Quinary high entropy oxide exsolution catalyst with dual anti-sintering/coking performance for biogas dry reforming: Insights into entropy driven lattice confinement and dynamic coke elimination mechanism

Biogas dry reforming (B-DRM) transforms CH 4 /CO 2 into syngas, yet conventional Ni based catalysts suffer severe sintering and coke deposition under high temperature conditions. High entropy oxides (HEOs) with disordered multi-cation lattices feature abundant oxygen vacancies and sluggish atomic diffusion, which can effectively resolve catalyst deactivation. Herein, a solvent free scalable mechanochemical ball milling strategy is proposed to synthesize single phase quinary (CaLaMgAlCe 0.5 Ni 0.5 )O x HEO precursors, avoiding tedious sol-gel chelation procedures. After H 2 reduction at 700 ℃, ultrafine Ni nanoparticles (5.17 nm) are uniformly exsolved and immobilized on the distorted HEO matrix via strengthened metal support interaction (SMSI). Systematic characterizations including XRD, XPS, H 2 -TPR, TEM, Raman and operando TPSR-MS are adopted to uncover structure-activity relationships and anti-deactivation mechanisms. Benefiting from entropy induced lattice confinement, the optimized catalyst restrains Ni agglomeration, with particle size merely increasing to 5.90 nm after 100 h continuous reaction at 750 ℃. The co-doping of alkaline-earth and rare-earth cations induces severe lattice distortion, enriching surface oxygen vacancies and moderate basic sites. Reversible Ce 3 + /Ce 4+ redox cycles activate CO 2 efficiently and generate reactive oxygen species in situ, which timely oxidize CH x carbon intermediates to construct a dynamic carbon generation gasification equilibrium, and the final coke deposition is only 14 wt%. The catalyst delivers steady CH 4 conversion above 90% with an ultra-low deactivation rate of 0.02% h −1 under high space velocity. This work clarifies the dual synergistic mechanisms of entropy driven lattice confinement for anti-sintering and redox-mediated dynamic coke elimination. The low cost scalable mechanochemical route provides a facile guideline for designing high stability non-noble DRM catalysts toward practical biogas upgrading.