Defects tailoring IrO2@TiN1+x nano-heterojunctions for superior water oxidation activity and stability

Abstract

Developing cost-effective Ir-based anode catalysts for proton exchange membrane (PEM) water electrolysis has been recognized as an efficient and pragmatic approach; however, many challenges remain to lower the Ir content while maintaining high electrocatalytic performance. Herein, an effective strategy of tailoring IrO₂@TiN_1+x nano-heterojunctions by defects is reported, aiming at enhancing the intrinsic oxygen evolution reaction (OER) activity of IrO₂ at a low Ir amount. A remarkable OER activity in an acidic solution is achieved for IrO₂@TiN_1+x with 7.3 times of mass activity and 1.8 times of specific activity relative to IrO₂. As the anode electrode in a PEM single cell, IrO₂@TiN_1+x also reveals the optimal activity with 1.916 V at 2 A cm⁻², which is 57 mV and 130 mV lower than that of IrO₂@TiN and IrO₂, respectively. Meantime, the IrO₂@TiN_1+x electrode manifests good stability at 1 A cm⁻² for 100 h. Electrochemical characterization analysis and DFT calculation results indicate that the increase in the number of active sites and the modulating electronic interaction between IrO₂ and TiN_1+x could multiply the active sites and accelerate the OER kinetics of IrO₂. Thus, the IrO₂@TiN_1+x nano-heterostructure reveals superior electrocatalytic performance and good stability at a low Ir content.