Particle-size effect of nanoscale platinum catalysts in oxygen reduction reaction:: an electrochemical and 195Pt EC-NMR study

被引:154
作者
Yano, Hiroshi
Inukai, Junji
Uchida, Hiroyuki
Watanabe, Masahiro
Babu, Panakkattu K.
Kobayashi, Takeshi
Chung, Jong Ho
Oldfield, Eric
Wieckowski, Andrzej
机构
[1] Yamanashi Univ, Interdisciplinary Grad Sch Med & Engn, Clean Energy Res Ctr, Kofu, Yamanashi 4008511, Japan
[2] Univ Illinois, Dept Chem, Urbana, IL 61801 USA
关键词
D O I
10.1039/b610573d
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Oxygen reduction reaction (ORR) measurements and Pt-195 electrochemical nuclear magnetic resonance (EC-NMR) spectroscopy were combined to study a series of carbon-supported platinum nanoparticle electrocatalysts (Pt/CB) with average diameters in the range of roughly 1 - 5 nm. ORR rate constants and H2O2 yields evaluated from hydrodynamic voltammograms did not show any particle size dependency. The apparent activation energy of 37 kJ mol(-1), obtained for the ORR rate constant, was identical to that obtained for bulk platinum electrodes. Pt/CB catalysts on Nafion produced only 0.7 - 1% of H2O2, confirming that the direct four-electron reduction of O-2 to H2O is the predominant reaction. NMR spectral features showed characteristic size dependence, and the line shapes were reproduced by using the layer-deconvolution model. Namely, the variations in the NMR spectra with particle size can be explained as due to the combined effect of the layer-by-layer variation of the s-type and d-type local density of states. However, the surface peak position of Pt-195 NMR spectra and the spin - lattice relaxation time of surface platinum atoms showed practically no change with the particle size variation. We conclude that there is a negligible difference in the surface electronic properties of these Pt/CB catalysts due to size variations and therefore, the ORR activities are not affected by the differences in the particle size.
引用
收藏
页码:4932 / 4939
页数:8
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