| Energy shortage and environmental pollution are two serious problems in today's society.The reserves of non-renewable resources such as petroleum,natural gas and minerals are limited.Petroleum can only be used for several years,and oil and natural gas can only be used for more than 100 years by human beings.In addition,the combustion products of these petroleum and coal resources will also have a bad impact on the environment.All these have prompted scientists to find more environmentally,friendly and effective new energy sources or energy supply ways to solve these problems.Hydrogen,own to its non-polluting,high energy density,easy storage and renewable new energy source,is considered as a perfect substitute for fossil fuels.Among many hydrogen production technologies,electrolytic water hydrogen production technology has attracted worldwide attention because of its simple equipment and zero pollution in the whole process.In addition,in order to solve the problems caused by the use of batteries,scientists began to seek more environmentally and friendly energy collectors,such as nanogenerators.This type of device can collect mechanical energy,friction energy,heat energy and other energy which are commonly wasted in nature,so as to achieve the effect of self-energy supply.By developing electric field polarization method,materials with better polarity will be used in energy collection devices and electrochemical catalysis.These polarized materials exhibit better performance in nanogenerators and electrocatalysis.In this paper,electric field-assisted method has been used to polarize nano-materials,which was applied to prepare nanogenerators to collect mechanical energy from the environment.In addition,different functional groups were selectively exposed by electric field assisted method or suitable materials with polarization properties were found to explore their performance in electrocatalytic reaction.The details are as follows:(1)Electric field-assisted polarized quartz material is used in the preparation of nanogenerators.Silicon material(Si)is one of the most abundant elements in the crust.In this part,we synthesized silicon nanowires in a 1200? tube furnace by oxide-assisted growth method.The silicon nanowires have a special core-shell structure,which consists of crystalline silicon core and amorphous silicon oxide shell.After the heat treatment of the core-shell structure of silicon nanowires,alpha-quartz will grow at the interface between the core and the shell,thus obtaining silicon nanowires/alpha-quartz composite materials,which will be used as piezoelectric materials to collect energy on nanogenerators.In this work,electric field polarization method has been applied to polarize the alpha-quartz material.By this way,the output performance of the polarized active material will be improved.In addition,considering the flexibility of the device,nanogenerators assembled on flexible substrates can meet the needs of future devices.(2)Electric field-assisted method polarized the graphene oxide quantum dot films to make them have better orientation,and explore the application of this material in nanogenerators.In the considering of the derivatives of graphene,graphene oxide quantum dots(GOQD)have many polar functional groups,such as hydroxyl,carboxyl,ether and amino groups,which are distributed disorderly on the surface of graphene quantum dots.However,the large-area aggregated GOQD cann't exhibit obvious polarizability due to disordered orientation.In this work,we make full use of the characteristics of polar functional groups on the surface of graphene oxide quantum dots,and make the quantum dots with different polar functional groups have an orderly arrangement under the electric field by the electric field assisted method.Next,the polarized GOQD film has been used to fabricate nanogenerators on flexible polyethylene terephthalate(PET)substrates.This flexible device,which can convert mechanical energy into electrical energy,will make the application of nanogenerators in the future electronic field possible.(3)The study of carbon dots with polarized layer in electrocatalysis.In recent years,Mo2C materials have been extensively studied in HER process.Because of its d-orbital electronic structure like platinum and good chemical stability,Mo2C materials are considered as promising non-noble metal catalysts for hydrogen evolution.However,the HER properties of pure Mo2C materials are not outstanding,and the d orbital with larger density has limited its activity to a certain extent.In this paper,heteroatom N is introduced to adjust the d-orbital electronic structure of Mo2C to enhance its catalytic activity.The research data in this chapter show that the addition of carbon point can significantly regulate the catalytic activity of the reaction.The composite catalyst N-Mo2C-CDs-2 has the best catalytic performance.It only needs 154 mV overpotential to achieve 10 mA·cm-2 current density and 35.2 mV·dec-1 of the Tafel slope.In addition,the catalytic activity of the catalyst even superior than the 20 wt%Pt/C when the overpotential beyonds 226 mV.The N-Mo2C-CDs-2 composite modified by carbon dots with polarized layer has the potential to be used in HER because of its high electrochemical activity,low preparation cost and excellent stability.(4)In the considering of the carbon dots,different functional groups are exposed with the electric field polarized,which promotes the reaction rate of nitrogen-doped carbon dots/platinum nanowire complexes on hydrogen evolution(HER)and oxygen reduction(ORR).In the HER process,the amino functional groups can be selectively exposed by electric field polarization,which promotes charge transfer at the interface and increases the reaction rate of the related active species.In the ORR process,negative charged functional groups such as hydroxyl group and carboxyl group can be selectively exposed,thus promoting the ORR reaction.In addition,in this chapter,we have studied the co-catalysts for oxygen reduction in acidic electrolytes by polarized carbon dots and platinum nanowire composites.Because platinum nanowires have high conductivity,many high index surfaces and are not easily lost in catalytic reactions,combined with the synergistic electronic effect between platinum nanowires and polarized carbon dots,the co-catalysts exhibit superior performance in oxygen reduction reaction and excellent methanol tolerance ability.These data combined with density functional theory(DFT)analysis show that carbon dots play an important role in the oxygen reduction of platinum nanowires.Polarized carbon dots with negative charge functional groups exposed functions as a material with strong oxygen adsorption,and the adsorbed oxygen is transferred to the surface of platinum nanowires for oxygen reduction reaction.Such a platinum nanowire co-catalyst modified by polarized carbon dots exhibits good catalytic activity and provides a good idea for the study of the interface.(5)To explore the application of CU3P nanomaterials with polarized properties in electrocatalysis.Exploring efficient,stable and low-cost electrocatalysts for water splitting is a major challenge for energy conversion systems.In this work,Cu3P-Co2P nanocomposites with multiple interfaces were used as catalysts for water splitting in alkaline solution.The quasi-layer structure of Co2P and the polarization plane of Cu3P have endowed the nanocomposites with large surface area and abundant active sites,which greatly facilitates the intrinsic charge transfer and improves the catalytic activity.In addition,Cu3P will reduce the lattice mismatch between Co2P and the nickel foam,thereby improving the stability of the catalyst.For the optimized CU3P·0.75Co2P catalyst,hydrogen evolution reaction(HER)requires only 124.6 mV low overpotential when the current density reaches 20 mA·cm-2.The Tafel slope of the catalyst is 65 mV·dec-1,and oxygen evolution reaction(OER)requires 334 mV oveipotential(@20 mA·cm-2).Based on the optimized CU3P·0.75Co2P catalyst,the overall water splitting voltage to derive the 10 mA·cm-2 current density is about 1.55 V.Both theoretical and experimental results show that the catalytic performance of Cu3P-Co2P nanocomposite catalyst can be improved by coupling Cu3P with the existing polarized plane.These findings have opened a new routine for the preparation of composite catalysts. |
PDF Full Text Request