MOCVD-Loading of Mesoporous Siliceous Matrices with Cu/ZnO: Supported Catalysts for Methanol Synthesis

摘要

The Cu/ZnO system is the basis of industrial methanol synthesis and an important component of fuel-cell technology. Furthermore, it is a prototype for the exploration of synergistic metal-support interactions in heterogeneous catalysis. Recently, high-resolution in situ TEM studies revealed dynamic structural changes of copper nanocrystallites (2-3 nm) deposited onto ZnO, which depended on the redox potential of the gas phase. The reducing conditions (H_2/CO) of methanol synthesis lead to a flattening of the copper particles which increases the coverage of the ZnO support. A positive correlation between the microstructural strain of ZnO-supported copper nanoparticles and catalytic activity has been described. The promotion of Cu(111) surfaces with zinc reveals that the formation of Cu/Zn alloys is also of importance. A common motif in discussion is the presence of CuZnOx species at the Cu/ZnO interface, which is in agreement with recent theoretical studies. These findings inspired us to look for new strategies in the synthesis of the catalysts, which allow a molecular control of the Cu/ZnO interface and offer new possibilities to its maximization.