Studying Heterogeneous Catalysis by the Scanning Electrochemical Microscope (SECM):  The Reduction of Protons by Methyl Viologen Catalyzed by a Platinum Surface

Selzer, Yoram; Turyan, and Iva; Mandler, Daniel

doi:10.1021/jp9833348

Cited by 46 publications

(70 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The RG effect at an unbiased substrate, which has not been considered in any previous SECM study, 21,23,33 was further confirmed by simulating approach curves for probes with different outer diameters (Figure 4a). With b/a = 10, current approach curves change from negative to positive as RG changes from 50 to 1.1.…”

Section: Rg Effect On the Detectable Substrate Sizesupporting

confidence: 56%

Probing Heterogeneous Electron Transfer at an Unbiased Conductor by Scanning Electrochemical Microscopy in the Feedback Mode

2007

View full text Add to dashboard Cite

The theory of the feedback mode of scanning electrochemical microscopy is extended for probing heterogeneous electron transfer at an unbiased conductor. A steady-state SECM diffusion problem with a pair of disk ultramicroelectrodes as a tip and a substrate is solved numerically. The potential of the unbiased substrate is such that the net current flow across the substrate/solution interface is zero. For a reversible substrate reaction, the potential and the corresponding tip current depend on SECM geometries with respective to the tip radius including not only the tip-substrate distance and the substrate radius but also the thickness of the insulating sheath surrounding the tip. A larger feedback current is obtained using a probe with a thinner insulating sheath, enabling identification of a smaller unbiased substrate with a radius that is approximately as small as the tip radius. An intrinsically slow reaction at an unbiased substrate as driven by a SECM probe can be quasireversible. The standard rate constant of the substrate reaction can be determined from the feedback tip current when the SECM geometries are known. The numerical simulations are extended to an SECM line scan above an unbiased substrate to demonstrate a "dip" in the steady-state tip current above the substrate center. The theoretical predictions are confirmed experimentally for reversible and quasi-reversible reactions at an unbiased disk substrate using disk probes with different tip radii and outer radii.Scanning electrochemical microscopy (SECM) is a powerful electroanalytical technique for probing interfacial reactions at a variety of substrates. 1-3 SECM is versatile partially because the substrates do not require an electrical connection to an external circuit, 4 which is in contrast to traditional electroanalytical techniques. 5 SECM measurement of unbiased substrates is advantageous when the substrates can not be conveniently connected to an external circuit or when the application of a potential causes an undesirable effect on the substrates. In particular, SECM feedback mode has been used in recent studies of charge transport at unbiased nanostructured systems such as metal nanoparticle arrays/films, 6-13 carbon nanotube network, 14 individual nanobands, 15 an array of protein nanopores, 16 and nanometer-thick polymer films. 17-20 A heterogeneous electron transfer process at an unbiased conductor can be studied by SECM in the feedback mode, where the process is driven and monitored using an ultramicroelectrode (UME) probe. Consider a disk UME positioned within a short distance (usually within about the tip diameter) of a disk-shaped conductive substrate (Figure 1). The UME tip is biased for electrolysis of a redox-active mediator, O, in the electrolyte solution (O + ne − → R; process 1 in Figure 1). The tip-generated species, R, diffuses to and reacts at the surface of the conductive

show abstract

Section: Rg Effect On the Detectable Substrate Sizesupporting

confidence: 56%

Probing Heterogeneous Electron Transfer at an Unbiased Conductor by Scanning Electrochemical Microscopy in the Feedback Mode

2007

View full text Add to dashboard Cite

show abstract

“…In the case of the result at shorter distance, it is possible that steady-state [8,36] or transient [5] surface phenomena are responsible for the larger differences observed. The experimental re- sults agreed well, within the experimental error, with the simulated prediction.…”

Section: à11mentioning

confidence: 94%

Evaluation of the Chemical Reactions from Two Electrogenerated Species in Picoliter Volumes by Scanning Electrochemical Microscopy

Wang¹,

Rodríguez‐López²,

Bard³

2010

ChemPhysChem

View full text Add to dashboard Cite

The volume created by the positioning of two scanning electrochemical microscope (SECM) probes (tip and substrate) at a micrometric distance defines a "picoliter beaker" where homogeneous electron-transfer reactions are studied. The SECM is used to concurrently electrogenerate in situ two reactive species and to evaluate the possibility of detecting their reactivity. Two reaction cases are studied: the first, called the "reversible case", occurs when the electrochemically generated species at the substrate electrode can also react at the tip to yield the same product as the reaction in the gap. The second case, named the "irreversible case", occurs when the electrochemically generated species at the substrate are not able to react at the tip. Digital simulations are performed and compared to experimental studies. These show that an unusual compensation between collection and feedback effects render the analysis inapplicable in the "reversible case". The "irreversible case" is shown experimentally.

show abstract

“…In terms of methodology, this work thus further contributes to a growing body demonstrating that SECM is a powerful tool for the investigation of the catalytic activity of nanostructured interfaces. [7,[44][45][46][47][48][49][50] Moreover, the work provides an impetus for inducing the HER mediated by redox-active solution species.…”

Section: Introductionmentioning

confidence: 99%

Incorporation of Functionalized Palladium Nanoparticles within Ultrathin Nafion Films: A Nanostructured Composite for Electrolytic and Redox‐Mediated Hydrogen Evolution

Li¹,

Bertoncello²,

Ciani³

et al. 2008

Adv Funct Materials

View full text Add to dashboard Cite

A novel ultrathin Nafion‐palladium nanocomposite film is developed by incorporating positively charged Pd nanoparticles, stabilized with dimethylaminopyridine (DMAP), into Nafion Langmuir‐Schaefer (LS) films. The films show considerable activity for the redox‐catalyzed hydrogen‐evolution reaction, the rate of which scales with film thickness. The Nafion film can be deposited on both insulating (glass) and electrode (indium‐tin oxide) surfaces. The quantity of Pd nanoparticles immobilized can be controlled simply via the thickness of the Nafion film. The morphology of the films are investigated using AFM, which allows the number density of nanoparticles to be estimated for the thinnest (10 layers; 18 nm) films. Incorporation of nanoparticles is also determined with cyclic voltammetry and UV‐visible spectroscopy. The former method allows estimation of the electrochemically active surface area of Pd wired to the underlying electrode. A novel scanning electrochemical microscopy (SECM) approach is used to investigate the kinetics of the hydrogen evolution reaction (HER) catalyzed by Pd nanoparticles within the Nafion film, which allows the intrinsic activity to be determined. Single nanoparticle reactivities are extracted and are comparable to the activity of native nanoparticles on glass and to bulk Pd. It is found that neither Nafion encapsulation nor DMAP functionalization impair the electrocatalytic activity of these nanoparticles towards the HER. Nafion encapsulation thus provides a framework for the formation of interfaces, whose activity scales with film thickness. The creation of 3D materials opens up the possibility of carrying out redox‐mediated hydrogen evolution using solution species as the electron donor.

show abstract

Studying Heterogeneous Catalysis by the Scanning Electrochemical Microscope (SECM): The Reduction of Protons by Methyl Viologen Catalyzed by a Platinum Surface

Cited by 46 publications

References 47 publications

Probing Heterogeneous Electron Transfer at an Unbiased Conductor by Scanning Electrochemical Microscopy in the Feedback Mode

Probing Heterogeneous Electron Transfer at an Unbiased Conductor by Scanning Electrochemical Microscopy in the Feedback Mode

Evaluation of the Chemical Reactions from Two Electrogenerated Species in Picoliter Volumes by Scanning Electrochemical Microscopy

Incorporation of Functionalized Palladium Nanoparticles within Ultrathin Nafion Films: A Nanostructured Composite for Electrolytic and Redox‐Mediated Hydrogen Evolution

Contact Info

Product

Resources

About