Supported Single Atom and Pseudo‐Single Atom of Metals as Sustainable Heterogeneous Nanocatalysts

Abstract

The field of heterogeneous nanocatalysis has developed catalysts with excellent activities, superior selectivities and high stabilities. Their properties can be easily tuned by tailoring the size, shape and morphology of the nanomaterial. Thus, nanocatalysis is no longer just a field of academic curiosity, but an evolving field for industries to develop green and sustainable processes with very high turnover numbers, rates, and stabilities. The key to increase the efficiencies of these catalysts is to maximize the number of active centers on the surfaces, which can be achieved by reducing the size of metal NPs to single atom and pseudo‐single atom sizes. This field is growing exponentially, and several reports have described the syntheses, characterizations, and applications of these catalysts for a variety of reactions. This Review discusses the recent advances in the synthesis and catalytic performance of single and pseudo‐single atoms/sub‐nanometer (<1 nm) catalysts. We have reviewed experimental and theoretical studies performed for different reactions and, in the last section a brief outlook on the future prospects.

Nanocarbon-Edge-Anchored High-Density Pt Atoms for 3-nitrostyrene Hydrogenation: Strong Metal-Carbon Interaction

“…Under hydrogenation reaction conditions, the nanometer-sized Pt oxide species can be easily reduced to the metallic state and sintered to Pt particles ( Huizinga et al., 1984 , Duan et al., 2018 ), which will strongly bind the adsorbed H species, resulting in the lack of weakly bound hydrogen species for catalytic reactions. Furthermore, the H 2 dissociation over Pt 1 /h-NCs may follow the heterolytic dissociation procedure to yield H δ+ and H δ− species on the Pt-carbon interface, which may significantly enhance the catalytic activity of hydrogenation reactions as reported in the literature ( Liu et al., 2016 , Wang et al., 2016 , Dhiman and Polshettiwar, 2018 ). The spillover effects of the activated H species over the carbon support cannot be ruled out.…”

Heteroatom‐Mediated Interactions between Ruthenium Single Atoms and an MXene Support for Efficient Hydrogen Evolution

“…[1,4,5] The catalytic activity and selectivity of SACs not only depend on the nature of the single atom but also on the solid supports that are used to disperse the metal. [6] Therefore, it is essential to…”

“…Thus far, graphene nanosheets, carbon nanotubes, and other carbon materials and metal oxides have been widely used as supports for SACs. [5][6][7] Unfortunately, these materials tend to be either poor electrical conductors, electrochemically inert, or hydrophobic, which hampers the practical application of SACs for water-based electrochemical reactions. [8,9] Thus, it is crucial to identify a solid support with excellent conductivity that is also electrochemically active and hydrophilic in order to better host isolated single atoms for electrocatalytic applications.…”

Synthesis of High Metal Loading Single Atom Catalysts and Exploration of the Active Center Structure

“…[23,[30][31] However, it is a great challenge to prepare SACs with high metal loading, since the high surface energy makes the atomically dispersed metal atoms aggregate easily. [32] Several review papers have summarized various synthesis methods, [33][34][35] including the wet-chemistry method, [20] atomic layer deposition (ALD) method, [36][37] anti-Ostwald ripening, [38][39] ball milling, [40] and mass selection with softlanding. [41] None of these reviews focus on the preparation of high metal loading SACs.…”