Ferromagnetic-Interaction-Induced Spin Symmetry Broken in Ruthenium Oxide for Enhanced Acidic Water Oxidation

In the quest to overcome the sluggish kinetics of the oxygen evolution reaction (OER)─a bottleneck in electrochemical water splitting─the mismatched spin quantum numbers between diamagnetic OH–/H2O and paramagnetic triplet-state O2 are identified as one of key impediments. These insights underpin the development of feasible strategies for crafting electrocatalysts with enhanced intrinsic OER performance via electron spin regulation. However, prominent acidic OER catalysts (e.g., RuO2, IrO2) employed in proton exchange membrane water electrolyzer (PEMWE) present a challenge in manipulating the electron spin configuration of active sites due to their nonferromagnetic nature. Here, we introduced a spin-symmetry-breaking strategy to alter the electron spin configuration of Ru4+ ions through the synthesis of Mn1–xRuxO2 metal oxide solid solution. By enhancing the ferromagnetic interactions between Ru4+ and Mn3+ ions, the spin density distribution of Ru4+ transforms from symmetric to asymmetric structure, thereby not only boosting the catalytic activity but also enhancing electrochemical stability. The optimized Mn0.4Ru0.6O2 reveals a low overpotential of 196 mV at 10 mA cm–2 and a sustained performance of over 120 h. And the Mn0.4Ru0.6O2-based PEMWE achieved 1.62 V at 1 A cm–2 with promising stability. This work paves the way for the strategic design of acidic OER electrocatalysts through spin-state configuration regulation.