Ponnurangam, SathishBirss, Viola I.Ai, Chengying2019-09-252019-09-252019-09-20Ai, C. (2019). Polyaniline-coated Nanoporous Carbon Scaffold for Energy Storage and Water Deionization Applications (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/111067The world’s rapidly growing population urgently calls for more clean water. However, current water treatment technologies, e.g., reverse osmosis and distillation, are very energy demanding. Capacitive deionization (CDI) has emerged as a promising new technology for the production of clean water from brackish or even seawater at a high efficiency and at low cost, also showing promise in storing energy while simultaneously achieving desalination. In this work, a novel nanoporous carbon scaffold (NCS), a binder-free, free-standing, and 100% carbon film with a highly tunable nanoporous structure, has shown excellent promise as a CDI electrode. However, its surface area of 200-400 m2/g for the 50 and 85 nm diameter pore-sized NCS materials, limits the obtainable double layer capacitance. To further increase the electrochemical capacitance of the NCS material, polyaniline (PANi), a conducting polymer with a very high electrochemical capacitance (~750 F/g), was deposited on the NCS using cyclic voltammetry (CV), resulting in a PANi/NCS composite. A range of conformal PANi layers of controllable thicknesses were obtained, without blocking the pores of the NCS, as observed by scanning electron microscopy (SEM). The conformal PANi coating is uniform throughout the thickness of the NCS, as seen from SEM and energy-dispersive X-ray spectroscopy element mapping. Both CV and galvanostatic charge/discharge (GCD) methods were used to demonstrate the capacitive behavior of the PANi/NCS composite, with the capacitance increasing by 5 to 20 times of that obtained from the original NCS, thus possessing an excellent energy and power density. The PANi-coated NCS also demonstrates good cyclic stability, retaining ca. 85% of its original capacitance after 1000 GCD cycles. Electrochemical impedance spectroscopy (EIS) confirmed that the time constant of the PANi/NCS composites decreased with an increase in the PANi thickness, from 3 to 20 nm. A flow-through CDI test was carried out using three different cell configurations, including a symmetric NCS cell, a symmetric PANi/NCS cell and an asymmetric cell containing a PANi/NCS anode and an NCS cathode. When using the asymmetric CDI configuration, the salt adsorption capacity was 2.6 mg/g (0.019 mg/m2), while the salt adsorption can be completed very rapidly in only 2-10 seconds.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.ElectrochemistryCapacitive deionizationNanoporous carbon scaffoldConformal polyaniline coatingEnergyEngineering--ChemicalEngineering--EnvironmentalMaterials Sciencemaster thesis10.11575/PRISM/37129