Investigations On The Electrochemical Reduction Behaviors And Preparation Technology Of Cu-Se Compound Thermoelectric Films In Sulfuric Acid Solutions

In recent years,the problems of environmental pollution and energy shortage caused by industrial development and population increase are becoming more and more serious.The green sustainable developmental thermoelectric conversion technology has been widely concerned by researchers,and thermoelectric materials have become the top priority of the researches.The special structure of p-type?-Cu₂Se thermoelect r ic material makes it an excel ent thermoelectric material at medium temperature.Based on this,for the purpose of the preparation of high-performance p-type?-Cu₂Se thin film thermoelectric materials,the electrochemical reduction kinetics of Cu^II and Se^IV in sulfuric acid solution have been studied systematically.Then intense researches on the preparation technology of p-type Cu-Se thin film materials were carried out.The structure,morphology and composition of the electrodeposited films were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and energy-dispersive spectroscopy?EDS?,and the optimized preparation technology for?-Cu₂Se was obtained.The reduction behaviors of Cu^II and Se^IV in sulfuric acid solution were analysed by cyclic voltammetry?CV?,linear sweep voltammery?LSV?and electrochemica l impedance spectroscopy?EIS?.The effects of non-ionic surfactant SA,cationic surfactant SB,temperatures and pH values of the solutions on the Cu unitary system,Se unitary system and Cu-Se binary system have been studied.The results show that in Cu unitary system,the electrochemical reduction of Cu²⁺to Cu⁰ experiences a two-step reaction process.Cu²⁺in the solutions was reduced to Cu⁺first and then to Cu⁰ on the surface of the electrode.A three-step electrochemical reduction process takes place in Se unitary system.Se⁴⁺existing in the form of H₂SeO₃ is first reduced to Se²⁺by a two-electron reaction step and then to Se⁰ subsequently at a more negative potential.With the potential moving negatively,the electrodeposited Se⁰ on the surface of the electrode is reduced to Se^2-further.In Cu-Se binary system,there are three major processes taking place which form CuSe,Cu₃Se₂ and Cu₂Se.Effects of Cu^II and Se^IVV concentrations in the solution,pH values and temperatures of the solutions and the electrodeposit io n potential were investiagated by Hull Cell test and potentiostatic deposition.The optimal techonology is:solution comprised of 70mM CuSO₄·5H₂O,45mM H₂SeO₃,2mL SA10000,pH value 2.0,temperature 30?,and the electrodeposting potential of 0.04V.Furthermore,the optinzied techonology of preparation thin films has been reported.The Seebeck coifficent of p-type?-Cu₂Se thin film with the best thermoelectric properities is 106.0?V/K,the power factor is 0.53 mW/?K²m?.