Asymmetric oxygen vacancies in La2FeMO6 double perovskite for boosting oxygen activation and H2S selective oxidation

Abstract

Tuning oxygen vacancy (V_O) in metal oxides catalysts that efficiently activates O₂ molecule to promote oxidation reactions remains challenging. Herein, transition metal (M = Mn, Co, and Mo) doping was used to moderate the coordination environment of V_O in La₂FeMO₆ and promote activity for selective oxidation of hydrogen sulfide (H₂S). Various techniques reveal that the introduction of Mn and Co forms the homogeneous double perovskite phase, which results in the formation of asymmetric V_O. Although these asymmetric V_O are more difficult to form than symmetric Fe-V_O-Fe due to the shorter bond distance and stronger bond strength of Fe-O, they are more conducive to the dissociation of O₂ molecules. Among them, the formed rich Fe-V_O-Mn sites from the alternate substitution of Mn to Fe boosted the activation of O₂ molecules of Mn-substituted LaFeO₃. Therefore, enhanced catalytic activity and outstanding sulfur selectivity were achieved as a result of promoted oxygen mobility and reducibility. This work provides an attractive strategy for rational design of advanced oxidation catalysts.