Electrochemical Oxidation of Highly Oriented Pyrolytic Graphite in Sulphuric Acid Solution under Potential Pulse Condition

Abstract

We investigated the electrochemical oxidation of highly oriented pyrolytic graphite (HOPG) in sulphuric acid solution under applying alternative potential pulses to elucidate the oxidation mechanism of carbon support of Pt/C catalyst under dynamic operation of polymer electrolyte fuel cells (PEFCs). After the potential pulse test between 0.6 and 1.0 V for 15 h, the capacitance of HOPG was increased and pits were found on the oxidised surface. With increase in the lower potential limit to 0.8 V, the increasing rate of capacitance was almost equal to that after holding at 1.0 V for 15 h, which suggests that carbon oxidation reaction could be accelerated in PEFCs by continual variation of the cell voltage. After the potential pulse test between 0.2 and 1.0 V, it was clarified that alcohol and carbonyl groups were accumulated on the surface of HOPG. The oxidation mechanism of HOPG under potential pulse condition was described.

Novel Graphitised Carbonaceous Materials for Use as a Highly Corrosion‐Tolerant Catalyst Support in Polymer Electrolyte Fuel Cells

“…Figure 8 shows CVs of GCNSs, CNSs and CB on Au disk electrodes before and after potential holding at 1.0 V. Based on a comparison of these CVs, although CNSs and CB showed an increase in capacitance, GCNSs showed no change between before and after potential holding. In our previous reports, an increase in capacitance in CVs was observed after potential holding at 1.0 V, and was caused by the oxidation of vulnerable sites of the carbon surface [25,26]. At a potential of 0.55-0.60 V (vs. RHE) in the CVs of CB (Figure 8c), there was a redox couple, which was attributed to the redox of quinone/hydroquinone [27].…”

Comparative DEMS study on the electrochemical oxidation of carbon blacks

“…Consequently, a measurable property of the electrocatalyst such as the electrochemical surface area (ECSA) of the supported Pt particles is often related to a parameter of the corrosion treatment, such as number of CVs [25,26,30], potential pulses [20] or potential hold time [22,32], analogous to in situ AST approaches. These methodologies have also been enhanced by utilising analytical techniques such as transmission electron microscopy (TEM) [25,26], secondary electron microscopy (SEM) [21], atomic force microscopy (AFM) [30,32], X-ray photoelectron microscopy (XPS) [20,30,32] and EQCM [24]. Alternatively, corrosion half-cell studies may also focus on the dissolution of pure Pt electrodes [33].…”

“…For example, studies using three-electrode electrochemical half cells have investigated the electrochemical oxidation of model carbons [20,21], carbon blacks [22e24] and HSA carbon supported Pt catalysts [22,25e29]. These studies typically involve applying a certain electrochemical treatment, using either CV [25,26,30], chronoamperometry [22] or potential pulse [22,31] perturbation to a potential of at least 1.2 V RHE , with the intention of electrochemically oxidising the carbon or electrocatalyst material.…”

Insights into electrocatalytic activity of epitaxial graphene on SiC from cyclic voltammetry and ac impedance spectroscopy

“…Due to rather poor electrocatalytic activity of intrinsic graphene and graphite [25][26][27], the electrodes were activated by anodization [28,29]. It has been shown that during electrochemical oxidation, several functional groups connect to the graphite basal plane and many multivacancies and small etch pits appear [30]. As it was noticed in [31], the activation of graphite toward Fe(CN) 6 3−/4− redox reaction is rather related to the lattice damage than surface oxides.…”