Ultrathin Carbon Coating and Defect Engineering Promote RuO₂ as an Efficient Catalyst for Acidic Oxygen Evolution Reaction with Super-High Durability

Developing acid-stable electrocatalysts with high activity for the oxygen evolution reaction (OER) is of paramount importance for many energy-related technologies. This work reports that ultrathin nitrogen-doped carbon coated oxygen-vacancy (Vo·) rich RuO₂ nanoparticles on carbon nanotubes (CNTs) (NC@Vo·-RuO₂/CNTs-350), synthesized through the controlled calcination in air, is an efficient acid-stable electrocatalyst for the OER. It only needs an overpotential of 170.0 mV to drive 10.0 mA cm⁻² and shows excellent stability with no distinguishable activity loss observed for >900 h. Its mass activity is >110 times higher than the commercial RuO₂. In particular, an electrolyzer assembled with this catalyst shows a record-low cell voltage of 1.45 V to deliver 10.0 mA cm⁻² and exhibits a low performance drop for >1000 h. The NC@Vo·-RuO₂/CNTs-350 also shows super-high catalytic activities and excellent stabilities for OER in neutral and alkaline media. DFT calculations indicate that its high catalytic activity mainly arises from the strong electronic coupling between RuO₂ and NC/CNTs, which increases the oxidation state and catalytic activity of Ru at the active site and improves the stabilities of lattice oxygen and surface Ru during the OER processes. The presence of Vo· can strengthen the electronic coupling between RuO₂ and NC/CNTs.