| Dry chemistry routes |
Atomic layer deposition |
(1) Precise control of parameters |
(1) Only materials with suitable ligands or functional groups could be chosen as support |
| (2) Excellent deposition uniformity and reproducibility |
(2) Not applicable for the commercial preparation |
| (3) The loading of the singly dispersed atoms could be adjusted via regulating the number of cycles |
|
| Pyrolysis synthesis |
Straightforward for the preparation of SACs |
Requires high pyrolysis temperature |
| Atom trapping |
The operation is simple |
(1) Need to provide mobile atoms and support that could capture mobile species |
| (2) High temperature synthesis |
| Two-step doping |
High stability |
Requires high energy atom/ion generator |
| Ball-milling |
Simple, green, scalable production |
The catalysts are prone to agglomeration |
| Wet chemistry routes |
Facile adsorption |
Simple and easy to operate |
Proper interaction between active metal components and catalyst support is required |
| Strong electrostatic adsorption |
Applicable for the preparation of high-quality precious metal SACs |
Adsorption behavior is affected by many factors |
| Wetness impregnation |
Simple to operate |
Generally metal atoms are not uniformly dispersed on the surface of support |
| Photoreduction |
No special equipment is required, easy to implement |
Catalytic active center generally is not uniform |
| Galvanic replacement |
Simple, versatile |
Limited by the requirement of an appropriate difference in electrochemical potentials between the two metals |
| Cyclic voltammetry |
Less additives are demanded and no interfering products are generated |
An electrochemical station is needed and the operation cost is high |
| Ion exchange |
It could produce highly loaded single atoms on the surface of the support |
Only applicable for the synthesis of limited types of SACs |
| Templated hydrothermal |
Simple, easy to operate |
Only applicable for the synthesis of limited types of SACs |
| Co-precipitation |
Applicable for preparing composite oxides containing two or more uniformly dispersed metal elements |
(1) Preparation parameters have a great impact on performance |
| (2) Some active atoms are not exposed and cannot participate in the reaction |
| One-pot wet chemistry |
(1) No special experimental setup and multi-step reaction conditions are required, which is beneficial for large-scale production |
(1) Limited by the solubility of various precursors |
| (2) High loading of isolated metals can be achieved |
(2) Impurities and by-products of individual steps have an impact |
| Metal leaching |
Preparation of monodispersed catalysts by a two-step method |
(1) Suitable for a small number of certain metals and supports |
| (2) Environmental pollution during the preparation process |
| Flame spray pyrolysis |
(1) It could mix all precursors at the atomic level |
Few application examples |
| (2) The shape and particle size of the catalysts can be effectively controlled |
| (3) Large-scale production |
