CH₄ Production From CO Conversion And H₂O₂ Formation From O₂ Reduction In Bioelectrochemical Systems

Bioelectrochemical system(BES)is a new technology that utilizes microorganisms to catalyze the anode and cathode reactions.It not only can be used for the removal of pollutants,but also can produce high value-added fuels and chemicals.Extending the application of BES in bioelectrochemical synthesis has been a research hotspot.This paper firstly studied the feasibility and mechanism of CH4 production from CO conversion in BES,and then the feasibility and mechanism of the cathode modification strengthening BES to prepare H2O2 were explored.The main contents of our research and the results are summarized as the follows:1.BES based on mixed bacteria cathodes was constructed.The influence of different potentials on CO conversion and CH4 production with a mixed-culture biocathode was studied,and the possible mechanism was preliminary analyzed.This study found that with the increase of cathode applied potential,the methane production increased from 0.142±0.009 mmol to 1.410±0.077 mmol,and the methane production rate increased from 0.0011 ±0.0001 mmol h-1 to 0.0110±0.0007 mmol h-1.And the study of the mechanism showed that microorganisms can directly use the cathode electron to reduction of carbon monoxide to produce methane,or use hydrogen reacts with carbon monoxide to produce methane.When microorganisms form a stable biofilm on the surface of the carbon felt,the cyclic voltammetry showed a clear redox peak and the electrochemical impedance spectroscopy showed that the transfer impedance was significantly reduced,indicating that the attachment of the microorganisms in the cathode was beneficial to electrons transfer process.Population analysis showed that Hydrogenotrophic Methanobacterium was the main archaea in the cathode.The content was 26.75%.It was not only a user of hydrogen but also an important electron trapper in microorganisms.2.Functionalized polypyrrole(PPy)film with anthraquinonedisulphonate(AQDS),neutral red(NR)or riboflavin(RF)incorporated as dopant were prepared by cyclic voltammetry electropolymerized of pyrrole(Py)at a carbon paper electrode from aqueous solution.The electrochemical properties of the modified electrode and its effect on oxygen diffusion were studied by cyclic cyclic voltammetry(CV)and chronoamperometry(CA)respectively.Then explored the feasibility by using modified electrode as cathode in BES(Bioelectrochemical system)to reduce oxygen production of hydrogen peroxide.This study found that the more the number of scanning cycles,the higher the electrocatalytic activity of the modified electrode and the more favorable the diffusion coefficient of oxygen on the electrode surface and further reduction to hydrogen peroxide.When the modified electrode was used as the cathode electrode in BES,the cumulative amount of hydrogen peroxide was increased compared with unmodified electrode,and AQDS-20 doping has the best effect on hydrogen peroxide accumulation.When initial catholyte pH is acidic,the amount of hydrogen peroxide produced was the most,the neutral condition was next,and the alkaline condition was the least.