In order to examine the relationship between the oxygen reduction reaction (ORR) activity of a fuel cell catalyst and its structure and/or electronic state, carbon-supported Pt and Pt alloys having various structures, compositions, and morphologies were studied. Regardless of the atomic ordering or morphology (core−shell or random alloy) of the catalyst, the ORR activity was primarily dependent on the Pt−Pt bond distance. Among these materials, Pt 2 Co, having the shortest Pt−Pt distance, exhibited the highest ORR activity. The activities of this catalyst per unit surface area and per unit mass were approximately 10 times and 6 times higher than those of a commercially available carbon supported Pt electrocatalyst (Pt/C). This work also found a monotonic increase in catalytic activity with decreasing Pt−Pt distance.

A carbon-supported Pt-shell Au-core electrocatalyst (Pt/Au/C) was prepared by sequential deposition of Pt ions on the surface of Au nanoparticles supported on carbon. The area-specific activity of the oxygen reduction reaction (ORR) for the prepared Pt/Au/C in 0.1 M HClO4 aqueous solution was approximately 2 times higher than that for a commercial carbon-supported Pt electrocatalyst (Pt/C). The core–shell structure was confirmed using electrochemical methods and Pt and Au K-edge X-ray absorption fine structure (XAFS) analysis. XAFS analyses indicated that the Pt–Pt bond distance for the Pt/Au/C catalyst was shorter than that for Pt foil and the Pt/C catalyst. In addition, the Au–Au distance was much shorter than that for Au foil. The reason for the high ORR activity of Pt/Au/C is considered to be shorter Pt–Pt bond distance as compared to that of Pt/C.

Time dependent density functional theory study of the near-edge x-ray absorption fine structure of benzene in gas phase and on metal surfaces J. Chem. Phys. 129, 064705 (2008) A new spectroelectrochemical cell for in situ measurement of Pt and Au K-edge X-ray absorption fine structure A new spectroelectrochemical cell to investigate the structure of Pt/Au nanoclusters using Pt and Au K-edge X-ray absorption fine structure (XAFS) measurements under the electrochemical conditions is developed. K-edge XAFS measurements for Pt and Au require a sample as thick as 1-2 cm, which prevents homogeneous potential distribution. We can measure in situ Pt and Au K-edge XAFS spectra and determine reasonable electrochemical surface areas using our developed spectroelectrochemical cell. This work provides a new approach to analyze Pt/Au core-shell nanoclusters. The new cell is designed to be applied to both spectra with high absorption-edge energies such as the K-edge of Pt and Au and those with low absorption-edge energy such as Pt L-edge. © 2014 AIP Publishing LLC.

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Reduction of Pt loading on fuel cell electric vehicles is strongly desired for fuel cell electric vehicles to be commercially viable. Activity enhancement for the sluggish oxygen reduction reaction of Pt-based electrocatalyst is the most essential to reduce Pt loading. Here, we provide a brief review of recent advances in Pt-based ORR electrocatalysts followed by electrocatalyst research activities of Nissan.