Electrocatalytic Oxidation of Dibenzothiophene and 4,6-Dimethyldibenzothiophene at Gold-Polyaniline (Au-PANI) Composite Electrodes

Abstract

In this study, glassy carbon electrodes modified with gold-polyaniline (Au-PANI) were evaluated for the ability to electrochemically oxidize dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Au-PANI was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron micrograph (TEM), and scanning electron micrograph (SEM). The role of nitrogen groups of PANI on the formation of Au-PANI was shown by FT-IR. XPS confirmed the various electronic states and environment of oxygen, nitrogen, gold, and carbon in Au-PANI film. TEM results indicated that Au particle size is in the range of 3.50–6.97 nm, while SEM results confirmed the heterogeneous nature of PANI and Au-PANI surfaces. In this study, density functional theory (DFT) with the B3LYP functional and 6-311++G** basis set was used to examine the electronic properties of DBT/4,6-DMDBT onto the surface of PANI nanocomposite. Electrochemical tests indicate that the Au-PANI exhibits high catalytic activity for DBT and 4,6-DMDBT electrooxidation. Oxidation products such as DBTO = dibenzothiophene sulfoxide; 4,6-DMDBTO = 4,6-dimethydibenzothiophene sulfoxide; DBTO2 = dibenzothiophene sulfone; and 4,6-DMDBTO2 = 4,6-dimethydibenzothiophene sulfone were confirmed by means of gas chromatograph coupled to mass spectrometer (GC-MS), 1H, and 13C NMR.