Research On Preparation And Performance Of Triboelectric Nanogenerator Based On Hexagonal Boron Nitride Nanosheet Composites

With the large-scale application and development of new technologies such as the internet of Things,artificial intelligence,and wireless sensing,there is an urgent need for a green and sustainable energy supply device to satisfy its needs.In recent years,a new type of energy conversion device based on contact electrification and electrostatic induction effects,the triboelectric nanogenerators(TENGs),is expected to meet these needs.The most prominent advantage of TENG over other energy conversion devices is that it can convert a wide variety of energy sources in the environment into electrical energy,such as green natural energy and irregular mechanical energy.Since the TENG was proposed,its working model,structural design,material selection,etc.have been optimized.However,for the practicality of TENG,its output performance needs to be further improved.The study found that the output performance of TENG was positively correlated with the amount of charge captured and stored by the friction materials.So,increasing the charging capacity of the friction material could effectively increase the output performance of TENG.Moreover,in the actual working situation,due to the influence of the environment,especially humidity,the surface once the triboelectric electrons are generated,the surface charge density of the friction layer will gradually decrease,which seriously affects the output performance of TENG.Therefore,designing a TENG with excellent output performance and output retention rate(in a high-humidity environment)is the first focus of this work.The study of the above-mentioned generator performance improvement mechanism is the second focus of this work.On the basis of raw materials,further improving output performance of TENG by optimizing them is the third focus of this work.Based on the above research priorities,this work introduces hexagonal boron nitride nanosheets(BNNS)before and after modification into the negative friction layer to improve the performance of TENG from different aspects.The wide bandgap 2D material BNNS has excellent properties such as large breakdown voltage and high resistivity,which makes it show great potential in improving output performance of TENG.Based on this,the main contents and conclusions of this work are as follows:(1)A few layers of BNNS were prepared by ultrasonic assisted peeling method,BNNS was introduced into polyimide(PI),and a TENG device based on a PI/BNNS/PI(PBP)negative friction layer was prepared.The experimental results show that the short-circuit current,open-circuit voltage,transfer charge and output power density of PBP-based TENG are 4.5μA,65.9 V,17.2 nC and21.4μW/cm~2,which are 5 times,6.1 times,4.7 times and 15 times that of pure PI(PP)-based TENG,respectively.In addition,PBP-based TENG has an excellent output retention rate in a high-humidity environment.When the relative humidity increased from 15%to 90%,the output retention rate of the PBP-based TENG was 75%,while the PP-based TENG was only 20%.(2)In order to better understand the mechanism of output performance enhancement,we analyzed the working principle and theoretical model of TENG,and the results show that increasing the dielectric constant and charge density of the friction material can effectively improve the performance of TENG.The introduction of BNNS on the hand improves the dielectric constant of the friction material.on the other hand,it improves the charge capture capacity of the friction material,and the combined action of the two has caused the improvement of PBP-based TENG performance.At the same time,the positive effect of BNNS is proved by testing the dielectric constant,dielectric loss and surface potential of the friction materials.(3)Based on the above enhancement mechanism,silane coupling agent-modified BNNS(BNNS-F)was prepared and introduced into PI film,and a TENG device based on PI/BNNS-F/PI(PBFP)negative friction layer was prepared.The transfer charge and output power density of PBP-based TENG reached 8.1 times and 25 times that of PP-based TENG,which can be attributed to the excellent electron capture capability of the fluorophores in BNNS-F.In addition,the mechanism of BNNS-F as an electron capture layer was explored by using the capacitance-voltage(C-V)curve of metal-insulator-semiconductor(MIS)devices based on PBFP film.