Effect of ceria surface modification on Au/TiO2 and Au/YSZ catalysts for the preferential oxidation of CO

• Novel insights into CO-PROX catalyst performance revealed through advanced operando DRIFTS and electron microscopy. • Ceria nanostructure modification significantly expands the operational temperature window of Au/TiO 2 and Au/YSZ catalysts. • Findings contribute to the design of more efficient and stable CO-PROX catalysts for PEM-FC applications. The development of efficient catalysts for CO preferential oxidation (CO-PROX) is crucial for H 2 purification in PEMFC technologies. While Au nanoparticles show high activity for low-temperature CO oxidation, their selectivity toward H 2 oxidation often decreases at higher temperatures. Modulating the metal-support interaction is key to achieving optimal catalytic performance and stability. Here, we investigate the effect of surface modification with ceria (CeO 2 ) nanostructures on Au/TiO 2 (reducible) and Au/YSZ (non-reducible) catalysts. Although the addition of ceria leads into a decrease in the number of active sites (evidenced by metal dispersion and DRIFTS experiments), it boosts CO conversion and selectivity at elevated temperatures, effectively shifting and broadening the optimal operating window to ranges suitable for high-temperature PEMFCs. A comprehensive characterization using STEM and DRIFTS reveals that ceria’s promotional role is highly dependent on the underlying oxide support, influencing both the ceria nanostructure and the electronic properties of the gold nanoparticles, which dictates the overall reaction pathway and catalyst stability. This work provides crucial insight for tailoring Au-based catalysts for diverse CO-PROX operational requirements.