期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 120, 期 35, 页码 19723-19736出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.6b05962
关键词
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资金
- EU (FP7 NMP project ChipCAT) [310191]
- COST Action [CM1104]
- Deutsche Forschungsgemeinschaft (DFG) within the Excellence Cluster Engineering of Advanced Materials
- Helmholtz-Institute Erlangen-Nurnberg (HI ERN), Forschungszentrum Julich GmbH
- Horizon program of the European Commission (project Materials Networking)
- Spanish MINECO (FEDER) [CTQ2012-34969, CTQ2015-64618-R]
- Generalitat de Catalunya [2014SGR97]
- Generalitat de Catalunya (grant XRQTC)
- Czech Ministry of Education [LH15277]
- ICREA Funding Source: Custom
Pt-doped CeOx thin film electrocatalysts have recently been shown to exhibit high activity and stability at the anode of proton exchange membrane fuel cells (PEM-FC). To identify, the role of the Pt dopant and the origin of the high stability of Pt-CeOx films, we applied electrochemical in situ IR spectroscopy on Pt-CeOx model thin film catalysts during methanol (1 M methanol) oxidation. The model catalysts were prepared by magnetron cosputtering of Pt (9-21 atom %), and CeO2 onto clean, and carbon-coated Au supports, All samples were characterized by scanning electron microscopy (SEM), energy-dispersive, X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) before and after reaction. At pH 1 (0.1 MHClO4) the Pt-CeOx dissolves partially during potential cycling, whereas the films: are largely stable at pH 6 (0.1 M phosphate buffer). Electrochemical IR spectroscopy of the adsorbed CO shows that Metallic Pt is formed on all Pt-CeOx samples during methanol oxidation. In comparison to Pt(111), Pt aggregates on Pt-CeOx show a CO on-top signal, which is red shifted by at least 25 cm(-1) and suppression of the bridging CO signals. Whereas the Pt particles on Pt-CeOx,films with high Pt concentration (>20 atom %) undergo rapid sintering during the potential cycling, small metallic Pt aggregates are stable under the Same conditions on films with lbw Pt concentration (<15 atom % Pt). By means of density functional theory (DFT) calculations we analyzed the spectral shifts of adsorbed CO as a function of nanoparticle size both on free and ceria-supported Pt particles, Comparison with the experiment suggests the formation of subnano-particles, i.e., particles with up to 30 atoms (<1 nm particle diameter), which do not expose regular (111) facet sites. At sufficiently low Pt loading) these subnano-Pt particles are efficiently stabilized by the interaction with the ceria support under conditions of the dynamically changing electrode potential.
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