Subsurface A-site vacancy activates lattice oxygen in perovskite ferrites for methane anaerobic oxidation to syngas
Jiahui He, Tengjiao Wang, Xueqian Bi, Yubo Tian, Chuande Huang, Weibin Xu, Yue Hu, Zhen Wang, Bo Jiang, Yuming Gao, Yanyan Zhu, Xiaodong Wang
Abstract
Abstract Tuning the oxygen activity in perovskite oxides (ABO 3 ) is promising to surmount the trade-off between activity and selectivity in redox reactions. However, this remains challenging due to the limited understanding in its activation mechanism. Herein, we propose the discovery that generating subsurface A-site cation (La sub. ) vacancy beneath surface Fe-O layer greatly improved the oxygen activity in LaFeO 3 , rendering enhanced methane conversion that is 2.9-fold higher than stoichiometric LaFeO 3 while maintaining high syngas selectivity of 98% in anaerobic oxidation. Experimental and theoretical studies reveal that absence of La sub. -O interaction lowered the electron density over oxygen and improved the oxygen mobility, which reduced the barrier for C-H bond cleavage and promoted the oxidation of C-atom, substantially boosting methane-to-syngas conversion. This discovery highlights the importance of A-site cations in modulating electronic state of oxygen, which is fundamentally different from the traditional scheme that mainly credits the redox activity to B-site cations and can pave a new avenue for designing prospective redox catalysts.