Electricity Generation Of Passive Microfluidic Fuel Cells Based On Cotton Fibers

In recent years,with the rapid development of mobile Internet technology,more and more portable electronic devices such as smart wristbands,smart phones,and smart watches have emerged.However,the traditional battery technology cannot keep up with the demand for portable electronic products in the market that they do not require frequent charging during long period of operation.The membraneless microfluidic fuel cell(MMFC)utilizes the laminar flow characteristics of the fuel and the oxidant,does not require a membrane to separate the anode and the cathode,and eliminates the problems associated with conventional fuel cell membranes.Due to its advantages such as large specific surface area,easy to integrate,high power density,easy portability,etc.,MMFCs are considered to be one of the most promising miniature power sources and have attracted widespread attention from researchers.At present,most of the microfluidic fuel cells require external drive equipment to maintain laminar flow of fuel and oxidant,reducing the net power output of the fuel cell,further limiting its practical application.In this study,a fiber-based passive microfluidic fuel cell with carbon paper anode was proposed.The fuel and oxidant are transported passively by the capillary force of the cotton thread,and the dependence of the microfluidic fuel cell on the external driving equipment is eliminated.The structure of the anode and cathode of the fuel cell was improved in terms of mass transfer.The passive microfluidic fuel cell with fiber-integrated anode and air-breathing cathode were designed.The effect of the fuel concentration,electrolyte concentration and reactant flow rate on the cell performance were discussed.The main research results of this study are as follows:(1)A fiber-based passive microfluidic fuel cell with carbon paper anode was fabricated.The cotton thread was used as the flow channel of the microfluidic fuel cell to realize the passive transportation of fuel and oxidant.Through adding the third fluid to separate the fuel and the oxidant,the diffusion mixing of the fuel and the oxidant was effectively avoided.It was found that at fuel concentration of 2M,electrolyte concentration of 2M and flow rate of 27.33?L/min,the maximum power density and current density were 19.9 mW/cm~2 and 111.2mA/cm~2,respectively.Compared with the fabric-based microfluidic fuel cell reported before,the performance of the proposed fuel cell in this study was increased by 3.5 times.(2)A fiber-integrated anode was prepared by repetitive dip deposition coating method to fabricate catalyst layer on cotton thread surface.A passive microfluidic fuel cell with fiber-integrated anode was constructed.At fuel concentration of 2M,electrolyte concentration of 2M and flow rate of 27.33?L/min,the maximum power density of the fuel cell was 21.84 mW/cm~2,and the limiting current density was 126.82mA/cm~2.Compared with the microfluidic fuel cell with carbon paper anode,the mass transfer of anode fuel to the electrode surface was effectively promoted,and the performance was increased by 138%at fuel concentration of 0.2 M.More stable performance was found when the fuel cell was discharged at constant voltage.(3)Combining the advantages of air self-breathing cathode and fiber-integrated anode,a passive microfluidic fuel cell with fiber-integrated anode and air-breathing cathode was constructed.It was found that the mass transfer at cathode at high current densities was enhanced,leading to the maximum current density was improved by 7%.Moreover,the cell performance showed a trend of increasing at first and then decreasing with increasing fuel concentration and electrolyte concentration,while increased gradually with an increase in the flow rate.