@misc{GuticKozlicaBajukBogdanovicetal., author = {Gutic, Sanjin J. and Kozlica, Dzevad K. and Bajuk-Bogdanovic, Danica and Mitric, Miodrag and Mirsky, Vladimir M. and Mentus, Slavko V. and Pasti, Igor A.}, title = {Electrochemical tuning of capacitive response of graphene oxide}, series = {Physical Chemistry, Chemical Physics}, volume = {35}, journal = {Physical Chemistry, Chemical Physics}, number = {20}, issn = {1463-9084}, doi = {10.1039/C8CP03631D}, pages = {22698 -- 22709}, abstract = {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.}, language = {en} } @misc{KaračićGutićVasićetal., author = {Karačić, Dalibor and Gutić, Sanjin J. and Vasić, Borislav and Mirsky, Vladimir M. and Skorodumova, Natalia V. and Mentus, Slavko V. and Pašti, Igor A.}, title = {Electrochemical reduction of thin graphene-oxide films in aqueous solutions - Restoration of conductivity}, series = {Electrochimica Acta}, volume = {410}, journal = {Electrochimica Acta}, issn = {1873-3859}, doi = {10.1016/j.electacta.2022.140046}, pages = {11}, abstract = {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.}, language = {en} } @misc{PaštiJanoševićLežaićĆirićMarjanovićetal., author = {Pašti, Igor A. and Janošević Ležaić, Aleksandra and Ćirić-Marjanović, Gordana and Mirsky, Vladimir M.}, title = {Resistive gas sensors based on the composites of nanostructured carbonized polyaniline and Nafion}, series = {Journal of Solid State Electrochemistry}, volume = {20}, journal = {Journal of Solid State Electrochemistry}, number = {11}, issn = {1433-0768}, doi = {10.1007/s10008-016-3344-y}, pages = {3061 -- 3069}, abstract = {Due to constant necessity to have reliable and sensitive gas sensors in many contemporary technologies, there is a permanent need for development of new sensing platforms with good sensing properties. Here, we demonstrate a novel type of resistive gas sensors based on carbonized polyaniline/Nafion composites. The sensing mechanism of such sensors is based on the sorption of gases by the composites which induce Nafion swelling and decreasing of conductivity. Chemosensitive properties can be tuned by the (i) choice of carbon materials with different conductivities, (ii) Nafion content in the composite, and (iii) thickness of the composite layer. We have shown that the sensors respond to water, acetone, ethanol, and ethanol vapors. For the last two cases, we have achieved high sensitivity, fast response, wide concentration range, and good recovery. The use of simultaneous two- and four-point techniques for these sensors provides an internal control of the sensor integrity.}, language = {en} }