Investigating molybdenum disulfide as a protective catalyst for solar-water splitting devices
Abstract/Contents
- Abstract
- Generating hydrogen by using solar energy to split water molecules is an appealing idea due to the renewable and sustainable nature of the inputs: sunlight and water. This idea can be achieved with photoelectrochemical hydrogen evolution in which a photoactive semiconductor is paired with an electrocatalyst. The field of unassisted, solar-driven water-splitting for hydrogen production has made remarkable progress in the past few decades. Solar to hydrogen (STH) efficiencies have increased from low single digits in the 1970s to 19% in 2018 -- rivaling the typical efficiencies of "off the shelf" solar cells. While efficiencies have become competitive, durabilities have not. The average commercial solar panel comes with a 25 year "lifetime guarantee", but the longest an unassisted water-splitting device of any efficiency has lasted to date is only 100 hours. This stability gap has remained largely unchanged these past few decades primarily due to the complex challenge of preventing semiconductor corrosion in aqueous environments. In this dissertation, we explore whether Molybdenum Disulfide nanomaterials can serve as protection layers and catalysts for solar water-splitting devices. We found that a very thin, conformal coating of MoS2 can improve the stability of GaInP2 by over 500 times as measured by light-limited current density. Furthermore, we found that our MoS2 protection layers were excellent catalysts for hydrogen evolution, rivaling a state-of-the-art Pt-based catalyst, and our MoS2 protected device was among the most active and stable single-absorber photocathodes to date. We further probed the interfacial energetics with transient photon reflectance and revealed that a conformal MoS2 catalyst interface imparts improved electron transfer in addition to catalytic activity compared to a nonconformal PtRu catalyst. This insight into the semiconductor-catalyst interface is potentially relevant to catalytically protected photoectrodes across the field. We also found that our Molybdenum Disulfide nanomaterials can be used to stabilize high-efficiency GaAs/GaInAsP tandem water-splitting devices and demonstrated the first-ever unassisted water splitting device that uses Molybdenum Disulfide protective catalysts. We compared these devices to the best unassisted water-splitting devices to date and revealed a two orders of magnitude "stability gap" between where the field currently is and where the field needs to be for feasible commercialization. This dissertation explores the field of photoelectrochemical water-splitting at multiple levels. We dive into the stability challenges facing the field and present detailed and novel strategies for overcoming them. We also put our results into a greater context, revealing important field-wide trends, and discussing the challenges that must be solved to enable this sustainable technology to change how we produce and consume energy.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2019; ©2019 |
| Publication date | 2019; 2019 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Britto, Reuben Joseph |
|---|---|
| Degree supervisor | Jaramillo, Thomas Francisco |
| Thesis advisor | Jaramillo, Thomas Francisco |
| Thesis advisor | Bao, Zhenan |
| Thesis advisor | Deutsch, Todd |
| Degree committee member | Bao, Zhenan |
| Degree committee member | Deutsch, Todd |
| Associated with | Stanford University, Department of Chemical Engineering. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Reuben Joseph Britto. |
|---|---|
| Note | Submitted to the Department of Chemical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2019. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2019 by Reuben Joseph Britto
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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