Proton Conduction Research And Ordered Structure Design Of Nanoporous Ultra-thin MEAs For PEMFCs

To achieve the goal of carbon peaking and carbon neutrality,the development of new clean energy is the key to future sustainable development.As an important carrier of clean energy conversion and utilization,fuel cell technology has become an ideal replacement for traditional fossil energy power due to its clean,efficient and high power density characteristics,among which hydrogen fuel cell technology is the mainstream direction of current development.To address the current problems of high cost and poor stability of hydrogen fuel cells,reducing the amount of Pt group metals in electrode materials and improving catalytic activity and structural stability are the keys to the current research on electrode catalysts for hydrogen fuel cells.Based on the advantages of high specific surface area and rapid mass transfer due to the unique ultrathin bicontinuous structure of nanoporous metal films.In this paper,an ultrathin catalyst layer was constructed using nanoporous metal films prepared by the dealloying method as the substrate material for the cathode of a hydrogen fuel cell,and a detailed study of the proton conduction mechanism and water management in the ionomer-free ultrathin membrane electrode assembly was carried out.Details are as follows:(1)The nanoporous gold thin film substrates were prepared by dealloying method and Pt modified nanoporous gold thin film electrodes were fabricated by electrodeposition method.Firstly,the nanoporous gold thin film electrode was used as a cathodic catalytic layer,and by controlling the relative humidity of the film electrode,it was found that the proton conduction in the nanoporous gold thin film electrode without ionomer addition has a strong dependence on humidity,and we believe that the proton conduction in the ligamentous pore channels of nanoscale porous gold is due to the nanofluidic channels constructed in the hydrated environment,and the surface will form a water film of nanometer-level thickness,in which the Grotthus mechanism dominates the proton conduction in the water film.Then the Pt-modified nanoporous gold film electrode was used as the cathodic catalytic layer to test the proton conductivity at different potentials,which verified the existence of two different proton conduction mechanisms at low and high potentials assumed in the literature.(2)The water flooding problem in membrane electrodes was improved by constructing ordered ultra thin film electrodes and optimizing the pore size structure of nanoporous metal catalysts.Based on a simple plasma treatment technique to form independent water-gas transport channels,the mass transport efficiency was significantly improved as demonstrated by water permeation coefficient and oxygen gain voltage value tests,with peak power density up to 957 m W cm^-2at a cathode Pt loading of 16?g cm^-2,compared to a commercial Pt/C catalyst(loading of 50?g cm^-2)with peak power density of 756 m W cm^-2,the mass-to-power efficiency of the nanoporous metal catalyst was 60 k W g^-1,which was four times higher than that of the conventional commercial Pt/C catalyst.The stability of the ordered ultrathin film electrode was also significantly improved in the stability and electrochemical impedance tests.The structural optimization to construct ordered mass transport fully exploits the structural advantages of nanoporous metal catalysts and proves its great application value.