多级结构钙钛矿-萤石纳米复合阴极制备及其CO2电催化还原反应研究

Solid oxide electrolysis cell (SOEC) can electrocatalyze CO2 into CO/syngas by using the clean and renewable energies, which realizes the reduction of CO2 emission and the carbon cycling utilization, showing very promising applications. Design and development of high performance perovskite cathode for CO2 electrocatalytic reduction is the hotspot in the field of SOEC. In this proposal, we suggest to build hierarchical perovskite-fluorite nanocomposite cathodes via the infiltration method based on the (La,Sr)MO3 (M=Ti, Cr, Fe…) perovskite materials and ZrO2/CeO2 fluorite materials, aiming to greatly improve the CO2 electrocatalytic reduction performance. The symmetrical cells consisting of cathodes will be constructed, and impedance spectroscopy characterization, calculation of the distribution function of relaxation times and complex nonlinear least squares fitting would be employed to study the elemental electrode processes of CO2 electrocatalytic reduction. The combination of physicochemical characterization on the cathodes with the above analysis can be used to establish the relationship between the microstructure of the cathodes and their elemental electrode processes as well as electrocatalytic performance. Furthermore, the activity enhancement mechanism and intrinsic structure-activity relationship for the hierarchical perovskite-fluorite nanocomposite cathodes could be elucidated, and finally, the mechanism of CO2 elecrocatalytic reduction on perovskite SOEC cathode will be disclosed. The research results could provide reference for the related studies of CO2 electrocatalytic reduction in SOEC.

固体氧化物电解池(SOEC)能够利用可再生能源产生的电能，将CO2电催化还原为CO/合成气，实现CO2的有效减排与碳资源的循环利用，表现出极具潜力的应用前景。研制高性能钙钛矿型SOEC阴极是当前CO2高温电解研究领域的热点之一。本项目拟基于(La,Sr)MO3 (M=Ti, Cr, Fe…)钙钛矿材料和铈基/锆基萤石结构材料，采用浸渍法制备具有多级结构的钙钛矿-萤石纳米复合阴极，以提高阴极的CO2电催化还原活性及稳定性；并通过构建阴极对称电解池，借助物理化学表征、阻抗谱表征、阻抗谱弛豫时间分布函数计算及等效电路拟合，研究解析SOEC阴极电催化还原CO2的电极反应历程，建立阴极微观结构与物化性质同其基元电极过程和电催化性能间的关联，阐明多级结构钙钛矿-萤石纳米复合阴极的活性增强机制，认识其构效关系的本质，进而揭示钙钛矿型阴极的CO2电催化还原机理，为SOEC电解CO2相关研究提供借鉴。

固体氧化物电解池（SOEC）能够利用可再生能源产生的电能将CO2电催化还原为CO或合成气，同时实现CO2的高效转化和可再生能源存储，表现出极具潜力的应用前景。SOEC电催化还原CO2在阴极催化剂上进行，其苛刻的反应条件限制了阴极催化剂的选择。钙钛矿氧化物由于其在氧化还原气氛中的稳定性被认为是当前极具前景的电催化还原CO2阴极催化材料。本项目以钙钛矿-萤石相复合阴极为研究对象，通过浸渍、原位溶出等手段构筑了具有多级结构的阴极催化剂，提高了SOEC电催化还原CO2的活性和稳定性；借助物理化学表征、原位谱学表征并结合理论计算，研究解析了SOEC阴极电催化还原CO2的电极反应历程，建立阴极微观结构与物化性质同其基元电极过程和电催化性能间的关联，阐明了多级结构钙钛矿-萤石复合阴极的活性和稳定性增强机制，设计制备了高性能的电催化CO2催化剂：.（1）通过将高活性Ce0.9Mn0.1O2-δ（CMO）纳米颗粒引入传统(La0.75Sr0.25)0.95Cr0.5Mn0.5O3-δ-Gd0.2Ce0.8O1.9（LSCM-GDC）阴极表面调控阴极表面电子给电子能力和氧空位浓度，显著增强CO2吸附活性。电化学性能测试结果表明，CMO纳米粒子引入之后LSCM-GDC阴极SOEC在800 oC和1.0V的电催化还原CO2的电流密度提高至原来的2.85倍。电催化还原CO2产物为CO，法拉第效率接近100%。.（2）采用共浸渍法成功制备了LSCM-GDC纳米复合颗粒担载在 (Y2O3)0.08(ZrO2)0.92（YSZ）多孔骨架表面的LSCM-GDC/YSZ多级结构阴极。纳米尺寸LSCM-GDC复合颗粒从同一个溶液中分相得到，均匀相间紧密排布，显著增加了阴极三相界面数量；且在SOEC运行过程中能够抑制同种颗粒长大，同时提高电催化还原CO2的活性和稳定性。在800 oC和1.4V电催化还原CO2的电流密度提高至传统LSCM-GDC阴极SOEC的1.68倍，稳定运行50h无衰减。.（3）通过原位溶出技术在Sr2.0Fe1.35Mo0.45Co0.20O6-δ（SFMC）-GDC阴极表面原位“锚定”CoFe合金纳米粒子来同时提高SOEC电催化还原CO2活性和稳定性。理论计算结果表明，CoFe合金纳米粒子和SFMC界面处存在金属纳米团簇和富含氧空位钙钛矿基底的协同催化作用，增强了CO2的吸附同时促