Electrochemical Stability and Degradation Mechanisms of Commercial Carbon-Supported Gold Nanoparticles in Acidic Media

Smiljanić, Milutin; Petek, Urša; Bele, Marjan; Ruiz-Zepeda, Francisco; Šala, Martin; Jovanovič, Primož; Gaberšček, Miran; Hodnik, Nejc

doi:10.1021/acs.jpcc.0c10033

Cited by 21 publications

(35 citation statements)

References 49 publications

(164 reference statements)

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“…This is in contrast to other studies showing that such changes occur after hundreds to thousands of cycles. [7,8,24] Second, size changes are observed for G6-NH 2 (Au 55 ) DENs even before faradaic oxidation or reduction currents are detected in the CVs. Both of these observations suggest that the size of the G6-NH 2 (Au 55 ) DENs is particularly sensitive to even modest potential excursions.…”

Section: Transmission Electron Microscopy (Tem)mentioning

confidence: 99%

“…The anodic current arises from oxidation of the AuNP surface, which may lead to formation of either AuO x or Au + in the case of smaller NPs. [7,8,57,58] When the potential is reversed, the reduction feature at~340 mV corresponds to reduction of oxidized Au products. This latter point will be discussed in more detail later.…”

Section: Electrochemical Cleaning Experimentsmentioning

confidence: 99%

“…[83,84] During the Ostwald ripening process, smaller and less stable NPs oxidize into soluble ions, which can then diffuse through solution before reducing onto the surface of larger, more stable NPs. [7,8,60,85] To investigate the possibility of Smoluchowski ripening, cleaning scans were carried out using higher-generation G8-NH 2 (Au 55 ) DENs. Previous studies have shown that highergeneration dendrimers having increased steric hindrance at their peripheries can suppress aggregation of Au 147 DENs during catalysis experiments.…”

Section: Proposed Mechanism Of Np Growth During Cleaning Scansmentioning

confidence: 99%

“…In the field of electrocatalysis it is common practice to subject nanoparticles (NPs) to electrochemical processes intended to remove impurities from the catalyst surface. [1][2][3][4][5][6][7][8] This is often referred to as 'electrochemical cleaning', and its purpose is to expose a pristine NP surface so that electrocatalytic performance can be accurately assessed. [9][10][11][12] It is becoming increasingly clear, however, that these types of pretreatments can significantly alter the properties of the catalysts under study.…”

Section: Introductionmentioning

confidence: 99%

“…For example, following pretreatment, structured bimetallic NPs can undergo atomic rearrangements, [13][14][15][16] the crystal structure, shape, and facets can change, [4,[17][18][19] and atoms can undergo selective dissolution. [7,8,13,16,[20][21][22] Even for polycrystalline gold surfaces, the rate of anodic Au dissolution during potential cycling is highly dependent on the surface structure of the electrode. [23] These atomic-level structural changes are further exacerbated for very small (<~5 nm) NPs due to their inherent instability.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical Cleaning Stability and Oxygen Reduction Reaction Activity of 1‐2 nm Dendrimer‐Encapsulated Au Nanoparticles

et al. 2021

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Here we show that just three electrochemical scans to modest positive potentials result in substantial growth of 1-2 nm Au dendrimer-encapsulated nanoparticles (DENs). We examined two sizes of Au DENs, denoted as G6-NH 2 (Au 147 ) and G6-NH 2 (Au 55 ), where G6-NH 2 represents a sixth-generation, amineterminated, poly(amidoamine) dendrimer and the subscripts, 147 and 55, represent the average number of atoms in each size of DENs. Ex situ transmission electron microscopy (TEM) and in situ X-ray absorption spectroscopy (XAS) results indicate that G6-NH 2 (Au 55 ) DENs grow to the same size as the G6-NH 2 (Au 147 ) DENs following these scans. Importantly, this growth occurs prior to the onset of detectable faradaic Au oxidation or reduction current. The observed growth in the size of the DENs directly correlates to changes in the electrocatalytic ORR activity. The key point is that after just three positive scans the G6-NH 2 (Au 147 ) and G6-NH 2 (Au 55 ) DENs are essentially indistinguishable in terms of both physical and electrocatalytic properties.

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Section: Transmission Electron Microscopy (Tem)mentioning

confidence: 99%

Section: Electrochemical Cleaning Experimentsmentioning

confidence: 99%

Section: Proposed Mechanism Of Np Growth During Cleaning Scansmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrochemical Cleaning Stability and Oxygen Reduction Reaction Activity of 1‐2 nm Dendrimer‐Encapsulated Au Nanoparticles

et al. 2021

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Low‐Powered E‐Switching Block Copolymer Structural Color Display with Organohydrogel Humidity Controller

Lee

Park

Mun

et al. 2022

Adv Materials Technologies

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In particular, PCs based on stimuliadaptive self-assembled colloids, [13][14][15] layer-by-layer, [16,17] and block copolymers (BCPs) [1,4,5,6,[8][9][10][11][12] are suitable for reflectivemode electric-switching (E-switching) SC displays because of their cost-effectiveness, facile development of full-visible color, and mechanical flexibility. The most common E-switching PC devices reported are fabricated into liquid cell-type systems in which various E-field-responsive PCs are embedded in various liquid media (Table S1, Supporting Information). [18][19][20][21][22][23][24][25] The liquid solvent medium employed in E-switching devices maintains a stable dispersion of ordered colloids in colloidal PCs [18][19][20][21] and swells targeted domains in BCP PCs with an E-field. [22][23][24][25] Despite the fast SC switching arising from the rapid kinetics of the solvent, most liquid-cell BCP SC display applications are limited because of their lack of mechanical flexibility and complex fabrication processes required to prevent solvent leakage.Solid-state E-switching PC devices have been developed to resolve this issue (Table S1, Supporting Information). [26][27][28][29] Recently, solid-state E-switching colloidal PC devices were established by encapsulating self-assembled colloidal particles in a polymer matrix. [26][27][28] Dielectric elastomer actuation was implemented in this system, where the external electrical stimulus induces Maxwell stress across the dielectric medium with the PCs. Field-dependent alteration in the periodicities of the colloidal PCs gives rise to E-switching SCs in the full visible range. However, it is unfortunate that such actuation of a few hundred micrometers-thick PC often requires a high E-field of ≈22.5 V µm −1 , [26] corresponding to an operation voltage ranging from 4 to 9 kV. [26][27][28] Only a few Soft-solid photonic crystals (PCs) based on periodically ordered block copolymer (BCP) nanostructures demonstrate stimuli-adaptive structural colors (SCs) and desirable mechanical properties suitable for reflective-mode electricswitching (E-switching) displays. However, the low electrochemical stability and humidity-dependent E-switching performance of hygroscopic ionic salts, often employed for E-field-adaptive structural alteration, limit their applications. In this study, a low-powered capacitive E-switching BCP SC display with an organohydrogel (OH) humidity controller is proposed, where a bilayer of a BCP and a polymer blend with hygroscopic E-field-adaptive ionic salts is sandwiched between Au electrodes. The display reliably exhibits reversible full-color E-switching (100 on/off cycles) at operating voltages of +2.5 to −2 V within the ionic salts' electrochemical window at ≈50% humidity. A patchable and reusable OH serves as a water reservoir (with optimized geometries and dimensions) to improve the display's humidity tolerance, providing a target humidity (≈50%). The proposed display performs at ambient humidity lower than 60% for over 10 days because of the long water retention an...

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Toward Eco‐Friendly E‐Waste Recycling: New Perspectives on Ozone‐Assisted Gold Leaching

Stojanovski,

Briega‐Martos,

Escalera‐López

et al. 2024

Adv Energy and Sustain Res

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Global demand for more effective methods to reclaim gold from electronic waste (E‐waste) has never been greater. Alternatives to hydrometallurgical methods, such as cyanide, are still limited. This work examines utilizing ozone and chlorides to recycle Au from E‐waste. It is started with a fundamental investigation of Au dissolution processes on the extended surface of Au polycrystalline and Au nanoparticulated electrodes. An online electrochemical scanning flow cell coupled with inductively coupled plasma mass spectrometry quantifies the rates and amounts of Au leaching. Identical‐location scanning electron microscopy (IL‐SEM) further correlates dissolution events with electrode morphological changes. It is demonstrated that ozone in the electrolyte imposes an anodic potential on the electrode, leading to anodic Au dissolution. Passivation disappears when small amounts of chlorides are added to the electrolyte, significantly enhancing the leaching yield. IL‐SEM images of gold nanoparticles (NPs) before and after exposure to ozone reveal heterogeneity in NP size‐dependent dissolution, showing higher dissolution for smaller particles. An effective Au leaching procedure is further demonstrated in a lab‐scale reactor using real E‐waste where almost complete recovery of Au is achieved. This research suggests that with engineering optimization in reactor applications based on ozone‐stimulated gold, dissolution can pave the way for environmentally friendly gold recycling.

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Electrochemical Stability and Degradation Mechanisms of Commercial Carbon-Supported Gold Nanoparticles in Acidic Media

Cited by 21 publications

References 49 publications

Electrochemical Cleaning Stability and Oxygen Reduction Reaction Activity of 1‐2 nm Dendrimer‐Encapsulated Au Nanoparticles

Electrochemical Cleaning Stability and Oxygen Reduction Reaction Activity of 1‐2 nm Dendrimer‐Encapsulated Au Nanoparticles

Low‐Powered E‐Switching Block Copolymer Structural Color Display with Organohydrogel Humidity Controller

Toward Eco‐Friendly E‐Waste Recycling: New Perspectives on Ozone‐Assisted Gold Leaching

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