Strain-Triggered Distinct Oxygen Evolution Reaction Pathway in Two-Dimensional Metastable Phase IrO2via CeO2Loading

A strain engineering strategy is crucial for designing a high-performance catalyst. However, how to control the strain in metastable phase two-dimensional (2D) materials is technically challenging due to their nanoscale sizes. Here, we report that cerium dioxide (CeO2) is an ideal loading material for tuning the in-plane strain in 2D metastable 1T-phase IrO2(1T-IrO2) via an in situ growth method. Surprisingly, 5% CeO2loaded 1T-IrO2with 8% compressive strain achieves an overpotential of 194 mV at 10 mA cm–2in a three-electrode system. It also retained a high current density of 900 mA cm–2at a cell voltage of 1.8 V for a 400 h stability test in the proton-exchange membrane device. More importantly, the Fourier transform infrared measurements and density functional theory calculation reveal that the CeO2induced strained 1T-IrO2directly undergo the *O–*O radical coupling mechanism for O2generation, totally different from the traditional adsorbate evolution mechanism in pure 1T-IrO2. These findings illustrate the important role of strain engineering in paving up an optimal catalytic pathway in order to achieve robust electrochemical performance.