Recent Advances on the Design of Group VIII Base-Metal Catalysts with Encapsulated Structures

Abstract

Inexpensive group VIII metal (i.e., Fe, Co, and Ni)-based solid catalysts have been widely used in various energy transformation processes such as Fisher-Tropsch (F-T) synthesis, reforming and water-gas shift reactions. The emerging encapsulation strategy, which represents active metal species are coated by protective shell or matrix, has been demonstrated as a powerful means to promote the catalytic performance (i.e., activity, stability and selectivity) of Fe-, Co-and Ni-based catalysts due to synergic effects from the well-defined structures. This review describes recent progress on the design and synthesis of encapsulated group VIII base-metal nanomaterials developed for energy and environmental catalysis including syngas conversion, CO 2 dry reforming, steam reforming, methane conversion and NH 3 decomposition. We start with an introduction of the catalysts with different encapsulating structures (e.g., core@shell, yolk@shell, core@tube, mesoporous structures and lamellar structures). Then, the synthetic methods of Fe-, Co-and Ni-based catalysts with encapsulated structures are described in detail. The functions of encapsulation structures in catalysis, including protecting metal nanoparticles (NPs) from sintering, promoting the activity due to the confinement effect and intensifying reaction processes in the form of multifunctional catalysts, are discussed respectively. Our perspectives regarding the challenges and opportunities for future research in the field are also provided.

Sintering and Coke Resistant Core/Yolk Shell Catalyst for Hydrocarbon Reforming

“…In recent years, core/yolk shell catalysts have been intensively reviewed with the focus on sintering mechanism, various encapsulated catalysts including core@tube, mesoporous structures and lamellar structures, various applications such as fuel cell catalysts, F‐T synthesis catalysts and hydrogenation reactions as well as hollow and yolk shell catalysts for bio, electro and photocatalysis . Due to the rapid advancement of core/yolk shell catalsyts in the hydrocarbon reforming catalysis field (Table ), it is necessary to summarize the recent progress achieved in the recent two to three years.…”

Immobilization of Molecular Catalysts for Enhanced Redox Catalysis

“…The immobilization of homogeneous catalysts on various insoluble supports such as a siliceous material makes the immobilized catalyst insoluble in the reaction solution, providing great advantages for the easy separation of the catalyst from the reaction mixture, the fast isolation of the reaction products, and catalyst recovery and recycling by simple filtration . The immobilization of homogeneous catalysts also allows insoluble catalysts, which would otherwise be aggregated, to be well dispersed in the reaction medium such as water, resulting in the significant enhancement in the catalytic activity.…”

“…In general, the supported catalyst may be more sterically hindered and hence less accessible to substrates as compared to its non‐supported counterpart, while the selectivity may be enhanced by the steric effect. Catalyst instability in the homogeneous phase is mainly caused by bimolecular deactivation pathways, which are prevented by immobilization of the catalyst to isolate the catalyst reactive sites …”

How do Core–Shell Structure Features Impact on the Activity/Stability of the Co‐based Catalyst in Dry Reforming of Methane?

“…[1] Group VIII metals are widely used in reforming, [2] and most of the them are more or less active for the DRM reaction. More importantly,t he H 2 /CO ratio of the derived syngas is close to one, desirable fordownstream process such as FT synthesis anda ldehyde production.…”