Suppressing O2 Interference for CO2 Methanation by Cu-Doped Ni-Based Catalysts in O2-Containing Flue Gas

Direct CO2 hydrogenation from primary carbon sources such as flue gas offers an attractive route for carbon-neutral fuel synthesis, yet the presence of O2 severely impairs catalyst performance due to preferential H2–O2 reactions and subsequent catalyst deactivation. Herein, we report a surface-engineered Ni/γ-Al2O3 (Ni/A) catalyst modified by Cu doping (Ni–Cu1/A), which exhibits enhanced oxygen resistance and sustained CH4 produce under oxidative conditions. Guided by a descriptor τ, defined as the ratio of O2 to CO2 adsorption energies, Cu was identified as an effective dopant to suppress O2 adsorption while preserving CO2 activation. Under a challenging atmosphere containing 6% O2, the optimized Ni–Cu1/A catalyst achieved a CH4 STY of 76.4 mmol gcat–1 h–1, significantly outperforming the undoped Ni/A catalyst, which drops to 63.1 mmol gcat–1 h–1 under the same conditions. Mechanistic analysis reveals that Cu incorporation weakens O2 adsorption by regulation of electronic structure, thereby mitigating exothermic H2–O2 side reactions and stabilizing Ni0 sites. This work presents a practical and scalable strategy for CO2 methanation in the presence of O2, offering a promising approach for direct catalytic conversion of flue gas by leveraging selective surface adsorption and electronic structure modulation.