Research On Electrode Materials For Novel Liquid Thermocells

Thermal energy in the natural environment is a kind of green environmental protection energy with abundant reserves,and converting low-grade heat into electrical energy has great practical significance to solve the problems of energy supply and environmental pollution.Liquid-state thermocells is a promising technology that could convert low-grade heat of heat energy into electrical energy.Solid-state thermoelectric cells have been studied for direct conversion of thermal energy into electrical energy,however,solid-state thermoelectric cells are expensive and often require large temperature gradient differences,which limits the application of solid-state thermoelectric cells.Liquid thermocells use the temperature dependence of the electrochemical redox potential(thermoelectric effect)to generate electricity and thus can convert the low-grade heat into electrical energy.In the past decade,great advancement has been achieved in the thermocell field.In the research of improving the performance of liquid thermocells,most researchers mainly study the electrolyte,and improve the redox ability of electrolyte by optimizing the electrolyte composition to improve the efficiency of thermocells.As an important part of thermocells,electrodes play a crucial role in performance.However,the effect of electrodes on the performance of thermocells has been lacking in past studies.In this work,we used a variety of carbon materials as electrodes,such as graphite,graphite paper,carbon fiber,graphite felt.In this experiment,we designed a novel liquid thermocells with metal-polyethylene terephthalate(PET film)-carbon material(MPC sandwich structure)electrode.In this experiment,the metal sheet is copper sheet,which not only plays the role of mechanical support but also has good thermal conductivity,which can enhance the mechanical strength of the liquid thermocells and reduce the loss of effective temperature difference between environment and electrolyte.The PET film is to avoid electrolyte penetration of carbon electrode and copper sheet contact reaction,at the same time,PET film can play a good sealing role,carbon material as a direct contact with the electrolyte electrode has good conductivity,thermal stability and high electrochemically accessible surface areas.The graphite felt shows the best performance,and the large number of redox reaction sites established by the high internal surface area of graphite felt,which greatly enhances the thermoelectric conversion efficiency.In order to confirm that this electrode structure has a wider range of applications,in addition to the common most common hydrothermal studies(potassium ferricyanide and potassium ferrocyanide mixture),we also studied the effect of different electrode structures on the electrical properties of thermosensitive crystallization liquid thermocells after adding auxiliary materials(guanidine salts).The results show that even after adding auxiliary materials,the optimization of this structure is not affected,and the electrical performance of liquid thermocells with MPC structure is still better than that of liquid thermocells with ordinary structures.We concluded that the novel liquid thermocells prepared by using MPC sandwich structure graphite felt as the inner electrode has low preparation cost,simple process,good mechanical strength,lighter mass,higher thermoelectric conversion efficiency can take advantage of the temperature difference between the human body and the environment to convert thermal energy into electrical energy.Through adjustment,a sustainable open circuit voltage of 162.0 m V and short circuit current of 23.0 m A was achieved for an individual liquid thermocells under a ?T of 50 K between the heater and cooler plates.The results of our new electrode material research provide technical support for the development of thermocells and lay the foundation for effective collection of low-grade heat.