B-site regulated Ru-based pyrochlores for acidic water oxidation.

Abstract

Ruthenium (Ru)-based pyrochlores have shown significant potential for oxygen evolution reaction (OER) in acidic media. However, their further application is severely limited by insufficient structural stability and moderate activity under harsh acidic conditions. Herein, density functional theory (DFT) calculations were performed to investigate the effects of 3d transition metals doping on the intrinsic activity and stability of Y₂Ru₂O_7-δ. Guided by theoretical predictions, a series of Y₂Ru_2-xM_xO_7-δ (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) materials was synthesized, and Y₂Ru_1.8Zn_0.2O_7-δ (YRZO) was identified as the optimal candidate. Both theoretical and experimental results demonstrate that Zn doping and cation vacancies synergistically optimize the adsorption energies of OER intermediates and stabilize high-valence Ru sites in YRZO, thereby accelerating reaction kinetics and reducing OER overpotentials. Meanwhile, Zn incorporation enhances the covalency of Ru-O bonds, which not only suppresses Ru dissolution but also delays the formation of surface reconstruction layers, thus significantly improving the long-term durability of the electrocatalyst. In situ characterizations verify that the OER process on YRZO proceeds via the adsorption evolution mechanism (AEM). The optimized YRZO exhibits a low overpotential of 272 mV at 10 mA cm^-2 and can reach 1000 mA cm^-2 at 1.597 V in a proton exchange membrane water electrolysis (PEMWE) device with exceptional stability over 1000 h. This work provides a rational strategy for designing highly active and stable acidic OER electrocatalysts by 3d transition metal doping of Y₂Ru₂O_7-δ-based pyrochlores.