Impact of bimetallic synergies on Mo-doping NiFeOOH: Insights into enhanced OER activity and reconstructed electronic structure

NiFe (oxy)hydroxide (NiFeOOH) is recognized as a highly active non-precious metal catalyst in alkaline water electrolysis due to its exceptional catalytic properties. In this work, high valence molybdenum (Mo) is introduced to improve the electronic structure and enhance the electrical conductivity of NiFeOOH for oxygen evolution reaction (OER). The introduction of Mo results in a Mo-doped NiFeOOH catalyst with a significantly reduced overpotential of 205 mV at 10 mA/cm² and a Tafel slope of 31.7 mV/dec, enabling stable operation for up to 170 h. Both empirical experiment and theory simulations are employed to gain insight into the 3d-electron interactions between molybdenum and nickel (Ni), iron (Fe) in Mo-doped NiFeOOH. The results indicate that Mo-doping enhances the valence states of Ni and Fe, leading to a shift in the d-band center of the bimetallic active sites. This modification affects the transformation of Mo-doped NiFeOOH into the γ-NiFeOOH active phase. This potent combination lends credence to its potential suitability and utility in OER applications.