Taming Complexity: Structural and Electronic Evolution of Copper Indium Oxide Under CO2 Hydrogenation Via Multi-Method X-ray Characterization

Abstract Transition metal-containing indium oxides exhibit structural flexibility and catalytic activity, yet their dynamic local transformations remain difficult to track. Here, by combining operando X-ray absorption spectroscopy experiments in hard and soft X-ray ranges with ab initio simulations, advanced spectroscopic analysis, and synchrotron-based X-ray diffraction, we tackle the challenging problem of revealing the local structure of the in situ formed Cu centers in the Cu–In–O system under CO2 hydrogenation conditions. Our approach provides a comprehensive picture of complex and interlinked processes taking place in doped oxide catalysts. In particular, we show that Cu, initially present as atomically dispersed Cu(II) species in an amorphous oxide environment, undergoes reduction and structural reorganization, forming a heterogeneous Cu–In alloy under reaction conditions. Moreover, this study demonstrates both, the analytical power as well as the intrinsic limitations of advanced XAS methods in disentangling the structural complexity of multicomponent oxide systems.