Preferential CO oxidation in a H2-rich gas by Au/CeO2 catalysts: Nanoscale CeO2 shape effect and mechanism aspect

The Au/CeO2 catalysts with nanoscale CeO2 shapes of rods, cubes and polyhedra were evaluated for the CO preferential oxidation (CO-PROX) in a hydrogen-rich gas, showing a strong effect of CeO2 morphology followed by this order: rods > polyhedra > cubes. The results of pulse experiment and kinetic study indicated that the oxidation of CO could be enhanced by H2 and H2O moisture, behaving a hydrogen isotope effect by H2/D2. The catalyst Au/CeO2-rods exhibited the lowest apparent activation energy for the CO oxidation either with or without hydrogen in comparison with the Au/CeO2-polyhedra and Au/CeO2-cubes. It was proposed that hydrogen reacted with adsorbed oxygen to yield highly oxidizing surface H-containing intermediates that could readily converted CO to CO2 at lower temperatures. The generation of such key intermediates might be involved into the rate-determining step.