Activation And Analysis Of Factors Affecting The Performance Of Direct Methanol Fuel Cells

As a series of fossil fuels,such as oil and natural gas,are being consumed too quickly,with the energy and environmental crisis has intensified,the renewable energy has become a global concern.Direct methanol fuel cells?DMFCs?have attracted wide attention due to their advantages of simple structure,convenient fuel replenishment,high volume and mass energy density,and are regarded as one of the most likely power sources for portable electronic products.However,the excessively high cell cost has restricted the commercialization of DMFC.The use of industrial grade methanol can significantly reduce the cost of DMFC generation,which is of great significance for its practical application.This article mainly takes the liquid-phase feed type DMFC as the research object,carries out the following research work:designed and assembled the DMFC single-cell system;the liquid-phase feed direct methanol fuel cell experimental test system was built;the activation of the DMFC,designed a set of variable current discharge activation system;the effects of DMFC's key operating parameters(operating temperature T_cell,methanol concentration C,methanol metering ratio K_Methanol,and air metering ratio K_Air)on the performance of the DMFC were analyzed,and the value range of the battery was further analyzed.The effects of different amounts of isopropanol on the performance of the battery were investigated too.The mechanism of the poisoning of isopropanol to the catalyst was preliminarily analyzed,and the method of applying a voltage pulse during the discharge process was proposed,which effectively alleviated the impurities in the industrial grade methanol.Isopropanol poisoning.The specific research content is as follows:1)Activation studies of DMFC.Compared with the existing activation methods,a variable current discharge activation program was designed.The self-assembled DMFC cells were activated and investigated by electrochemical impedance spectroscopy?EIS?.EIS shows that the variable current discharge activation process effectively reduces the impedance of the DMFC,and the performance of the single cell is optimized for only400 min in the activation,and the single cell performance is increased by 47.6%at the current density of 200 mA/cm²,and the peak power density of the single cell.Increased by 69.5%;circuit simulation results show that the activation increases the electric double layer capacitance and improves the activity of the catalyst.2)Optimization of the DMFC test.The results show that the best battery operating temperature Tcell is 70 ^oC;too high or too low methanol concentration C has an adverse effect on the performance of DMFC;when the air metering ratio is 2,3,when the methanol metering ratio is 4 single cell performance is the most Good,when the air metering ratio is 4,6,the optimal methanol metering ratio is 2;under different methanol metering ratio,when the air metering ratio is 6,the single battery performance is best;increasing the temperature and air metering ratio is beneficial to improve the battery performance.Electrochemical test results show that the greater the methanol flow rate,the higher the concentration,the more serious methanol crossover.3)The effect of isopropanol on the performance of DMFC and its mitigation strategy.The isopropanol was mixed with the methanol solution.The higher the isopropanol content,the worse the performance of the battery.The polarization curve test,constant current discharge,cyclic voltammetry?CV?test and electrochemical impedance spectroscopy?EIS?were used to examine the experimental results.It can be seen later that because the isopropanol mixed in the methanol solution causes catalyst poisoning,the activated surface area of the DMFC membrane electrode is reduced.By preliminary analysis of the poisoning mechanism of isopropanol to DMFC on the catalyst,a method of applying a voltage pulse during the discharge was proposed,which effectively relieves the poisoning effect of isopropanol.