Interface engineering breaks both stability and activity limits of RuO 2 for sustainable water oxidation.

Designing catalytic materials with enhanced stability and activity is crucial for sustainable electrochemical energy technologies. RuO 2 is the most active material for oxygen evolution reaction (OER) in electrolysers aiming at producing 'green' hydrogen, however it encounters critical electrochemical oxidation and dissolution issues during reaction. It remains a grand challenge to achieve stable and active RuO 2 electrocatalyst as the current strategies usually enhance one of the two properties at the expense of the other. Here, we report breaking the stability and activity limits of RuO 2 in neutral and alkaline environments by constructing a RuO 2 /CoO x interface. We demonstrate that RuO 2 can be greatly stabilized on the CoO x substrate to exceed the Pourbaix stability limit of bulk RuO 2 . This is realized by the preferential oxidation of CoO x during OER and the electron gain of RuO 2 through the interface. Besides, a highly active Ru/Co dual-atom site can be generated around the RuO 2 /CoO x interface to synergistically adsorb the oxygen intermediates, leading to a favourable reaction path. The as-designed RuO 2 /CoO x catalyst provides an avenue to achieve stable and active materials for sustainable electrochemical energy technologies.