期刊
ACS CATALYSIS
卷 8, 期 8, 页码 6775-6790出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.8b00553
关键词
oxygen reduction reaction (ORR); mass-selected nanoclusters; SECCM; carbon corrosion; reactive oxygen species; catalyst poisoning; nanocluster migration
资金
- Fonds Wetenschappelijk Onderzoek (FWO) in Flanders [12I7816N]
- EPSRC, Birmingham Science City
- Royal Society
- Advantage West Midlands (AWM)
- European Regional Development Fund (ERDF)
- Leverhulme Trust
- University of Warwick Chancellor's International Scholarships
- Marie Curie Individual Fellowship [702048 NEIL]
A major challenge in electrocatalysis is to understand the effect of electrochemical processes on the physicochemical properties of nanoparticle or nanocluster (NC) ensembles, especially for complex processes, such as the oxygen reduction reaction (ORR) considered herein. We describe an approach whereby electrocatalysis at a small number of well-defined mass-selected Pt NCs (Pt-923 +/- 37, diameter, d approximate to 3 nm), deposited from a cluster beam source on carbon-coated transmission electron microscopy (TEM) grids, can be measured by a scanning electrochemical cell microscopy (SECCM) setup, in tandem with a range of complementary microscopy and spectroscopy techniques. The SECCM setup delivers high mass transport rates and allows the effects of transient reactive intermediates to be elucidated for different Pt surface coverages (NC spacing). A major observation is that the ORR activity decreases during successive electrochemical (voltammetric) measurements. This is shown to be due to poisoning of the Pt NCs by carbon-/oxygen-containing moieties that are produced by the reaction of reactive oxygen intermediates (Rls), generated by the ORR, with the carbon support. The effect is most prominent when the Pt surface coverage on the carbon support is low (<6%). Furthermore, the NC deposition impact energy drastically affects the resulting Pt NC stability during electrochemistry. For lower impact energy, Pt NCs migrate as a consequence of the ORR and are rearranged into characteristic groups on the support. This previously unseen effect is caused by an uneven flux distribution around individual NCs within the ensemble and has important consequences for understanding the stability and activity of NC and nanoparticle arrays.
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