Redox processen in polynary copper oxides and copper oxide / mesoporous silica composites

摘要

Dynamic redox processes in different complex copper oxides and oxide / mesoporous silica composites are characterized. In the spinel-type Cu_xMn_(3-x)O_4 the atomic and electronic structures are described with respect to the reversible process Cu~(2+) + Mn~(3+) <->Cu~(1+) + Mn~(4+), the crucial dynamic equilibrium for the catalytic oxidation of CO to CO_2 at ambient temperatures. A comparison with the perovskite-type LaCu_(1-x)Mn_xO_(3-#delta#) is presented. In the K_2NiF_4-type La_(2-x)Sr_xCu_(1-y)Ru_yO_(4-#delta#) the electronic structure is characterized with respect to the equilibrium Cu~(2+) + Ru~(5+) <->Cu~(3+) + Ru~(4+). Analogous redox processes are characterized in composite compounds made up of copper oxides inserted in mesoporous MCM-type silica. Due to their structural order in the nanoscopic range, the investigation of these materials required multiple, complementary characterization methods, i.e. X-ray diffractometry, thermal analysis, scanning and transmission electron microscopy, magnetic measurements, XPS, and particularly X-ray absorption spectroscopy (EXAFS / XANES) measurements.