Description:
Active and highly stable OER electrocatalyst for PEM-based water electrolysis are currently in high demand. Herein, we report a rutile iridium-titanium oxide solid solution (IrTiO x ) through a facile one-step annealing of a Ti-based metal-organic framework precursor. The composite exhibits excellent OER activity and stability in acidic media, with a low overpotential of 296 mV at 10 mA cm -2 while the OER activity was gradually enhanced during a 100-h galvanostatic stability test at a constant current of 10 mA cm -2 in 0.5 M H 2 SO 4 , outperforms the state-of-the-art IrO 2 -based electrocatalysts. We further demonstrate the structure evolution of iridium-titanium oxide during OER operations. In contrast to the initial uniform distribution of Ir and Ti over the entire architecture, after OER stability test, a core-shell like morphology with two separate rutile IrO 2 and TiO 2 phases are formed, in which the particle surface is covered with an IrO x -rich layer and entire particle became hollow. We ascribed the structure evolution to the Ti leaching and metal ion diffusion via Kirkendall effect under the electrochemical conditions. We propose that the structure evolution of iridium-titanium oxide during the electrochemical process is responsible for the gradually enhanced OER activity of IrTiO x