Platinum-Like Catalytic Behavior of Au+

The catalytic properties of gold catalysts leached with sodium cyanide solutions were investigated for the propylene epoxidation reaction with H-2/O-2 mixtures. Unexpectedly, the selectivity of the Au/TS-1 catalysts changed from propylene oxide to propane as a result of the cyanide treatment. Measurements by in situ X-ray absorption spectroscopy at in situ reaction conditions demonstrated that the active catalyst before leaching consisted of gold in the zero-valent state, while after the cyanide treatment had gold in the Au+ state. Examination of the catalysts by high resolution transmission electron microscopy revealed the formation of precipitates of a material with lattice spacings corresponding to Na[Au(CN)(2)]. It is found that leaching with cyanide does not result in positively-charged gold ions substituting in cation vacancies, as previously thought, but instead produces a gold(I) cyanide precipitate with catalytic hydrogenation properties typical of platinum. These results explain previously reported findings on highly dispersed gold nanoparticles, in which the peripheral atoms are positively charged.