Combining the bioelectricity generation with Photo-Electrocatalytic reduction of CO2 for pollutants degradation and ethanol generation

Abstract

Under this investigation, a p-n heterojunction nanocomposite (CuS/MgFe2O4) was synthesized using a simplified hydrothermal technique. According to the results of UV–vis diffuse reflectance spectroscopy (DRS) research, the creation of a p-n heterojunction structure lowered the band-gap value and improved the optical characteristics of the synthesized CuS/MgFe2O4 nanocomposite in contrast to CuS and MgFe2O4 nanoparticles. To investigate the electrocatalytic and photo-electrocatalytic properties of nanoparticles in the CO2 reduction reaction, first, the synthesized catalysts were immobilized by the electrophoretic deposition method (EPD) on a graphite electrode, and then various electrochemical techniques such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were performed in the phosphate electrolyte (0.1 M, pH = 8) saturated with CO2 gas in the presence and absence of light. As a consequence, CuS/MgFe2O4/Graphite displayed a 2.2 and 1.3-fold increase in cathodic current density under light illumination compared to MgFe2O4/Graphite and CuS/Graphite, respectively. Using CuS/Graphite, MgFe2O4/Graphite, and CuS/MgFe2O4/Graphite as photocathodes in a two-chamber microbial fuel cell (MFC) caused a 13, 29, and 45 times increase, respectively, in the maximum power density compared to unmodified graphite. Gas chromatography-mass spectrometry (GC–MS) analysis revealed the presence of ethanol as the only detected CO2 conversion product, with a Faradic efficiency of about 35 %.