Study On Thermoelectric Effect Of Graphene Oxide Composite Membrane In Solution System

While China’s economy is developing steadily,it also brings serious environmental pollution and energy crisis.Dependence on fossil energy forces China to step up its research and development of new clean energy sources.The ocean contains a large amount of temperature difference energy,which is considered as a potential green and pollution-free energy.In this paper,nanoporous biomimetic composite membranes are prepared from graphene oxide,and the mechanism of temperature difference energy-electric energy conversion in nanofluids is studied.Firstly,uniform and stable graphene oxide dispersions are obtained by ultrasonic cell grinder.Negatively charged graphene oxide composite membranes are prepared on cellulose substrate by vacuum filtration.After amination modification of graphene oxide,carboxyl groups on graphene oxide surface are replaced by amino groups,and a modified graphene oxide composite membrane with positive charge is obtained.Among them,graphene oxide composite membranes exhibit cationic selectivity,while modified graphene oxide composite membranes exhibit anionic selectivity.Secondly,we construct a series system experimental device and discuss the influence of different conditions on the temperature difference energy-electric energy conversion of nanofluids.We find that when there is a temperature gradient in the system,there will be a current from the high temperature end to the low temperature end.Comparing the effects of temperature,concentration,ion species and membrane thickness on diffusion current,membrane voltage and output power,we obtain the maximum output power of 2.81 nW in KCl solution with temperature gradient of 45 K,concentration of 10 mM and membrane thickness of 1 μm.Finally,the mechanism of temperature difference energy-electric energy conversion in nanofluids under temperature gradient is studied by thermodynamic analysis and numerical simulation.When there is a temperature gradient in the system,the diffusion coefficient of ions at the high temperature end is larger than that at the low temperature end,which makes the Brownian motion of ions at the high temperature end more intense.Under the ion selectivity of nanopore,anions and cations transport asymmetrically,which lead to the generation of diffusion current.Ion diffusion coefficient and ion selectivity of nanopore will affect the temperature difference energy-electric energy conversion.On the one hand,increasing the temperature gradient will increase the difference of ion diffusion coefficient at high/low temperature end,which will lead to the increase of diffusion current.On the other hand,increasing the concentration,decreasing the surface charge density and decreasing the pore length will weaken the ion selectivity of nanopore,resulting in the decrease of diffusion current.In this paper,the energy conversion of nanofluids has been studied in depth,and the physical mechanism affecting the temperature difference energy-electric energy conversion of nanofluids has been revealed,which can provide inspiration for utilizing the clean ocean temperature difference energy.