Au–Cu alloy nanoparticles supported on silica gel as catalyst for CO oxidation: Effects of Au/Cu ratios

Au–Cu bimetallic catalysts with Au/Cu ratios ranging from 3/1 to 20/1 were prepared on silica gel support by a two-step method. The catalysts were characterized by ICP, XRD and TEM. The results showed that, irrespective of Au/Cu ratios, all the bimetallic nanoparticles had significantly reduced particle sizes (3.0–3.6 nm) in comparison with monometallic gold catalysts (5.7 nm). Both CO oxidation and PROX reactions were employed to evaluate the catalytic activities of Au–Cu bimetallic catalysts. For CO oxidation, the alloy catalysts show non-monotonic temperature dependence showing a valley in the intermediate temperature range. The catalyst with Au/Cu ratio of 20/1 gave the highest activity at room temperature, but its activity showed the deepest valley with increasing the reaction temperature. On the other hand, the catalyst with Au/Cu ratio of 3/1 exhibited the best performance for PROX reaction. For the Au/Cu ratios investigated, the bimetallic catalysts showed superior performance to monometallic gold catalysts, demonstrating the synergy between gold and copper.