Structure and Catalytic Performance of Pt–Cu Bimetallic Catalysts Synthesized by a Radiation-Induced Reduction Method in the Aqueous Phase: Influence of Support Material and Sulfate Ion in the Precursor

The structure of bimetallic nanoparticles has a great impact on catalytic performance. By radiation-induced reduction of metal ions in the aqueous phase, supported bimetallic Pt–Cu catalysts were synthesized with various Cu loadings, support materials, and copper sources. These parameters had a great impact on the structural properties of Pt–Cu nanoparticles. On carbon black, Pt–Cu alloy nanoparticles were readily formed with little oxide phase. On CeO2 support, Pt–Cu was highly oxidized for the low-Cu region (Cu/Pt < 1), and Pt–Cu alloy nanoparticles were formed together with CuO x for the high-Cu region (Cu/Pt > 1). The structure of CeO2-supported catalysts obtained from two different copper sources (CuSO4 and CuCl2) suggested that such a drastic change in oxidation state is the result of two competing effects, CeO2 to oxygenate metals and the sulfate ion to stabilize them in the metallic state. The reaction characteristics in preferential CO oxidation reflected the Pt–Cu structure (oxidation state) determined by those parameters in the synthesis stage. The low-Cu oxidic samples showed excellent light-off performance, which was attributed to high oxygen transport from CeO2 to metals through the metal–CeO2 interface. The high-Cu samples comprising a Pt–Cu alloy and CuO x showed excellent selectivity, which was attributed to the metal–CuO x interface predominating over metal–CeO2. The latter exhibited 100% CO conversion in a wide temperature range in excess O2 conditions.