Impact of Structure and Composition on the Dealloying of AuxAg(1–x) Alloys on the Nanoscale

Kamundi, Martha; Bromberg, Lori Ana; Fey, Edmond; Mitchell, Corey; Fayette, Matthew; Dimitrov, Nikolay

doi:10.1021/jp301603t

Cited by 27 publications

(41 citation statements)

References 46 publications

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“…28,29,32 Figure 3 shows CV results of Pb UPD performed before and after the dealloying process in order to demonstrate the applicability of all-electrochemical processing of NPG 7 deposited on EOGC. The shape of the CV curves is different to the commonly established one in our previous work 36,37 owing to the high background current on the affected by the EO glassy carbon substrate. Despite the nearly featureless appearance of the CV curves it is still obvious that the dealloying supposed to generate NPG structure 1,7,36 does lead to SA increase ( Figure 3A, dashed red curve).…”

Section: Resultscontrasting

confidence: 88%

“…The shape of the CV curves is different to the commonly established one in our previous work 36,37 owing to the high background current on the affected by the EO glassy carbon substrate. Despite the nearly featureless appearance of the CV curves it is still obvious that the dealloying supposed to generate NPG structure 1,7,36 does lead to SA increase ( Figure 3A, dashed red curve). This inference is strengthened by the SEM images in Figure 3B where the morphology typical for a NPG deposit is presented for the sample characterized electrochemically in Figure 3A.…”

Section: Resultscontrasting

confidence: 88%

“…This paper is aimed at utilizing electrochemical oxidation to fabricate high quality NPG layers featuring enhanced adhesion on the GC substrate. By employing some of our previously developed routines and comparing results of this activity to our previous work on thermochemical oxidation, 7,25,36 the research in this paper will primarily focus on (i) the morphology of the GC substrate and NPG layer as a result of electrochemical oxidation studied by Scanning Electron Microscopy (SEM) and the unique characteristics of electrochemically oxidized GC during deposition, dealloying 7,25 and Pb UPD surface area (SA) determination; 37 (ii) the wettability of differently pre-treated GC surfaces assessed by contact angle measurements and its surface morphology after oxidation; (iii) the adhesion of Au 0.3 Ag 0.7 thin films on electrochemically oxidized and control (untreated) GC substrates by measuring the surface area by Pb UPD and the total amount of dissolved Ag of identical alloy-deposit batches before and after a rotating disk electrode (RDE) adhesion assessments which simulate an unsteady testing environment.…”

Section: Npg Based Catalyst On Glassy Carbon (Gc)mentioning

confidence: 99%

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Enhanced Adhesion of Ultrathin Nanoporous Au Deposits by Electrochemical Oxidation of Glassy Carbon

Xia

Rooney

Ambrozik

et al. 2015

J. Electrochem. Soc.

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Electrochemical (EO) and Thermochemical (TO) oxidation have been considered as means for improved adhesion of metals to glassy carbon (GC) substrates. This paper is aimed at studying the effect of EO on the all-electrochemical processing of nanoporous gold (NPG) catalysts with emphasis on their adhesion to a GC substrate. It has been shown by two independent assessment approaches that EO improves twice the amount of retained NPG on GC helping to keep about 90% originally existing material after a two-hour rotation disk electrode test at 1600 rpm. This work also demonstrates that EO modifies the GC in a way making it more passive in the alloy deposition and subsequent dealloying processes. This effect results in a progressive nucleation density decrease with the depth of oxidation which in turn leads to a lack of continuity of the NPG layer. This trend is also accompanied by a decrease in deposition efficiency as a substantial part of the cathodic current is spent on the reduction of the pre-oxidized GC surface. Our study identifies the best outcome of the trade-off scenario between nucleation density, deposition efficiency and adhesion strength to be associated with depth of oxidation in the range 0.10 to 0.25 μm. NPG based catalyst on glassy carbon (GC).-Nanoporous Au (NPG) is a nano-material with three dimensional (3D) continuous structure featuring Au with interconnected nano-sized pores and ligaments.1 NPG and other nanoporous metals have been intensively investigated in recent years. This conductive material has an open, 3D porous framework with surface areas that even in an ultrathin NPG layer configuration could be an order of magnitude larger than the area of planar Au. Besides its continuous crystal lattice throughout the porous network, it has a pore size that is adjustable via simple thermal post-processing, which makes it potentially applicable in various fields such as electro-and gas-phase catalysis, optics, sensors and actuators. [2][3][4][5] It is known that nanoparticulate gold possesses remarkable catalytic activity toward oxidation reactions, should the particles be well supported and smaller than 5 nmin size. 6 Recently, ultrathin films of NPG have been shown to serve as catalysts for fuel cell applications as an alternative to their nanoparticle (NP) counterparts.7-9 These films are generated electrochemically under precise potential/current control, which minimizes material loss and surface contamination over the multi-step NP synthetic routines. 7,10 Compared to nanoparticle synthesis which often lacks control due to the large number of the processing steps, ultra thin films of NPG are cost effective, simple to fabricate, and show better reproducibility in terms of quality and reactivity. Another advantage of NPG films is that the edge effect that lowers the catalytic activity characteristic for NP based catalysts does not exist in NPG films due to its continuous nature. 11In our previous work, we established an all-electrochemical synthetic method for a NPG-based catalyst that maximized t...

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Section: Resultscontrasting

confidence: 88%

Section: Resultscontrasting

confidence: 88%

Section: Npg Based Catalyst On Glassy Carbon (Gc)mentioning

confidence: 99%

See 1 more Smart Citation

Enhanced Adhesion of Ultrathin Nanoporous Au Deposits by Electrochemical Oxidation of Glassy Carbon

Xia

Rooney

Ambrozik

et al. 2015

J. Electrochem. Soc.

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“…The pore structure of nanoporous gold depends on the method used to dealloy, the processing conditions (temperature, time, and electrolyte), and the initial composition of the alloy. The composition of the alloy strongly affects the porosity and surface area of the material regardless of the method used [58,[76][77][78]. Dealloying works over a narrow compositional range: ∼26 to 36 at % Au [58,77,78].…”

Section: 2mentioning

confidence: 99%

Nanoporous Gold Electrodes and Their Applications in Analytical Chemistry

Collinson

2013

ISRN Analytical Chemistry

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Nanoporous gold prepared by dealloying Au:Ag alloys has recently become an attractive material in the field of analytical chemistry. This conductive material has an open, 3D porous framework consisting of nanosized pores and ligaments with surface areas that are 10s to 100s of times larger than planar gold of an equivalent geometric area. The high surface area coupled with an open pore network makes nanoporous gold an ideal support for the development of chemical sensors. Important attributes include conductivity, high surface area, ease of preparation and modification, tunable pore size, and a bicontinuous open pore network. In this paper, the fabrication, characterization, and applications of nanoporous gold in chemical sensing are reviewed specifically as they relate to the development of immunosensors, enzyme-based biosensors, DNA sensors, Raman sensors, and small molecule sensors.

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“…Instead, a low-density cluster deposit of NPG was fabricated on GC, which was attributed to the poor surface catalytic activity [14]. The poly-disperse spherical particles are the representative outcome of conventional synthetic routines on GC electrodes [15]. Contrary to the expectation that electrodeposition would generate alloy deposits that adhere better to the GC than physically adsorbed NPs, a considerable loss of NPG spherical clusters was observed during performance testing of accordingly fabricated Pt-NPG catalysts [7].…”

Section: Nanoporous Gold (Npg)-based Catalyst On Glassy Carbon (Gc)mentioning

confidence: 99%

Enhanced Adhesion of Continuous Nanoporous Au Layers by Thermochemical Oxidation of Glassy Carbon

et al. 2014

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Abstract:The fabrication of a nanoporous gold (NPG)-based catalyst on a glassy carbon (GC) support results normally in large isolated and poorly adhering clusters that suffer considerable material loss upon durability testing. This work exploits thermochemical oxidation of GC, which, coupled with the utilization of some recent progress in fabricating continuous NPG layers using a Pd seed layer, aims to enhance the adhesion to the GC surface. Thermochemical oxidation causes interconnected pores within the GC structure to open and substantially improves the wettability of the GC surface, which are both beneficial toward the improvement of the overall quality of the NPG deposit. It is demonstrated that thermochemical oxidation neither affects the efficiency of the Au 0.3 Ag 0.7 alloy (NPG precursor) deposition nor hinders the achievement of continuity in the course of the NPG fabrication process. Furthermore, adhesion tests performed by a rotating disk electrode setup on deposits supported on thermochemically-oxidized and untreated GCs ascertain the enhanced adhesion on the thermochemically-oxidized samples. The best adhesion results are obtained on a continuous NPG layer fabricated on thermochemically-oxidized GC electrodes seeded with a dense network of Pd clusters.

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Impact of Structure and Composition on the Dealloying of Au_xAg_(1–x) Alloys on the Nanoscale

Cited by 27 publications

References 46 publications

Enhanced Adhesion of Ultrathin Nanoporous Au Deposits by Electrochemical Oxidation of Glassy Carbon

Enhanced Adhesion of Ultrathin Nanoporous Au Deposits by Electrochemical Oxidation of Glassy Carbon

Nanoporous Gold Electrodes and Their Applications in Analytical Chemistry

Enhanced Adhesion of Continuous Nanoporous Au Layers by Thermochemical Oxidation of Glassy Carbon

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