Study On The Construction And Performance Of Organic-inorganic Hybrid Double-layer Membrane

Fuel cells have always attracted attention due to their high efficiency,stability and non-polluting products.Direct borohydride fuel cell(DBFC)is a technology that directly uses liquid as fuel.Theoretically,it has a high open circuit voltage of 1.64 V,an energy density of 5.67 Ah g-1 and a conversion rate of 91%.It has been studied in recent years as one of the hot spots.However,it is necessary to use expensive perfluorosulfonic acid resin membrane as the electrolyte membrane in DBFC,which prevents the practical progress of DBFC.The development of an anionic electrolyte membrane with excellent performance is one of the keys to reducing the cost of DBFC.In this paper,the conventional layer(PVA-AER film prepared with polyvinyl alcohol(PVA)and anion exchange resin(AER)as raw materials)and catalytic layer(Co-prepared by CoCl2·6H2O,PVA and AER as raw materials)are firstly used to develop a new type of organic-inorganic hybrid double-layer anion exchange membrane.X-ray diffractometer,X-ray near-side absorption structure spectrum,scanning electron microscope and X-ray fluorescence spectrum were used to test the microstructure,surface morphology and distribution of specific elements of the film.The water absorption rate,swelling rate and fuel permeability of the membrane are tested,and the cell performance,fuel utilization rate and durability of the DBFC using the double-layer membrane are further investigated.The experimental results show that the double-layer membrane exhibits a negative expansion ratio in thickness.the doublelayer design combining the catalytically active layer and the conventional layer has a permeability(1.34× 10-6 cm2 s-1),significantly lower than that of Co-PVA-AER film(1.97×10-6 cm2 s-1)and PVA-AER film(2.80×10-6 cm2 s-1).The output power of DBFC using double membrane is 1.73 Wh,which is about 1.36 times(1.27 Wh)of that of the DBFC using Co-PVA-AER membrane.The coulombic efficiency of the fuel is further increased to 37.4%.The cell performance of the DBFCs using double-layer membranes work at 30℃is 1.52 times and 1.25 times that of a single cell composed of PVA-AER membrane or Co-PVA-AER membrane.Its maximum power density can reach 327 mW cm-2 at 60℃,which is 2.14 times and 1.26 times than that of the DBFC using PVAAER film or Co-PVA-AER film under the same conditions.And the DBFC using double-layer membranes shows excellent stability for more than 100 h when it can be discharged at 50 mA cm-2.Then the anion exchange membrane is surface-textured on the plane of the cathode catalyst to increase the surface area of the three-phase reaction zone where the electrolyte membrane is in contact with the catalyst layer.The cell performances of DBFC using the textured membrane and normal membrane are tested and compared.The maximum power density of the DBFC using the textured membrane wis higher than that of the DBFC using PVA-AER and Co-PVA-AER films by 26%and 44.9%at 30℃ with 21.7%and 21.3%at 60℃.The above results indicate that changing the microstructure of the three-phase reaction zone in the membrane electrode can effectively improve the power generation performance of the battery.Therefore,we will further explore the influence of using alkaline ion exchange resin to regulate the ion conduction of the electrode layer in the membrane electrode on the cell performance finally.The influence of the anion exchange resin on the cell performance of DBFC is investigated by adding the anion exchange resin into the anode and cathode.The results show that the use of anion exchange resin(IRA-402)to strengthen the membrane electrode anode can improve the open circuit voltage and power generation performance of the exchange membrane fuel cell,and reduce the cathode polarization loss.At 30℃,the maximum power density of the double-layer membrane is 176.8 mW cm-2,and the maximum power density of the double-layer membrane of the reinforced anode membrane electrode is 198.72 mW cm2.But at 60℃,the power generation performance of the membrane before and after strengthening is similar.Therefore,for the double-layer membrane,the reinforced membrane electrode can improve the power generation performance of the battery at low temperatures,but after the temperature rises,the heat resistance of the alkaline resin is not enough to effectively improve the power generation of the double-layer membrane.It is further found that the performance improvement of the gel-type anion exchange resin is better than that of the macroporous anion exchange resin,and the strong anion exchange resin is better than the weak anion exchange resin.Based on the above research,a low-cost and high-performance anion exchange membrane could be developed by the double layer and surface texture of anion exchange membranes.The cell performance of the DBFC could be further improved by optimization the structure of membrane electrodes,which providing the experimental basis for commercial of direct sodium borohydride fuel cell.