Surface defect healing in annealing from nanoporous carbons to nanoporous graphenes

Abstract

Nanoporous graphene (NPG) materials have the pronounced electrochemical stability of the seamless graphene structures developed over the 3D space. We revisited the Raman spectra of nanoporous carbons (NPCs) synthesized using...

Toward three-dimensionally ordered nanoporous graphene materials: template synthesis, structure, and applications

“…2), coupled with a high specific surface area ( S BET ∼2000 m 2 g −1 ) and a weak 002 diffraction in the XRD pattern indicate the presence of a single-layered graphene structure in NPGs. 86 The red-shifted G′ band at ∼2670 cm −1 , compared with that of typical graphite, 110,111 corroborates the presence of a single-walled graphene structure. 44,110 The red-shifted G′ band may also reflect the value of Young's moduli 96 by the introduction of curvature.…”

“…The Raman spectra of NPGs indicate that they consist mostly of hexagonal aromatic rings, but some pentagons and heptagons exist, which introduce curvature to the NPGs in their grain boundaries. 86 An intense G band at approximately 1587 cm −1 , as in typical graphene 110,111 (Fig. 2), coupled with a high specific surface area ( S BET ∼2000 m 2 g −1 ) and a weak 002 diffraction in the XRD pattern indicate the presence of a single-layered graphene structure in NPGs.…”

“…Nanosized γ-alumina is a promising template material for synthesizing nanoporous graphene (NPG) materials since it is one of the most efficient catalysts for catalytic C–H activation. 89 CH 4 -CVD takes place on alumina nanoparticles (ANPs) with the initial associative dissociation of CH 4 as the kinetic bottleneck, 59 and this is followed by acid etching and annealing 86,90–93 to give NPGs as minimally stacked porous graphene analogs (Fig. 2).…”

“…The economical preparation of carbon materials is also important for practical applications. 102 Template materials investigated to date, such as nanostructured silica, 103,104 γ-ANPs, 59,86 θ-ANPs, 92 and zeolite, 11 require the use of hazardous HF aqueous solutions for their removal after CVD, which makes the synthetic process tedious. For practical industrial applications, HF should be replaced with the less hazardous HCl.…”

“…2) in the Raman spectra can be mainly attributed to edges, 6,7 but TPD analysis indicates a very low occurrence of edges. 86,92 Therefore, the prominent D band of the NPGs is mainly attributed to in-plane disorder instead of edges.…”