Synthesis of silica supported AuCu nanoparticle catalysts and the effects of pretreatment conditions for the CO oxidation reaction

Abstract

Supported gold nanoparticles have generated an immense interest in the field of catalysis due to their extremely high reactivity and selectivity. Recently, alloy nanoparticles of gold have received a lot of attention due to their enhanced catalytic properties. Here we report the synthesis of silica supported AuCu nanoparticles through the conversion of supported Au nanoparticles in a solution of Cu(C(2)H(3)O(2))(2) at 300 °C. The AuCu alloy structure was confirmed through powder XRD (which indicated a weakly ordered alloy phase), XANES, and EXAFS. It was also shown that heating the AuCu/SiO(2) in an O(2) atmosphere segregated the catalyst into a Au-CuO(x) heterostructure between 150 °C to 240 °C. Heating the catalyst in H(2) at 300 °C reduced the CuO(x) back to Cu(0) to reform the AuCu alloy phase. It was found that the AuCu/SiO(2) catalysts were inactive for CO oxidation. However, various pretreatment conditions were required to form a highly active and stable Au-CuO(x)/SiO(2) catalyst to achieve 100% CO conversion below room-temperature. This is explained by the in situ FTIR result, which shows that CO molecules can be chemisorbed and activated only on the Au-CuO(x)/SiO(2) catalyst but not on the AuCu/SiO(2) catalyst.

Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments

“…After 100 min of reaction, the 0.7% Au/SBA-15-CeO 2 catalyst showed high catalytic activity (100% lactose conversion) and a 100% selectivity towards LBA, when it was used at a catalyst/lactose ratio of 0.2 under alkaline (pH 9.0) and mild reaction temperature (65 °C). [129,[133][134][135][136][137][138][139] and bimetallic [140][141][142][143] gold catalysts supported amorphous SiO 2 , as well as for the preparation of Au/SiO 2 -based catalysts [136], has demonstrated that amorphous silica can be also employed as a support to prepare active Au/SiO 2 catalysts. Although this synthesis method has not been intensively investigated, it can be regarded as highly efficient for the preparation of gold catalysts supported on MSM.…”

Understanding the synergistic effects of gold bimetallic catalysts

“…Based on the chemical properties of the second metal, we can classify gold-based bimetallic catalysts into two types. The first type is Au-BM catalysts, where BM refers to base metals such as Cu [21][22][23][24][25][26], Ag [27][28][29][30][31][32][33][34][35], Co [36][37][38], and Ni [39][40][41], and the second type is Au-PGM catalysts, where PGM refers to platinum group metals such as Pt [42,43], Pd [44][45][46][47], Rh [48], and Ir [49]. This classification may not cover all the gold bimetallic catalysts, but it will facilitate understanding the synergistic effect between gold and the second metal in catalysis.…”

Evolution of surface of Pd-Rh bimetallic nanocubes and its correlation with CO oxidation

“…What's more, pretreatments of catalysts, i.e., activation procedures which usually are conducted before the catalytic evaluations, can significantly influence their overall performances [21][22][23][24]. Hence, an "appropriate" activation method will lead to an optimal property of a catalyst.…”