Research on the Key Technologies of Metal Based Micro Direct Methanol Fuel Cell

Author:Li Yang

Supervisor:zhang yu feng zhang xue lin


Degree Year:2019





At present,battery life demand for the portable and high energy-consumption(smart phones,tablet computers and wearable devices)device has greatly stimulated researchers and enterprises to study micro-sized and high energy-density energy.The urgent need to develop micro-sized and high-density energy has led many scholars to start the research on micro-fuel cell.Micro Direct Methanol Fuel Cell(μDMFC),as one of the representatives of new energy,has unique advantages at such as abundant fuel source,high energy density,environment friendly,low start-up and operating temperature,convenient fuel storage,transportation,etc.With the rapid development of material science and Micro Electro Mechanical System(MEMS)technology in recent decades,the efficiency and stability ofμDMFC have been greatly improved.However,at present,μDMFC technology has not been widely promoted,there is still a certain distance from large-scale commercialization.The main technical bottlenecks are the low power density,cost,portability and the low fuel concentration in practice.Foucs on the improvement ofμDMFC electrochemical characteristics,complexity and prortability,a new type of metal fiber membrane electrode is prepared and tested.A lateral venting configuration based on super hydrophobic metal surface is designed and realized.A newμDMFC super hydrophilic end plate has been designed and prepared.These works are of great significance for theμDMFC power density increase,complexity reduction and portability.First,the reactants/products concentration distribution and current density distribution of anode and cathode with different structures were simulated and analyzed in this paper.Simulation results show that the current collectors and MEA integratedμDMFC have higher mass transfer rate,the laterval ventingμDMFC shows excellent gas removal ability,the super hydrophilic metalμDMFC shows very fast water diffusion rate.Simulation results are consistent with the following experimental test results.Second,a metal fiber MEA is prepared by replacing the traditional carbon fiber MEA.Its mechanical strength characteristic gurantees the elimination of the expensive anode and cathode collector plate in theμDMFC,greatly lowing the structural complexity of theμDMFC,implement the current collectors and MEA interated configuration.At the same time,the excellent cathode porous structure of metal fiber electrode lead to an excellent performance at room temperature.Test results show that,comparing with traditional carbon paper film electrodeμDMFCs,the discharging time extends a lot.And at room temperature 25℃,the maximum power density increased by 33.9%and the energy conversion efficiency to 27.36%.Third,by aluminum based superhydrophobic process and micro channel structure design,an anode end plate structure with lateral venting micro channels is realized.CO2can easily vent from anode diffusion layer without flow field,greatly improving the polarization characteristics and voltage output stability ofμDMFC.More than 10%CO2can vent from the lateral venting channels,making the totally enclosed anode liquid storage possible,avoiding fuel leakage in the process of portable use of the fuel cell,optimizing the portability of the fuel cell.Finally,based on the aluminum alloy substrate,a super hydrophilic metal cathode end plate has been prepared.Combined with the design of micro drainage channel,the cathod flood phenomenon ofμDMFC disappeared at room temperature,the performance ofμDMFC increased more than 30%during long discharging.Half-cell test results show that the cathode potential is very stable,the anode potential drop rate is only 1/4 of the conventional battery.Moreover,due to the effective treatment of cathode production,the portability of fuel cell during operation is greatly improved.