Non-metallic phosphorus-induced lattice engineering in LaFeO3 perovskite: Oxygen vacancy modulation for enhanced methane conversion in chemical looping partial oxidation

Chemical looping partial oxidation of methane (CL-POM) with perovskite-type oxygen carriers is receiving increasing attention for syngas production in terms of low energy consumption and high security. In response to the low CH 4 conversion of typical LaFeO 3 perovskite oxygen carrier, the effect of P doping on lattice oxygen activity of LaFe 1-x P x O 3 (x = 0, 0.1, 0.3, 0.5) was investigated. In contrast to conventional metal-doping techniques, the incorporation of non-metallic dopants into perovskite lattice provides significant advantages in terms of reaction efficiency and economic feasibility. The experiment and characterization results combined with DFT (Density Functional Theory) calculations showed that P doping decreased the oxygen vacancy formation energy and increased the concentration of oxygen vacancies, thereby improving the surface oxygen activity and bulk oxygen diffusion performance of the oxygen carrier. P doping significantly reduced the reaction temperature between LaFeO 3 and CH 4 , mainly because P doping can improve the lattice oxygen mobility by adjusting the distortion of octahedral structure. The appropriate doping ratio of P was beneficial for achieving the matching between the mobility of bulk oxygen ions inside the oxygen carrier particles and the activation of CH 4 molecules, so that the supply of oxygen met the demand for CL-POM. The CH 4 conversion and syngas yield of LaFeO 3 was greatly increased by P doping. In the prepared oxygen carriers, the LaFe 0.7 P 0.3 O 3 sample exhibited the best reaction performance. In 20 consecutive cycles, LaFe 0.7 P 0.3 O 3 oxygen carrier exhibited excellent cycling stability with average CH 4 conversion of 90 % and syngas yield of 5.14 mmol/g. The findings of this study provide valuable guidance for designing efficient perovskite-type oxygen carriers through non-metallic element doping, specifically tailored for CL-POM. • P doping decreased oxygen vacancy formation energy and boosted reactivity of LaFeO 3 . • LaFe 0.7 P 0.3 O 3 achieved 90 % CH 4 conversion and 5.14 mmol/g syngas yield in CL-POM. • DFT and experiments confirmed P doping enhancing bulk lattice oxygen mobility.