Oxygen activation on nanometer-size gold nanoparticles

The structure, electronic properties, and catalytic activity toward oxygen activation of gold nanoclusters with size between 10 and 42 atoms were investigated with first principle methods. Nanoparticle symmetry, bond lengths, and surface charge distribution were analyzed and compared to those of macroscopic gold surfaces. Irregular charge distribution was found on the surfaces of nanoparticles consisting of fewer than 30 gold atoms. Nanoparticles with more than 30 atoms were characterized with core-shell charge separation, e.g, positively charged core and negatively charged surface. The charge distribution on those nanoparticles significantly differs from the charge distribution on macroscopic gold surface. The structure and electronic properties of the gold nanoparticles were related to their catalytic activity toward the aerobic oxidation of organic molecules, e.g., cyclohexane. It was found that oxygen is activated by partially negatively charged surface gold atoms. Nanoparticles with sizes between 10 and 30 gold atoms could only activate oxygen over the negatively charged surface active sites, whereas larger nanoparticles could activate oxygen over the whole surface. The results are in good agreement and provide detailed understanding of recently published experimental data of aerobic oxidation on subnanometer gold nanoparticles (ACS Catal.2011, 1, 2-6).