Nonmetal–Metal Strategy to Reduce Ru–O Covalency while Promoting Local Reactive Water Concentration for Efficient Acidic Oxygen Evolution

Affordable, active, and durable oxygen evolution reaction (OER) catalysts are crucial for proton exchange membrane water electrolysis (PEMWE). The low-cost RuO₂, relative to IrO₂, is attractive for acidic OER while suffering from durability. To resolve this activity-stability dilemma of RuO₂, we propose a universal nonmetal-metal strategy to reduce Ru-O covalency while promoting local reactive water concentration for efficient acidic OER. The nonmetal-metal dual-dopant via complementary regulation of O 2p and Ru 4d bands weakens the Ru-O covalency, constraining the lattice oxygen participation and Ru dissolution. Operando evidence further unravels that the best-performing B-Cr-RuO₂, via surface OH, increases the local reactive water concentration and the connectivity of H-bond networks, enabling an order of magnitude enhancement in intrinsic activity without sacrificing durability over RuO₂. Consequently, the B-Cr-RuO₂-incorporated PEMWE delivers attractive performance for practical applications, requiring a voltage of only 1.54 V@1.0 A cm^-2 and maintaining a durable operation at industrial current densities.