Au, particle size effect

S. H. Overbury, L. Ortiz-Soto, H. G. Zhu, B. Lee, M. D. Amiridis, and S. Dai, Comparison of Au catalysts supported on mesoporous titania and silica Investigation of Au particle size effects and metal-support interactions, Catal. Lett. 95(3-4), 99-106 (2004). 

The use of renewable feedstocks (i.e., biomass) in the production of fuels and value-added chemicals has attracted major interest from researchers and governments because of the anticipated shortages of traditional petrochemical industrial feedstocks [199]. An excellent overview of the milestones relating to the use of bioderived alcohols in the synthesis of higher value chemicals was recently presented by Hutchings et al. [200]. In this area as well, particle size effects can be identified yet care must be taken, as illustrated by a recent paper by Simakova et al. [201], which showed a bimodal Au particle size effect in the catalytic activity of Au-TiOj system in the gas-phase oxidation of ethanol. 

This paper,11 which is a model of its kind, reported a study of the reaction on two Au/SiC>2 catalysts, having respectively 0.15 and 5% gold unfortunately both had somewhat broad particle size distributions, namely 3 9 nm (0.15% Au) or 3-7 nm (5% Au), with a significant number of very large (>10nm) particles. This complicated the interpretation of the results, as no clear particle size effect could be seen. However, silicalite-1 (Si-MFI) and TS-1 (a titanium-containing silicalite, Ti-MFI) were also used, and the size of the channels constrained the particle size to be less than 3nm in both cases. These size differences accounted for the marked variations in activity observed at 433 K ... 

J. Lu, X. Zhang, J. J. Bravo-Suarez, K. K. Bando, S. T. Oyama, Direct propylene epoxidation over barium promoted Au/Ti-TUD catalysts with Hz and Op Effect of Au particle size, J. Catal. doi 10.1016/j.jcat.2007.06.006. 

Such intricate, interactive relationships between metal nanoparticle and support can be reflected in pronounced metal particle size effects in photocatalytic reduction efflciency, as illustrated by the case of Au-TiOj system (Figure 9.19) [194]. 

This clear size dependence on ORR activity was in agreement with previous observation by Chen and Chen [36]. However, contrarily, Bron [29] reported no size effect for particle sizes in the range between 2.7 and 42 tun supported on carbon black in acidic solutions, whereas Guerin et al. [28] observed that the activity decreased for diameters <3 nm with decreasing particle size. From these previous discussions, it is evident that the effect of Au particle size on the kinetics of O2 reduction on Au nanoparticles, both in acidic and alkaline media, is a matter of controversy and very different trends can be observed in the literature. In addition, to have a full picture of the situation, it is important to note that theoretical studies predicted an increase in ORR activity with decreasing Au particle size [44]. In our opinion, and in agreement with some of the conclusions reported by Briille et al. [43],... 

Inasaki T, Kobayashi S (2009) Particle size effects of gold on the kinetics of the oxygen reduction at chemically prepared Au/C catalysts. Electrochim Acta 54(21) 4893-4897... 

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