Triggering the Direct Oxygen Coupling at the Au/RuO₂ Heterointerface to Enhance the Oxygen Evolution Reaction in Acid

Water electrolysis is a sustainable way to produce green hydrogen using renewable electricity. However, overcoming the sluggish kinetics of the oxygen evolution reaction (OER) at the anode is still a challenge. The OER performance of RuO₂ is limited by the linear scaling relationship imposed by the conventional adsorbate evolution mechanism (AEM). As a proof of concept, it is shown that sputtering a network-like Au layer on top of RuO₂ triggers an unexpected direct oxygen coupling pathway at the heterointerface to lower the energy barrier, thereby reducing the OER overpotential in acid. Combining the experimental and theoretical investigations, it is proven that the oxygen (O) species formed on the Au surface via redox processes can couple with another terminal O on the RuO₂ surface. The formation of the key Au-OO-Ru intermediate is evidenced by the cation inhibition effect and the detection of ³⁴O₂ from an ¹⁸O-labelling experiment. This work demonstrates the direct oxygen coupling at the heterointerface active sites, which not only extends the design principle for OER catalysts in acid, but also deepens the understanding of manipulating the OER pathway.