Friction-assisted electrochemical oxidation of iridium surfaces for enhanced catalysis

Iridium oxide (IrO_x) has emerged as a prominent catalyst for the acidic oxygen evolution reactions (OER). However, its direct preparation on the surface of Ir is rare, severely restricting its applications in catalysis and sensing technologies. In this work, we report an innovative method to locally generate amorphous IrO_x layers on Ir surfaces through the synergistic action of friction and anodic potentials. This approach enables the rapid preparation of sub-micrometer-thick IrO_x layers within 200 s. The microscopic topography of the Ir substrate has a significant impact on local reactant surface excess. Additionally, friction lowers the surface potential required for the oxidation of Ir and also introduces defects that enhance the electrocatalytic activity of the oxide. The resulting IrO_x characterized by unique nanostructures demonstrates significant OER activity in acidic environments, significantly surpassing that of metallic Ir. These findings highlight the great potential of friction-assisted anodization for advancing micro-reactors and micro-sensor arrays.