxidation and dissolution of metal species, and thus contributing to the significantly improved OER activity and long-term stability of the catalyst.