Uncovering strain-induced mechanistic divergence of the oxygen evolution reaction on RuO₂

Regulating internal strain offers a powerful yet underexplored route to tune catalytic activity in the oxygen evolution reaction (OER). Here, we establish a proof-of-concept that internal compressive strain in RuO₂ boosts OER performance by modulating lattice oxygen reactivity. From both geometric and electronic perspectives, the influence of internal strain on the competition between the two mechanisms of OER, adsorbate evolution mechanism (AEM) and the lattice oxygen mechanism (LOM), is systematically investigated. Experimentally, a wet-chemical strategy is developed to manipulate the thermogravimetric properties of the Ru(OH)_x precursor, inducing preferential growth along the [002] direction at reduced temperatures during the crystallization process of RuO₂. The insufficient lateral relaxation leads to the formation of single-crystalline nanocone structures with built-in compressive strain. As a result, the strained RuO₂ exhibits a 4.6-fold enhancement in mass activity compared to its unstrained counterpart. Operando Raman and in situ ATR-FTIR spectroscopy, together with molecular probe experiments, reveal a strain-enhanced participation of lattice oxygen during the reaction. These findings establish internal strain as a key regulator of lattice oxygen chemistry and highlights crystallization-mediated strain engineering as an effective route towards advanced OER electrocatalysts.