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Issue 30, 2018
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Exploring the electrochemical performance of graphite and graphene paste electrodes composed of varying lateral flake sizes

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Abstract

We report the fabrication, characterisation (SEM/EDX, TEM, XRD, XPS and Raman spectroscopy) and electrochemical properties of graphite and graphene paste electrodes with varying lateral flake sizes. The fabricated paste electrodes are electrochemically analysed using both outer-sphere and inner-sphere redox probes, namely; hexaammineruthenium(III) chloride, N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), potassium ferrocyanide(II) and ammonium ferrous(II) sulphate. Upon comparison of different graphite paste electrodes, a clear correlation between the lateral flake sizes (La), ranging from 1.5 mm–0.5 μm, and electrochemical activity (heterogeneous electron transfer (HET) kinetics) is evident, where an improvement in the HET is observed at smaller lateral flake sizes. We infer that the beneficial response evident when employing laterally smaller flakes is due to an increased number of edge plane like-sites/defects available upon the electrode surface, facilitating electron transfer. Interestingly, given that the overall lateral flake sizes of the graphenes utilised (10.0–1.3 μm) were significantly smaller than those studied previously, an improvement in HET kinetics was also evident with the reduction of lateral flake size; the extent to which is redox-probe dependent. Improvements are observed up to a distinct point, termed the ‘lateral size threshold’ (ca. ≤2 μm) where the electrochemical reversible limit is approached. Further support is provided from density functional theory (DFT), exploring the electronic structure (i.e. HOMO–LUMO) as a function of flake size, which demonstrates that the coverage of edge plane like-sites/defects comprising the geometric structure of the relatively small graphene flakes is such that effectively the entire flake has become electrochemically active. In this study, the importance of lateral flake size with respect to electrochemical reactivity at carbon-based electrodes has been demonstrated alongside a structural relationship upon HET performance, a phenomenon that has not previously been described in the literature. Such work is both highly important and informative for the field of electrochemistry and electrode performance, with potential implications in a plethora of areas, ranging from novel renewable energy sources to electroanalytical sensing platforms.

Graphical abstract: Exploring the electrochemical performance of graphite and graphene paste electrodes composed of varying lateral flake sizes

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Supplementary files

Article information


Submitted
06 Apr 2018
Accepted
11 Jul 2018
First published
11 Jul 2018

This article is Open Access

Phys. Chem. Chem. Phys., 2018,20, 20010-20022
Article type
Paper

Exploring the electrochemical performance of graphite and graphene paste electrodes composed of varying lateral flake sizes

A. J. Slate, D. A. C. Brownson, A. S. Abo Dena, G. C. Smith, K. A. Whitehead and C. E. Banks, Phys. Chem. Chem. Phys., 2018, 20, 20010 DOI: 10.1039/C8CP02196A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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