Surface Reconstruction for Forming the [IrO₆]–[IrO₆] Framework: Key Structure for Stable and Activated OER Performance in Acidic Media
2021
Ma, Cheng-Long | Wang, Zhi-Qiang | Sun, Wei | Cao, Li-Mei | Gong, Xue-Qing | Yang, Ji
The surface reconstruction of iridium-based derivatives (AₓIryOz) was extensively demonstrated to have an excellent oxygen evolution reaction (OER) performance in an acidic medium. It is urgent to use various spectroscopy and computational methods to explore the electronic state changes in the surface reconstruction process. Herein, the underestimated Lu₂Ir₂O₇ was synthesized and investigated. Four typical forms of electrochemistry impedance spectra involved in the reconstruction process revealed three dominating forms of reconstructed pyrochlore in the OER stage, including the inner intact pyrochlore, mid metastable [IrO₆]–[IrO₆] framework, and the outer collapse amorphous layer. The enhancing electron transport efficiency of the corner-shared [IrO₆]–[IrO₆] framework was revealed as a critical role in acidic systems. The density of state (DOS) for the constructed [IrO₆]–[IrO₆] framework corroborated the enhancement of Ir–O hybridization and the downshift of the d-band center. Additionally, we contrast the pristine and reconstruction properties of the Pr₂Ir₂O₇, Eu₂Ir₂O₇, and Lu₂Ir₂O₇ in alkaline and acidic media. The DOS and the XANES results reveal the scale relationship between the O 2p band center and the intrinsic activity for bulk pyrochlore in alkaline media. The highest O 2p center and the highest Ir–O hybridization of Lu₂Ir₂O₇ exhibited the best OER performance among the Ir-based pyrochlore, up to a ninefold improvement in Ir-mass activity compared to IrO₂. Our findings emphasize the electrochemical behavior of the reconstruction process for activated water-splitting performance.
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