Understanding the formation of active site in copper ceria system for carbon dioxide catalytic conversion

Abstract

Copper-based catalysts, particularly those supported by ceria (CeO₂), provide a cost-effective substitute for noble metals in hydrogenation reactions. The interaction between Cu and CeO₂ improves dispersion and generates essential active sites, such as Cu⁺ and oxygen vacancies, vital for catalytic efficiency. This study explores the creation of active sites in Cu/CeO₂ catalysts through adjustments in metal content and calcination conditions. The findings reveal that the 2 wt%Cu/CeO₂ catalyst calcined at 600 °C achieved the highest CO₂ conversion via reverse water gas shift reaction (RWGS) to CO, approximately 60 % at 600 °C, with minimal coke formation. Additionally, the catalyst also exhibited reactivity in the dry reforming of methane at elevated temperatures (above 800 °C). The characterization data suggest that the strong interaction among finely dispersed CuO and the CeO₂ support enhances electron transfer, leading to a higher density of surface oxygen vacancies and Cu⁺ species, which in turn promotes the redox cycle. The density of Cu⁺/(Cu⁺+Cu²⁺) and surface oxygen vacancy correlates very well with the synthesis conditions and catalytic activity towards CO₂ conversion. The results suggest that Cu loading and calcination temperature in Cu/CeO₂ system could significantly enhance the presence of active sites for effective CO₂ hydrogenation.