Ultra-stable metal nano-catalyst synthesis strategy: a perspective

Abstract

Supported metal nanoparticles (NPs) as an important heterogeneous catalyst have been widely applied in various industrial processes. During the catalytic reaction, size of the particles plays an important role in determining their catalytic performance. Generally, the small particles exhibit superior catalytic activity in comparison with the larger particles because of an increase in lowcoordinated metal atoms on the particle surface that work as active sites, such as edges and corner atoms. However, these small NPs are typically unstable and tend to migrate and coalescence to reduce their surface free energy during the real catalytic processes, particularly in high-temperature reactions. Therefore, a means to fabricate stable small metal NP catalysts with excellent sinter-resistant performance is necessary for maintaining their high catalytic activity. In this study, we have summarized recent advances in stabilizing metal NPs from two aspects including thermodynamic and kinetic strategies. The former mainly involve preparing uniform NPs (with an identical size and homogeneous distribution) in order to restrain Ostwald ripening to achieve stability, while the latter primarily involves fixing metal NPs in some special confinement materials (e.g., zeolites, mesoporous silica and mesoporous carbons), encapsulating NPs using an oxide-coating film (e.g., forming core-shell structures), or constructing strong metal-support interactions to improve stability. At the end of this review, we highlight our recent work on the preparation of high-stability metal catalysts via a unique interfacial plasma electrolytic oxidation technology, that is, metal NPs are well embedded in a porous MgO layer that has both high thermal stability and excellent catalytic activity.

A core-shell catalyst design boosts the performance of photothermal reverse water gas shift catalysis

“…The sintering of catalyst particles reduced the number of active sites, which is responsible for the performance decay under reaction conditions. It is well known that smaller nanoparticles possess higher surface free energy and lower Tammann temperatures, leading to a stronger tendency of agglomeration [47][48][49]. However, it was found that the stability of SP-2 under photothermal catalytic conditions was mildly improved but at the expense of decreased activity.…”

Total- and semi-bare noble metal nanoparticles@silica core@shell catalysts for hydrogen generation by formic acid decomposition

“…On this hand, NAs are designed to avoid these effects and improve recyclability and stability [50]. In particular, the hollow silica capsules efficiently protect the core catalyst from coalescence phenomena by simply acting as a physical shield [7]. NAs, mcNAs, and scNAs do not display significant morphologic changes after the catalytic tests.…”

“…Indeed, NPs can be affected by sintering/stability and recovery issues [6]. An elegant strategy to both reduces NPs sintering while increasing their lifetime is the core@shell design, in which the active part is confined in the core and an external shell protect the catalyst [7]. This approach has the intrinsic advantage to increase the NPs recyclability and stability to coalescence due to the protective shell [8].…”

“…This approach has the intrinsic advantage to increase the NPs recyclability and stability to coalescence due to the protective shell [8]. Moreover, the core@shell approach is usually versatile due to the easily tunable behaviors associated with the composition of the NPs [7,9,10]. On the other hand, the confinement of the active part reduces its accessibility and decreases the overall catalytic activity for some reactions [8].…”

The Synthesis of V2O3 Nanorings by Hydrothermal Process as an Efficient Electrocatalyst Toward N2 Fixation to NH3

“…The precise nanofabrication is of great significance in both fundamental research and practical applications. The past few decades have witnessed a remarkable progress in the synthesis of zero-, one-, and two-dimensional nanomaterials (Chiu et al, 2011;Cao et al, 2020;Wang et al, 2020), which have aroused widespread interest due to the fascinating size/figure-dependent properties. During a variety of nanostructures, ringlike architectures exhibit novel properties with ring cavities and present promising application prospects in catalysis, sensors, energy storage, and advanced optical/electric nanodevices (Chen et al, 2017).…”