Dissertation
A wireless unitized photovoltaic-electrochemical device for stable hydrogen production
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2020
DOI: 10.17077/etd.005513
Abstract
Solar water splitting has long been touted as a favorable pathway for the efficient storage of renewable energy. Currently, a solar water splitting plant on a commercial scale has not yet been achieved. The primary driving factors that limit their commercial adoption are: (1) materials with low efficiency for solar spectrum absorbance, and/or (2) expensive and unstable systems based on high-efficiency photoelectrodes or materials. Significant factors in the high costs of the materials include the light-absorbing semiconductor and the oxidation and reduction electrocatalysts. Device lifetime is limited primarily by the poor stability of the photovoltaic material in harsh electrolytes in which the electrocatalysts are most active. The oxidation and reduction electrocatalysts also need increases in efficiency to limit the energetic losses that occur from the electrochemical water splitting reactions, which limit the overall solar-to-fuel efficiency. Clearly, significant advances must be made in the metrics of device stability, efficiency, and cost-reduction for this technology to gain any substantial market adoption and begin to open the pathway for emissions-free energy storage. This thesis aims to advance the research in this area by taking steps in each of the barriers mentioned above through the following: (i) the synthesis of a low-cost, platinum group metal-free (PGM-free) oxygen electrode; (ii) the development of a novel electrode architecture to lower Pt content in a hydrogen electrode; (iii) a generalized toolkit to stabilize existing commercial photovoltaic material for photoelectrochemical applications; and (iv) the integration of each of these aspects together into a proven, scalable, solar water splitting device design.
The main outcomes from this research are: (1) The development of a PGM-free oxygen evolution reaction (OER) catalyst with over 1000 hours of stable operation in alkaline electrolyte. (2) Design and synthesis of novel bifunctional oxygen electrodes with the best-in-class electrode demonstrating a combined OER and oxygen reduction reaction (ORR) overpotential of 748 mV, among the best achieved so far using PGM-free elements. (3) The development of a low-PGM hydrogen evolution reaction (HER) catalyst achieving superior catalytic performance to bulk platinum at a loading level of 0.059 mgPt/cm2, below DOE targets for 2025 of <0.125 mgPGM/cm2. (4) The achievement of a record photoelectrochemical stability of over 1000 hours for silicon-based tandem light absorbers in alkaline electrolytes for water splitting reaction. (5) The creation of a novel design architecture for unassisted integrated photoelectrochemical (PEC) devices with solar-to-hydrogen (STH) conversion efficiencies of 2.9% for 5 hours on a low-cost silicon-based tandem light absorber, and 10.5% for 48 hours on a high-efficiency III-V tandem light absorber. (6) Achieving the highest reported solar-to-chemical (STC) efficiency to date of a photoelectrochemical system with 21.56% STC for the chloralkali process.
Details
- Title: Subtitle
- A wireless unitized photovoltaic-electrochemical device for stable hydrogen production
- Creators
- Jonathan Gerrit Koonce
- Contributors
- Syed Mubeen (Advisor)C Allan Guymon (Committee Member)Johna Leddy (Committee Member)David G Rethwisch (Committee Member)Xiaonan Shan (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemical and Biochemical Engineering
- Date degree season
- Summer 2020
- DOI
- 10.17077/etd.005513
- Publisher
- University of Iowa
- Number of pages
- xiv, 143 pages
- Copyright
- Copyright 2020 Jonathan Gerrit Koonce
- Language
- English
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 126-137).
- Public Abstract (ETD)
Water splitting is the electrochemical process of extracting hydrogen and oxygen gases through the application of electric current in water. By producing and capturing hydrogen in this manner, energy can be stored in the form of hydrogen gas, an energy-dense fuel. However, most hydrogen that is produced is currently made from steam methane reforming, a greenhouse gas emitting process. Water splitting provides a pathway for hydrogen production that is emission-free, and the necessary energy required can be generated from solar electricity. Currently, because of the abundance of cheap fossil fuels, clean hydrogen production is more expensive to produce and is therefore not competitive from an economic standpoint. To minimize the costs of solar hydrogen production and make it economically viable, advancements must be made to improve device lifetimes and efficiencies. In doing so, hydrogen can be used to store solar-generated energy, which will allow the use of this energy as-needed to offset the intermittent nature of solar power generation.
- Academic Unit
- Chemical and Biochemical Engineering
- Record Identifier
- 9983987796102771
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