Fe–Mn Heterojunction Modulated Electronic Environment for Enhanced CO ₂ Capture and In Situ Conversion

ABSTRACT Calcium looping dry reforming of methane (CaLDRM) on calcium‐based dual‐functional materials (DFMs, generally using Ni as the active sites) is potential in overcoming the thermodynamically equilibrium constrains of conventional DRM reaction, which enables the in situ capture and direct conversion of CO ₂ under relatively mild conditions. However, the inherently unfavorable properties of CaO, including the low oxygen mobility and inert electrical framework results in the inferior activation capacity of CO ₂ , leading to a high coking tendency and poor stability of calcium‐based DFMs. To address these challenges, Fe–Mn heterojunctions are constructed to enable modulation of the electronic environment and oxygen vacancy of the CaO support. In this study, municipal solid waste incineration bottom ash is employed as a thermally stable and low‐cost source of Fe and Ca oxides. The optimized DFM delivered remarkable CH ₄ and CO ₂ conversions of 95.9% and 92.7% (maintaining a constant H ₂ /CO ratio close to unity) without obvious deactivation over 10 cycles at a relatively low temperature of 675°C. The possible reason is that the built‐in electric field at the heterointerface drove the directional electron transfer from Fe to Mn, generating electron‐rich Mn sites. Simultaneously, the deficiency of electrons at the Fe sites weakened Fe–O bonds and hence induced the formation of abundant oxygen vacancies. In situ characterizations and theoretical calculations reveal that the electron‐rich Mn sites and oxygen vacancies served as electron donors and anchor sites of active O/OH species, respectively, which synergistically facilitated CO ₂ adsorption and activation. These results highlight the heterojunction engineering as an effective strategy for developing efficient DFMs for CaL‐DRM reaction.