Preparation Of Graphene Oxide/Polyethyleneimine Hydrogen Barrier By Self Assembly

Climate problem is a severe challenge to the earth’s ecosystem since the industrial revolution,energy problem is the fundamental problem of human social development,and the world energy transformation characterized by clean and low-carbon is an effective measure to solve the energy problem and deal with climate change.As an important green energy,hydrogen has the advantages of clean,efficient and renewable.It can not only reduce people’s dependence on fossil fuels,but also reduce the emissions of greenhouse gases and pollutants.High pressure gaseous hydrogen storage has many problems,such as low volume specific capacity,high risk factor and so on,which has become the key to restrict the large-scale application of hydrogen.Therefore,the preparation of high hydrogen barrier materials and improving the safety and reliability of existing hydrogen storage methods are the important premise to solve the sustainable development and utilization of hydrogen energy.At present,the composite films with excellent gas barrier properties can be prepared by the composite of polymer and lamellar materials.Among many inorganic lamellar materials,graphene oxide is easy to be prepared on a large scale with good dispersion stability.The lamellar structure has a large diameter thickness ratio and no gas permeability,so it has a good application prospect in the field of gas barrier materials.Layer-by-layer self-assembly technology can be used to prepare high hydrogen barrier film,which is easy to operate and has obvious barrier enhancement,but the film preparation cycle is long,which is not conducive to the preparation of barrier film.Therefore,ultrasonic and atomization assisted methods are selected to improve the film preparation efficiency and shorten the film preparation cycle.Polyethyleneimine（PEI）/Graphene oxide（GO）composite films were prepared under ultrasonic irradiation.The results show that ultrasonic irradiation can increase the density of materials,reduce the diffusion channels of hydrogen molecules,improve the horizontal orientation of GO layers,and extend the diffusion path of gas molecules.The hydrogen permeability of 20 films assembled under ultrasonic irradiation is equivalent to that of 30 films assembled under non ultrasonic irradiation,greatly shorten the film making cycle.In order to further simplify the self-assembly process and make the coating more uniform and complete,the gas barrier film was prepared by atomization deposition method.This method can not only effectively avoid the desorption and diffusion of the adsorbed self-assembly material to the solution body,but also save the washing step of deionized water,which is convenient for operation.When the concentration of GO is 0.9 mg/ml,the hydrogen transmission rate of the self-assembled 10 layer films is 25.861 cm³·m^-2·day^-1·0.1MPa^-1,which is 90.77%lower than that of the bottom film.The roughness of the films is significantly higher than that of the ultrasonic assisted films,which may be related to the island morphology formed by droplets.Due to the high content of GO in the films,the films begin to show wrinkle morphology.The thickness of the film increases linearly with the self-assembly process.The thickness of the film reaches 800 nm when 20 layers are self-assembled,which is corresponding to the decrease of hydrogen transmission with the increase of layers.