Analysis On The Electrochemical Reduction Process Of Graphene Oxide And Its Electrocatalytic Application

Graphene oxide （GO） has many good catalytic activity because of the oxygen-containing functional groups on the surface. It can tune the defect and sp2 fraction by careful and controllable removal of oxygen groups through the reduction method, and it is great importance for the electrochemical properties of GO. In this study, it utilized the electrochemical synthetic method to reduced GO by applying different negative potentials （-0.5 V～-1.8 V） in order to get different reduction degree of graphene oxide （ERGOs）. And the structure features, the catalytic properties of these materials were characterized. So that it can speculate the reduction mechanism and the electric catalytic activity of ERGOs in the process of electrochemical reduction.In this study, all the ERGOs were characterized with Raman spectra to study the change about the defect and the crystallite size （La）, and it showed that the defect decreased with the increase of the reduction potential. Fourier transform infrared spectroscopy （FT-IR） and X-ray photoelectron spectroscopy （XPS） were used to characterize functional groups on the surface of ERGOs. It found that the C/O ratio increases with the increase of the reduction degree, and functional groups also changed. Also the study inferred the changing order of oxygen-containing functional groups in the range of -0.5 V～-1.8 V. The carboxyl （O-C=O） was easy to remove, and next was carbon-oxygen bond （C-O） and carbonyl carbon oxygen （C=O）.It used potassium ferricyanide, hydroquinone （HQ） and ascorbic acid （AA） to study the electrochemical properties and the catalytic performance of ERGOs. The result suggested that the catalytic about ERGO to [Fe（CN）6]3-/4-was associated with the defect. It concluded that the higher La was benefit for the electrical conductivity of ERGO. Therefor the electrochemical behavior of [Fe（CN）6]3-/4-was associated with the conductivity of ERGO. ERGOs modified electrodes has catalysis to HQ and AA, and the reaction mechanism was associated with the C=O on the surface of ERGOs.ERGO.0.8V and ERGO₁.4V obtained from the above was applied to catalyze the TTC and Cr6+ analyzing the structure and the characteristics of functional groups, respectively. Studies have shown the redox reaction occurred on ERGO-0.8v/GC about TTC. Compared with the carbon nanotubes modified electrodes, the redox reaction shifted negatively with the oxidation potential at 0-0.5 V, demonstrating the catalytic effect of ERGO-0.8V on TTC. Also, it shown that in the concentration of 0 mg/L～160 mg/L about TTC, the peak current has good linear responses with the TTC concentration, which displayed the reliability of this kind of sensor. Therefore, we can correlate the oxygen-containing groups adjusting was the main effect factor for unique electrocatalysis of ERGO, and the defects density and sp2 domains having profound influence on it as well. The redox peaks at 0～0.5 V on the ERGO electrode may be contributed to the transform between carboxyl C=O and hydroxyl C-OH, corresponding to the conversion between hydroquinone and quinone. Cr6+ was reducted on the ERGO-1.4v modified electrode with the reduction peak appeared at 0.35 V, which was corresponding for Cr6+ conversion to Cr5+. The peak current has good linear responses with the Cr6+ concentration （0.05 mM～1 mM）. It speculated that C=O and O-C-O on the surface provided a large number of adsorption sites for Cr6+, and it is good for electric catalytic reaction about ERGO to Cr6+.