Application Of GOM/PET Structure In Reverse Electrodialysis Field

With the development of industrialization and urbanization of human society,there is an increasing demand for energy.However,it is estimated that the fossil fuels such as coal,oil and natural gas widely used by people are only enough for several decades.The crude oil and gas will be depleted in 2042,and only coal reserves are available up to 2112.Therefore,more and more research groups devote themselves to finding new energy sources that could be safer,more efficient and renewable.Different from solar and wind energy,the energy generated from water is hugely attractive due to its abundant,sustainable and safe properties and has grown enormously in the past few years.Among them,the blue energy,which can be harvested by mixing solutions with different salinities,has been gaining increased attention by researchers in recent years.The amount of energy supplied to the earth in one day by the sun is sufficient to satisfy the energy consumption of mankind for one year.As we all know,most of the surface of earth is covered by ocean,so there are plenty of solar energy stored in ocean.Salinity gradient energy is indirectly related to solar energy by water evaporation,and it can generate about 0.8 k Wh m^-3 per litre mixed of seawater and freshwater.To harness this kind of blue energy,the researchers developed reverse electrodialysis(RED)technology,which uses a selective membrane to generate the net current in the nanochannel.Polymer membranes with nanochannels and 2D lamellar membranes are commonly used as selective membranes,which have been applied in the RED field.The advantages of polymer nanochannels lie in their controllable shape and strong rectification effect,which make them become the important materials for studying the mechanism of RED.However,the thickness of polymer is usually on the micron scale,which hinders the improvement of their ionic flux.The advantages of two-dimensional materials lie in their ultra-thin membranes,multiple channels and high osmotic current.Based on this,a large number of two-dimensional materials such as GO and MXene are widely investigated in RED field.However,due to its uniform structure,the lack of rectification effect hinders the further improvement of its energy conversion efficiency.In this paper,GOM/PET nanochannel are obtained by spin-coating graphene oxide membrane(GOM)on the nanochannel.The rectification effect and RED performance of GOM/PET nanochannels in different solution environments was systematically investigated through comparative experiments.At the same time,finite element simulation clarifies that the synergistic effect of 1D nanochannel and 2D lamellar nanochannels can effectively improve the RED performance of the device.The results obtained in our study are:1.In our experiments,the ultrathin(?20 nm)GOM can be obtained on different porous polymer substrates by spin-coating method.Besides,the GOM can uniformly cover the nanopore with less wrinkle and the surface is smooth;2.The mechanism of the rectification effect was explained by studying the rectification effect of PET conical nanochannel and combining the simulated electric field and ion distribution.The rectification effect of GOM/PET nanochannel was studied,and the results showed that spin-coated GOM could effectively improve the rectification coefficient of original PET conical nanochannel;3.GOM/PET nanochannel can significantly improve the RED performance of PET conical nanochannel,and can improve the osmotic current and osmotic voltage at the same time.In addition,the maximum power of GOM/PET nanochannel can reach118.2 p W,and the efficiency is up to 40.3%,the power generation is higher in the field of single nanopore RED device,which is even comparable with single atomic layer RED device;4.By measuring the performance of RED at different temperatures,it is explained that the increase of osmotic current after spin-coating GOM is caused by the reduction of ion transmembrane energy barrier.Finally,the finite element simulation shows that1D/2D structure can combine the advantages of them to synergically improve the performance of RED in 1D and 2D nanochannels.In this paper,the rectification effect and RED performance of PET conical nanochannel and GOM/PET composite nanochannel were compared.The results show that GOM can effectively improve the rectification effect and RED performance under different cationic solutions,p H values and PET nanochannel shapes.In addition,the transmembrane energy barrier of ions was studied in this paper to illustrate the effect of GOM on the membrane flux improvement from the perspective of energy.Finally,the advantages of the synergistic effect of 1D/2D structure were illustrated through simulation.These results provide ideas and theoretical guidance for the preparation of novel composite structure rectifier and RED devices.