CoO_x clusters-decorated IrO₂ electrocatalyst activates NO₃^- mediator for benzylic C-H activation

Electrochemical conversion of petrochemical-derived hydrocarbons to high-value oxygenates can utilize renewable energy and reduce carbon emissions. However, this involves the challenging activation of inert C(sp³)-H bonds at room temperature. Here, we introduce an electrocatalyst:mediator assembly in which CoO_x clusters-decorated IrO₂ electrocatalyst activates NO₃^- mediator to a highly reactive radical capable of abstracting a hydrogen atom from benzylic C-H. The interface between CoO_x and IrO₂ promotes NO₃^- activation by facilitating the desorption of NO₃^● radical for subsequent reaction. Our strategy is demonstrated through the selective oxidation of toluene to benzaldehyde with high Faradaic efficiency of 86( ±1)% at 25 mA/cm², a factor of >3 times higher than the bare electrocatalyst. The electrocatalyst:mediator assembly is operated stably for 100 h, with minimal decline in performance. When translated into a flow system, a Faradaic efficiency of 60( ±4)% at 200 mA/cm² was achieved.