Disentangling the roles of temperature and glycine in the reduction and functionalization of graphene oxide

Graphene is a two-dimensional nanomaterial composed of carbon atoms arranged in a hexagonal lattice, widely recognized for its high crystalline quality, electrical conductivity, corrosion resistance, and mechanical strength. Among the various synthesis methods, the chemical oxidation of graphite followed by reduction remains one of the most scalable and widely used approaches. In this work, graphene oxide was synthesized using a modified Hummers method in which the controlled addition of water enhanced oxidation efficiency. To disentangle the individual roles of temperature and glycine in graphene oxide reduction and functionalization, three synthesis routes were systematically compared: thermal reduction of graphene oxide in the absence of glycine, interaction of graphene oxide with glycine at room temperature, and thermal reduction in the presence of glycine. Unlike previous studies that combine amino acids and thermal treatment, this work systematically decouples the effects of temperature and glycine on graphene oxide reduction and functionalization. Structural and spectroscopic analyses demonstrated that the reduction of graphene oxide is governed by thermal treatment, while glycine does not induce reduction at room temperature and acts exclusively as a functionalizing agent under reflux conditions by incorporating nitrogen-containing groups. Electrochemical evaluation by cyclic voltammetry revealed that thermally reduced graphene oxide exhibits superior capacitive behavior in basic electrolytes, whereas thermally reduced graphene oxide in the presence of glycine shows enhanced electrochemical activity in acidic media, highlighting the effect of nitrogen functionalization on charge storage mechanisms. These findings resolve existing ambiguities in the literature regarding the role of amino acids in graphene oxide reduction and demonstrate that the combined use of thermal treatment and glycine functionalization provides a low-cost, sustainable, and scalable strategy for tailoring graphene-based materials for electrochemical applications. • A modified Hummers method was used for graphene oxide synthesis, where controlled water addition, combined with thermal reflux, proved critical for achieving effective reduction and functionalization with glycine. • Characterization techniques such as SEM, TEM, AFM, X-Ray diffraction, FTIR, Uv-Vis and Raman spectroscopy confirmed successful reduction and structural modification of GO. • Reflux was confirmed as the critical condition for achieving reduction, whereas glycine played a complementary role in functionalization when combined with reflux. • The study compares the performance of three materials: GO, TRGO and TRFGO showcasing enhanced properties in acidic and basic media that can lead to electrochemical applications.