The annealing effect of structured nickel octahedra nanoparticles on the performance of NiO supported on silica in combined steam and dry reforming of a model biogas mixture

The octahedral family of NiO nanoparticles is gaining significant attention as an assembly with unique physicochemical properties and outcomes in electromagnetics, shielding, and absorption. In this study, a mesoporous structured Ni_60%SiO₂(Comm), chosen owing to its NiO species existing in an octahedral shape, was evaluated for synthesis gas (syngas: H_2(g) and CO_(g) mixtures) production via combined steam and dry reforming of a model biogas mixture (T= 800 °C, (H₂O_(g) + CO_2(g))/CH_4(g)= 1.2). To the best of our knowledge, the consideration of Ni octahedra-based nanomaterials as potential catalysts for reforming reactions, particularly biogas reforming, towards syngas generation has not been yet considered in the available literature. In comparison to a standard Ni_5%SiO₂ catalyst, slightly higher reactivity levels along with significantly lower amounts of carbonaceous deposits were obtained over the commercial Ni_60%SiO₂(Comm) catalyst for 10 h on stream. The high coke resistance of originally shaped NiO octahedra was ascribed to an annealing effect, generated during H_2(g)-treatment (prior to catalysis), yielding mesoporous metallic Ni⁰ nanorods with H_2(g)-storage capacities. Stored hydrogen within Ni⁰ layers acted as active centers for continuous in situ coke gasification, preventing thus C_(s) accumulation while keeping Ni⁰ sites accessible for catalysis.