文摘
Nanoparticles of gold on TiO2 are highly chemoselective for the reduction of substitutednitroaromatics, such as nitrostyrene. By combining kinetics and in situ IR spectroscopy, it has been foundthat there is a preferential adsorption of the reactant on the catalyst through the nitro group. IR studies ofnitrobenzene, styrene, and nitrostyrene adsorption, together with quantum chemical calculations, showthat the nitro and the olefinic groups adsorb weakly on the Au(111) and Au(001) surfaces, and that althougha stronger adsorption occurs on low-coordinated atoms in gold nanoparticles, this adsorption is not selective.On the other hand, an energetically and geometrically favored adsorption through the nitro group occurson the TiO2 support and in the interface between the gold nanoparticle and the TiO2 support. Suchpreferential adsorption is not observed with nanoparticles of gold on silica which, contrary to the Au/TiO2catalyst, is not chemoselective for the reduction of substituted nitroaromatic compounds. Therefore, thehigh chemoselectiviy of the Au/TiO2 catalyst can be attributed to a cooperation between the gold nanoparticleand the support that preferentially activates the nitro group.