Graphene and its derivatives have been reported in many articles as "metal-free" carbon electrocatalytic materials. Its synthesis procedures are generally based on the chemical oxidation of graphite and subsequent thermal or chemical reduction. Because graphene oxide has a large surface area and typically contains a variety of oxygen functionalities, metallic ions (impurities) from reaction mixtures can be adsorbed on its surface. These impurities can significantly enhance the electrocatalytic activity and thus lead to data misinterpretation; such impure samples are referred to as "metal-free" catalysts. In this paper, we report the synthesis of impurity-free graphene, which is compared with graphene prepared by standard methods based on the thermal and chemical reduction of two graphene oxides. Detailed analysis of graphene prepared by standard methods shows a direct relation between metallic impurities and the electrocatalytic activity of graphene. In contrast, impurity-free graphene exhibits poor electrocatalytic activity.
Bibliographical noteFunding Information:
This work was supported by Czech Science Foundation (GACR no. 16-05167S) and by specific university research (MSMT no. 20-SVV/2018). This work was created with the financial support of the Neuron Foundation for science support. This work was supported by the project Advanced Functional Nanorobots (reg. no. CZ.02.1.01/0.0/0.0/15_003/ 0000444 financed by the EFRR). NAA analysis was supported by Center of Accelerators and Nuclear Analytical Methods infrastructure (Ministry of Education, Youth and Sports of the Czech Republic Project no. LM2015056).
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physics and Astronomy(all)