Mitigating over-oxidation and optimizing electronic structure of ruthenium sites by binary Ni-Mo₂N support for enhanced oxygen evolution reaction

Ruthenium-based catalysts face significant challenges of electrochemical dissolution and slow reaction kinetics for the oxygen evolution reaction (OER). Here, we have shown the enhancement of the activity and stability of Ru doped on a binary Ni-Mo₂N support with three-dimensional (3D) filamentous network structure (Ru/Ni-Mo₂N) for OER. X-ray photoelectron spectroscopy (XPS) reveals the increase of the electron density around Ru sites by the interaction with Ni-Mo₂N. Density functional theory (DFT) calculations confirm that this interaction induces a downshift of the d-band center of Ru sites, leading to optimized adsorption energies of intermediates on Ru and enhanced OER performance. Moreover, the sacrificial behavior of Ni effectively mitigates Ru over-oxidation and dissolution, thereby enhancing OER stability. Also, the 3D filamentous network structure with abundant pores is favorable to accelerate the transfer of electrolyte. As a result, the Ru/Ni-Mo₂N requires an overpotential of 251 mV to achieve 20 mA·cm⁻², being 83 mV lower than that of Ru-Mo₂N. An anion exchange membrane water electrolyzer (AEMWE) (Pt/C||Ru/Ni-Mo₂N) delivers a voltage of 1.78 V at 500 mA·cm⁻², superior to that of the Pt/C||RuO₂ (1.97 V@500 mA·cm⁻²), and exhibits stable operation for over 500 h. This study demonstrates the critical role of the binary support in enhancing the catalytic activity and stability of Ru-based catalysts.