Bulk preparation of holey graphene via controlled catalytic oxidation

Abstract

Structural manipulation of the two dimensional graphene surface has been of significant interest as a means of tuning the properties of the nanosheets for enhanced performance in various applications. In this report, a straightforward and highly scalable method is presented to prepare bulk quantities of "holey graphenes", which are graphene sheets with holes ranging from a few to tens of nm in average diameter. The approach to their preparation takes advantage of the catalytic properties of silver (Ag) nanoparticles toward the air oxidation of graphitic carbon. In the procedure, Ag nanoparticles were first deposited onto the graphene sheet surface in a facile, controllable, and solvent-free process. The catalyst-loaded graphene samples were then subjected to thermal treatment in air. The graphitic carbons in contact with the Ag nanoparticles were selectively oxidized into gaseous byproducts, such as CO or CO2, leaving holes in the graphene surface. The Ag was then removed by refluxing in diluted nitric acid to obtain the final holey graphene products. The average size of the holes on the graphene was found to correlate with the size of the Ag nanoparticles, which could be controlled by adjusting the silver precursor concentration. In addition, the temperature and time of the air oxidation step, and the catalyst removal treatment conditions were found to strongly affect the morphology of the holes. Characterization results of the holey graphene products suggested that the hole generation might have started from defect-rich regions present on the starting graphene sheets. As a result, the remaining graphitic carbon structures on the holey graphene sheets were highly crystalline, with no significant increase of the overall defect density despite the presence of structural holes. Preliminary experiments are also presented on the use of holey graphene sheets as fillers for polymeric composites. The results indicated that these sheets might be better reinforcing fillers than the starting graphene sheets due to their perforated structure. Other unique potentials of these materials, such as for energy storage applications, are also discussed.

Facile synthesis of diverse graphene nanomeshes based on simultaneous regulation of pore size and surface structure

“…Due to their homogeneity, the resultant GNMs are especially suitable for the electrical applications as a semiconductor with a constant band gap. Etching-method is a promising approach for large-scale and low-cost preparation for GNMs, and suitable for the applications requiring large quantity, high porosity and abundant active sites222324252627282930. Noticeably, except for regulating pore size - essentially regulating neck width between neighbouring pores, the surface modification of functionalised graphene is another common method to modulate band gap, since the physicochemical properties of carbon materials are strongly dependent on the ratio of sp 2 to sp 3 bonds31, which embodied in the positive correlation between the optical gap of reduced graphene oxide (rGO) and the atomic ratio of O/C3233, and the different roles of each oxygen functional groups in the optical gap regulation of rGO34.…”

Printing nanostructured carbon for energy storage and conversion applications

“…This avoids the need for surfactants or functional groups, which increase contact resistance, as in the printed CNT electrodes. Additionally, by printing porous graphene [201,202], it may be possible to significantly increase the surface area and capacitance of printed SCs. Catalyst layers (CL) are either applied to the gas diffusion layer, to produce a gas diffusion electrode (GDE), or applied to the membrane, to make a catalyst coated membrane (CCM).…”

High stability and reactivity of defective graphene-supported Fe n Pt13−n (n = 1, 2, and 3) nanoparticles for oxygen reduction reaction: a theoretical study

“…In fact, defective graphenes can also be deliberately obtained after several tens of seconds of irradiation with an electron beam (Hashimoto et al 2004) or by treatment with hydrochloric acid (Coleman et al 2008). The presence of the defects strongly influences the electronic and magnetic properties, as well as chemical reactivity of graphene (Coleman et al 2008;Carlsson and Scheffler 2006;Ma et al 2004). For example, carbon vacancies can induce magnetism by destroying the symmetry of nonmagnetic pristine graphene (Ma et al 2004;Yazyev and Helm 2007;Singh and Kroll 2009;Palacios and Yndurain 2012).…”

“…It should be pointed out that various types of defects, such as vacancies, stacking faults, and domain boundaries, can be formed during the synthesis of graphene (such as reduced graphene oxide) (Banhart et al 2010;Hashimoto et al 2004;Gomez-Navarro et al 2010;Wang et al 2012). In fact, defective graphenes can also be deliberately obtained after several tens of seconds of irradiation with an electron beam (Hashimoto et al 2004) or by treatment with hydrochloric acid (Coleman et al 2008). The presence of the defects strongly influences the electronic and magnetic properties, as well as chemical reactivity of graphene (Coleman et al 2008;Carlsson and Scheffler 2006;Ma et al 2004).…”