Evolution behavior and active oxygen quantification of reaction mechanism on cube Cu₂O for CO self-sustained catalytic combustion and chemical-looping combustion

Catalytic combustion (CC) and chemical looping combustion (CLC) are promising technologies for energy saving and emission reduction of CO₂ in treatment of steelmaking off-gas. This work firstly reports and compares the evolution behavior and quantitative reaction mechanisms of cube Cu₂O model catalyst for CC and CLC reactions. The Cu₂O-CC exhibited the higher activity and stability than Cu₂O-CLC. The typical characterization results suggested that the only surface unstable Cu₂O was oxidized to CuO, and the excellent synergistic effect of metal-oxide interface (100) between Cu⁺/Cu²⁺ and active lattice oxygen species for Cu₂O-CC reaction. But, for CLC reaction, Cu₂O structure was collapsed, which caused the agglomeration of CuO_x species and gradual decrease of reaction stability. Three different active oxygen species (surface cycle lattice oxygen, bulk lattice oxygen, and adsorbed oxygen) and the detailed reaction pathways were proposed by the in situ IR spectroscopy, isotopic (¹⁸O₂) transient exchange experiments and DFT simulation. The intrinsic activity of surface cycle lattice oxygen was higher in terms of TOF (13.5 × 10⁻³ s⁻¹) and facile formation of C¹⁶O¹⁸O on the cubic interface of Cu₂O-CC through adsorbed CO during CC process. The contribution degrees of Mars-van-Krevelen (M-K) and Langmuir–Hinshelwood (L-H) mechanisms for CC and CLC reactions were 76.6% and 23.4% for CC, and 89.7% and 10.3% for CLC on Cu₂O catalyst, respectively.