Electrochemical Nonadiabatic Electron Transfer via Tunneling to Solution Species through Thin Insulating Films

Hill, Caleb M.; Kim, Jiyeon; Bodappa, Nataraju; Bard, Allen J.

doi:10.1021/jacs.6b12104

Cited by 36 publications

(41 citation statements)

References 45 publications

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“…ii) the SO 4 2− ion stimulate the aggregation of PSQ film by formation of ion‐pair with fixed surface sites of film and, this could enhance the charge transport kinetics by decreasing the distance between redox centres of ferrocyanide‐PSQ film as depicted in Scheme S1 (see more explanation in mechanistic analysis). Furthermore, the possible reason for the observed only negative current in the upper plot of CV in Figure may be the current follows diffusion limited mechanism as illustrated by Chen et al., and other groups …”

Section: Resultsmentioning

confidence: 84%

Electrochemical Diagnosis of Chemical Switch: Impact of Structural Changes on Charge Transport Mechanism of “Redox Anion Bound Polysilsesquioxane” Film

Silambarasan

Joseph

2018

ChemElectroChem

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Herein, we report the structurally dependent charge transport mechanism of ferrocyanide ions immobilized in a protonated amine functionalized polysilsesquioxane (PSQ) film (Redox polymer film). This redox polymer film shows anion actuated reversible "active to inactive" electrochemical interfaces when the electrolyte anion is changed from chloride to perchlorate as a result of swelling and hydrophobic collapse of the PSQ film, respectively. This concept was successfully applied for switchable electrocatalytic oxidation of ascorbic acid by a [Fe(CN) 6 ] 4À -PSQ film. In addition, it was shown in cyclic voltammetric (CV) studies that the presence of HPO 4 2À and CO 3 2À is leading to strong irreversible structural collapse of the PSQ film, whereas, the presence of SO 4 2À and S 2 O 8 2À is leading to reversible structural changes of the PSQ film within chloride ion medium. Reversible structural transition between swelling and aggregation (voltammetric response reversibly changing from peak to sigmoidal shape) described in this work is new and provides mechanistic insight into redox polymer electrochemistry and allows differentiating electron hopping from physical motion of redox polymers. Moreover, ion-exchange between bound redox anions and divalent anions in the electrolyte at fixed positive surface sites of PSQ film was explained in terms of Jones-Dole B-coefficient. Electrochemical impedance spectroscopy, Atomic force microscopy, Contact angle measurement and UV-visible spectroscopy analysis of above phenomenon were consistent with CV results.

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Section: Resultsmentioning

confidence: 84%

Electrochemical Diagnosis of Chemical Switch: Impact of Structural Changes on Charge Transport Mechanism of “Redox Anion Bound Polysilsesquioxane” Film

Silambarasan

Joseph

2018

ChemElectroChem

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“…Nanostructuring induced band bending confinement provides a rational solution to narrow the potential barriers . For the contacts formed by nanostructured semiconductor, the major potential drop can be confined in the first layer of the building blocks that connect to the metal .…”

Section: Resultsmentioning

confidence: 99%

“…Besides, to avoid the extracted electrons in carbon nanostructures from leakage (Figure b), the ultrathin interlayers that are coated on the carbon nanostructures should be dopant‐free . Furthermore, the electrons in carbon nanostructures can be transferred to the reducing sites through the ultrathin interlayers via tunneling to the co‐catalysts (Figure b and Figure S4) . In this work, inspired by the simulated voltammetry behaviors with consideration of band bending confinement and electron tunneling (Figure , Figure S3, and Figure S4), we adopt homogeneously formed ultrathin CdS interlayers that are coated on graphene sheets as the model system to demonstrate the superiority of electronic bridging for the photocatalytic behaviors in carbon supported semiconductor (CdS) photocatalysts.…”

Section: Resultsmentioning

confidence: 99%

Nanostructuring Confinement for Controllable Interfacial Charge Transfer

Qiao

Tao

Liu

et al. 2019

Small

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Carbon nanostructures supported semiconductors are common in photocatalytic and photoelectrochemical applications, as it is expected that the nanoconductors can improve the spatial separation and transport of photogenerated charge carriers. Transfer of charge carriers through the carbon‐semiconductor interface is the key electronic process, which determines the role of charge separation channels, and is sensitively influenced by band structures of the semiconductor near the contacts. Usually, this electronic process suffers from excessive energy dissipation by thermionic emission, which will undesirably prevent the interfacial charge transfer and eventually aggravate the recombination of photogenerated charge carriers. Unfortunately, this critical issue has hardly been consciously considered. Here, ultrathin dopant‐free tunneling interlayers coated on the surface of graphene and sandwiched between the carbon sheets and the semiconductor nanostructures are adopted as a model system to demonstrate energy saving for the interfacial charge transfer. The nanostructuring confinement of band bending within the ultrathin interlayers in contact with the graphene sheets effectively narrows the width of the potential barriers, which enables tunneling of a substantial number of photogenerated electrons to the co‐catalysts without unduly consuming energy. Besides, the dopant‐free tunneling interlayers simultaneously block the transferred electrons in the sandwiched graphene sheets from leakage.

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“…We consider likely that the clusters originate at the sites of initial primary defects, to which only the upd process is sensitive, as it requires exposed substrate atoms to proceed. The h--BN layer is sufficiently thin for electron tunnelling to occur, thus allowing electrochemical electron transfer [37]. Consequently, for opd, the condition of exposed substrate atoms does not exist, and in principle opd Cu may be formed on top of the intact h--BN layer through the normal nucleation and growth process.…”

Section: Comparison Of the Voltammetric Behaviourmentioning

confidence: 99%

Copper underpotential deposition on boron nitride nanomesh

Mertens

2017

Electrochimica Acta

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The boron nitride nanomesh is a corrugated monolayer of hexagonal boron nitride (h--BN) on Rh(111), which so far has been studied mostly under ultrahigh vacuum conditions. Here, we investigate how copper underpotential deposition (upd) can be used to quantify defects in the boron nitride monolayer and to assess the potential window of the nanomesh, which is important to explore its functionality under ambient and electrochemical conditions. In dilute sulfuric acid, the potential window of h--BN/Rh(111) is close to 1 volt, i.e. larger than that of the Rh substrate, and is limited by molecular hydrogen evolution on the negative and by oxidative removal on the positive side. From copper upd on pristine h--BN/Rh(111) wafer samples, we estimate a collective defect fraction on the order of 0.08-0.7% of the geometric area, which may arise from line and point defects in the h--BN layer that are created during its chemical vapour deposition. Overpotential deposition (opd) is demonstrated to have significant consequences on the defect area. We hypothesise that this non--innocent Cu electrodeposition involves intercalation originating at initial defects, causing irreversible delamination of the h--BN layer; this effect may be used for 2D material nanoengineering. On the relevant timescale, upd itself does not alter the defect area on repeated cycling; therefore, metal upd may find use as a general tool to determine the collective defect area in hybrids between 2D materials and various substrate metals.

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Electrochemical Nonadiabatic Electron Transfer via Tunneling to Solution Species through Thin Insulating Films

Cited by 36 publications

References 45 publications

Electrochemical Diagnosis of Chemical Switch: Impact of Structural Changes on Charge Transport Mechanism of “Redox Anion Bound Polysilsesquioxane” Film

Electrochemical Diagnosis of Chemical Switch: Impact of Structural Changes on Charge Transport Mechanism of “Redox Anion Bound Polysilsesquioxane” Film

Nanostructuring Confinement for Controllable Interfacial Charge Transfer

Copper underpotential deposition on boron nitride nanomesh

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