Coke formation during high-temperature CO2 electrolysis over AFeO3 (A = La/Sr) cathode: Effect of A-site metal segregation
Coke formation during high-temperature CO2 electrolysis over AFeO3 (A = La/Sr) cathode: Effect of A-site metal segregation
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DOI：
10.1016/j.apcatb.2020.119642
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发表时间：
2021-04-01
影响因子：
22.1
通讯作者：
Ozkan, Umit S.
中科院分区：
文献类型：
--
作者：
Deka, Dhruba J.;Kim, Jaesung;Ozkan, Umit S.
在本研究中，采用不同a位占比的掺锶铁酸镧钙钛矿氧化物（LSF）作为阴极催化剂，在800℃下进行CO2电解，采用XRD， EXAFS， XPS， FTIR和程序升温脱附等方法对材料的性能进行了表征。Fe k边EXAFS表明，随着电子和离子电导率的提高和a位占用率的降低，Fe原子的氧空位浓度和氧化态增加。XPS谱显示，a位过量的LSF92表面Sr原子的分离程度大于a位不足的LSF72。这些分离出的a位金属氧化物，特别是SrO，本质上是碱性的，因此与酸性CO2强烈结合形成稳定的SrCO3，从而促进碳的形成。本研究强调了a位化学计量调制对CO2电解过程中碳形成的影响，这对提高SOEC的长期性能至关重要。
In this study, strontium-doped lanthanum ferrite perovskite oxides (LSF) with different A-site occupancies were used as cathode catalysts for CO2 electrolysis at 800 degrees C. XRD, EXAFS, XPS, FTIR, and temperature-programmed desorption were used to characterize the properties of the material. Fe K-edge EXAFS indicated that oxygen vacancy concentration and oxidation states of Fe atoms increased with concomitant improvement of electronic and ionic conductivities with a decrease in the A-site occupancy. XPS spectra revealed that Sr atoms segregated on the surface of A-site excess LSF92 to a greater degree than that on the A-site deficient LSF72. These segregated A-site metal oxides, especially SrO, are alkaline in nature and hence strongly bind to acidic CO2 forming stable SrCO3, which consequently facilitates carbon formation. This study highlights the effect of A-site stoichiometric modulation on carbon formation during electrolysis of CO2, which is crucial for improving the long- term performance of an SOEC.