The Preparation And Catalytic Reaction Of Flexible Proton Exchange Membrane Fuel Cell

With the rapid development of flexible electronic devices,flexible power supplies have also attracted more and more attention.Current flexible energy supplies are usually flexible lithium-ion batteries,flexible supercapacitors and flexible solar cells.However,it is becoming increasingly difficult for these flexible energy supplies to keep up with the increasing energy demands of flexible electronic applications.Therefore,there is a strong demand for a flexible energy supply with high energy density,as well as long-term stability and light weight.Flexible proton exchange membrane fuel cells(PEMFC)have the potential to increase both power density and energy density,which could provide the future for flexible electronic devices.For flexible fuel cells,the preparation and packaging of flexible stacks seriously affect the stack performance,the hydrogen source matching the flexible stack is rigid container,and the reaction mechanism of formic acid dehydrogenation is not yet clear.Based on the flexible proton exchange membrane fuel cell,this paper studies the flexible PEMFC planar stack and its matching flexible hydrogen source,and develops a fully flexible fuel cell power system.We also investigate the catalytic mechanism involved in the formic acid dehydrogenation by the single-molecule detection technology.The main researches of this dissertation are as follows:1.Based on the new flexible PEMFC technology invented by our group,we screen fuel cell membrane electrode materials and sizes to obtain single fuel cell with higher power density and appropriate sizes.six different types of flow fields are designed and printed by 3D printing technology.The effects of different flow fields and hydrogen flow rates on the discharge performance of the fuel cell stacks are explored.At the same time,the polarization curve of single fuel cells and temperature are monitored.The experimental results show that the flow field has great influence on the discharge performance of the planar stack.The flow field of Type-6 can reach a maximum power of 3.68 W and 32%power conversion efficiency at 90 mL/min hydrogen flow rate.Finally,the Type-6 flow field is used to amplify the battery pack to eight single cells,and the maximum power is 4.53 W.This high-output power,light-weight planar stack has great significance for its application in portable electronic products.2.We prepared a unique bifunctional aerogel catalyst by chemically supporting homogeneous catalyst Cp*IrCl2(dabpy)on aerogel.The catalyst has a bifunctional ability to store liquid formic acid in aerogel as semi-solid and catalyze formic acid dehydrogenation.By adjusting the Cp*IrCl2(dabpy)loading,the amount of ethylenediamine,the ratio of sodium formate and formic acid,temperature and the cycle life of the catalyst,the activity of the aerogel catalyst is investigated.We have used this bifunctional catalyst to develop a flexible hydrogen generator,which can stably produce hydrogen under different bending operations.Finally,a flexible hydrogen generator and flexible PEMFC plane stack are combined to manufacture a fully flexible fuel cell power source.The fully flexible power system operates 100 LED lights with an open circuit voltage of 4.28 V and a maximum power of 2.053 W.The theoretical energy density is 722 Wh·kg-1 and the actual energy density is 135.91 Wh·kg-1.This system promises to meet the high energy requirements of flexible electronics.3.We used dark-field microscopy to examine the process of single Pd-Ag nanosheets catalyzing the formic acid dehydrogenation.The generation of nanobubbles on hundreds of Pd-Ag nanosheets was counted,and it was found that some nanobubbles in the system have three different states.We analyze the nanobubbles by establishing three dynamic models:direct transition model,intermediate state model 1(IM-1)and intermediate state model 2(IM-2)and use the three kinetic models to fit the histogram of wait times for transitions in the nanobubble system.The fitting results of the IM-2 intermediate state model are more in line with the experimental assumptions.The transition path from no to large nanobubbles and large nanobubbles to no nanobubbles may contain multiple intermediate states,and there are other transitions between different intermediate states.The effect of formic acid concentration on the state transition of nanobubbles is also studied,and the relative energy levels are assigned to different states to discuss possible properties and mechanisms of the observed transition pathways.These results indicate the complex mechanism behind the evolution and stability of single nanobubble,which is very helpful for understanding the basic properties of nanobubbles.4.A series of coordination catalysts with different ligands were synthesized.Cp*IrCl2(dabpy)with good tolerance and high activity is screened out.Cy3 and Cy5 dye molecules are grafted in the catalyst ligand through DNA by amide condensation method.Finally,the concentration of fluorescent molecules in the microfluidic reaction cell are adjusted.At the concentration of 20 pM-50 pM,the ligand molecules are monodispersed on the substrate surface.These results lay the experimental foundation for single-molecule FRET.On the other hand,in order to investigate the influence of external forces on the activity of precious metal catalysts,we construct a magnetic ball-?DNA-gold magnetic tweezers system based on the characteristics of ?DNA and Au-S bonds,and found that gold has non-specific adsorption of ?DNA.Further research found that hydrophobic substrates can avoid DNA adsorption on the gold substrates.Based on the result,we successfully connect?DNA to the gold substrate through Au-S bonds,and use Sybr-? dye to visualize the DNA under a microscope.?DNA can be straightened by water flow.This study openes up a way to investigate the effect of external force on catalytic reactions.