Microwave‐Assisted Rapid Synthesis of Graphene‐Supported Single Atomic Metals

Abstract

Graphene-supported single atomic metals (G-SAMs) have recently attracted considerable research interest for their intriguing catalytic, electronic, and magnetic properties. The development of effective synthetic methodologies toward G-SAMs with monodispersed metal atoms is vital for exploring their fundamental properties and potential applications. A convenient, rapid, and general strategy to synthesize a series of monodispersed atomic transition metals (for example, Co, Ni, Cu) embedded in nitrogen-doped graphene by two-second microwave (MW) heating the mixture of amine-functionalized graphene oxide and metal salts is reported here. The MW heating is able to simultaneously induce the reduction of graphene oxide, the doping of nitrogen, and the incorporation of metal atoms into the graphene lattices in one simple step. The rapid MW process minimizes metal diffusion and aggregation to ensure exclusive single metal atom dispersion in graphene lattices. Electrochemical studies demonstrate that graphene-supported Co atoms can function as highly active electrocatalysts toward the hydrogen evolution reaction. This MW-assisted method provides a rapid and efficient avenue to supported metal atoms for wide ranges of applications.

Densely Populated Single Atom Catalysts

“…The existence of single atoms can be determined by combining morphological information with corresponding structural characteristics. For example, XAFS has been used to probe the possible bonding between the cobalt and the light atoms, using both a Fourier transform and wavelet transform (WT) ( Figure ) . Fourier transform magnitudes EXAFS of Co K‐edge showed that the Co sites are in a radial bonding distribution similar to CoN 4 C 4 (Figure g–j).…”

“…The analysis further indicated that the Ni structure was a four‐coordinate Ni‐C 4 structure with a planar quadrilateral geometry. These techniques give a clear insight to detect the single atom surrounding environment …”

“…h) Wavelet transforms for the k 2 ‐weighted EXAFS of Co‐NG‐MW and reference samples with optimum resolutions at 2.0 Å. i,j) Co K‐edge EXAFS analysis of Co‐NG‐MW in K and R spaces, respectively. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

Carbon‐Rich Nonprecious Metal Single Atom Electrocatalysts for CO2 Reduction and Hydrogen Evolution

“…To date, Pt‐based catalysts are the best and most practical electrocatalysts with their Gibbs free energy of H* (∆ G H ) close to zero, although their practical application is limited by the high cost toward HER. However, the increasingly favored SACs via suitable synthetic strategies open a new door for exploring NPMSACs, such as single Ni atoms on graphene nanosheets, single Ni atoms on hollow carbon nanospheres, single Ni atoms on 3D nanoporous graphene, single Co atoms on GO nanosheets, single Co atoms on porphyrinic triazine‐based frameworks, single Fe atoms on Pc‐derived nanocarbons, single Mo atoms on graphene, and single W atoms on MOF‐derived nanocarbons to catalyze the HER. DFT calculations revealed that nonprecious metal atoms anchored on the grain boundary of supports can act as active NPMSAC materials for HER because their unique structures can tune the ∆ G of H 2 adsorption toward the ideal value.…”

“…The inset zooms in to the onset area of Co‐NG‐MW. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”