Cooperative effect of gold nanoparticles with CUS aluminium from nanoalumina support in the catalysis of an electron transfer reaction

In this paper, firstly mesoporous gamma and alpha-alumina with nanorod morphology, exhibiting high surface area (629.44 m ² g ^-1), large pore volume (2.25 cm ³ g ^-1) and pore size (140.3 ) have been synthesised by a non-surfactant-templating sol-gel method. Then, new nanocatalysts, i.e. Au-NAl350, Au-NAl550, Au-NAl750, and Au-NAl1100 were prepared by deposition of gold nanoparticles on the various synthesised nanostructured alumina supports with different physicochemical properties; surface area (20.56-629.44 m ² g ^-1), pore volume (0.63-2.25 cm ³ g ^-1) and pore size (73.88-143.76 ). Textural, morphological and structural characterisations of both nanoalumina supports and nanogold/nanoalumina catalysts were done by nitrogen physisorption, XRD, ²⁷Al MAS NMR, TEM and FTIR study of low temperature CO-adsorption. The effect of physiochemical properties of the nanoalumina supports on the structure and catalytic activity of nanogold active phase were studied in the catalytic reduction of ferricyanide to ferrocyanide by thiosulphate under three reaction temperature; 20, 40 and 60 °C. It was found that the Au-NAl550 nanocatalyst with large surface area (579 m ² g ^-1), pore volume (2.13 cm ³ g ^-1) and pore size (141.05 ) has the highest catalytic activity. The characterisation results showed that Au nanoparticles highly and uniformly dispersed on the high surface area nanoalumina support. The metallic character of the gold nanoparticles, acidity and activity of catalyst were determined by structure, acidity and texture of the nanoalumina support. It was confirmed that the reduction reaction is totally controlled by the surface properties of catalyst.