Towards understanding the role of carbon atoms on transition metal surfaces: Implications for catalysis

Gold catalysts containing interstitial carbon atoms boost hydrogenation activity

“…These results indicate that the heterolytic dissociation of H 2 by Au and C is dominant for the hydrogenation, similar to that by perimeter sites over Au/TiO 2 14 . It should be mentioned that the subsurface carbon atom on Au(111) diffuses to the surface as a result of H adsorption, in good agreement with the dynamic mobility of C atoms on transition metal (111) surfaces under working conditions of low C coverage 39 . As a result, the presence of subsurface C would facilitate the mobility of carbon in the lattice, possibly to some C-free areas of the surface 39 .…”

“…It should be mentioned that the subsurface carbon atom on Au(111) diffuses to the surface as a result of H adsorption, in good agreement with the dynamic mobility of C atoms on transition metal (111) surfaces under working conditions of low C coverage 39 . As a result, the presence of subsurface C would facilitate the mobility of carbon in the lattice, possibly to some C-free areas of the surface 39 . This would further enhance the H adsorption.…”

“…However, a continuous exchange of C atoms in Au between surface and subsurface has been reported so that a dynamic equilibrium is established. The mobility of carbon in the lattice may cause residual vacancies and in turn produce a relatively uniform lattice expansion 39 . Indeed, on one occasion an increasing concentration of CH 4 was fed into the furnace, and graphene sheets were formed and covered the Au surface (Supplementary Fig.…”

“…Figure 2a shows measured and fitted Au 4 f XPS spectra for Au nanocatalysts, and the major peaks for Au 0 in all can be fitted with minors of Au + and Au 3+ , which may originate from undercoordinated sites 39 . There are many possible reasons for the shifts in binding energy.…”

“…This selective adsorption and activation on Au surfaces containing interstitial C compared to pure surfaces explains the high chemoselectivity observed for the C–Au/OMC catalysts compared to commercial Au/C and Au/SiO 2 . In addition, a continuous exchange of C atoms between surface and subsurface possibly occurs, which may facilitate the adsorption of H 2 39 . The dynamics of C movement in the Au lattice may also be responsible for the desorption of products to inhibit accumulation on the surface, which enhances the reusability.…”