Electrochemical oxidation of dihydronicotinamide adenine dinucleotide (NADH): comparison of highly oriented pyrolytic graphite (HOPG) and polycrystalline boron-doped diamond (pBDD) electrodes

Abstract

(2016) Electrochemical oxidation of dihydronicotinamide adenine dinucleotide (NADH) : Comparison of highly oriented pyrolytic graphite (HOPG) and polycrystalline boron-doped diamond (pBDD) electrodes. Physical Chemistry Chemical Physics. Permanent WRAP URL:http://wrap.warwick.ac.uk/81637 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work of researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. The electro-oxidation of nicotinamide adenine dinucleotide (NADH) is studied at bare surfaces of highly oriented pyrolytic graphite (HOPG) and semi-metallic polycrystalline boron-doped diamond (pBDD). A comparison of these two carbon electrode materials is interesting because they possess broadly similar densities of electronic states that are much lower than most metal electrodes, but graphite has carbon sp 2 -hybridization, while in diamond the carbon is sp 3 -hybridised, with resulting major differences in bulk structure and surface termination. Using cyclic voltammetry (CV), it is shown that NADH oxidation is facile at HOPG surfaces but the reaction products tend to strongly adsorb, which causes rapid deactivation of the electrode activity. This is an important factor that needs to be taken into account when assessing HOPG and its intrinsic activity. It is also shown that NADH itself adsorbs at HOPG, a fact that has not been recognized previously, but has implications for understanding the mechanism of the electro-oxidation process. Although pBDD was found to be less susceptible to surface fouling, pBDD is not immune to deterioration of the electrode response, and the reaction showed more sluggish kinetics on this electrode. Scanning electrochemical cell microscopy (SECCM) highlights a significant voltammetric variation in electroactivity between different crystal surface facets that are presented to solution with a pBDD electrode. The electroactivity of different grains correlates with the local dopant level, as visualized by field emission-scanning electron microscopy. SECCM measurements further prove that the basal plane of HOPG has high activity towards NADH electro-oxidation. These new insights on NADH voltammetry are useful for the design of optimal carbon-based electrodes for NADH electroanalysis.

Nanoscale Electrochemical Mapping

“…Macroscopic measurements at O-pBDD revealed that while it is less active than HOPG, it is also less susceptible (but not immune) to surface fouling, while microscopic voltammetric measurements (with SECCM) revealed a strong grain dependence, with activity scaling with local (grain-dependent) dopant density. 212 Local electrochemical measurements with SECCM can be coupled with co-located ex situ electron back scatter diffraction (EBSD) characterization to resolve structure-activity at the individual grains and GBs that comprise a polycrystalline surface. 184,213 This "pseudo single-crystal approach" was employed to understand the microscopic factors (surface termination and doping level) determining the electrochemical solvent window (i.e., the potential range over which the solvent/electrolyte is stable to electrolysis) of O-pBDD and hydrogen-terminated polycrystalline BDD (H-pBDD) in aqueous potassium chloride.…”

Scanning Probe Microscopy for Nanoscale Electrochemical Imaging

“…SECCM is also a useful tool to investigate local electrochemical reactions of graphite , and graphene. , In particular, the influence of the edge states of graphite/graphene in electrochemistry is a hot topic because of their unusual density of states phenomena. Unwin and co-workers first observed that the basal plane of pristine graphite in any grade of highly oriented pyrolytic graphite (HOPG) sample shows electron transfer activities .…”

“…Furthermore, SECCM imaging showed that the basal plane supports faster electron transfer, which is not clearly observed at the step edges. Once HOPG is cleaved and exposed to air, its surface conductivity and electrochemical response deteriorate, which is strongly associated with the electrochemical activity on the top layer. − Thus, for immaculate exfoliated graphene surfaces, samples should be carefully prepared by controlling the atmosphere, considering oxidation or surface contamination by the atmosphere Figure b shows an SECCM image of the surface of graphene with various numbers of step edges (layers).…”

“…SECCM is also a useful tool to investigate local electrochemical reactions of graphite 195,196 and graphene. 197,198 In particular, the influence of the edge states of graphite/graphene in electrochemistry is a hot topic because of their unusual density of states phenomena.…”

A Flexible Platform of Electrochemically Functionalized Carbon Nanotubes for NADH Sensors

“…Oxidation of NADH at conventional electrodes, namely glassy carbon, Pt, and Au, requires particularly high overpotentials and induces massive passivation of the surface [4,5,6,7]. For this reason, many materials have been developed and studied so far, aiming at realization of efficient amperometric sensors for the detection of this analyte [8,9,10].…”