High Loading of Transition Metal Single Atoms on Chalcogenide Catalysts

Abstract

Transition metal doped chalcogenides are one of the most important classes of catalysts that have been attracting increasing attention for petrochemical and energy related chemical transformations due to their unique physiochemical properties. For practical applications, achieving maximum atom utilization by homogeneous dispersion of metals on the surface of chalcogenides is essential. Herein, we report a detailed study of a deposition method using thiourea coordinated transition metal complexes. This method allows the preparation of a library of a wide range of single atoms including both noble and non-noble transition metals (Fe, Co, Ni, Cu, Pt, Pd, Ru) with a metal loading as high as 10 wt % on various ultrathin 2D chalcogenides (MoS2, MoSe2, WS2 and WSe2). As demonstrated by the state-of-the-art characterization, the doped single transition metal atoms interact strongly with surface anions and anion vacancies in the exfoliated 2D materials, leading to high metal dispersion in the absence of agglomeration. Taking Fe on MoS2 as a benchmark, it has been found that Fe is atomically dispersed until 10 wt %, and beyond this loading, formation of coplanar Fe clusters is evident. Atomic Fe, with a high electron density at its conduction band, exhibits a superior intrinsic activity and stability in CO2 hydrogenation to CO per Fe compared to corresponding surface Fe clusters and other Fe catalysts reported for reverse water–gas-shift reactions.

Emerging Ultrahigh‐Density Single‐Atom Catalysts for Versatile Heterogeneous Catalysis Applications: Redefinition, Recent Progress, and Challenges

“…According to the assembly method of carrier and metal atoms, the synthetic approaches for AFCs includes the following three categories: [10] 1) "top-down approach", which usually starts from the existing support, such as preparing graphene sheets [30,43] or metal compounds [11,68] in advance, and then creating carbon vacancies or metal vacancies to capture single metal atoms, beyond external or internal metal coordination on 3D molecule supports; [9,37,56] 2) "bottom-up approach", from metal and organic precursors, the carbon support or polymer support is constructed synchronously when loaded with transition metal single atoms, such as pyrolytic carbon [36,47,53,61] and polymer (or MOFs) [46,48,57] -supported metal single atoms; 3) distinctive "top-down approach", such as crosslinking and self-assembly of GQD support, [10] or partial self-sacrifice of metallic support and loss of bulk metal atoms. [11] The comparison of parameters (the atomic density is obtained by crude statistics based on AC-STEM images, in 2 Â 2 nm À2 region) of above-mentioned AFCs prepared by different synthetic approaches are systematically summarize in Table 1.…”

“…The experimental results of previous studies showed that there is a strong positive correlation (or normal distribution [68,165,169,227] ) between the high catalytic activity and site concentration (i.e., atomic density), and the ultrahigh-density SACs can generate high site-specific activity (i.e., mole specific activity [84,140] ) in a certain high loading range. At present, the metal loading of SACs can be easily controlled at more than 10 wt% (once reaching wt.…”

“…Copyright 2020, Wiley-VCH. I-O) Reproduced with permission [68]. Copyright 2021, American Chemical Society.…”

Synthesis of atomic platinum with high loading on metal-organic sulfide

“…Exploring the interaction between the noble metal and sulfur for metal atom or nanoparticles formation as heterogeneous catalysts has also been well proceeded in the catalysis community. For example, Zheng et al [20] reported a novel deposition method using thiourea-coordinated metal complex to load noble metal atoms onto two-dimensional chalcogenides. By introducing sulfur into carbon materials, the strong interaction between the noble metal and sulfur could serve the purpose of anchoring and stabilizing the noble metal atom.…”

Carbon Nitride Supported High‐Loading Fe Single‐Atom Catalyst for Activation of Peroxymonosulfate to Generate 1O2 with 100 % Selectivity

“…[16] No characteristic peaks associated with Fe compounds were observed in Fe 1 / CN. [17] As shown in Figure 1 a and b, atomic force microscopy (AFM) and transmission electron microscopy (TEM) images captured the lamellar structure of Fe 1 /CN, which had a thickness of approximately 4 nm, and did not contain Fe nanoparticles. Furthermore, AC-HAADF-STEM and energy-dispersive X-ray (EDX) images demonstrated that all the Fe atoms (the bright spots highlighted by orange circles) were atomically dispersed on the CN support (Figure 1 c and d).…”