Changes of Oxygen Adsorption State of Pt Nanoparticle Catalyst on the Carbon Support By the Ion Irradiation

Pt nanoparticles (NPs) on an Ar+-irradiated glassy carbon (GC) substrate were recently found to show a higher oxygen reduction reaction (ORR) activity than those on the non-irradiated one [1]. This finding suggests that the Pt nanoparticles would be electronically modified by vacancy introduction due to the irradiation into GC. Our theoretical research revealed that vacancies in graphite would lower a d-band center of the Pt nanoparticles [2]. The downshift of d-band center of Pt 5d electrons leads to higher ORR activity because the downshift causes the downshift of the antibonding orbital level of the oxygen adsorbed states of Pt (Pt-O) closing to Fermi level and then results in weaker Pt-O bond [3]. However, it has not been revealed whether the Pt-O antibonding level of Pt NPs is downshifted by the ion irradiation into the carbon support. Therefore, we performed in situ x-ray absorption fine structure (XAFS) measurements, which can observe the unoccupied states of the Pt 5d orbital binding with the adsorbed oxygen, of Pt NPs on the irradiated GC and derived the oxygen adsorbed surface states.