Preparation And Properties Of Copper-based Electrocatalysts With Its Trifunction

With the development of science and technology and the improvement of people's quality of life,the use of non-renewable energy such as coal,oil and natural gas has neither long-term development nor benefit on air quality.It is well known that oxygen evolution and reduction reaction and water splitting reaction are important theoretical components of metal-air cell and fuel cell,which makes the research of this kind of catalyst very hot.Pt,RuO2 and IrO2 as the high efficient catalysts have the disadvantages of high cost,low Earth abundance,and can not be used as a multifunctional catalyst at the same time.Therefore,the development of cheap non-precious metals and even three-functional catalysts is an important exploration in practical technology of batteries.This paper summarizes many types of catalysts related to electrocatalytic water decomposition and zinc-air batteries,summarizing their metal selectivity,material synthesis and structural characteristics,and designing and synthesizing non-precious metals.A series of studies have been carried out on Cu-based catalysts,he results show that the Cu-based catalyst has the electrocatalytic performance comparable to that of the precious metal catalyst,and can be used as a multifunctional electrocatalyst at the same time,and becomes an effective material that can replace the commercial precious metal catalyst..The main research contents are as follows:1.This paper chooses conductive copper foam as the substrate and then to grow CuF/Cu(OH)2 nanowires by electroplating in-situ.Next,a layer of ZIF-67 particles were coated on the surface of the Cu(OH)2 nanowires by a soaking method at room temperature to obtain CuF/Cu(OH)2@ZIF-67.Finally,CuF/Cu(OH)2@ZIF-67 was calcinated at different temperatures change to CuF/CuCo-NC heterostructure.The structure and morphology of these components were characterized by XRD,Raman,XPS,SEM and TEM.Different calcination temperatures have different effects on the structural morphology of the material and the degree of ripening of the metal atoms.The electrochemical performance of these materials were tested by electrochemical testing of HER,OER and overall water splitting.In 1.0 M KOH solution,the overpotentials of HER and OER were 59 mV and 245 mV,respectively,at a current density of 10 mA/cm2.Owing to the mature agglomeration of metal nanoparticles are more serious at high temperature,and the rod-like structure of CuF/CuCo-NC will gradually collapse,500? is the best annealing temperature by morphological characterization and electrochemical performance.The higher the temperature,the lower the electrochemical performance.At the same time,the electrochemical performance of ZIF-67-500 and CuF/Cu(OH)2-500 is far less than that of CuF/CuCo-NC-500.It is shown that the excellent electrochemical performance of CuF/CuCo-NC-500 is the result of the interaction of metal Co,Cu and foamed copper.The XPS characterization proves that the CuF/CuCo-NC-500 structure contains special metal-nitrogen(M-N)structure.A large amount of data indicates that the material with M-N structure also has good oxygen reduction reaction(ORR)performance.Therefore,in this paper,CuF/CuCo-NC-500 was used for electrochemical oxygen reduction.The results show that CuF/CuCo-NC-500 has an onset potential and a half wave potential comparable to Pt/C in a 0.1 M KOH solution which were 0.96 V and 0.84 V,respectively.It is worth mentioning that the limiting current density of CuF/CuCo-NC-500 can reach 21 mA/cm2 due to the conductive effect of the foamed copper substrate.2.It is well known that the electrocatalytic total water-resolving reaction is composed of two reactions of the OER of the positive electrode and the HER of the negative electrode,and the metal-air battery is realized by the synergistic action of the two semi-reactions of OER and ORR in the charge-discharge cycle.Experiments have shown that due to the current-conducting effect of copper foam a current density of 10 mA/cm2 can be achieved with only a full desorption water voltage of 1.52 V.At the same time,it is sufficient to achieve a current density of 500 mA/cm2 only at a full dehydration voltage of 1.78 V.Based on the excellent OER and ORR performance of CuF/CuCo-NC-500,this paper then used CuF/CuCo-NC-500 as the positive electrode and zinc plate as the negative electrode to assemble the zinc-air battery.The energy density of the battery can reach 145 mW/cm2,and the battery capacity density is as high as 98%at a discharge current of 5 mA.The battery has a long-term stability of more than 360 hours at a charge and discharge current of 10 mA,and the battery round-trip efficiency is always higher than 58%.In this paper,a zinc-air battery with two CuF/CuCo-NC-500 as anodes is used to electrolyze water which the double CuF/CuCo-NC-500 used as the positive and negative electrode and the hydrogen evolution rate can reach 69 ?L s-1.3.In order to further develop the catalytic properties of copper-based materials,a one-dimensional copper nano wire was prepared by solution method as a synthetic template,and a certain amount of copper nanowires and pyromellitic acid ligands were mixed at 80 °C.A one-dimensional Cu-based MOF material HKUST-1 was obtained after solvothermal reaction for 20 hours.The structure and morphology of the one-dimensional HKUST-1 were characterized by XRD,SEM,AFM,TGA,etc.The synthesis mechanism of one-dimensional MOF materials was analyzed from the thermodynamics such as ligand concentration and reaction time.Due to the poor conductivity of HKUST-1 and the not good performance of metallic copper in electrocatalytic water decomposition,it is difficult to make a breakthrough in electro performance.