The Interface between platinum nanoparticle catalysts and an Ar-irradiated carbon support

Kakitani, Kenta*; Kimata, Tetsuya*; Yamaki, Tetsuya*; Yamamoto, Shunya*; Taguchi, Tomitsugu*; Shimoyama, Iwao   ; Matsumura, Daiju   ; Iwase, Akihiro*; Kobayashi, Tomohiro*; Terai, Takayuki*; Mao, W.*

Pt nanoparticles (NPs) on the Ar-irradiated carbon support were found highly active for the oxygen reduction reaction (ORR). This suggests that irradiation defects of the support would affect Pt NPs, but the mechanism of the activity improvement has not been clear. We performed here transmission electron microscopy and X-ray absorption near edge structure (XANES) measurements to investigate the effect of the Pt NP-support interface in terms of the size and chemical states of the Pt NPs. The Pt NPs were prepared on the glassy carbon substrate by sputter deposition; their sizes were 5.1 and 3.8 nm on the 380 keV Ar-irradiated and pristine substrates, respectively. In XANES spectra at Pt M and L edges, the peak intensity was lower for the irradiated sample, indicating the suppression of Pt oxidation by the irradiation defects. Accordingly, fast kinetics originating from this interfacial chemical-state change, not an increase in the particle size, can explain the high ORR activity.