Subsurface A-site vacancy activates lattice oxygen in perovskite ferrites for methane anaerobic oxidation to syngas.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38926349.
- Also identified by DOI 10.1038/s41467-024-49776-y and PMC identifier 11208437.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Tuning the oxygen activity in perovskite oxides (ABO<sub>3</sub>) 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>sub.</sub>) vacancy beneath surface Fe-O layer greatly improved the oxygen activity in LaFeO<sub>3</sub>, rendering enhanced methane conversion that is 2.9-fold higher than stoichiometric LaFeO<sub>3</sub> while maintaining high syngas selectivity of 98% in anaerobic oxidation. Experimental and theoretical studies reveal that absence of La<sub>sub.</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.