Highly Active and Stable Nitrogen-Doped Ruthenium Oxide/Titanium Nitride Composite Anode Electrocatalyst for Practical Proton Exchange Membrane Water Electrolyzers

Abstract

The application of ruthenium-based catalysts in proton-exchange membrane water electrolyzers is impeded by lattice oxygen mechanism and the subsequent structural collapse. Herein, a design strategy for the preparation of N-doped RuO₂ using TiN nanoparticles as the nitrogen source is presented. The in- situ characterization and theoretical calculation reveal the optimized oxygen evolution reaction (OER) mechanism on the resulting N-RuO₂/TiN catalyst. The incorporation of low-electronegativity N and the formation of interfacial Ru−O−Ti bridge structure lead to the redistribution of electron density on adjacent Ru sites, weakening the Ru–O covalency and inhibiting the reactivity of lattice oxygen during electrocatalytic OER. Meanwhile, the altered electronic structures also optimize the adsorption energy of intermediates, consequently facilitating the formation of the pivotal intermediate *OOH and enhancing the electrocatalytic activity. The N-RuO₂/TiN electrocatalyst displays a extremely low OER overpotential of 159 mV at 10 mA cm⁻² in 0.5 m H₂SO₄. Particularly, the water electrolysis single cell with N-RuO₂/TiN as anode electrocatalyst conveys an extremely low voltage of 1.78 V at 3A cm⁻² and degradation rate of 26 µV h⁻¹ during a 1100 h operation at 1 A cm⁻². This work also provides an excellent catalyst for industrial-level electrolysis.