Cu-Ce-O catalyst revisited for exceptional activity at low temperature CO oxidation reaction

Abstract

In the present study, CexCu1−xO2−δ (x = 0, 0.3, 0.5, 0.8, 0.9, and 1) catalysts were synthesized using a facile and reproducible combustion method and were evaluated towards the CO oxidation (CO-OX) and CO preferential oxidation (CO-PROX) reactions as inexpensive and active catalytic materials. Pure ceria and copper oxide were compared to CexCu1−xO2−δ mixed metal oxides for benchmarking purposes. The catalysts were prepared using citric acid (C6H8O7) as fuel and nitrate salts of cerium and copper as oxidizers under fuel rich conditions. A variety of techniques including XRD, EDX, BET, SEM, Raman, XPS, H2-TPR and CO2-TPD, were used to analyze the microstructural, thermal and redox properties that may influence CO oxidation performance. A profound effect of Cu content was revealed that not only impacts the structural and redox properties of the catalysts but also affects the catalytic activity. The Ce0.8Cu0.2O2−δ catalyst presented the most promising performance among many similar (Cu-Ce-based catalysts) as well as noble supported catalysts published in the literature with T50 = 62 °C and T100 = 78 °C, an activity that coincides with the availability of labile oxygen species at low temperature (T < 100 °C) and the enhanced CO2 desorption at low temperature (low CO2-philicity) of this catalyst.