Improving the Performance of Electroanalytical Devices for Sensing and Energy Storage

摘要

My graduate research was focused on improving the performance and expanding the application of two categories electrochemical devices that are used in energy storage and sensing: electrochemical double-layer capacitors and ion-selective electrodes.;The energy density of an electrochemical capacitor is determined by 1/2 CV2, where V is the potential difference between the plates of a capacitor and C is the capacitance density. Therefore, extending the operational voltage of such devices, which is limited by the electrochemical window of the electrolyte, can improve the device energy density. Optimizing the structure and improving electrochemical stability of electrolytes that can be utilized in electrochemical capacitors, was one of the goals of research presented in this thesis. Chapter 2 reviews the conventional methods for quantifying the electrochemical stability of electrolytes, and discusses their limitations. A new method for quantifying electrochemical stability of ionic liquids and electrolytes is suggested and several advantages of the proposed method is demonstrated for variety of systems. The effect of electrolyte structure on its electrochemical stability and accessible potential window is discussed in Chapter 3 and Chapter 4 highlights advantages of application of ionic liquids as electrolytes in electrochemical capacitors.;Ion-selective electrodes, ISEs, are electrochemical sensors that determine the concentration of a wide range of ions and are used for billions of measurements in clinical, environmental, and chemical process analyses every year. However, two factors limit the application of ISEs in biological analyses: (1) Interference of biological molecules (2) Large sample volumes needed for ISE measurements. Recently, fluorophilic compounds have been applied in the ion-selective membrane of ISEs in an effort to reduce the interference of biological molecules. Chapters 5 to 7 show the reliability of sensing with fluorous-phase ion-selective electrodes in the environmental and biological samples. A part of my thesis research is focused on reducing the sample volume needed for detection with these sensors. This goal was achieved by development of highly fluorophilic electrolytes which were used to decrease the resistivity of the fluorous sensing membranes, allowing fabrication of fluorous-phase micro-ISEs and significantly decreasing the sample volume required for sensing.