Effect of Lattice Interactions on the Structural Evolutions of Cu₂O Thin Film Model Heterostructures during Solar Energy Conversion Reactions

Metal oxide heterostructures, formed by interfacing different metal oxide crystals, are utilized in various fields. Such interfaces are typically constructed using different materials and synthesis methods, complicating the isolation of interface-specific effects when fundamental reaction processes. The present study strategically employs Cu 2 O thin films exhibiting two distinct domains formed by weak and strong thin film–substrate lattice interactions to model metal oxide heterostructures with different interfacial interactions. The crystalline and electronic structural evolutions of different domains and planes are studied during gas–solid interactions and photocatalytic energy conversions using three-dimensional (3D) reciprocal space mapping and near-ambient X-ray absorption spectroscopy (XAS). The results reveal that heterostructures with strong lattice interactions experience less pronounced changes in the crystalline and electronic structures during such reactions. The Cu 2 O {200} planes in both domains exhibit more pronounced crystalline distortions compared to the Cu 2 O {111} planes. This study introduces a novel approach to fundamentally studying metal oxide heterostructures and proposes design strategies for optimizing heterostructures used in energy harvesting and conversion applications.