Degradation Of Rhodamine B And Electricity Generation By Ag/AgCl/GO-based Photocatalytic Fuel Cell

The deteriorating situations in water pollution and energy crisis have become this generation’s primary concerns, and will probably last into the next generation. The discharge of pollutants and the excessive consumption of energy negatively impact the environment. To overcome these problems in wastewater treatment, new energy-efficient wastewater treatment technologies need to be developed. One kind of attractive technology is the microbial fuel cell （MFC） which treats waste water and produces electricity. But the power output and low pollutant removal rate of MFC are major obstacles to its application and development. Photocatalytic fuel cell （PFC） has the advantages of MFC and photocatalysis. However, TiO₂-based photoanodes are only driven by UV light. To increase the light response in the visible range, modifications on TiO₂ photoanodes are required. High cost Pt-black is often used as cathode catalyst which only can receive electrons passively. To overcome the above problems and improve pollutant degradation efficiency, PFC with Ag/AgC I/GO-based photoelectrode was built in this study. Its operating condition was optimized and the degradation mechanism is discussed. In this thesis, the following results are obtained.（1） Ag/AgCl/GO was prepared through a precipitation-light reduction method with Ag（NH3）2OH as Ag source, and ZnIn₂S₄ was prepared through a facile hydrothermal synthesis process at low temperature. UV-vis diffuse reflectance spectra showed that the prepared catalyst was highly responsive to visible light. No matter illuminated with UV or visible light, the degradation efficiency of RhB can reach 84.66%. The photoelectrode was prepared by brush-coating with silica sol as the binder. It would have the best stability when the catalyst proportion was 1 mg/uL and load weight was 0.1 g. The degradation efficiency of RhB was 75.65% and 79.94% by Ag/AgCl/GO and ZnIn₂S₄-based electrode under visible light respectively.（2） After 1 h operating in PFC with Ag/AgCl/GO-based photoanode and stainless steel cathode under visible light, the degradation efficiency was 68.80% and the current density was about 4.23×10^-3 mA/cm². The performance of the PFC can be the best when RhB concentration was 15 mg/L, external resistance was 1 Ω and pH value was at 9.（3） Stainless steel electrodes loaded with anodic Ag/AgCl/GO and cathodic ZnIn₂S₄, formed a one-chambered PFC, in which RhB was degraded under visible light （2W LED）. After 1 h of irradiation,87.40% of the RhB was degraded and a 0.52 mA/cm2 current density was generated when the external resistance was 1 Ω. The effect of pH and initial RhB concentration on the cell voltage and degradation rate were studied. The single-chambered PFC can operate in a broad range of pH, and low acidic pH or highly alkaline pH can promote degradation.（4） The operating principle was studied through building PFCs with different paired photoelectrodes. The current density and cell voltage are affected by the degradation efficiency over the electrodes, and the photocatalytic electrode with higher degradation activity functioned as the anode, because of its relatively richer supply of electrons compared to the other. In the PFC with anodic Ag/AgCl/GO and cathodic ZnIn₂S₄ catalysts, the VB of Ag/AgCl/GO and the photo activity defined its good anodic property. In the anode chamber,-OH was formed from the reaction of holes with OH- or H2O and the pollutants were oxidized mainly by-OH. In the cathode chamber of the PFC, the electrons mainly react with O₂ and generate O₂-·, so in the cathode chamber, the oxidation of pollutants is mainly by ROS generated from the reductive reaction of electrons with oxygen. When in anoxic condition, the electrons directly participated in the reduction of NO3-. Based on this principle, with biological or iron anode in PFC system, the photocatalyst acted as cathodic catalyst can still achieve high performance.In conclusion, the Ag/AgCl/GO-based PFC system effectively improved the response to visible light and the degradation of RhB. The research on the degradation mechanism offered experimental and theoretical basis for the wastewater treatment of PFC. As a new technology of wastewater treatment, it has a broad application prospect in the field of wastewater treatment, because of no secondary pollution, low energy consumption and high efficiency.