Surface Modification And Properties Of Aluminum Alloy Bipolar Plate For Proton Exchange Membrane Fuel Cell

Aluminum alloy material with low density,high strength,good conductivity,good processing performance is potential ideal proton exchange membrane fuel cell?PEMFC?bipolar plate material.In recent years,domestic and foreign scholars have carried out much new exploration and research work in order to enhance the corrosion resistance of aluminum alloy materials in the PEMFC environment,but so far the problem is still not well solved.In order to solve the corrosion problem of the aluminum alloy bipolar plate in the PEMFC environment,three methods are used to modify the aluminum alloy surface as follows:1.APTES/rGO composite film was prepared on the surface of aluminum alloy by layer-by-layer self-assembly method.The formation mechanism of the composite film was analyzed by means of infrared spectroscopy,XPS,SEM,mapping and other characterization methods.In order to characterize the corrosion resistance and long-term operational stability of the composite film,the composite films were characterized by electrochemical polarization spectroscopy,electrochemical impedance spectroscopy and potentiostatic polarization.The results show that the corrosion potential of APTES/rGO composite film modified aluminum alloy is 572 mV higher than that of bare aluminum alloy,and the corrosion current density is reduced by three orders of magnitude.The composite film has an effective protection rate of 99.35%,and the composite film has very good operation stability in the positive or negative PEMFC environment.2.Cyclic voltammetry was used to electrodeposit SnO₂-G composite film on the surface of aluminum alloy.The effects of deposition voltage range,scanning speed and GO concentration on the properties of the composite film were studied.The results show that the best voltage range is 0.6^-1.1 V,the best scanning speed is 25 mV/s,and the best GO concentration is 0.06 mg/m L.The corrosion potential of SnO₂-G composite film prepared in the optimum conditions is 441 mV positive relative to the bare aluminum alloy in the simulated liquid PEMFC,and the corrosion current density is reduced by 4 orders of magnitude compared with the bare aluminum alloy.The composite film on the aluminum substrate protection efficiency as high as 99.99%,indicating that the SnO₂-G composite film prepared by this method in PEMFC simulation liquid has a very good protective effect.In order to further characterize the stability of the SnO₂-G composite film,the potentiostatic polarization test and the immersion stability test of the composite film prepared under the optimal conditions were carried out.The results show that the composite film has good stability under both positive and negative PEMFC conditions.The protective efficiency of the composite film remains as high as 99.33%after soaked in PEMFC for 72 h,indicating that the composite film in the PEMFC simulation liquid has good long-term stability.3.PVDF/HO-h-BNNS composite film was prepared on the surface of aluminum alloy by coating method.Hydroxylated hexagonal boron nitride nanoplates?HO-h-BNNS?were prepared by ball milling and ultrasonic stripping method.The structure and composition of the prepared HO-h-BNNS were characterized.Then HO-h-BNNS and PVDF composite were used to prepare PVDF/HO-h-BNNS composite film on the surface of aluminum alloy to improve the corrosion resistance of aluminum alloy in PEMF simulation liquid.The best conditions for the preparation of composite films were studied by SEM,TG and electrochemical methods.The results showed that the optimal conditions for the preparation of PVDF/HO-h-BNNS composite membrane were as follows:the concentration of HO-h-BNNS was 0.3 mg/m L and the drying temperature was 120?.Finally,the electrochemical performance of the composite membrane prepared under the optimal conditions was studied.The results show that the protective efficiency of the composite film after soaking in PEMFC for 48 h is as high as 99.149%,and the composite film has very good stability in PEMFC simulation liquid.The composite films prepared by these three different methods all play a good protective role on the aluminum alloy substrate.The formation mechanism,composition and properties of the three composite films are analyzed in detail in the text.