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河北祥鹄科学仪器有限公司

Microwave-assisted rapid synthesis of graphene supported monatomic metals

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[Abstract]:
Abstract Graphenesupportedmonatomicmetals(G-SAMs)haveattractedgreatinterestrecentlyduetotheirexcellentcatalytic,electronicandmagneticproperties. ItisveryimportanttodevelopeffectivesynthesismethodsofG-
Abstract
  Graphene supported monatomic metals (G-SAMs) have attracted great interest recently due to their excellent catalytic, electronic and magnetic properties.

  It is very important to develop effective synthesis methods of G-SAMs with monodisperse metal atoms for exploring their basic properties and potential applications. A series of monodisperse atomic transition metals (such as Co,Ni,Cu) in nitrogen-doped graphene have been synthesized by a convenient, fast and general strategy.A two-second microwave heating of a mixture of graphene oxide and metal salts for amine functionalization.

  The simple step of microwave heating can induce the reduction of graphene oxide, the doping of nitrogen and the incorporation of metal atoms into the lattice of graphene. Rapid microwave technology can minimize metal diffusion and aggregation and ensure the dispersion of unique monometallic atoms in graphene lattice.

  Electrochemical studies show that graphene supported Co atoms can be used as highly active electrocatalysts for hydrogen evolution. This microwave-assisted method provides a fast and efficient way to load metal atoms and is suitable for a wide variety of applications.
Detailed information
The University of California, Los Angeles, Huangyu research group and the Imran Shakir team of Kingundefineds University of Saudi Arabia proposed microwave heating technology to rapidly (2 seconds) prepare a variety of graphene loaded monatomic (including cobalt,copper,nickel, etc.).

The researchers first mixed the metal salts with the solution of graphene oxide, and used the strong interaction between metal ions and amino groups to distribute metal ions uniformly on the surface of graphene oxide. The dried mixture was then placed in a domestic microwave oven and heated at 1000W for 2s. In the process of microwave heating, graphene is excited by absorbing microwave and producing high temperature in an instant. The reduction of graphene, the doping of nitrogen and the intercalation of metal atoms in the lattice of graphene are realized simultaneously by one step method.

 

 

 

                 Fig1.

The Raman spectrum(Raman)XX-ray diffraction pattern (XRD)and XX-ray photoelectron spectroscopy(XPS)show that microwave treatment can effectively remove the oxygen-containing groups on the surface of graphene oxide. At the same time, the defects on graphene surface were reduced and nitrogen doping was realized.

微信图片_20181207092808.jpg

 

Fig 2. Morphology and atomic structure characterization of cobalt monoatom supported on graphene

The spherical aberration correction electron microscope andXthe X-ray absorption fine structure spectrum (Fig2)show that the cobalt metal is uniformly distributed on the graphene substrate in the form of a single atom, and the valence state is% 1. It is found that the peripheral coordination environment of the graphene-loaded MN4C4-type single-atom (Nat. Caal., 2018, 1, 63) synthesized by the conventional thermal method is more disordered compared with the metal single-atom synthesized by the microwave method, and the defect degree is higher.

 微信图片_20181207092849.jpg

Fig 3. Atomic structure characterization of graphene supported nickel and copper monatomic atoms

In addition to the graphene loaded cobalt single atom, the researchers expanded the microwave heating method, successfully synthesized the graphene loaded nickel monoatomic and copper monoatomic (Fig.3), and proved the universality of the method.

 微信图片_20181207092937.jpg

Fig 4. Graphene-loaded cobalt atom as high-efficiency hydrogen evolution catalyst

Electrochemical measurements show that the graphene supported cobalt atom exhibits excellent hydrogen production (HER) activity under acidic conditions, and its initial overpotential approach to 0 mV,Tafel slope is 80mV dec-1 (Fig.4). At the same time, the catalyst has good electrochemical stability.

 

Conclusion
 A rapid, efficient, simple and universal method for the synthesis of graphene supported on a single atom was developed by microwave heating. It provides an effective synthetic approach for the application and exploration of graphene supported monatomic atoms in the field of catalysis and other related fields.

 

Background
Microwave‐Assisted Rapid Synthesis of Graphene‐Supported Single Atomic Metals Adv. Mater., 2018, 30, 1802146, DOI: 10.1002/adma.201802146.

Published in Advanced Materials, 2018,30, 1802146 SCI Impact Factor:21.95

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