Quenching-Controlled Interfacial Electronics Switching the Oxygen Evolution Pathway in RuO ₂ –CoWO ₄ Nanoscale Reconstruction

Controlling activity and durability in acidic oxygen evolution reaction (OER) electrocatalysts remains challenging due to structural degradation and uncontrolled lattice oxygen participation. Although heterostructure engineering improves OER performance, the role of thermal history in governing reaction pathways within identical heterostructures remains unclear. Here, we report a nanoscale RuO 2 @CoWO 4 (RCWO) heterostructured electrocatalyst prepared via molten salt synthesis followed by water quenching (WQ) or furnace cooling (FC), enabling direct comparison of quenching-dependent OER mechanisms. Both WQ- and FC-treated catalysts form comparable RuO 2 –CoWO 4 heterostructures with strong Ru–O–Co interfacial bonding; however, their dominant OER pathways differ fundamentally. Rapid WQ effectively suppress nanoscale grain growth and preserves Co–O–Co connectivity, favoring an adsorbate evolution mechanism. In contrast, slow FC induces lattice oxygen activation and structural relaxation, promoting a lattice-oxygen-mediated mechanism (lattice oxygen mechanism). As a result, the AEM-dominant WQ-RCWO catalyst achieves a low overpotential of 197 mV at 10 mA cm –2 in 0.5 M H 2 SO 4 and maintains stable operation for over 1000 h. This work establishes quenching-driven heterostructure engineering as an effective strategy for selective OER pathway control in acidic electrocatalysis.