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

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 Ir content while maintaining high electrocatalytic performance. Herein, an effective strategy of tailoring IrO2@TiN1+x nano-heterojunction by defects is reported aiming at enhancing intrinsic oxygen evolution reaction (OER) activity of IrO2 at a low Ir amount. A remarkable OER activity under acid solution is achieved for IrO2@TiN1+x with 7.3 times of mass activity and 1.8 times of specific activity relative to IrO2, respectively. As anode electrode in a PEM single cell, IrO2@TiN1+x also reveals the optimal activity with 1.916 V at 2 A cm-2, which is lower 57 mV and 130 mV than that of IrO2@TiN and IrO2. Meantime, the IrO2@TiN1+x electrode manifests good stability at 1 A cm-2 for 100 h. Electrochemical characterization analysis and DFT calculation results demonstrate that the increase of active sites and the modulating electronic interaction between IrO2 and TiN1+x, which could multiply active sites and accelerate the OER kinetics of IrO2. Thus, the IrO2@TiN1+x nano-heterostructure reveals superior electrocatalytic performance and good stability at a low Ir content.