Reversible exsolution of iron from perovskites for highly selective syngas production via chemical looping dry reforming of methane

The chemical looping dry reforming of methane reaction (CL-DRM) has attracted attention for its ability to reduce carbon emissions by converting two greenhouse gases (methane and carbon dioxide) into syngas. However, the major barrier against the CL-DRM application is lack of highly selective and stable oxygen carriers. We report a method to obtain high syngas selectivity by modulating the ability of oxygen carriers to react with methane in CL-DRM. Here, we investigate the redox reactivity of different elements doped LamSr1-mFenAl1-nO3 (m = 0.6, 1; n = 0.8, 1) oxygen carriers for the CL-DRM. It is found that the two doped with Al at the B -site perovskites have better reactivity due to the exsolution of Fe nanoparticles which promotes the reduction reaction between the parent perovskites and methane. Different parent perovskite affects the strength of the exsolved Fe, which consequently influences its reactivity with methane. The experimental results show that up to 5.76 mmol/g syngas yield and nearly 100 % CO selectivity are achieved in 20 redox reactions of LaFe0.8Al0.2O3 oxygen carriers. Simultaneously the exsolved Fe is re -dispersed into the perovskites through a CO2 oxidation reaction, which also achieves the regeneration of the oxygen carrier. By tuning the composition of the perovskite and the exsolve Fe through the exsolution system, the synergistic effect between the metal and the parent perovskite can be exploited to improve the methane reactivity. These insights offer valuable guidance for the design of efficient oxygen carriers for CL-DRM.