Preparation And Performance Of Solid Oxide Electrolytic Cell Supported By Oxygen Electrode

Solid oxide electrolytic cell（SOEC）as a device that can effectively convert electrical energy into chemical energy,has received wide attention for its high reliability and great application prospects.Currently,the most widely studied is fuel electrode-supported SOEC,but the long-term stability of fuel electrode-supported SOEC can be seriously affected by the large volume change caused by Ni-based fuel electrode in the continuous redox process and the fracture of electrolyte-oxygen electrode interface.The perovskite oxygen electrode-supported SOEC is characterized by a thin fuel electrode,which makes the Ni redox volume change smaller and the high bonding strength of the electrolyte-oxygen electrode interface,which solves the problem of long-term SOEC stability.However,the perovskite oxygen electrode-supported SOEC suffers from the problem that the porosity of the perovskite support decreases after high temperature sintering,which leads to the reduction of the three-phase interface（TPB）and hindered gas transport,making the performance of the oxygen electrode-supported SOEC lower.To solve this phenomenon,an oxygen electrode-supported SOEC with a dendritic microchannel structure was prepared using the template-phase conversion method.The dendritic microchannel support of this SOEC has several advantages:good resistance to sintering,which ensures the porosity of the support and promotes the rapid release of gas,so that the SOEC electrolysis does not produce concentration polarization;it is conducive to catalyst loading and improves the SOEC performance.Meanwhile,the electrolyte with oxygen electrode of microchannel oxygen electrode-supported SOEC forms a strong interfacial bond after high temperature co-fired,which can achieve long-term stable electrolysis at high current density.The details of the study and the conclusions are as follows:（1）Application of microchannel oxygen electrode-supported SOEC to electrolysis of H₂O.In this study,the prepared oxygen electrode-supported SOEC were characterized morphologically as well as by performance using XRD,SEM,electrochemical workstation,DRT analysis,and 2D numerical simulation.The results show that the oxygen electrode of the oxygen electrode-supported SOEC maintains a large number of dendritic microchannels after high temperature sintering,which is conducive to rapid oxygen generation and release,and the microchannel oxygen electrode-supported SOEC can be electrolyzed at low water vapor concentration of 15%without significant concentration polarization;the performance of the oxygen electrode-supported SOEC was further improved by loading Pd-GDC nanocatalyst inside the dendritic microchannels,and the current density of SOEC was doubled from 0.56 A cm^-2 to 1.15 A cm^-2 at 1.3 V,doubling the current density.In addition,the strong interfacial bonding formed by the high-temperature co-fired oxygen electrode and electrolyte greatly solved the performance degradation of SOEC at high currents,enabling SOEC to operate stably for 110 h at a high current density of 2.5 A cm^-2 for H₂O electrolysis.（2）In order to achieve precise regulation of the ratio of syngas（H₂+CO）production by SOEC co-electrolysis（H₂O+CO₂）,the microchannel oxygen electrode-supported SOEC was further applied to co-electrolysis.Results show that since the current-voltage curve of the microchannel oxygen electrode-supported SOEC co-electrolysis is free from the phenomenon of concentration polarization,the ratio of synthesis gas produced can be controlled more precisely by controlling the ratio of incoming H₂O to CO₂.The F-T synthesis method allows the precise preparation of different ratios of syngas into other chemical fuels;meanwhile,the microchannel oxygen electrode-supported SOEC has a strong oxygen electrode and electrolyte binding interface,which makes SOEC co-electrolysis stable at a current density of 1.0 A cm^-2for 100 hours.（3）To address the problem that the fuel electrode of conventional SOEC needs to pass H₂to prevent Ni from oxidation,the Ni-based material of the fuel electrode was replaced by a perovskite material,and a similar symmetrical perovskite electrode-supported SOEC was prepared for pure CO₂ electrolysis.The test results show that because the similar symmetrical perovskite electrode-supported SOEC does not need to pass H₂ as a protective gas,which reduces the open circuit voltage to 0.1 V and significantly reduces the power loss.In addition,the CO₂ electrolysis of perovskite cathode-supported SOEC and perovskite anode-supported SOEC were tested separately,and the experimental results demonstrated that the perovskite anode-supported SOEC showed activation polarization while the perovskite cathode-supported SOEC had no activation polarization,which proved that the cathode was the limiting part of SOEC performance,and the cathode with microchannel structure eliminated the activation polarization phenomenon.Moreover,the perovskite cathode-supported SOEC can electrolyze CO₂ at a high current density of 3.0 A cm^-2 and exhibits high stability.