Cold Plasma for Synthesizing High Performance Bimetallic PdCu catalysts: Effect of Reduction Sequence and Pd/Cu Atomic Ratios

Alumina supported bimetallic PdCu catalysts were prepared by simple incipient wetness impregnation followed by the process of atmospheric-pressure cold plasma reduction using Pd(NO₃)₂ and Cu(NO₃)₂ as Pd and Cu precursors, respectively. The influence of reduction sequence and Pd/Cu atomic ratios on the structure and performance of the catalysts were investigated. The highest CO oxidation activity was obtained for the PdCu catalyst (PdCu/Al₂O₃–P) prepared by co-impregnation and reduction of the Pd and Cu precursors with a Pd/Cu atomic ratio of 1:1. Meantime, the PdCu/Al₂O₃–P catalyst prepared by cold plasma exhibits much higher performance than that prepared by conventional thermal reduction. The optimum results from the alloying degree, crystallite size and dispersion of PdCu nanoparticles, and the chemisorbed oxygen species on the surface of the support. As a result of the interaction between Pd and Cu species, high alloying degree, small size and high dispersion of PdCu nanoparticles in PdCu/Al₂O₃–P were obtained. In addition, due to the fast (6 min reduction) and low temperature reduction process, more active chemisorbed oxygen species were formed on the surface of PdCu/Al₂O₃–P. The results of diffuse reflectance fourier transform infrared and catalytic stability show that the interaction between Pd and carbon species is weakened, which may facilitate the adsorption and activation of O₂. These make PdCu/Al₂O₃–P an excellent catalyst for CO oxidation. Atmospheric-pressure cold plasma is proved to be a facile and efficient method for fabricating high performance bimetallic PdCu catalysts, which may have potential applications for preparing other bimetallic catalysts.