Dimensional Regulation of Monoclinic Phase Iridium Dioxide Switches the Mechanism for Acid Water Oxidation
Sihui Pan, Hanzhuo Luo, Penghao Li, Chenchen Li, Long Chen, Wei‐Hsiang Huang, Chih‐Wen Pao, Youyong Li, Zhiwei Hu, Yujin Ji, Mingwang Shao, Qi Shao
Abstract
Abstract Electrochemical water splitting represents a promising strategy for hydrogen production, with oxygen evolution reaction (OER) being a critical half‐reaction. Iridium dioxide (IrO 2 ) is an advanced OER catalyst owing to excellent stability. However, regulating key intermediates and decreasing reaction barriers remain great challenges. Here, 2D metastable‐phase IrO 2 nanosheet (M‐IrO 2 NS) by a mixed molten salt method is reported. M‐IrO 2 NS exhibits a 3% compressive strain along the a ‐axis ( a = 4.30 Å vs 4.43 Å) compared to 1D metastable‐phase IrO 2 nanoribbon (M‐IrO 2 NR). In 0.5 M H 2 SO 4 , M‐IrO 2 NS exhibits a low overpotential of 186 mV at 10 mA cm −2 and a high mass activity of 2071.8 mA mg Ir −1 at 1.5 V versus reversible hydrogen electrode (RHE). When integrated into a proton exchange membrane water electrolysis (PEMWE), M‐IrO 2 NS maintains a current density of 2.83 A cm −2 at 1.8 V for 1600 h without degradation. Mechanistic investigations reveal a transition from adsorbate evolution mechanism (AEM) in M‐IrO 2 NR to oxide pathway mechanism (OPM) in M‐IrO 2 NS, confirmed by the Fourier transform infrared measurements, density‐functional‐theory calculations and mass spectrometry measurements. This study demonstrates the impact of dimensional regulation on optimizing the OER and provides a new platform for electrocatalyst development.