Thermal CO Oxidation and Photocatalytic CO(2) Reduction over Bare and M-Al(2)O(3) (M = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) Cotton-Like Nanosheets

Aluminum oxide (Al(2)O(3)) has abundantly been used as a catalyst, and its catalytic activity has been tailored by loading transition metals. Herein, γ-Al(2)O(3) nanosheets were prepared by the solvothermal method, and transition metals (M = Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au) were loaded onto the nanosheets. Big data sets of thermal CO oxidation and photocatalytic CO(2) reduction activities were fully examined for the transition metal-loaded Al(2)O(3) nanosheets. Their physicochemical properties were examined by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, and X-ray photoelectron spectroscopy. It was found that Rh, Pd, Ir, and Pt-loading showed a great enhancement in CO oxidation activity while other metals negated the activity of bare Al(2)O(3) nanosheets. Rh-Al(2)O(3) showed the lowest CO oxidation onset temperature of 172 °C, 201 °C lower than that of bare γ-Al(2)O(3). CO(2) reduction experiments were also performed to show that CO, CH(3)OH, and CH(4) were common products. Ag-Al(2)O(3) nanosheets showed the highest performances with yields of 237.3 ppm for CO, 36.3 ppm for CH(3)OH, and 30.9 ppm for CH(4), 2.2×, 1.2×, and 1.6× enhancements, respectively, compared with those for bare Al(2)O(3). Hydrogen production was found to be maximized to 20.7 ppm during CO(2) reduction for Rh-loaded Al(2)O(3). The present unique pre-screening test results provided very useful information for the selection of transition metals on Al(2)O(3)-based energy and environmental catalysts.