Advances of atomically dispersed catalysts from single-atom to clusters in energy storage and conversion applications

Spontaneous FeIII/FeII redox cycling in single-atom catalysts: Conjugation effect and electron delocalization

“…Therefore, Fe clusters were slightly generated during the synthesis of the catalyst, which might facilitate the adsorption performance toward anions. 32 Figure S1 C presents X-ray diffraction curves of the catalysts, where two peaks with large widths centered around 24.70° (2θ) and 43.70° (2θ) could be attributed to the amorphous carbon (002) and crystalline carbon (100). 33 A Fe-containing crystalized phase was absent throughout the pattern, further proving the size of the clusters is very small.…”

Elucidation of single atom catalysts for energy and sustainable chemical production: Synthesis, characterization and frontier science

“…• A vapour phase deposition approach where metal atoms are atomically deposited in a layer-by-layer manner by exposing the substrate to the reactive precursor vapours [14,27] • The self-limiting gas surface reaction enabled precise control on the catalyst design and development [118,129] • Metal aggregation can be mitigated by lowering the ALD growth temperature [130] • Restricted by expensive operational and capital costs [127] • Weak interaction between the synthesized catalysts and substrates jeopardized the stability of the SACs [131] Surface organometallic chemistry and coordination site strategy…”

“…All these compounded issues lead to a higher fabrication cost [127]. Together with the low stability of the synthesized SAC [122,131], both serve as the key factors that need to be considered under large-scale production [186].…”

The synthesis of single-atom catalysts for heterogeneous catalysis

“…When the particle sizes are reduced to single atoms, however, the surface free energy increases sharply, leading to the easy migration and agglomeration of single atoms for forming metal clusters or nanoparticles in the preparation or catalysis reaction process. 22 To overcome this difficulty, the most direct and convenient method is to decrease the content of active metals in the catalysts and seek for the anchoring sites supported by solid host materials with a high specific surface area to form chemical bonds with single metal atoms. [23][24][25][26][27][28][29] This method facilitates elongating the spatial distance between adjacent metal atoms for generating stable single metal atoms sites, thereby inhibiting the agglomeration and growth of single atoms.…”