The Properties Of LSCM-GDC Composite Cathode For Ni,Cu-loaded Solid Oxide Electrolytic Cells

As an important part of clean energy,hydrogen energy has been fully developed and utilized in recent years.Solid oxide electrolysis cell（SOEC）is an efficient energy conversion device that can convert electrical energy and thermal energy into chemical energy,that is,water vapor is electrolyzed to generate high-purity hydrogen under high temperature condition,which has broad application prospects in the field of new energy.The SOEC cathode is an important part of the device and is the key place for the electrolysis of water to generate hydrogen.Therefore,the study of cathode materials with high stability and strong catalytic activity is of great significance for the development of the SOEC.The oxide La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ（LSCM）with perovskite structure has high chemical stability and certain electrocatalytic activity at high temperature,which is the current focus of SOEC cathode material researches.In this paper,a composite electrode with a molar ratio of 1:1is constructed by LSCM material and Ce_0.8Gd_0.2O_2-δ（GDC）with a cubic fluorite structure,and different amounts of Ni and Cu as metal catalysts are loaded by impregnation method.In turn,the ionic conductivity and electrocatalytic activity of LSCM material is improved.Electrode material LSCM,electrolyte material Ce_0.8Sm_0.2O_2-δ（SDC）and GDC are prepared by sol-gel method.The GDC is brushed on the surface of the electrolyte SDC by screen printing.After high temperature sintering,the LSCM-GDC composite cathode material is brushed on the GDC by the same method,and the composite electrode is obtained by sintering at a high temperature of 1250℃ for 3 hours.As an interlayer material,GDC improves the stability and bonding degree between the electrode and the electrolyte.Nitrate solution containing metal Ni and Cu is added to the composite cathode,and the composite electrode loaded with Ni and Cu is obtained after vacuum drying,calcination and reduction reaction.The Ni and Cu loaded composite electrodes are tested using the three-electrode system.At the working temperature of 650～850℃and the open circuit voltage state,cathodic polarization curves and electrochemical impedances are tested under 4%（v/v）H₂O/H₂reducing atmosphere and 4%（v/v）H₂O/N₂oxidizing atmosphere,respectively.With the increase of the working temperature,the electrochemical performance of the electrodes also improves,and compared with the oxidizing atmosphere,the performance of each electrode in the reducing atmosphere is better.The cathodic polarization curves and electrochemical impedances of each electrode at 800℃ are selected to explore the effects of different loading metals and loading amounts on the electrochemical performance of the electrodes.The results show that the performance of Ni-loaded electrodes is better than that of Cu-loaded electrodes.And under reducing and oxidizing atmospheres,the performance of electrodes with different Ni loading amounts is quite different.In a reducing atmosphere,the 2%Ni-loaded composite electrode has the best performance.Taking the open-circuit voltage as the origin,its current density at-0.1V overpotential is 3.89 A·cm^-2,and the sum of the total polarization resistances of R_p1and R_p2was 0.21Ω·cm².However,in the oxidizing atmosphere,the performance of 1%Ni-loaded composite electrode is the best,with a current density of 1.02 A·cm^-2and a total polarization resistance of 4.59Ω·cm²under the same conditions.When the total loading is 1%,the co-loading of Ni and Cu will further improve the electrochemical performance on the basis of single Ni or Cu loading.In a reducing atmosphere,the current density of the composite electrode with a nickel-copper ratio of 2:8 reaches 2.36 A·cm^-2at-0.1 V overpotential,and the fitted polarization resistance is 1.02Ω·cm².