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 H-2 and H2O moisture behaving a hydrogen isotope effect by H-2/D-2 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 (C) 2010 Elsevier B V All rights reserved