<p>Developing acid-stable and active ruthenium dioxide (RuO₂) catalysts for the oxygen evolution reaction (OER) is crucial for facilitating the large-scale applications of proton exchange membrane water electrolysis (PEMWE) for hydrogen production. Here, we propose a strain heterogeneity engineering strategy to simultaneously enhance the OER stability and activity of RuO₂ electrocatalysts by introducing single-atom platinum (Pt). In a PEM water electrolyzer, the resultant Pt-RuO₂ catalyst archives 3 A cm⁻² at a low voltage of 1.791 V and maintains a stable performance for over 500 h at 500 mA cm⁻². These performance metrics highlight its potential for practical applications. Experiments and calculations analyses confirm that the bulk tensile strain effectively stabilizes the entire structure of electrocatalysts, while the regions of compressive strain are identified as highly active catalytic sites, where the weakened binding energy of oxo-intermediates improves the catalytic activity.</p>