R. Kundu, H. Ramsurn
The University of Tulsa,
Keywords: graphene, synthesis, biomass
Summary:Graphene has been called a “wonder material” due to its unique properties. It was discovered by Dr. Novoselov and Dr. Geim in 2004 who won the Nobel prize in 2010. Graphene is a single layer of carbon (sp2) which could be obtained by exfoliation of graphite. It has the potential to be used in biosensors to detect diseases like cancer, in microprocessors, in batteries etc. Although graphene was invented almost 16 years ago, most of the graphene available in today’s market has less than 60% purity, greatly hindering the development of graphene-based products . To produce high purity graphene, chemical vapor deposition (CVD) has been used to produce flakes of graphene on copper. Although CVD produces high purity graphene, this method requires greenhouse gases like methane as a source of carbon along with H2 (flammable) at very high temperatures. In most cases, CVD also requires vacuum in the reactor. These constraints make the process expensive and dangerous and not easy to scale up. A patent pending process (PCT Application Number PCT/US19/57850) has been developed to produce high purity graphene which involves the use of biomass as feed. The novelty of this process is that it does not require vacuum nor flammable gases like methane and H2. This makes the process simpler, safer and environment friendly but more importantly less expensive. We have used biomass as a source of carbon for the growth of graphene on metal foils such as cobalt and iron. The biomass was first pretreated and then used as a feed for graphene growth. Few-layer graphene was synthesized from pretreated biomass by high temperature (700-1200 C) treatment at ambient pressure in the presence of metal foils. Any dimension of graphene sheets can be produced using this method and the size of graphene sheets is only limited by the size of the reactor. The so-produced graphene was analyzed using Raman Spectroscopy (Figure 1) and X-Ray photoelectron spectroscopy (XPS) (Figure 2). The Raman spectroscopy showed the presence of few-layer graphene where 2D/G ratios (ratio of the intensities of 2D and G peaks at 2700 cm-1 and 1580 cm-1 respectively) were observed to be less than 1. The XPS analysis of the foil with graphene revealed the presence of high purity (over 90%) sp2 carbon (from graphene). This graphene can be easily transferred onto any material (such as quartz) by simply etching away the metal foil using polymethyl methacrylate (PMMA) as a support. References:  A.P. Kauling, A.T. Seefeldt, D.P. Pisoni, R.C. Pradeep, R. Bentini, R.V. Oliveira, K.S. Novoselov, A.H. Castro Neto, The Worldwide graphene flake production, Advanced Materials 30(44) (2018) 1803784.