Photoelectrochemical Degradation of Organic Pollutants Using BiOBr Anode Coupled with Simultaneous CO2 Reduction to Liquid Fuels via CuO Cathode

This study develops a novel system consisting of BiOBr as a photoanode and CuO as photocathode for coupling photoelectrocatalytic (PEC) oxidation of tetracycline (TC) with photoelectrocatalytic reduction of CO2 to form useful chemicals, such as CH3OH and CH3CH2OH. Under illumination, the degradation efficiency of TC was compared using photoelectrocatalytic (PEC), photocatalysis (PC), and electrocatalysis (EC) after 2.5 h. About 80% of TC was removed in the PEC process against 39% and 63% removed in PC and EC processes, respectively, and the kinetic constants of them are estimated to be 0.418, 0.211, and 0.286 h–1, respectively. Apparently, the results show the system of PEC has a synergistic effect between PC and EC for the degradation of TC. Furthermore, the onset potential of the total current was approximately −0.6 V (vs AgCl/Ag), and the yield of CH3OH and C2H5OH is the best at the bias potential of −0.7 V. And the yield of CH3OH and C2H5OH was 125.9 and 26.5 μmol/L, respectively. Results of UV–vis absorption spectra, total organic carbon, liquid chromatography-mass spectra, nuclear magnetic resonance, and in situ IR confirm the carbons change from organic pollutants to CO2 and then to liquid fuels. Finally, we proposed a catalytic mechanism to explain the synergetic effect of PEC oxidation and PEC reduction and the synergetic effect of PC and EC. The present work provides a new avenue to achieve the one-pot conversion of organic pollutants to liquid fuels and puts forward a new idea to couple PEC oxidation and PEC reduction.