Oxygen Activity Tuning via FeO6 Octahedral Tilting in Perovskite Ferrites for Chemical Looping Dry Reforming of Methane
Oxygen Activity Tuning via FeO6 Octahedral Tilting in Perovskite Ferrites for Chemical Looping Dry Reforming of Methane
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DOI：
10.1021/acscatal.2c00920
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发表时间：
2022-06
期刊：
影响因子：
12.9
通讯作者：
Xue Xia;Wenxi Chang;Shuwen Cheng;Chuande Huang;Yue Hu;Weibin Xu;Li Zhang;Bo Jiang;Zhehao Sun;Yanyan Zhu;Xiaodong Wang
中科院分区：
文献类型：
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作者：
Xue Xia;Wenxi Chang;Shuwen Cheng;Chuande Huang;Yue Hu;Weibin Xu;Li Zhang;Bo Jiang;Zhehao Sun;Yanyan Zhu;Xiaodong Wang
钙钛矿型氧化还原催化剂的合理设计仍然是一个挑战，由于有限的理解之间的关系，结构畸变和晶格氧活性。在此，一系列的模型催化剂的组成LaFe 0.8M0.2O3（M = Al，Ga，Fe，和Sc）的设计，以阐明的结构-活性关系。结合实验结果和密度泛函理论（DFT）计算，证实了FeO 6八面体的倾斜度而不是Fe-O键长对氧活度的调节起主导作用.通过掺杂半径较小的氧化还原惰性阳离子来减少八面体倾斜，可以大大提高Fe-O键的共价性，降低氧空位形成能。这不仅有助于反应物的活化，而且还加速了氧的迁移率。因此，具有最小FeO 6八面体倾斜（6.6°倾斜）的LaFe 0.8Al 0.2O3表现出比LaFe 0.8Sc 0.2O3（9.5°倾斜）高70%的上级合成气产率，同时具有更好的用于甲烷化学链干重整的CO2转化率。这一发现突出了几何效应在调节氧活性中的重要性，为开发用于通过Mars-van Krevelen机制进行的化学循环过程和反应的潜在氧化还原催化剂铺平了道路。
Rational design of perovskite-type redox catalysts is still challenging due to the limited understanding of the correlation between structural distortion and lattice oxygen activity. Herein, a series of model catalysts with a composition of LaFe0.8M0.2O3(M = Al, Ga, Fe, and Sc) were designed to shed light on the structure–activity relationship. Combined experimental results and DFT calculations verify that the tilting degree of the FeO6octahedron rather than the Fe–O bond length plays a dominant role in modulating the oxygen activity. Reducing the octahedral tilting via doping redox-inert cations with a smaller radius can greatly enhance the Fe–O bond covalency and reduce the oxygen vacancy formation energy. This not only contributes to the activation of reactants but also accelerates the oxygen mobility. Consequently, LaFe0.8Al0.2O3with the smallest FeO6octahedral tilting (6.6° tilting) manifests superior syngas productivity that is 70% higher than that of LaFe0.8Sc0.2O3(9.5° tilting) with simultaneously better CO2conversion for chemical looping dry reforming of methane. This discovery highlights the importance of geometric effect in adjusting the oxygen activity, paving an avenue for developing prospective redox catalysts for chemical looping processes and reactions proceeding via a Mars–van Krevelen mechanism.