Fabrication of Single‐Atom Catalysts with Precise Structure and High Metal Loading

Abstract

several channels, [2] such as surface effects, quantum size effects, metal-support interactions, and cluster configurations. Notably, local coordination environments can drastically affect their physicochemical properties. Generally, increasing the active site density and corresponding intrinsic activity are key tactics to enhance the performance of many catalyst systems. [3] SACs, with isolated metal atoms dispersed/anchored on different supports, are currently one of the most important catalyst systems due to their maximum atom efficiency, unsaturated active sites, and well-defined reaction mechanisms. [4] Two strategies are commonly employed to improve the performance of SACs: 1) increasing the metal loading of SACs (e.g., by increasing the defect density, metal concentration, or choosing appropriate supports) and 2) enhancing the intrinsic activity of SACs (e.g., by adjusting the local coordination structure). Thus, the field of SACs is progressing rapidly and engendering extensive research attention. Although a variety of SACs have been constructed via a bottomup strategy, these SACs suffer from low yields, low metal loadings, and inhomogeneous and poorly defined coordination environment for metal single atoms, and/or a requirement for complicated or expensive equipment. [5] These drawbacks seriously hinder further study of their potential applications, especially at the industrial level. In this regard, it is highly desirable to develop efficient methods for constructing SACs with high mass activity and well-defined atomistic structures. Bottom-Up Strategies for SACsBottom-up strategies are commonly used to prepare SACs by depositing low amount of metal atoms onto the supports. [6] Generally, the metal precursors usually undergo adsorption, reduction, and finally confinement by the vacancy defects of the supports. However, during the synthesis and catalysis processes, the SACs tend to fuse and aggregate due to their high surface energies, which usually requires the lowering of metal loadings. [7] Additionally, the inhomogeneous and poorly defined vacancy defects on the supports make it difficult to identify and control the precise structure of the obtained SACs, (e.g., dispersion tendencies, coordination number, chemical state, and binding mode), seriously hindering advanced investigation of SACs. At present, several bottom-up strategies for accessing In recent years, single-atom catalysts (SACs) have attracted particular interest and have been demonstrated to be a promising material in energy conversion and chemical transformation due to their optimal atom utilization and unique size quantum effect. The development of a versatile and simple synthetic approach for SACs is important for further investigation of their properties. In this regard, several physical and chemical methods have been developed to access SACs by varying the interaction between metal centers and the coordination defects of the supports. The common challenges for SACs in industrial applications are accurate control over the local struct...

A general route via formamide condensation to prepare atomically dispersed metal–nitrogen–carbon electrocatalysts for energy technologies

“…[1][2][3]12 Therefore, extraordinary catalytic activity and selectivity can be expected from the MNC-based SAECs due to their largely altered and promoted reaction pathway. [13][14][15][16] Despite their extremely promising potential, most of the SAECs are currently synthesized through pyrolysis of metal salts with nitrogen and carbon sources, [17][18][19][20][21] including small molecules (such as pyrrole, 22 sodium alginate, 23 and dopamine 9 ), polymers (such as polyaniline, 24 polyphthalocyanine 8 ), carbon materials (such as graphene oxide, 17 heteroatom-doped carbon, 19 ) and MXene. 26 However, the weak coordination bonding between the metal cations and N/C sources, and the inevitable hightemperature annealing for acquiring conductivity often result in low-quality SAECs that suffer from metal aggregation.…”

Single vs double atom catalyst for N2 activation in nitrogen reduction reaction: A DFT perspective

“…The uniform dispersion of atomic catalyst with high density of active sites and stability is a major challenge in SAC research. The whole scientific research community have tried various kinds of methods both theoretically 10 and experimentally [11][12][13][14][15] to understand and solve this challenge.…”

Palladium Single Atoms on TiO2 as a Photocatalytic Sensing Platform for Analyzing the Organophosphorus Pesticide Chlorpyrifos

“…[14,15] Previous reports have fully demonstrated the extraordinary activity and stability of SA catalysts in hydrogen evolution reaction (HER), [16,17] oxygen reduction reaction (ORR), [18] and oxygen evolution reaction (OER). [19] Despite booming growth regarding energy-related application, the bioapplication of SA catalysts is still in its infancy, [20,21] and SA catalyst applied for detection of pesticides residues was never reported until now. Herein, we first adopt PdSA supported TiO 2 as an advanced photocatalytic sensing platform for highly sensitive detection of chlorpyrifos via restricting the photocatalytic H 2 evolution activity of PdSA by chlorpyrifos.B enefiting from the highly uniform and atomic dispersion of Pd active sites,P dSA/TiO 2 exhibits the much enhanced photocatalytic HER performance and adequate sensitivity for chlorpyrifos determination.…”