Experimental Study On The Mass Transfer And Electrochemical Reaction Process In Paper-based Microfluidic Fuel Cell

As demand for portable,sustainable,clean power sources increases for small electronics in diagnostics and sensing,which stimulates research and development of new miniature power sources.Paper-based microfluidic fuel cells(PMFC)have gradually become an alternative energy source due to their simple structure,low cost,and no pollution.Existing PMFCs mainly use precious metals as catalysts to realize the electrochemical reaction of fuel and oxidant in a suitable laboratory environment,which have the disadvantages of high catalyst cost,low utilization rate,etc.,and the potential impact of environmental conditions on output performance is not fully realized.This has limited the application and promotion of PMFC in the field of portable devices.At present,research on catalyst layer performance optimization and environmental changes of the catalyst layer is still relatively scarce,so it is urgent to carry out research on the preparation parameters and environmental factors of different catalyst layers.In this paper,the influence of different preparation parameters and operating parameters on mass transfer electrochemical reaction of fuel cells was systematically studied by means of electrochemical characterization and macroscopic performance test.The main research work of this paper includes:(1)A pneumatic automatic spraying experimental platform was built,which optimized the preparation process of the catalyst layer,and catalyst layers with different loadings and distributions of palladium catalysts were prepared by a pneumatic automatic sprayer.A PMFC performance test platform with temperature and humidity regulation was built,which realized the simulation of PMFC working environment and performance test.(2)In this study,the microscopic characterization of the catalyst layers with different preparation parameters was carried out by scanning electron microscopy.Combined with polarization curve,power density curve and electrochemical impedance spectroscopy,the effect of catalyst layers preparation and structural properties on the performance of PMFC was analyzed.The results show that proper increase of Nafion solution content in catalyst solution can improve the start-up reaction time and output performance of fuel cell.Excessive Nafion solution can reduce the active area of the catalyst,increase the start-up reaction time,and reduce the output performance of fuel cell.In the case of a certain length of the catalytic electrode,the material diffusion and ion transport in the paper-based flow channel with shorter catalyst electrode and parallel placement are the best.To improve the output performance of fuel cell,catalyst load and fuel concentration should be adjusted simultaneously.The stepped distribution of the catalyst layer mainly improves the reduction reaction of PMFC cathode oxides and promotes the electrochemical reaction rate.The optimized PMFC was successfully applied to thermohygrograph and blood glucose meter and operated continuously for at least 3 hours.(3)Ambient temperature and relative humidity have effects on the start-up reaction time and output performance of PMFC.Appropriately increasing the temperature improves the start-up reaction time and performance,and excessively increasing the ambient temperature will reduce the catalyst utilization rate.At this time,both the fuel concentration and the catalyst activity become the main factors limiting the output performance of the fuel cell.Relative humidity has little effect on the performance of fuel cells at medium and low temperatures.For the higher temperature operating environment,increasing the relative humidity can slow down the evaporation rate of the liquid,reduce the flow rate of the liquid,and provide sufficient reaction time for the fuel and oxidant,which can improve the output performance of the fuel cell.