Investigation of Role of Oxobridge in the Immobilized Dinuclear Ir Complex for Electrochemical Oxygen Evolution Reacton by In Operando Raman Spectroscopy

Since the mechanism of metal oxide electrocatalysts has been numerously researched, mainly two mechanisms are known; adsorbate evolution mechanism and lattice oxygen participating mechanism. Especially, the lattice participating mechanism allows faster OER kinetics than that of the adsorbate mechanism, but its also induces deactivation of metal oxide during OER. In metal oxide, the dangling metal atoms will eventually be dissolved, and the stability is limited. Therefore, we focus the metal-ligand complex on overcoming the trade-off relationship of metal oxide catalyst. In-operando Raman spectroscopy, we observe the cleavage/regeneration of <i>μ</i>–O bridges between two Ir complex centers of our Ir dinuclear complex, which is immobilized on conducting supporter. In particular, our self-design electrochemical cell for in-opernado Raman spectroscopy allows to obtain Raman spectra under very similar operation conditions (current density vs. applied potential during Raman spectroscopy measurement). Also, this technique does not require specific substrates (such as Au or etc.) to enhance the signal to ratio like surface-enhanced Raman spectroscopy (SERS). Although oxygen atoms in the oxo bridge is released during OER, the dissolution of Ir atom was limited due to strong ligand bonding. The metal complex, [Ir(dmimd)(OH)(H₂O)(<i>μ</i>-O)]₂²⁺, immobilized catalytic electrode shows one of the best electrochemical activities among organometal complex-OER catalysts. The role of <i>μ</i>–oxo bridges in the Ir complexes was investigated by in-operando Raman spectroscopy during the OER through, and it is concluded that the dinuclear structure with oxo bridge is a key structure for both excellent electrochemical activity and stability.