Unsupported powdered gold

Nevertheless, unsupported powdered gold (mean diameter, 76 nm) proved to be active for CO oxidation [138,139], and so did naked gold [140] and gold nanotubes [141] under mild conditions. In addition, investigations by Flytzani-Stephanopoulos and co-workers [142-144] on the water-gas shift (WGS) reaction (see Sect. 6.4.1) have challenged the idea that gold nanoparticles are essential, but these investigators have not exhaustively proved the complete absence of Au(0). 

Although unsupported powdered gold (mean diameter 76 nm) is active for CO oxidation [138,139], most of the studies made by Haruta and other groups have been on supported gold catalysts, often using Ti02 which is considered a very active support [3,5,31,32,34,43,44,49,62,71,75,99,110,111,137-139,155,... 

Y. lizuka, T. Tode, T. Takao, K. Yatsu, T. Takeuchi, S. Tsubota, and M. Haruta, A kinetic and adsorption study of CO oxidation over unsupported fine gold powder and over gold supported on titanium dioxide, J. Catal. 187(1), 50-58 (1999). 

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