Preparation Of Carbon Cloth-based Flexible Self-supporting Electrode And Their Electrochemical Performance

The rapid development of global economy lead to the increasing demand for energy in recent years.The extensive use of fossil fuels as traditional energy sources has led to serious environmental problems.Therefore,it is urgent to develop new energy to reduce the dependence on fossil energy.Ammonia has caused great concern as a new type of green energy,which obtains high liquefaction temperature,excellent safety and the ability to be prepared by renewable energy.Furthermore,it is expected to develop new energy utilization methods,such as the new energy conversion device—supercapacitor,which have attracted much attention for their short charging and discharging time and long cyclic life.In this paper,the corresponding solutions focusedon the problems of ammonia synthesis and the performance improvement of supercapacitor.Haber method is mainly used in industry for ammonia synthesis.However,low efficiency,huge energy consumption,and the use of fossil energy exist in Haber method.Therefore,researchers are interested in electrochemical synthesis of ammonia because of its low energy consumption and the use of renewable energy to achieve ammonia production.However,electrochemical synthesis of ammonia involves nitrogen reducation reaction(NRR),which is a kinetically sluggish reaction.Thus,it is necessary to develop high-performance electrode materials for NRR with enhanced activity,durability and selectivity.The first part of this thesis involves carbon cloth as support,and then the precursor of the active material Mo is directly loaded on the carbon cloth by dipping and calcining.Ultra-small Mo nanoparticles were successfully prepared after hydrogen reduction.To understand the mechanism of the formation,in-situ TEM was used to study the reducation process of Mo precursor on the carbon cloth.It was observed that active components were re-dispersed into small pieces from large particles and combined with DFT to explain the phenomenon theoretically.Carbon cloth as flexible self-supporting working electrode reduce the contact resistance.The synthesized Mo/carbon cloth self-supporting electrode was used as the cathode for NRR.At room temperature and atmospheric pressure,the Faraday efficiency reaches the highest(22.3%)when the voltage reaches 0 V with NH3 yields of 7.02 ? g h-1 mg-1cat.,even comparable to some precious metal based catalysts.The by-product hydrazine(N2H4)was not detected,suggesting the excellent selectively of the catalyst.In the second part of this paper,LC-WO3/TCC was synthesized by growing LC-WO3 on porous carbon cloth(TCC)in-situ by a one-step hydrothermal method.Carbon cloth as flexible self-supporting working electrode reduce the contact resistance and improve the electrochemical performance of the device.Different materials were prepared by adjusting hydrothermal conditions,and factors such as crystallinity on the electrochemical properties and the kinetic analysis of the energy storage mechanism were studied.The results show that LC-WO3 with rich structural defects and disorders provides facilitated redox reactions,and capacitive-dominant energy storage property,thus offering higher specific capacitance(474 F/g)and enhanced capacitance retention performance compared to HC-WO3.Further assembling a flexible solid-state asymmetry SC,based on LC-WO3 in-situ grown on porous carbon cloth,exhibits an excellent areal specific capacitance of 1693 mF/cm2,high energy density of 7.6 mWh/cm3 and long cycle life with 92%capacitance retention after 10 000 cycles,as well as excellent mechanical flexibility and stability.In short,in this paper,two kinds of carbon cloth-based flexible self-supporting electrodes with excellent performance have been developed for the exploitation of new energy such as ammonia energy,and new energy utilization methods such as supercapacitor.These two strategies provide new ideas for catalyst design and its application in electrochemical ammonia synthesis,it demonstrates a new approach for optimizing the charge storage performance of pseudocapacitive materials in advanced SCs,and provides a promising for the application of low-crystalline anode material in low-cost flexible electronics.