Three-dimensional Multi-physical-fields Coupling Simulation Research On Co-electrolysis Performance Of Solid Oxide Electrolysis Cell

Due to the increasing demand of power and the serious environmental problems,renewable energy power generation technology and carbon dioxide capture,storage and utilization?CCU?technologies have received worldwide attention.The difficulty of connecting renewable energy generation to the power grid makes energy storage a research hotspot.The solid oxide electrolysis cell?SOEC?can efficiently convert electric energy generated by renewable energy to chemical energy which can be easily stored,and at the same time,it can convert carbon dioxide into carbon monoxide,which achieves the carbon neutral recycling of carbon dioxide.Therefore,it is very important to conduct performance optimization research on SOEC.In this paper,a three-dimensional simulation model for co-electrolysis of water and carbon dioxide in solid oxide electrolysis cell is established.The model considers the complex electrochemical reactions,chemical reactions,heat and mass transfer process in SOEC.The reliability of the model is confirmed by comparing the simulation results of the model with the experimental data.Based on the model,the effects of operating parameters and cell structural composition on SOEC performance are studied in detail.In addition,the distribution of physical field parameters and current density distribution in the electrolysis cell are analyzed for different flow field structures.First,the impact of operating parameters on SOEC performance is analyzed.The results show that the electrolysis voltage is reduced when the operating pressure is higher than 8 atm compared to the atmospheric pressure operation.At the same time,the methanation reaction is activated at approximately 3 atm,which significantly reduces the thermal neutral voltage?TNV?and electrolysis efficiency of the SOEC.Increasing the mole fraction of CO₂ in the inlet gas and reducing the gas utilization improved the electrolysis obviously,but the higher the CO₂ content,the higher the electrolysis voltage.Compared with the co-flow arrangement,the counter-flow arrangement of the anode and cathode gas can significantly reduce the electrolysis voltage at a large current density.Secondly,the structural composition optimization of SOEC is analyzed.The results show that the addition of anode gas diffusion layer?AGDL?on the anode side significantly improves the oxygen diffusion process,thereby reducing the Nernst voltage and the ohmic overpotential,and increasing the AGDL can further improve the SOEC performance to some extent.Compared with the traditional flow field,the gas distribution and temperature distribution of SOEC with a metal foam flow field are more uniform,which significantly reduces the SOEC electrolysis voltage and improves the electrolysis efficiency.Finally,the traditional flow field and foam flow field structure are optimized based on the single cell.The parallel flow field has the lowest pressure drop compared to the serpentine flow field.Since the gas of the multi-channel parallel flow field or the parallel serpentine flow field is mutually complement between the channels,the concentration gradient of it is larger.Relatively speaking,the gas distribution and chemical reaction rate are the most uniform in the multi-channel serpentine flow field,so that the cathode activation loss is minimized and the SOEC performance is better.For the foam flow field,the distribution of physical field parameters and electrolysis reaction rate for SOEC with two inlets is more uniform than that with one inlet,so that the SOEC performance is better.Compared with the ordinary foam flow field,the combined flow field of the cavity foam makes the distribution of the reaction gas more uniform,thereby significantly reducing the electrolytic voltage.