Preparation And Research On High Temperature Electrolysis By A Hollow Symmetrical Planar Cell Based On Double-sided Cathodes

High temperature electrolysis of H₂O,CO₂ and co-electrolysis can be performed in solid oxide electrolysis cell?SOEC?.Using excess electricity and heat,SOECs can convert steam to hydrogen and greenhouse gas CO₂ to CO.Because the running temperature of SOEC is high,it requires less electricity but the convert efficiency is higher.,it makes SOEC a most efficient way for large-scale fuel gas production in future.The conventional planar solid oxide electrolysis cell?SOEC?will suffer from some problems such as substrate warping and electrolyte cracking after running for a long time.These problems result from tensile stress induced by asymmetric temperature distribution and low redox stability of the cell.To solve the problems of the conventional planar SOEC,a novel design is proposed in this work.At first,in this paper,a new structure type of hollow symmetry SOEC is designed and fabricated based on the Ni base hydrogen electrode and YSZ electrolyte cell material.In order to prove the cell electrochemical performance and running stability,we focus on the research of NiO-YSZ power preparation,dry pressing,screen printing and YSZ electrolyte sintering,which is key technology for cell performance.Secondly,the experiment of electrolyzing CO₂ with hollow symmetry planar SOEC was investigated.Result showed that improving running temperature,concentration of reactants and working voltage could accelerate the reaction rate of electrolyzing CO₂ with SOEC,meanwhile decrease the resistance of cell.In the experiment of electrolyzing pure CO₂,hollow symmetry planar SOEC had a better performance on high temperature circulating and long tern stability compared with conventional planar SOEC.At 750?,after 50h constant current electrolyzing at a current density of 0.33A/cm²,the voltage decrease from 1.18V to 1.08V with a degradation rate of 7.8%/100h.The new type of SOEC worked at operating temperature for a long time,the coarsening of fuel electrode may be the main reason for degradation of the performance for SOEC.Finally,co-electrolysis of H₂O/CO₂ were demonstrated in a hollow symmetry planar SOEC.Results indicated that higher temperature and working voltage could promote co-electrolysis.Analyzing and comparing the IV curve of electrolysis of H₂O,CO₂ and co-electrolysis showed that in the process co-electrolysis,H₂O and CO₂ were both electrolyzed,competition existed between them.A reaction pathway for methane production was studied from high temperature co-electrolysis experiment,increasing voltage and content of hydrogen was helpful for methane generation.