Generating Active Metal/Oxide Dynamic Interface through Triggering Hydroxyl Reverse Spillover for High-Performing Proton Exchange Membrane Electrolyzers

Monitoring the reconstruction of atomic and electronic structure of the reaction interface under realistic working conditions remains a significant challenge in achieving highly efficient acidic oxygen evolution (OER). Herein, we introduce a bias-induced activation strategy to modulate in situ catalyst leaching and trigger hydroxyl reverse spillover on the IrO x /SrTiO 3– x catalyst for enhanced OER performance. Through extensive operando measurements including X-ray absorption spectroscopy (XAS), differential electrochemical mass spectrometry (DEMS), and X-ray photoelectron spectroscopy (XPS) combined with OH radical quenching experiment, we confirm the involvement of a reverse OH spillover mechanism in the OER process. The bias-induced Sr leaching facilitates the formation of lattice oxygen-mediated hydroxyl radical species (OH*), which accumulate at the Ti–O–Ir interface and promote the OH spillover. The reverse spillover of lattice OH facilitates a reaction pathway that bypasses the conventional scaling relationships, enhancing catalytic efficiency. Moreover, the Ti–O–Ir interface stabilizes IrO x by maintaining Ir sites at lower oxidation states, even under challenging high-potentials, ensuring long-term stability. As a result, the optimized IrO x /SrTiO 3– x catalyst demonstrates exceptional performance in scalable water electrolyzers, requiring only 2.003 V to attain 3 A cm –2 (close to the DOE 2025 target), and showing no activity decay during an 800 h test at 1 A cm –2 . This reverse lattice oxygen spillover mechanism offers an insight into engineering catalytic properties beyond conventional OER design principles, particularly in surface redox chemistry, and opens pathways for highly efficient, durable electrochemical energy conversion systems.