Graduation Year

2019

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Arash Takshi, Ph.D.

Committee Member

Manoj Ram, Ph.D.

Committee Member

Elias Stefanakos, Ph.D.

Committee Member

Sylvia Thomas, Ph.D.

Committee Member

Ryan Toomey, Ph.D.

Committee Member

Humberto Gutierrez, Ph.D.

Keywords

Conducting Polymers, Dye Sensitized Solar Cell, Hybrid Device, Polyvinyl Alcohol, Supercapacitor

Abstract

Redox-active materials in the bulk of gel electrolytes are unquestionably holding the primary roles in developing energy harvesting and storage technology. Both technologies are necessary in order to cope with the current challenges of the environmental crises of global warming and finite non-renewable sources while the demand for energy modern societies have been speedily increased. One of the most challenges of making a hybrid device of energy conversion and storage is the cost of the fabrication process. Therefore, gel electrolyte-based materials with redox-active properties can potentially be a promising solution to improve the performance of electrochemical and photoelectrochemical devices for low-cost applications by using abundant and low-cost materials such as polyvinyl alcohol, polyaniline, and polypyrrole.

The essential target of this dissertation was to make a gel electrolyte with redox-active properties that can be applied with an electrical double layer capacitor, photoactive supercapacitor, dye-sensitized solar cell, and electrochromic windows. Two different types of gel electrolyte based polyvinyl alcohol as host polymer have been examined with several electrochemical cells. The first type was polyvinyl alcohol mixed with acids in deionized water to form the gel electrolyte. The second type was a composite gel electrolyte of polyvinyl alcohol, acid, conducting polymer (i.e., polyaniline), and oxidized material (i.e., ammonium persulfate).

To address the issues and advantages of using these types of gel electrolytes, several approaches to making electrochemical and photoelectrochemical devices based on redox-active gel electrolytes have been addressed in this dissertation. The first approach was to examine a redox activity of polyvinyl alcohol with acids solutions by a comparison study of making electrical double-layer capacitors based on liquid and gel electrolytes. The results showed the superiority of the electrical double layer capacitor-based gel electrolyte to the concurrent based liquid electrolyte due to the redox activity of the PVA and its capability of storing charges in addition to the effect of a double-layer capacitor.

The second approach was to make photoactive supercapacitor devices based on conducting polymer materials, synthetic dyes, and redox-active gel electrolyte. Harvesting energy is taking place at the anode electrode by electrochemically deposited a nanocomposite thin film of conducting polymer (i.e., Polyaniline or Polypyrrole)/Dyes. Energy storage occurs at both electrodes’ anode and the cathode (i.e., CNT) in addition to the bulk gel electrolyte. Even though the results represented the photovoltaic and storage effect of the device, the results of the photovoltaic effect mainly were relatively weak and needed further improvement. From this point of view, the movement of ionic charges and electronic charges to reach the electrode/ electrolyte interface in the gel medium is slow, leading to affect the performance of the device.

The third approach presented in this dissertation was to develop the gel mentioned above by adding polyaniline, a conducting polymer, and ammonium persulfate, oxidizer material, to form PANI composite gel electrolyte. To test the validation of this composite gel electrolyte, different electrochemical and photoelectrochemical devices were fabricated, which are an electrical double later capacitor, a photoactive supercapacitor, a dye-sensitized solar cell, and an electrochromic window. The results showed improvement in terms of energy storage and photovoltaic effect due to the present of polyaniline and ammonium persulfate intercalated with polyvinyl alcohol. Not only that but also this composite gel was workable with electrochromic applications.

In the end, low cost, abundant, and non-toxic materials such as polyvinyl alcohol, polyaniline, and ammonium persulfate are promising due to their redox-active properties that can substantially reinforce the total performance of electrochemical and photoelectrochemical devices.

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