Toward Efficient Cerium Utilization in Sustainable CO-PROX Catalysts: Interfacial Engineering of Cu-Ce on SrTiO3

Designing sustainable catalysts requires maximizing atom efficiency while minimizing the use of critical raw materials. Driven by this challenge, the CuOx-CeO2 active phase was constructed on morphology-controlled SrTiO3 nanocubes using a low lanthanide loading (2, 4, and 8 Ce wt %). The catalysts were tested on the CO preferential oxidation in H2-rich streams (CO-PROX) and compared to a CuO/CeO2 reference. Advanced STEM characterization in combination with H2-TPR analyses revealed that Cu-based species increase their dispersion with increasing ceria loadings, thereby enhancing CuOx-CeO2 interfacial sites. This higher density of interfacial sites is associated with a larger population of Cu+ active centers involved in CO oxidation, thereby enhancing catalytic performance. The optimized catalyst containing only 8 wt % Ce closely matches the conversion of CuO/CeO2 up to 200 °C. However above this temperature the behavior diverges, accompanied by a significant decrease in activity. Further insight about the CuOx-CeO2 interface and the formation of Cu+ active sites promoted by increasing ceria loadings was obtained from XPS and DRIFTS measurements. These techniques suggest that the electronic state of ceria remains unaffected by the SrTiO3 support, while subtle changes in selectivity may also be influenced, in addition to ceria loading, by the crystallographic nature of the lanthanide nanostructure. Furthermore, in situ and identical-location STEM experiments reveal that copper species dynamically redisperse under reducing conditions without compromising catalytic performance. This work demonstrates that catalytic performance can be tuned through the rational design of nanointerfaces, providing a route toward atom-efficient catalysts with reduced critical raw material incorporation.