Studies Of Biomimetic Electrochemical Cell And Its Application

In the electrochemical field,the mass transfer and the reduction of the effective area of the electrode due to gas product coverage are major issues in the electrolysis process.The electrolysis processes include electrolytic refining of copper and hydrogen production by electrolysis of water which requires high energy.Therefore,it is of great significance to strengthen the study of mass transfer in electrochemical industry.In this paper,the application of self-designed biomimetic electrochemical cell(i.e.,electrochemical cell consists of several components,which of each component completes a function and is connected in series to complete the electrochemical reaction)was studied to improve mass transfer,increase electrolysis efficiency and reduce energy consumption.On the basis of this,the nickel foam composite electrodes have been studied in order to improve the performance of the electrolysis of water.We used a self-designed biomimetic electrochemical cell for electrolytic copper to improve mass transfer of ions through the forced convection of electrolyte.The results show that the flow of electrolyte can improve electrolytic refining of copper and the result is better when the electrolyte flow direction is the same as that of the S042-(i.e.,from cathode to anode).Such as,cell voltage and power consumption decreases with increasing the speed of circulation at a constant current density of 50 A·m-2,while the current efficiency increases with the increase of the circulating speed,and finally tends to be stable.At high electrolyte circulation rate of 600 mL·h-1(approximately equal to 0.056 cm·s-1 in the electrochemical cell),the cell voltages of different flow directions reduce by 35.5%and 36.9%respectively,and the electrolysis efficiencies both increase from 94.4%to 98.9%.The results show that it is feasible to improve the mass transfer process of electrochemical reaction by forced convection of electrolyte.We have also designed water electrolysis device labeled NF?NF with a polymer gel electrolyte and a gas diffusion layer which was made of pure nickel foam electrode materials.This design is to study the effect of the removal of the product in time on the electrochemical reaction,i.e.,the gas product escape from the gas diffusion layer as soon as possible,so as to reduce the shielding effect of the gas on the electrode.The results show that 6 M KOH and 7.4 wt.%PAAS gel electrolyte(the best gel electrolyte composition)shows the best electrochemical performance,considering both mechanical and electrochemical properties.Then,we studied the electrochemical properties of the best gel electrolyte and the corresponding KOH solution electrolyte.It was found that the water electrolysis performance of polymer gel electrolyte is better than that of KOH solution electrolyte,and it also maintain long-term electrochemical stability.At cell voltage of 2 V,the cells deliver the current densities of 95.14 mA·cm-2 and 70.00 mA·cm-2,respectively.At constant current density of 100 mA·cm-2,the cell voltages were 2.10 V and 2.16 V,respectively.This suggested that the use of gel electrolytes and gas diffusion layers can achieve our initial vision.To improve the performance of electrolysis water device with the gel electrolyte,the preparation and properties of the catalysts were also studied.First,Fe/NF and Ni-Fe/NF electrodes were prepared by galvanostatic electrodeposition at current densities of 2 mA·cm-2,4 mA·cm-2 and 8 mA·cm-2.The performances of electrolytic water of the NFINF cell made of cathode electrode of pure nickel foam,anode electrode of as-prepared electrode material and electrolyte of PAAS polymer gel were studied.The results show that the Fe/NF and Ni-Fe/NF electrodes can greatly improve the electrochemical performances of the water electrolysis compared to NFINF cell assembled with the best gel electrolyte.Fe/NF and Ni-Fe/NF electrodes show the best electrochemical performance at a deposition current density of 2 mA·cm-2 and 4 mA·cm-2,respectively.The electrodes achieve maximum current density of 250.4 mA·cm-2 and 293.7 mA·cm-2 at 2 V,respectively.At constant current density of 100 mA·cm-2,the cell voltage are 1.94 V and 1.91 V,respectively.The ?-Co(OH)2/NF electrode was prepared by potentiostatic electrodeposition at different deposition time.The properties of water electrolysis of the ?-Co(OH)2/NFINF cell were studied,The cell was made of pure nickel foam as negative electrode,?-Co(OH)2/NF electrode as positive electrode material and PAAS polymer gel electrolyte.We found that?-Co(OH)2/NF electrode shows the best electrochemical performance at the deposition time of 60 min.By comparing NFINF electrolytic cell assembled with the best gel electrolyte,we found that ?-Co(OH)2/NF positive electrodes greatly enhanced the performance of water electrolysis.The electrode achieve maximum current density of 280.4 mA·cm-2 at cell voltage of 2 V.At constant current density of 100 mA·cm-2,the electrolytic cell voltage is about 1.94 V.The performance of electrolysis water of the ?-Co(OH)2/NFINi-Fe/NF cell was studied.The cell was made of pure nickel foam as negative electrode,?-Co(OH)2/NF electrode as positive electrode material and PAAS polymer gel electrolyte.The results show that the cell delivers high current density of 344.2 mA·cm-2 at cell voltage of 2 V.At constant current density of 100 mA·cm-2,the cell voltage is as low as 1.88 V.At current density of 10 mA·cm-2,the cell delivers a steady voltage output within 14 h,indicating that it can maintain excellent long-term electrochemical stability.