Synthesis and Characterization of Pillared Graphene and Holey Graphene

Abstract

Pillared graphene (pG) and holey graphene (hG) are derivatives of graphene designed to overcome issues with agglomeration and restacking between graphene sheets, which limit surface area and ion diffusion. These two types of graphenes have enhanced catalytic properties due to holes and pillars between the sheets. Graphene oxide (GO) is synthesized from graphite using Tour’s method and then reduced to reduced graphene oxide (rGO) with ascorbic acid as a reducing agent. Pillaring agents (maleoyl chloride, fumaryl chloride, oxalyl chloride) are inserted using Friedel–Crafts acylation, and holes are created using gradual thermal annealing. The infrared spectroscopic data confirmed the presence of polar groups such as hydroxyl and carboxyl groups on GO and rGO indicating that both GO and rGO were synthesized successfully. On IR analysis of the pillared graphenes synthesized using the three pillaring agents (maleoyl chloride, fumaryl chloride, oxalyl chloride) and the holey graphenes, it reveals the various vibrational stretches such as C-H, C=O, C=C, and C-O stretches at specific wavenumbers. The functionalized holey graphenes also showed similar vibrational bands. Overall, the results indicate successful synthesis of both pillared and holey graphenes using three different pillaring agents. XRD confirms the reduction of GO to rGO, this is evidenced by a decrease in interlayer spacing and the absence of an OH functional group in the IR spectra. It also reveals that the pillared graphene and holey graphene materials are fairly crystalline and also shows that the materials are amorphous. SEM showed that the holey graphenes comprise grains that are very tightly packed and compact. The low-resolution SEM micrographs confirm the XRD results, that the materials are amorphous. TEM analysis confirmed the presence of pores in the holey graphene - hrGOFC0.15, hGOMC0.15, and hrGOOC0.15 layers; therefore, the holey graphenes were successfully synthesized.