Spherical Porous Nanoclusters of NiO and CeO₂ Nanoparticles as Catalysts for Syngas Production

Abstract

Spherical porous nanoclusters composed of NiO and CeO2 nanoparticles were successfully developed by a refined gas-phase controlled synthesis method, which were shown to be useful for syngas production via a high-performance catalysis of dry reforming of methane (DRM) coupled with partial oxidation of methane (POM). The synthetic method combines the principles of aerosol-phase evaporation-induced aggregation of polyethylene glycol (PEG; as soft template) followed by thermal decomposition of the self-assembled precursor crystallites for the creation of mesopores in the hybrid nanostructure directly in gas phase. Specific surface area, pore volume, and metal surface area in the Ni–Ce–O hybrid nanostructure increased by using the PEG. The results show a remarkably high turnover frequency of methane (0.93 s–1 at 600 °C) by using the developed Ni–Ce–O porous nanostructure as catalyst, where the H2/CO ratio was tunable for attaining a high syngas selectivity. Both a high light-off stability and 100 h operation stability were achieved through a remarkable reduction of coke formation on the Ni–Ce–O hybrid nanostructure. The work demonstrates a facile aerosol route for fabricating hybrid nanoporous clusters as useful catalysts for methane-based combined reactions.

Design of Aerosol Nanoparticles for Interfacial Catalysis

“…Through a gas-phase evaporation-induced self-assembly (EISA) of the precursor solution, the soluble precursors are dried and crystallized to form dried precursor particles. In the following stage (i.e., first thermal treatment), the dried precursor aerosols thermally decompose to form metal oxide NPs. ,,− Sometimes, precursors can be involved in a heterogeneous form (i.e., droplet consisting of stabilized solid nanoparticles and liquid precursors) for a direct deposition of metal/metal oxide onto the surface of a catalyst support (Scheme b). , In some cases, metal oxide NPs can be subsequently reduced to metallic NPs by H 2 in the second thermal treatment step, showing that the synthetic method provides a facile way to tune the surface state of the nanoparticles in the aerosol state. , As a result, ultrafine metal/metal-oxide-based NPs are formed, where a massive amount of material interface is created by design for promoting different catalytic reactions. ,,, …”

“…(c) Aerosol-based synthesis of a Ni–Ce–O nanostructure using PEG as a soft template: (1) NiCe-0PEG and (2) NiCe-0.1PEG. Reproduced with permission from ref . Copyright 2020 American Chemical Society.…”

“…Methane and carbon dioxide are both major greenhouse gases that contribute to climate change. Dry reforming of methane with CO 2 (DRM; CH 4 + CO 2 → 2H 2 + 2CO) has attracted great interest as it is an environmentally friendly route to synthesize valuable chemical feedstock (i.e., syngas), meanwhile reducing the emission of two critical greenhouse gases (CH 4 and CO 2 ). ,,, Despite the excellent catalytic properties of noble metals (e.g., Pt and Pd), their high cost and rarity limit their industrial applications. , Nickel-based nanoparticles are becoming a great alternative catalyst material due to their relatively low cost and high availability. However, Ni-based catalysts have low activity under low-temperature operation and are prone to sintering and carbon deposition during the DRM process. ,, Thus, aerosol-based approaches have been taken to develop Ni-based hybrid functional nanoparticles as a catalyst with improved activity and thermal stability.…”

“…Functional nanoparticles (NPs) are attractive as catalysts for various industrial applications. − For instance, transition metal/metal-oxide-based nanoparticles are frequently used as nanocatalysts due to their large surface-to-volume ratio, providing sufficient active sites available for catalysis. , Generally, the catalytic performance of nanoparticles is governed by their material properties (e.g., particle size, shape, surface state, crystallinity, porosity, chemical composition, etc. ), ,, and unique interfaces are created by design to enable a strong metal–support–promoter interaction for promoting catalysis. ,, For instance, a nanocatalyst with a massive amount of oxygen vacancies at the metal–support interface is beneficial in catalyzing a redox reaction.…”

Optimizing the Ni/Cu Ratio in Ni–Cu Nanoparticle Catalysts for Methane Dry Reforming

“…Moreover, the need for a high temperature tends to result in Ni nanoparticles sintering, especially the particles supported on oxides. , The drawbacks hinder stable MDR performance over most of the developed Ni catalysts. Synthesizing low carbon deposition and trace sintering Ni nanoparticles for MDR is a considerable challenge. − …”