Operando HERFD-XANES and surface sensitive Δμ analyses identify the structural evolution of copper(II) phthalocyanine for electroreduction of CO2

Abstract The quantitative understanding of how atomic-level catalyst structural changes affect the reactivity of the electrochemical CO2 reduction reaction is challenging. Due to the complexity of catalytic systems, conventional in situ X-ray spectroscopy plays a limited role in tracing the underlying dynamic structural changes in catalysts active sites. Herein, operando high-energy resolution fluorescence-detected X-ray absorption spectroscopy was used to precisely identify the dynamic structural transformation of well-defined active sites of a representative model copper(II) phthalocyanine catalyst which is of guiding significance in studying single-atom catalysis system. Comprehensive X-ray spectroscopy analyses, including surface sensitive Δμ spectra which isolates the surface changes by subtracting the disturb of bulk base and X-ray absorption near-edge structure spectroscopy simulation, were used to discover that Cu species aggregated with increasing applied potential, which is responsible for the observed evolution of C2H4. The approach developed in this work, characterizing the active-site geometry and dynamic structural change, is a novel and powerful technique to elucidate complex catalytic mechanisms and is expected to contribute to the rational design of highly effective catalysts.