Green Synthesis of Graphene Oxide Flakes and Foams directly from Table Sugar

Abstract

Large scale of graphene oxide (GO) sheets and three-dimensional foams were fabricated directly from table sugar solution (TS) without using blowing agents. Using table sugar or biomass-derived carbohydrates as precursors provides a green, safe, and potentially scalable route for graphene oxide synthesis. These carbohydrate-based methods minimize hazardous reagents and waste through simple thermal decomposition processes. Compared to conventional techniques, they offer lower costs, fewer chemical risks, and greater sustainability, making them suitable for industrial applications. The use of catalytic carbonization (CC) on copper foil as well as non-catalytic (NC) hydrothermal carbonization in a sealed container produces separate GO sheets with 2.5 ± 0.1 cm in size. Non-catalytic growth produced GO 3-D foams with surface area ~7.5 ± 0.1 cm² and average grain sizes (7.97 ± 0.01 µm) comprising of 75.7% and 24.3% of carbon and oxygen respectively. HRTEM and SAED confirmed its hexagonal structure formation. After synthesis by graphitization, foams showed diminished groups containing oxygenated functionalities and C/O ratio increased from 0.13 to 1.5 as per XPS and FTIR results. On the other hand, 3D conductivity of the reduced GO or rGO increased by 0.87Ωm⁻¹ compared to 0.04 Ωm⁻¹ for GO. The present eco-friendly method offers scalability towards high-quality production of both GO and rGO for various applications.

1. Introduction

Graphene with an extraordinary electronic and mechanical properties, attract many researchers and give rise to a variety of applications (Aïssa, Memon, Ali, & Khraisheh, 2015; Bae, Kim, Shin, Ahn, & Hong, 2012; Novoselov & Geim, 2007; Partoens & Peeters, 2006). Exfoliation of high oriented pyrolytic graphite (HOPG) considered as the main process to appeal off graphene sheets out of graphite stacks in agitative liquid medium (Hernandez, Lotya, Rickard, Bergin, & Coleman, 2010; Stankovich et al., 2006). Other studies implemented laser (Chyan et al., 2018) and MnO2 in Hummer’s method (Sujiono et al., 2020) to end with floating graphene layers. Furthermore, when it comes to the high quality and low scalability, CVD method was chosen as favorable method (Kim et al., 2011; Xuesong Li et al., 2009; Reina et al., 2009). In conventional Graphene CVD growth process depends on pure Cu and Ni substrates and highly purified methane and hydrogen gases under high vacuum and temperature with controllable cooling, heating and gas flow rates systems.

On the other hand, green synthesis of graphene and graphene oxide by a direct thermal heating of row sources of carbon like saccharose and other natural sugars were utilized. In CVD, the fabrication is preferred on catalyst like copper substrates at temperature range 1000-1050 °C (Ruan, Sun, Peng, & Tour, 2011). The use of polycrystalline copper foil as a substrate is widespread due to its low carbon solubility, which limits carbon precipitation and thus favors the growth of predominantly monolayer graphene (Li et al., 2009). In addition, for non-sugar sources such as PMMA (Byun et al., 2011), Polystyrene (Wu et al., 2013), flower petals (Ray et al., 2012), sugar-urea (Pan, Jin, Fu, Liu, & Zhang, 2013), graphitized anthracite coal (Zhou et al., 2012), plastic (Sharma et al., 2014), coconut shell waste (Sujiono et al., 2020), cookies and chocolate (Yan et al., 2011) were investigated as a good alternative sources with more modifications. This self-limiting behavior is critical for achieving high-quality graphene films, as confirmed by numerous studies utilizing both conventional thermal chemical vapor deposition (CVD) and more advanced methods (Li et al., 2009). Electromagnetic induction heating further enhances process efficiency and graphene quality by rapidly achieving the target temperature and minimizing defect density (Byun et al., 2011). The geometry of the copper substrate, reaction conditions, and the concentration of source precursors all in...