Ni-Fe bimetallic hexaaluminate for efficient reduction of O₂-containing CO₂ via chemical looping

Direct utilization of impure CO₂, especially with O₂ impurities, bridges the technology gap between carbon capture and utilization (CCU), by reducing the overall carbon footprint. In this work, we developed Ni-substituted LaFe₃Al₉O₁₉ hexaaluminates as oxygen carriers to efficiently reduce CO₂ into high value-added substances, with the presence of a large amount of O₂ impurities via a chemical looping scheme. With O₂ to CO₂ ratio of 0.857:10, LaFe_2.9Ni_0.1Al₉O₁₉ exhibited high CO₂ conversion of ∼ 92% and synthesis gas yield of ∼ 4.26 mmol/g with a suitable H₂/CO ratio (∼ 2.0) during the redox cycles. Even with extremely high content of O₂ (O₂ to CO₂ ratio of 38:10), an acceptable CO₂ conversion (over 50%) and synthesis gas yield (∼ 3.84 mmol/g, H₂/CO ratio, ∼ 2.0) were obtained. These results benefited from the synergistic effect of Ni and Fe that low amounts of Ni sufficed to activate methane splitting and Fe increased the resistance to coke formation during CH₄ partial oxidation. Meanwhile, in O_2-containing CO₂ splitting step, Ni-Fe bimetallic hexaaluminate enhanced the ability of the oxygen carriers to activate CO₂ and suppressed the oxidative competition of O₂ compared with pure Fe hexaaluminate. Our work presents a promising approach for direct utilization of impure CO₂ and achieving carbon–neutral economic development. © 2022 Elsevier B.V.