MitigatingA‑Site Segregation in PyrochloreOxides: Enhancing Oxygen Evolution Reaction Performance through SurfaceEngineering

Significant progress has been achieved in enhancing the oxygen evolution reaction (OER) performance of pyrochloric oxides through geometric and electronic structure regulation. However, the issue of A-site cation segregation in these materials remains underexplored. In this study, Bi₂Ru₂O₇, a promising OER electrocatalyst, is synthesized via a sol–gel method, and its surface is modified using l-ascorbic acid to address Bi³⁺ segregation. This treatment selectively removes the Bi₂O₃ passivation layer, inducing an amorphous RuO_<i>x</i> layer that forms a heterostructure with crystalline Bi₂Ru₂O₇. This engineered structure significantly enhances catalytic performance, reducing the overpotential to 259 mV at 10 mA cm^–2 and maintaining stability after continuous operation for >30 h. Comprehensive characterization, electrochemical testing, and density functional theory calculations reveal that the improvements stem from an increased number of oxygen vacancies and enhanced electron transfer. This work underscores the importance of surface engineering to mitigate A-site segregation, providing a new strategy for optimizing Ru-based pyrochlores in energy conversion technologies.