Electrochemical hydrogenation and desulfurization of thiophenic compounds over MoS2 electrocatalyst using different membrane-electrode assembly

Abstract

The desulfurization-hydrogenation of thiophene and benzothiophene in hexadecane as a model diesel fuel was studied through a divided cell with the incorporation of a membrane electrode assembly (MEA) under different current density at a constant charge. The reduction of the thiophenic compounds was investigated using a prepared MoS2 nano-electrocatalyst, Nafion (commercial proton exchange membrane), and synthesized sulfonated poly ether ether ketone (SPEEK). Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) were used to characterize the MoS2 electrocatalyst, which confirmed the formation of 23-25 nm ball-like nano-threads of MoS2. Also, the electrocatalyst and/or MEA was electrochemically analyzed by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The gas chromatography-mass spectroscopy (GC-MS) analysis of the reactants and products revealed the direct desulfurization on the thiophene reduction process and the desulfurization along with the desulfurization pathway on the benzothiophene reduction experiment. A maximum desulfurization efficiency of 79.6% at 20 mA cm-2 and 51.5% at 30 mA cm-2 under the constant charge of 300 C was obtained for thiophene using the MoS2-Nafion and MoS2-SPEEK system, respectively. Moreover, a maximum hydrogenation and desulfurization efficiency of 28% and 59.1% occurred at 50 mA cm-2 and 70 mA cm-2, respectively, for the benzohiophene-Nafion system under the constant charge of 400 C. The distribution of the products affirmed that the desulfurization reaction contributed more at a higher current density against the hydrogenation process at a lower current density.