Definitive Evidence for Fast Electron Transfer at Pristine Basal Plane Graphite from High‐Resolution Electrochemical Imaging

Lai, Stanley C. S.; Patel, Anisha N.; McKelvey, Kim; Unwin, Patrick R.

doi:10.1002/anie.201200564

Cited by 150 publications

(200 citation statements)

References 45 publications

Supporting

Mentioning

187

Contrasting

Unclassified

Order By: Relevance

“…~10 -3 cm s -1 for macroscopic systems) in this configuration. 8 In conclusion, we have demonstrated a SECCM-based approach to land and characterize single NPs on electrodes with minimal electrode preparation and the ability to select the measurement location. The results obtained with this approach are consistent with previous NP landing studies on UMEs 3a-f but with enhanced sensitivity due to the lower background signals owing to a smaller contact area.…”

Section: Introductionmentioning

confidence: 90%

“…HOPG is an interesting substrate as it serves as a model for novel sp 2 carbon materials and there has been recent debate on the active sites for electron transfer. 8 Furthermore, the surface of HOPG is easily refreshed (through cleaving with adhesive tape) and has low background currents, making it an attractive collector electrode for NP landing experiments. Typical current-time plots obtained for the landing of AuNPs on HOPG at various potentials (Figure 2a-d) show a few general trends.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Landing and Catalytic Characterization of Individual Nanoparticles on Electrode Surfaces

et al. 2012

Self Cite

View full text Add to dashboard Cite

We demonstrate a novel and versatile pipetbased approach to study the landing of individual nanoparticles (NPs) on various electrode materials without any need for encapsulation or fabrication of complex substrate electrode structures, providing great flexibility with respect to electrode materials. Because of the small electrode area defined by the pipet dimensions, the background current is low, allowing for the detection of minute current signals with good time resolution. This approach was used to characterize the potential-dependent activity of Au NPs and to measure the catalytic activity of a single NP on a TEM grid, combining electrochemical and physical characterization at the single NP level for the first time. Such measurements open up the possibility of studying the relation between the size, structure and activity of catalyst particles unambiguously.

show abstract

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Landing and Catalytic Characterization of Individual Nanoparticles on Electrode Surfaces

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…31,[34][35][36] Studies of basal plane graphite 32,33 are particularly pertinent, in light of the considerable recent revision of, and interest in, the local electrochemical activity of highly oriented pyrolytic graphite (HOPG). [37][38][39][40][41] Previous studies proposed that the step edge density on basal plane HOPG correlated with various electrochemical measurements in aqueous solution, specifically the double layer capacitance (C°), the electron transfer kinetics for the redox couple ferri/ferrocyanide, and the surface coverage (Γ ads ) of adsorbed electroactive anthraquinone-2,6-disulfonate (AQDS). 26,27,42 These studies found that cleaved HOPG surfaces with greater step edge coverage tended to display higher Γ ads for AQDS adsorption (at a particular bulk concentration).…”

Section: Introductionmentioning

confidence: 99%

“…However, the only attempt to correlate step edge density and Γ ads focused on samples with a very narrow range of step densities (from 0.7% to 1.6%) with relatively high uncertainty in the absolute step edge density values. 26 Moreover, the ferri/ferrocyanide couple has since been shown to be problematic on the basal surface of graphite 41 and other surfaces. 43 These various issues, and further points outlined below, raise significant questions as to the validity of AQDS adsorption as a marker of step edge density and, more broadly, the veracity of older models of HOPG electrochemistry.…”

Section: Introductionmentioning

confidence: 99%

Molecular Functionalization of Graphite Surfaces: Basal Plane versus Step Edge Electrochemical Activity

et al. 2014

Self Cite

View full text Add to dashboard Cite

The chemical functionalization of carbon surfaces has myriad applications, from tailored sensors to electrocatalysts. Here, the adsorption and electrochemistry of anthraquinone-2,6-disulfonate (AQDS) is studied on highly oriented pyrolytic graphite (HOPG) as a model sp 2 surface. A major focus is to elucidate whether adsorbed electroactive AQDS can be used as a marker of step edges, which have generally been regarded as the main electroactive sites on graphite electrode surfaces. First, the macroscopic electrochemistry of AQDS is studied on a range of surfaces differing in step edge density by more than 2 orders of magnitude, complemented with ex-situ tapping mode atomic force microscopy (AFM) data. These measurements show that step edges have little effect on the extent of adsorbed electroactive AQDS. Second, a new fast scan cyclic voltammetry (FSCV) protocol carried out with scanning electrochemical cell microscopy (SECCM) enables the evolution of AQDS adsorption to be followed locally on a rapid timescale. Subsequent AFM imaging of the areas probed by SECCM allows a direct correlation of the electroactive adsorption coverage and the actual step edge density of the entire working area. The amount of adsorbed electroactive AQDS and the electron transfer kinetics are independent of the step edge coverage. Last, SECCM reactive patterning is carried out with complementary AFM measurements, to probe the diffusional electroactivity of AQDS. There is essentially uniform and high activity across the basal surface of HOPG. This work provides new methodology to monitor adsorption processes at surfaces and shows unambiguously that there is no correlation between the step edge density of graphite surfaces and the observed coverage of electroactive AQDS. The electroactivity is dominated by the basal surface, and studies that have used AQDS as a marker of steps need to be revised.3

show abstract

“…This is particularly true for the Fe 2+/3+ redox process. 47,50 Based on our recent work, 21,[24][25][26][27][28][29]33,51 SECCM provides a powerful method to investigate whether structural effects hold for the oxidation of Fe 2+ on polycrystalline platinum.…”

Section: Introductionmentioning

confidence: 99%

Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe²⁺/Fe³⁺ Redox Reaction

et al. 2013

Self Cite

View full text Add to dashboard Cite

The influence of electrode surface structure on electrochemical reaction rates and mechanisms is a major theme in electrochemical research, especially as electrodes with inherent structural heterogeneities are used ubiquitously. Yet, probing local electrochemistry and surface structure at complex surfaces is challenging. In this paper, high spatial resolution scanning electrochemical cell microscopy (SECCM) complemented with electron backscatter diffraction (EBSD) is demonstrated as a means of performing ‘pseudo-single-crystal’ electrochemical measurements at individual grains of a polycrystalline platinum electrode, while also allowing grain boundaries to be probed. Using the Fe2+/3+ couple as an illustrative case, a strong correlation is found between local surface structure and electrochemical activity. Variations in electrochemical activity for individual high index grains, visualized in a weakly adsorbing perchlorate medium, show that there is higher activity on grains with a significant (101) orientation contribution, compared to those with (001) and (111) contribution, consistent with findings on single-crystal electrodes. Interestingly, for Fe2+ oxidation in a sulfate medium a different pattern of activity emerges. Here, SECCM reveals only minor variations in activity between individual grains, again consistent with single-crystal studies, with a greatly enhanced activity at grain boundaries. This suggests that these sites may contribute significantly to the overall electrochemical behavior measured on the macroscale.

show abstract

Definitive Evidence for Fast Electron Transfer at Pristine Basal Plane Graphite from High‐Resolution Electrochemical Imaging

Cited by 150 publications

References 45 publications

Landing and Catalytic Characterization of Individual Nanoparticles on Electrode Surfaces

Landing and Catalytic Characterization of Individual Nanoparticles on Electrode Surfaces

Molecular Functionalization of Graphite Surfaces: Basal Plane versus Step Edge Electrochemical Activity

Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe²⁺/Fe³⁺ Redox Reaction

Contact Info

Product

Resources

About

Definitive Evidence for Fast Electron Transfer at Pristine Basal Plane Graphite from High‐Resolution Electrochemical Imaging

Cited by 150 publications

References 45 publications

Landing and Catalytic Characterization of Individual Nanoparticles on Electrode Surfaces

Landing and Catalytic Characterization of Individual Nanoparticles on Electrode Surfaces

Molecular Functionalization of Graphite Surfaces: Basal Plane versus Step Edge Electrochemical Activity

Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe2+/Fe3+ Redox Reaction

Contact Info

Product

Resources

About

Pseudo-Single-Crystal Electrochemistry on Polycrystalline Electrodes: Visualizing Activity at Grains and Grain Boundaries on Platinum for the Fe²⁺/Fe³⁺ Redox Reaction