Synthetic routes contaminate graphene materials with a whole spectrum of unanticipated metallic elements

Abstract

The synthesis of graphene materials is typically carried out by oxidizing graphite to graphite oxide followed by a reduction process. Numerous methods exist for both the oxidation and reduction steps, which causes unpredictable contamination from metallic impurities into the final material. These impurities are known to have considerable impact on the properties of graphene materials. We synthesized several reduced graphene oxides from extremely pure graphite using several popular oxidation and reduction methods and tracked the concentrations of metallic impurities at each stage of synthesis. We show that different combinations of oxidation and reduction introduce varying types as well as amounts of metallic elements into the graphene materials, and their origin can be traced to impurities within the chemical reagents used during synthesis. These metallic impurities are able to alter the graphene materials' electrochemical properties significantly and have wide-reaching implications on the potential applications of graphene materials.

Transient absorption spectroscopy and photochemical reactivity of CAU-8

“…Literature data show that GO can have around 100 ppm of Mn accompanied by other first row transition metals, such as Cu and Zn in much lesser quantities. [24] In our case, inductively coupled plasma atomic emission spectroscopy (ICP-AES) of GO was performed and detected the presence of Mn and Cu in 628 and 110 ppm, respectively. Other metals present in the sample are Zn and Al (<50 ppms).…”

An Oxygen Reduction Study of Graphene-Based Nanomaterials of Different Origin

“…But still, the question remains why these materials (Graphene1 and Graphene2) show rather good electrocatalytic properties compared with rGO. One explanation might be that these materials may contain some metal impurities originated from the synthesis process, which might enhance the ORR process, since Pumera and co-workers have shown that ORR electrocatalysis on graphene-based surfaces is primarily caused by the metal impurities [48,49]. It should be noted that in order to confirm this statement, the energy dispersive X-ray spectroscopic (EDX) measurements were carried out with Graphene1 and Graphene2 samples.…”

“…It has been reported that in alkaline medium the electrochemically reduced GO has higher electrocatalytic activity towards the ORR than GO [47]. Recently, the ORR studies on rGO synthesised by different methods have revealed that depending on the synthesis process, the electrochemical behaviour of rGO towards the ORR is rather different [48,49]. Clearly, these conflicting results may be attributed to the variation in experimental conditions, but still, inspired by the previous works that electrodes modified with different origin of graphene give a different electrochemical response towards the ORR, we are interested in comparing graphene-family nanomaterials, including two commercially available graphene (graphene nanopowder from Graphene Supermarket and graphene nanoplatelet aggregates from Strem Chemicals) and reduced graphene oxide (rGO).…”

Role of impurities on the optical properties of rectangular graphene flakes

“…Impurities can impact the optical properties of GFs depending on the location, strength, and range of influence of the impurity potentials 10,14,15,40 .…”

“…Recently, it has been shown that common methods for generating graphene and GFs can introduce a variety of localized impurities 40 in the sample, and these impurities can have a significant effect on the electronic and optical properties. While there has been some work done on how long-range disorder affects the absorption spectra of large armchair edge hexagonal GFs 37 , there has been little discussion of how localized impurities affect the electronic properties of GFs in general.…”