Exploration of the temperature-dependent correlations present in the structural, morphological and electrical properties of thermally reduced free-standing graphene oxide papers

Harihara Ramamoorthy,Ratchanok Somphonsane,Krongtham Thamkrongart,Tinna Chiawchan,Kanokwan Buapan

doi:10.1007/s10853-021-06262-w

Abstract

We report on a corroborative study of the structural, morphological and electrical property alterations of free-standing graphene oxide (GO) papers subject to thermal reduction. Structural analysis performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman techniques prove that the onset of major structural changes, characterized by removal of oxygen functionalities, occur in the 200–300 °C temperature range. The results are corroborated with related morphological changes observed using Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) imaging. Elemental analysis shows the GO paper reduced at 600 °C to contain an 85 wt. % carbon content and a remnant oxygen level of 13.31 wt. %. At the highest reduction temperatures, we see evidence of vacancy-type defects impeding the overall effectiveness of the reduction process. Detailed electrical resistance measurements and current–voltage (I-V) profiling conducted using four-point probe method reveals a several orders of magnitude drop in the sample resistance once the reduction temperature exceeds 200 °C, in good agreement with the structural and morphological changes. The fundamental insights revealed through these studies will be important for future applications where the electrical and mechanical properties of free-standing GO and reduced graphene oxide (rGO) are exploited in practical devices.Graphical abstract

Highlights

In the past decade, graphene has grabbed a great deal of attention in the 2D materials research community [1, 2]
It can be clearly seen that for the original graphene oxide (GO) paper there are four strong peaks in the transmittance data, which confirms the presence of different oxygenated functional groups
The second important peak that occurs in the Fourier transform infrared spectroscopy (FTIR) spectrum is that of the carbonyl

Summary

Introduction

Graphene has grabbed a great deal of attention in the 2D materials research community [1, 2]. Among the several remarkable properties that this wonder material boasts of are its high mechanical strength, ultra-high mobility of its conducting electrons, efficient thermal conductivity and its surface conformability While many of these properties pertain to graphene studied in its pristine form, it is worthwhile to note they arise from investigations of micrometer-scale sample sizes that are obtained by the mechanical exfoliation of graphite using the infamous scotch-tape technique [2]. Large-scale and pristine graphene have been successfully realized via bottom-up synthesis techniques such as chemical vapor deposition (CVD) [3,4,5], but the technique suffers from the associated high-cost and technological challenges of scalability [5] To circumvent these problems, top-down synthesis routes of graphene alternatives such as reduced graphene oxide (rGO) have been gaining increasing attention in the recent past. The GO is rendered defective and highly electrically insulating in comparison to its graphite parent

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