TY - GEN A1 - Gutic, Sanjin J. A1 - Kozlica, Dzevad K. A1 - Bajuk-Bogdanovic, Danica A1 - Mitric, Miodrag A1 - Mirsky, Vladimir M. A1 - Mentus, Slavko V. A1 - Pasti, Igor A. T1 - Electrochemical tuning of capacitive response of graphene oxide T2 - Physical Chemistry, Chemical Physics N2 - The increasing energy demands of modern society require a deep understanding of the properties of energy storage materials, as well as the tuning of their performance. We show that the capacitance of graphene oxide (GO) can be precisely tuned using a simple electrochemical reduction route. In situ resistance measurements, in combination with cyclic voltammetry measurements and Raman spectroscopy, have shown that upon reduction GO is irreversibly deoxygenated, which is further accompanied by structural ordering and an increase in electrical conductivity. The capacitance is maximized when the concentration of oxygen functional groups is properly balanced with the conductivity. Any further reduction and deoxygenation leads to a gradual loss of capacitance. The observed trend is independent of the preparation route and the exact chemical and structural properties of GO. It is proposed that an improvement in the capacitive properties of any GO can be achieved by optimization of its reduction conditions. Y1 - 2018 U6 - https://doi.org/10.1039/C8CP03631D SN - 1463-9084 SN - 1463-9076 VL - 35 IS - 20 SP - 22698 EP - 22709 ER - TY - GEN A1 - Karačić, Dalibor A1 - Gutić, Sanjin J. A1 - Vasić, Borislav A1 - Mirsky, Vladimir M. A1 - Skorodumova, Natalia V. A1 - Mentus, Slavko V. A1 - Pašti, Igor A. T1 - Electrochemical reduction of thin graphene-oxide films in aqueous solutions – Restoration of conductivity T2 - Electrochimica Acta N2 - Graphene oxide finds applications in different fields of science, including energy conversion. Electrochemical reduction of graphene oxide (GO) significantly improves its conductivity. However, the kinetics of this process depends on the solvent, supporting electrolyte, pH, and numerous other factors. Most studies report the macroscopic views and ex-situ properties of reduced GO. To expand the knowledge about GO reduction, in this study, we used cyclic voltammetry (CV), simultaneous 2 points and 4 points resistance measurement (s24), conductive atomic force microscopy (AFM), and theoretical calculations. Using CV, we demonstrated that the choice of supporting electrolyte (KCl or LiCl) influences the potential range in which electrochemical GO reduction occurs. The activation energy of this process was estimated to be below 30 kJ mol‒1 in both electrolytes, being significantly lower than that required for thermal reduction of GO. Simultaneous in situ s24 resistance measurements suggest that GO films reach a highly conductive state at deep negative potentials, with an abrupt, irreversible switch from non-conductive to the conductive state. However, conductive AFM presents a more exact picture of this process: the reduction of GO films starts locally while the formed conductive islands grow during the reduction. This mechanism was confirmed by theoretical calculations indicating that the reduction starts on isolated oxygen-functional groups over the GO basal plane, while clustered OH groups are more difficult to reduce. The presented results can help in tailoring reduced GO for a particular electrochemical application by precisely controlling the reduction degree and percentage of the conductive area of the reduced GO films. KW - Electrochemical reduction of graphene oxide KW - Supporting electrolyte effect KW - Simultaneous 2-point 4-point resistance measurements KW - Conductive atomic force microscopy KW - Theoretical calculations Y1 - 2022 UR - https://www.sciencedirect.com/science/article/pii/S0013468622002183 U6 - https://doi.org/10.1016/j.electacta.2022.140046 SN - 1873-3859 SN - 0013-4686 VL - 410 ER -