Switchable Acidic Oxygen Evolution Mechanisms on Atomic Skin of Ruthenium Metallene Oxides

RuO₂ has been considered as a promising, low-cost, and highly efficient catalyst in the acidic oxygen evolution reaction (OER). However, it suffers from poor stability due to the inevitable involvement of the lattice oxygen mechanism (LOM). Here, we construct a unique metallene-based core-skin structure and unveil that the OER pathway of atomic RuO₂ skin can be regulated from the LOM to an adsorbate evolution mechanism by altering the core species from metallene oxides to metallenes. This switch is achieved without sacrificing the number of active sites, enabling Pd@RuO₂ metallenes to exhibit outstanding acidic OER activity with a low overpotential of 189 mV at 10 mA cm^-2, which is 54 mV lower than that of the counterpart PdO@RuO₂ metallenes. Additionally, they also exhibit robust stability with negligible activity decay over 100 h at 50 mA cm^-2, outperforming most reported RuO₂-based catalysts. Multiple spectroscopic analyses and theoretical calculations demonstrate that the Pd-metallene core, acting as an electron donor, increases the migration energy of subsurface oxygen atoms and optimizes the adsorption energy of intermediates on the active Ru sites, enabling a switch in the reaction mechanism. Such a unique metallene-based core-skin structure offers a novel way for tuning the catalytic behaviors of electrocatalysts.