Carbon-Supported Au Nanoparticles: Catalytic Activity Ruled Out by Carbon Support

The catalytic oxidation of glycerol produces high added value chemical products. Gold-based catalysts showed activity and selectivity depending on particle size and specific preparation method. Moreover, the support plays a fundamental role in modulating the stability of the catalytic system. However, the literature is still lacking of a precise disclosure of these important relationships. Herein, we synthesized two series of gold catalysts on different carbon supports (Vulcan-XC72R, X40S and Norit GSX), the first synthesized by solvated metal atom deposition (SMAD) and the second by Sol Immobilization technique (SOL). First of all, the specific physico-chemical properties of the supports and the synthesis procedure influenced the dispersion and the size of Au NPs making a direct comparison among the different carbon difficult. In particular, on Vulcan-XC72R, AuNPs showed narrow size and good dispersion, whereas on Norit GSX and X40S-Camel a notably wider size distribution has been revealed. XPS analyses showed Au exposure changed accordingly to the presence of oxygen species, lower O content corresponding to lower Au exposure. Unexpectedly however this does not correspond to a lower activity, being the lowest Au/C (%at), the Vulcan ones, the most active catalysts. Comparing SOL and SMAD prepared samples on the same carbon, the SOL ones always result more active.