Chirality Induced Operando Probing of Analyte-Surface Hybrid States in Heterogeneous Redox Processes

Abstract

Surface redox processes in sensing and heterogeneous catalysis usually proceed via synergistic overlap of charge density clouds between reactant and surface species. The intricate quantum environment of interacting molecular orbitals gives rise to quasi-hybrid surface states which eventually determine the catalytic reaction pathways. While this crucial aspect has been investigated primarily using theoretical models, so far, no experimental methodologies have been reported that provide an operando perspective of such mechanistic processes. Here we introduce an optical chirality-induced operando Raman approach that facilitates real-time monitoring of electron-exchange mechanisms in hybrid p-p orbital states, with a polarity-resolved Stark tuning rate of 2.5 cm^-1 per kV/cm. As illustrated by a multi-technique operando investigation of hybrid Au_CuO_δ (δ<1) based NO₂ sensors, the preferential filling of degeneracy-broken π* 2px and π* 2py orbitals in NO₂ with p orbitals of surface hydroxyl species under varying perturbative conditions has been identified by 14%→25% variation in intensity of circular polarization under electric field-dependent surface-light interactions. First-principles calculations were employed to corroborate the experimental findings by introducing polarity-dependent first-order perturbation to hybrid NO₂-OH states under chemisorbed conditions. The above approach is expected to boost understanding of electron exchange mechanisms in heterogeneous processes, enabling the strategic design of sensors and catalysts.