Cyanographene and Graphene Acid: The Functional Group of Graphene Derivative Determines the Application in Electrochemical Sensing and Capacitors

Well‐defined, stoichiometric derivatives of graphene afford many opportunities in fine‐tuning of graphene properties and hence, extend the application potential of this material. Here, we present the electrochemical properties of cyanographene (G−CN), and graphene acid (G−COOH) in order to understand the role of the covalently attached functional groups on the graphene sheet in electrochemical sensing for the detection of biomarkers. G−CN shows better performance for the negatively charged analytes ascorbic and uric acids when compared to G−COOH. The less‐favourable performance of G−COOH is explained by repulsion between negatively charged analytes and negatively charged functional groups of G−COOH. The capacitance of both materials is in a comparable range, but chronopotentiometry reveals that G−CN shows a greater capacitance than G−COOH. The identified differences in electrochemical properties imprinted by the functional group show that its chemical nature can be exploited in fine‐tuning of the selectivity of electrochemical sensing and energy storage applications.