Modification of expanded graphite resulting in enhancement of electrochemical activity in the process of phenol oxidation

Abstract

The aimed modification of expanded graphite electrodes (EG) was divided into two independent parts consisting of chemical treatment in the mixture of concentrated H 2 SO 4 /HNO 3 and subsequent heat treatment performed at elevated temperature in air. The electrochemical features of modified samples were examined in the model process of phenol electrooxidation which was realized in alkaline medium by the cyclic voltammetry technique. Taking into account the charges of anodic peaks corresponding to the phenol oxidation it was found that a two-step treatment of EG brought about over two-fold improvement of its electrochemical activity as compared to the initial cycle of regarded process. The reason for such a behavior can be ascribed to the changes in chemical composition of the EG surface as well as the changes in porous structure including almost a two-fold development of specific surface area and by a four-fold increase of the sample volume affected by the thermal treatment. According to the X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy data, the modification of EG resulted in a significant increase of the surface oxygen groups containing C-O.

Multiple anodic regeneration of exfoliated graphite electrodes spent in the process of phenol electrooxidation

“…Electrochemical oxidation of phenol Figure 1 displays cyclic voltammograms recorded during the electrooxidation of 0.1 M phenol at the electrode made of original EG. The well-defined anodic peak seen for the first cycle at the potential of 0.38 V can be ascribed to the reaction of phenol oxidation [12][13][14]. As can be seen from this figure, the intensities as well as anodic charges markedly fell for the second and third cycles.…”

“…Before each measurement, 15 mg of electrode material was inserted into a pocket, made of porous polymer material, around the current collector. The details of electrode preparation procedure were described in our previous papers [12][13][14][15]. The processes of voltammetric oxidation of phenol were performed at a scan rate of 0.1 mV s −1 in the potential range from the rest potential of electrode (E R ) to 0.8 V.…”

“…Among the materials commonly applied to electrooxidation of phenol are metals (e.g., Pt, Au,) [2,3,5] and oxides (e.g., IrO 2 , PbO 2 , RuO 2 ) [6,7]. A completely different group of electrodes used for phenol electrooxidation are carbon materials, such as diamond [8,9], glass-like carbon [10,11], carbon fibers [11], and exfoliated graphite (EG) [12][13][14][15]. The minimization of passivation effect can be reached by the modifications of applied electrolyte as well as by the use of appropriate conditions of electrooxidation.…”

Influence of expanded graphite coming from the electrochemical oxidation of phenol on cement-polymer matrix

“…The process of exfoliation was performed in a muffl e furnace at the temperature 800°C for 4 min. H 2 SO 4 -GIC used for exfoliation was prepared by anodic oxidation of graphite powder, with particles 32 to 71 μm in diameter, in 18 M H 2 SO 4 15 .…”

“…Therefore, the electro-oxidation of the hazardous pollutants from wastewater has been extensively studied during the recent years. In the electrochemical oxidation, the organic compounds adsorbed on the surface of anode are converted to carbon dioxide which can be easily removed 1- 4 . One of the anode processes which is conventionally used to remove organic pollutants from sewage is the electrochemical oxidation of phenol.…”