Single-Atom (Iron-Based) Catalysts: Synthesis and Applications

Abstract

Supported single-metal atom catalysts (SACs) are constituted of isolated active metal centers, which are heterogenized on inert supports such as graphene, porous carbon, and metal oxides. Their thermal stability, electronic properties, and catalytic activities can be controlled via interactions between the single-metal atom center and neighboring heteroatoms such as nitrogen, oxygen, and sulfur. Due to the atomic dispersion of the active catalytic centers, the amount of metal required for catalysis can be decreased, thus offering new possibilities to control the selectivity of a given transformation as well as to improve catalyst turnover frequencies and turnover numbers. This review aims to comprehensively summarize the synthesis of Fe-SACs with a focus on anchoring single atoms (SA) on carbon/graphene supports. The characterization of these advanced materials using various spectroscopic techniques and their applications in diverse research areas are described. When applicable, mechanistic investigations conducted to understand the specific behavior of Fe-SACs-based catalysts are highlighted, including the use of theoretical models. CONTENTS 1. Introduction 13620 2. Scope of This Review 13623 3. Synthesis of Fe-SACs 13623 3.1. N-Doped Graphene-Based Fe-SACs 13623 3.2. Nitrogen-Doped Porous Carbon-Based Fe-SACs 13626 3.3. C 3 N 4 -Based Fe-SACs 13634 4.

Modulation of Mo–Fe–C Sites Over Mesoscale Diffusion‐Enhanced Hollow Sub‐Micro Reactors Toward Boosted Electrochemical Water Oxidation

“…Over the past decade, the structure-property relationships of carbon-supported SACs with unsaturated, saturated, and super-saturated coordination environments have been systematically studied. [37][38][39][40][41] Recently, noncarbon supports, such as metal oxides, metal chalcogenides, and metal hydroxides, have been demonstrated potentially for the construction of SACs than carbon supports. [42][43][44][45] Because of the multifarious anchoring mechanisms, [46,47] it may be more profitable to maximize the atomic utilization and stability of SACs in noncarbon hosts.…”

Inducing atomically dispersed Cl–FeN4 sites for ORRs in the SiO2-mediated synthesis of highly mesoporous N-enriched C-networks

“…Such an atomistic approach to the design and synthesis of heterogeneous catalysts has unveiled unique opportunities to processes intensification and their selectivity improvement other than offering valuable solutions to the drastic reduction of the active metal loadings. [14][15][16][17][18] At odds with the deep interest aroused by SACs, as witnessed by the exponential growth of manuscripts and review articles published in the last few years, their fabrication strategy has often relied on trial-and-error approaches where the complex chemical nature of these hybrids was frequently dictated by high-temperature etching/doping thermal phases if not by the thermal decomposition of costly and time-consuming precursors. Seminal examples of highly catalytically active materials in the form of atomically dispersed metal ions within complex carbonaceous networks were obtained by the carbonization of sophisticated coordination compounds such as metal-organic-frameworks (MOF), [19][20][21] metal-organic polymers 22,23 and mixture of coordinating polymers with N-containing molecules.…”

“…Such an atomistic approach to the design and synthesis of heterogeneous catalysts has unveiled unique opportunities to process intensification and their selectivity improvement other than offering valuable solutions to the drastic reduction of the active metal loadings. 14–18…”

Quantitative Molecular Simulations

“…31 The focus of theoretical and experimental investigation are not only on formation and breaking of chemical bonds but also the diffusion processes as well as the prediction of scattering experiments. [32][33][34] The systems considered range from monocrystalline surfaces of metals, metal oxides, minerals or ionic compounds to graphene sheets, amorphous porous carbon 35 and water surfaces. 36,37 They can be modified by adsorbing ultra-thin layers on metal support, using metal alloy or nanostructuring by metal cluster or single atoms or vacancies.…”