Abstract
The effect of the relationship between particle size (d), inter-particle distance (x i ), and metal loading (y) of carbon supported fuel cell Pt or PtRu catalysts on their catalytic activity, based on the optimum d (2.5–3 nm) and x i /d (>5) values, was evaluated. It was found that for y < 30 wt%, the optimum values of both d and x i /d can be always obtained. For y ≥ 30 wt%, instead, the positive effect of a thinner catalyst layer of the fuel cell electrode than that using catalysts with y < 30 wt% is concomitant to a decrease of the effective catalyst surface area due to an increase of d and/or a decrease of x i /d compared to their optimum values, with in turns gives rise to a decrease in the catalytic activity. The effect of the x i /d ratio has been successfully verified by experimental results on ethanol oxidation on PtRu/C catalysts with same particle size and same degree of alloying but different metal loading. Tests in direct ethanol fuel cells showed that, compared to 20 wt% PtRu/C, the negative effect of the lower x i /d on the catalytic activity of 30 and 40 wt% PtRu/C catalysts was superior to the positive effect of the thinner catalyst layer.
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Acknowledgments
The authors thank the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP, Proc: 2010/20045-0) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Proc. 131469/2011-8; 160503/2011-6) for financial assistance to the project.
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Corradini, P.G., Pires, F.I., Paganin, V.A. et al. Effect of the relationship between particle size, inter-particle distance, and metal loading of carbon supported fuel cell catalysts on their catalytic activity. J Nanopart Res 14, 1080 (2012). https://doi.org/10.1007/s11051-012-1080-5
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DOI: https://doi.org/10.1007/s11051-012-1080-5