Research On Construction And Operation Of Biofuel Cells Based On Gas-Solid-Liquid Interfaces

Compared with traditional fuel cells and electrochemical sensors,biofuel cells and sensors have important practical significance because they could directly convert chemical energy in renewable energy sources（glucose,lactose,methanol,ethanol,and lactic acid）into electrical energy.However,in the exploration of electrochemical biofuel cells and sensors,there were two main problems.On the one hand,the interaction mechanism between microorganisms or enzyme proteins and electrodes hindered electron transfer.On the other hand,the low solubility of gas molecules in aqueous solution limited the power density output of biofuel cells.Therefore,the development of electrode materials that could effectively promote the participation of gas and the transfer of electrons between microorganisms or enzyme proteins and electrodes had become an important issue for the development of electrochemical biofuel cells（BFCs）and sensors.This thesis was dedicated to the development of novel gas diffusion electrode materials to achieve the goals of improving the activity of immobilized enzymes and microorganisms,promoting the diffusion of poorly soluble gas to the electrode surface,and increasing the power output of biofuel cells.The specific research content was as follows:（1）A membraneless glucose-O₂ biofuel cell based on a gas diffusion bioanode/cathode was prepared.The gas diffusion electrode was prepared by immobilizing porous carbon paper（CP）modified with glucose oxidase（GOx）or laccase（Lac）.One side of the assembled enzyme was in contact with aβ-D-glucose aqueous solution,and the other side was directly in direct contact with the gas phase,O₂ in the air could diffuse directly from the gas phase to the active site of the enzyme through the pores of the hydrophobic carbon paper to participate in the enzyme reaction.Due to the high adhesion of the enzyme to gas molecules,a hydrophobic interface was obtained which was more favorable for enzyme reaction.In a traditional saturated air electrolyte solution,the maximum power output density of the battery was only9.64μW cm^-2（0.43 V）,while the maximum power output density fixed in saturated oxygen significantly increased to 53.0μW cm^-2（0.45 V）,The obtained single-liquid biofuel cells could obtain a maximum power density of 49.0μW cm^-2 in human serum.Such biofuel cells constructed with gas diffusion electrodes showed more advantages such as high output power density,low cost,and"chip"integration miniaturization,which had great potential for implantable self-powered sensors.（2）Study on in-situ assembly and electrochemical catalytic behavior of methane oxidizing bacteria（methylosinus）on the surface of gas diffusion electrodes.Using the metabolism of exoelectric bacteria to collect electrical energy from organic substrates and obtained valuable products had attracted widespread attention.This work designed an alumina template（PAA）nanochannel reactor with a gas diffusion electrode.Under the action of methane monooxygenase（MMO）and inhibitor Na Cl,methane oxidizing bacteria could oxidize a certain proportion of methane and oxygen to methanol,but the low solubility of gas molecules in the aqueous solution of the mixed gas limited the gas-soluble reaction.The use of anodized aluminum oxide with a nanochannel membrane facilitated the immobilization of methane-oxidizing bacteria in situ,which was in contact with phosphate buffer on one side and directly contact with the gas phase on the other.After filling a certain proportion of methane and oxygen in the reaction system,it was observed that CH₄/O₂ could directly participate in the internal reaction of methane-oxidizing bacteria from the gas through the proposed nanochannel to detect the accumulation of methanol.