Unwin, Patrick R., Guell, Aleix G. and Zhang, Guohui (2016) Nanoscale electrochemistry of sp2 carbon materials : from graphite and graphene to carbon nanotubes. Accounts of Chemical Research, 49 (9). pp. 2041-2048. doi:10.1021/acs.accounts.6b00301 ISSN 0001-4842.

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Abstract

Carbon materials have a long history of use as electrodes in electrochemistry, from (bio)electroanalysis to applications in energy technologies, such as batteries and fuel cells. With the advent of new forms of nanocarbon, particularly, carbon nanotubes and graphene, carbon electrode materials have taken on even greater significance for electrochemical studies, both in their own right and as components and supports in an array of functional composites.

With the increasing prominence of carbon nanomaterials in electrochemistry comes a need to critically evaluate the experimental framework from which a microscopic understanding of electrochemical processes is best developed. This Account advocates the use of emerging electrochemical imaging techniques and confined electrochemical cell formats that have considerable potential to reveal major new perspectives on the intrinsic electrochemical activity of carbon materials, with unprecedented detail and spatial resolution. These techniques allow particular features on a surface to be targeted and models of structure–activity to be developed and tested on a wide range of length scales and time scales.

When high resolution electrochemical imaging data are combined with information from other microscopy and spectroscopy techniques applied to the same area of an electrode surface, in a correlative-electrochemical microscopy approach, highly resolved and unambiguous pictures of electrode activity are revealed that provide new views of the electrochemical properties of carbon materials. With a focus on major sp2 carbon materials, graphite, graphene, and single walled carbon nanotubes (SWNTs), this Account summarizes recent advances that have changed understanding of interfacial electrochemistry at carbon electrodes including: (i) Unequivocal evidence for the high activity of the basal surface of highly oriented pyrolytic graphite (HOPG), which is at least as active as noble metal electrodes (e.g., platinum) for outer-sphere redox processes. (ii) Demonstration of the high activity of basal plane HOPG toward other reactions, with no requirement for catalysis by step edges or defects, as exemplified by studies of proton-coupled electron transfer, redox transformations of adsorbed molecules, surface functionalization via diazonium electrochemistry, and metal electrodeposition. (iii) Rationalization of the complex interplay of different factors that determine electrochemistry at graphene, including the source (mechanical exfoliation from graphite vs chemical vapor deposition), number of graphene layers, edges, electronic structure, redox couple, and electrode history effects. (iv) New methodologies that allow nanoscale electrochemistry of 1D materials (SWNTs) to be related to their electronic characteristics (metallic vs semiconductor SWNTs), size, and quality, with high resolution imaging revealing the high activity of SWNT sidewalls and the importance of defects for some electrocatalytic reactions (e.g., the oxygen reduction reaction). The experimental approaches highlighted for carbon electrodes are generally applicable to other electrode materials and set a new framework and course for the study of electrochemical and interfacial processes.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry T Technology > TA Engineering (General). Civil engineering (General)
Divisions:	Faculty of Science, Engineering and Medicine > Science > Chemistry
Library of Congress Subject Headings (LCSH):	Electrochemistry, Electrochemical analysis , Carbon -- Imaging, Carbon nanotubes , Graphene, Electrodes, Carbon
Journal or Publication Title:	Accounts of Chemical Research
Publisher:	American Chemical Society
ISSN:	0001-4842
Official Date:	20 September 2016
Dates:	Date Event 20 September 2016 Published 8 August 2016 Available 8 August 2016 Accepted 16 June 2016 Submitted
Volume:	49
Number:	9
Page Range:	pp. 2041-2048
DOI:	10.1021/acs.accounts.6b00301
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Date of first compliant deposit:	15 September 2016
Date of first compliant Open Access:	8 August 2017
Funder:	European Union (EU), Engineering and Physical Sciences Research Council (EPSRC)

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