Valence Modulation of CeO2/CuxO Inverse Catalysts via Crystal Plane Engineering for CO Preferential Oxidation

The CO preferential oxidation is vital for proton exchange membrane fuel cell (PEMFC) stability, and the reverse catalyst design shows promise for improving its activity and durability. Herein, cubic and octahedral Cu2O crystals were synthesized via the solid-phase method. Subsequent decoration with CeO2 yielded inverse CeO2/Cu2O catalysts, and oxidative treatment converted Cu2O to CuO, forming the final CeO2/CuO catalysts. The CeO2/Cu2O catalyst exhibits superior activity compared to CeO2/CuO, with CeO2/Cu2O-8 demonstrating the lowest complete CO conversion temperature (168 °C) and the widest operating window (168–200 °C). This enhanced performance originates from unsaturated copper sites, which facilitate faster electron transfer and oxygen vacancy formation while providing high specific surface area and elevated Ce3+ content. This study established fundamental insights for designing inverse catalysts through crystal plane engineering in CO-PROX, potentially extending to other catalytic systems requiring precise surface control.