Ions Transport And Energy Conversion On Nanoporous Interface

The fast depletion of fossil fuels not only intensify the energy crisis,but also causes severe environmental pollutions.Converting distributed energy into electricity is of great importance for human sustainable development and motivates the research of advanced renewable technologies.The new interface effects and phenomena of nanoporous materials provide an opportunity for the renewable energy technologies,which can be used to collect various energy from the environment,such as heat,ocean energy and mechanical energy.In the thesis,we firstly review the special construction of the nanoporous interface and the related physical chemistry properties and theories,and we particularly introduce the research progress of the ions transport and energy conversion on nanoporous interface.Salinity power generation and electrokinetic conversion based on ions selectivity of nanochannels and carriers transport on solid-liquid interface are systematically simple,which can realize the conversion of distributed energy to high quality electricity,and these two technologies have great promising in application.However,the mechanism of burgeoning energy conversion based on the interactions between ions and nanomaterials is insufficient and still lack of consensus;the efficiency of the energy conversion system is generally low and and it is short of device integration optimization design and energy multipurpose ultilization.Thus it can be seen that,the basic research of energy conversion processes based on ions motion on nanoporous interface is still facing challenges.According to the above issues,the main results are shown as follow:1.Induced potential in nanoporous carbon films through water vapor absorption:We discovered and revealed the induced voltage in nanoporous carbon films through water vapor absorption.Sustainable electrical potential of tens of millivolts can be induced by water vapor adsorption on a piece of nanoporous carbon film that has two sides with different functional group contents,converting the environmental heat to electricity.Integrated experiments,and Monte Carlo and ab initio molecular dynamics simulations reveal that the induced potential originates from the nonhomogeneous distribution of functional groups along the film,especially carboxyl groups.Sufficient adsorbed water molecules in porous carbon facilitate the release of protons from the carboxyl groups,resulting in a potential drop across the carbon film because of the concentration difference of the released free protons on the two sides.The output power can be improved by device scale and materials optimizing.The unique phenomenon observed in this study may be utilized in the design of self-powered sensors and energy harvesting devices,and provides new prospects for adsorption phenomenon,showing certain scientific significance and potential applications.2.Solar desalination and photo-driven salinity power generation:The nanoporous membrane with ion-selective property can be used to extract the mixing Gibbs free energy between different concentration salt solutions,which is also known as salinity power generation.Currently,the salinity power facilities are established on the river mouths,which limit the operation location and output power.We firstly presented a hybrid device with the functions of solar desalination and salinity power generation,realizing energy multipurpose utilization.The rapid evaporation of water at the light absorber surface during solar desalination would induce a high concentration comparable with that of brine underlying the interface,which can be used to produce electricity,providing a novel avenue for blue energy utilization.The solar thermal efficiency of carbon nanotube modified filter paper is excellent,which can achieve up to 75%under one solar illumination.Such design enable salinity power to operate without constriction in certain geographical areas,such as river mouths,and the hot sweater and brine can realize higher power density.We proved that,the theoretical real-time salinity power generated between the surface water and bulk seawater could be 12.5 W m^-2 during steam production under one sun illumination for the optimized device.It is easy to build a large-scale hybrid prototype（10 cm×10 cm）to demonstrate the practicability of this design under natural sunlight.Under natural sunlight with average solar flux of 0.7 kW m^-2,the output power density is 0.3 W m^-2.Solar desalination and salinity power collection can be considered to be directly conducted on the sea,obtaining a potential amount of freshwater and large-scale blue energy.3.Electrokinetic effect of nanoporous membrane and all-in-one energy generation and storage integration:Electrokinetic batteries are based on ion-selective membranes and continuous redox reactions on the electrodes,converting the fluid mechanical energy to electricity;however,the electrokinetic batteries do not possess energy storage functions,thus they should be combined with other energy storge devices to realize energy management systems.We designed a self-charging supercapacitor energy collection device based on electrokinetic effect.Pressure-driven electrolyte flow through the nanochannels generates streaming potential,which can be used to charge the capacitive electrodes,accomplishing simultaneous energy generation and storage,and this configuration is suitable for various low-frequency mechanical vibration conversion.At a scan rate of 2 mV s^–1,the capacitance of the device is about 2.2 mF cm^–2.The device exhibits an ultra-small leakage current,thus can effectively store and keep energy.The device stores electric charge density of 0.4 mC cm^–2 after fully charging under pressure,and the energy efficiency is⁰.1%,nearly to the efficiency of electrokinetic battery;in addition,the capacitive device energy efficiency can be improved to⁰.5%via nanochannels optimizing.To further promote the performance of the capacitive power cell,employing better electrode materials and nanochannel membrane is an effective way.We designed a closed prototype,and the integrated devices can be operated at high potential window through series connection and power electronic units.The energy generated by electrokinetic effect induced by the overlapped electrical double layer in nanochannels,is eventually stored in the electrical double layer in nanoporous electrodes,realizing the integration of energy generation and energy storage.