Selective Knockout of Gold Active Sites

Nowicka, Anna; Hasse, Ulrich; Sievers, Gustav; Donten, Mikołaj; Stojek, Zbigniew; Fletcher, Stephen; Scholz, Fritz

doi:10.1002/ange.201000485

Cited by 18 publications

(19 citation statements)

References 22 publications

(16 reference statements)

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“…This has been attributed to active sites on the surface that consists of atoms or clusters of atoms that have low co-ordination number and have the ability to partake in electrocatalytic reactions [21,22,25,26]. Recent work by Scholz has demonstrated in the case of gold that active or defect sites are located on the asperities of an electrode surface which are the loci of partially filled d orbitals that can stabilise free radical intermediates [27,28]. These sites have been shown to dictate electrocatalytic reaction rates for inner sphere reactions that involve free radical intermediates such as oxygen reduction and hydrogen evolution.…”

Section: Resultsmentioning

confidence: 99%

Probing the surface oxidation of chemically synthesised gold nanospheres and nanorods

2014

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In this study, the electrochemical behaviour of commercially available gold spheres and rods stabilised by carboxylic acid and cetyl trimethyl ammonium bromide (CTAB) moieties, respectively, are investigated. The cyclic voltammetric behaviour in acidic electrolyte is distinctly different with the nanorods exhibiting unusual oxidative behaviour due to an electrodissolution process. The nanospheres exhibited responses typical of a highly defective surface which significantly impacted on electrocatalytic activity. A repetitive potential cycling cleaning procedure was also investigated which did not improve the activity of the nanorods and resulted in deactivating the gold spheres due to decreasing the level of surface defects.

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Section: Resultsmentioning

confidence: 99%

Probing the surface oxidation of chemically synthesised gold nanospheres and nanorods

2014

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“…The effect of treating the pc-Au surface with hydroxyl radicals on the electrochemical nucleation of Pt on pc-Au It has been shown earlier that OH • radicals can effectively smooth the surface of gold [6] and selectively knockout the active centers of oxygen reduction [7]. These results encouraged us to study the effect of OH • radicals on the active sites of Pt nucleation.…”

Section: Electrochemical Studiesmentioning

confidence: 96%

“…From the work of Nagahara et al, it is clear that the adsorption of [PtCl 4 ] 2− occurs on regular surface sites and not at specific active sites in the sense of surface defects. Hence, it is understandable that the treatment of the pc-Au surface which is known to affect only active sites (surface defects) [6,7] is not affecting the spontaneous Pt deposition.…”

Section: Electrochemical Studiesmentioning

confidence: 99%

“…In order to obtain a better understanding of the nature of active sites, we have recently started to apply the following approach: The surface of an electrode is treated with hydroxyl (OH • ) radicals and the effect of that treatment on the electrochemical and the electrocatalytic behavior of the electrode is monitored, as well as the surface is characterized by spectroscopic and microscopic techniques [6][7][8][9]. The main results of these studies can be summarized as follows:…”

Section: Introductionmentioning

confidence: 99%

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The effects of pretreatment of polycrystalline gold with OH• radicals on the electrochemical nucleation and growth of platinum

Sievers

Hasse

Scholz

2011

J Solid State Electrochem

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The nucleation and growth of platinum on polycrystalline gold was studied by chronoamperometry, cyclic voltammetry, and atomic force microscopy before and after treatment of the gold surface with hydroxyl (OH • ) radicals. Two different procedures of mechanical polishing of the gold surface ("coarse polish" and "fine polish") were applied before the treatment with OH • radicals. The nucleation and growth of Pt was much better reproducible on electrodes which underwent a "coarse polish". The treatment of the Au surface with OH • radicals decreased the number of active sites; however, the nucleation growth mode remained the same (3-D instantaneous). The spontaneous Pt deposition (no externally applied potential) on Au was unaffected by the treatment with OH • radicals. In situ atomic force microscopy experiments showed that the Pt starts to grow only on some of the Au grains, most probably on those which have active sites on their surface. This leads to a roughening of the electrode surface upon Pt deposition. Treatment with OH • radicals did only quantitatively diminish the amount of deposited Pt, but qualitatively the imaging of the Pt growth remained the same. Obviously, the OH • radicals lead to a knockout (decreasing number) of active sites for Pt nucleation, while the nature of the remaining active sites stays unaffected.

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“…It is known that the hydroxyl radicals generated in Fenton's reagent quickly dissolve gold asperities or small irregularities from mechanically polished gold surfaces which make the surfaces much smoother [11,12]. Such treatment of the regular gold-electrode surface caused the reduction of its electrocatalytic properties.…”

Section: Introductionmentioning

confidence: 99%

Polypyrrole–gold nanostructured composite, active and durable electrocatalytic material

Malinowska

Gniadek

Rapecki

et al. 2014

J Solid State Electrochem

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The consequences of treatment of gold nanocrystals present in polypyrrole-gold composites and electrodeposited gold nanocrystals (PPY-Au and Au NPs) with OH radicals generated in Fenton's reaction were investigated. Particularly, the changes in the morphology and the electrochemical properties of those materials are shown. For both materials, the etching effect was noticed. Contrary to significantly reduced catalytic activity, the changes observed in size and shape of gold nanostructures were less pronounced. In the case of PPY-Au composite material, the etching effects were less intense. Even after a 60-min radical treatment of the PPYAu composite material, the gold-nanocrystal catalytic activity remained high. The limited dissolution of the gold nanocrystals in the PPY-Au composites, compared to bare Au NPs, can be explained by the presence of the polymer which served as a kind of protective barrier against the oxidizing agent. A decrease in the electrocatalytic properties vs. the electrooxidation of ethanol of both forms of gold nanocrystals were observed after the treatment with hydroxyl radicals.

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Selective Knockout of Gold Active Sites

Cited by 18 publications

References 22 publications

Probing the surface oxidation of chemically synthesised gold nanospheres and nanorods

Probing the surface oxidation of chemically synthesised gold nanospheres and nanorods

The effects of pretreatment of polycrystalline gold with OH• radicals on the electrochemical nucleation and growth of platinum

Polypyrrole–gold nanostructured composite, active and durable electrocatalytic material

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