Electron Spin Catalysis with Graphene Belts

Abstract

Here, we report kinetic studies using electron spin resonance spectroscopy on spin catalysis reactions caused by using graphene belts which were synthesized by a radical coupling method. The results show that σtype free radical species provide the dominant sites for catalytic activity through the spin-spin interaction, although there are some other influencing factors. The spin catalysis mechanism can be applied both in the oxygen reduction reaction (ORR) and in organic synthesis. The graphene belt spin catalyst shows excellent performance with a high ORR half-wave potential of 0.81 V and long-term stability with almost no loss of activity after 50 000 cycles in alkaline media. It also shows excellent performance in a benzylamine coupling with molecular oxygen to generate the corresponding imine at an average conversion of � 97.7 % and an average yield of � 97.9 %. This work opens up a new research direction for understanding aerobic processes in the field of spin catalysis.

Alcohol imination catalyzed by carbon nanostructures synthesized by C(sp2)-C(sp3) free radical coupling

“…The observation of inhomogeneous aggregates is attributed to the coupling between dangling bonds, and reactions between the oxygen-containing groups, such as hydroperoxides ROOH, benzyloxy radicals, hydroxyl-containing compounds, and benzyl radicals, carboxyl groups, etc., which are generated by O 2 and/or CO 2 in the reaction system as inhibitors in the radical coupling reaction. 29 , 30 X-ray diffraction (XRD) measurements were carried out to explore the presence of any crystallinity ( Figure 3 B). The patterns contain a broad diffraction peak in the 2θ range 18–24° and a hump in the range 40–50°, indicating that the three samples are amorphous in nature.…”

“…This is energetically favorable for removing two neighboring hydrogen atoms (namely, creating an H vacancy pair which generates holes), 43 because of generating a hydrogen molecule with an energy gain of 0.33 eV, 44 as demonstrated by theoretical calculations for a hydrogenated graphene (i.e., graphene) structure 43 , 44 ( Figure S8 B); (3) two molecules of Structure 1 can couple with Structure 2 to form 1,1,2,2-tetraphenylethene (Structure 3 ); (4) the growth of the units of Structure 3 after repeating the above-mentioned steps leads to large size nanosheets, which can be terminated by coupling with benzyl radicals after dehydrogenation of the methyl group in toluene to form the PCS-1 nanosheets (Structure 4 ). 29 , 30 This will generate bridged CH 2 groups between the benzene ring and structure 4 . This can account for the existence of the signal from methylene C H 2 at 41.9 ppm, which is observed in both the CP-MAS and the CPPI spectra, ( Figures 4 C and 4D), as well as the sheet morphology ( Figures 2 B–2i).…”

Single Non‐Blinking Graphene Quantum Dots Identified by Single‐Particle Catalysis

“…[43] This result is also supported by the Raman spectrum (Figure 1e), where the disordered carbon (D-peak) at 1368 cm −1 is weaker than the ordered sp 2 bonded carbon (Gpeak) at 1576 cm −1 . The Raman I D /I G ratio is widely used to evaluate the quality of carbon and graphene nanomaterials [44][45][46] because the ratio is related to the density of defects, edge smoothness, and structures. The I D /I G for the GQDs is ≈0.87, which is lower than that of GQDs prepared by acidic treatment of carbon fibers, [47] and comparable to that of GQDs prepared by hydrothermal fusion.…”

Non‐Blinking Luminescence from Charged Single Graphene Quantum Dots

“…We know that quantum confinement is a keyword for defining quantum dots. 2D graphene is one kind of specific semiconductor, [4,5] with a zero bandgap and a zero effective mass of charge carrier, which leads to an infinite exciton Bohr radius, therefore, quantum confinement will be valid at any size. [6] Furthermore, the energy of charge carriers in graphene follows sizescaling laws that differ from other semiconductors.…”