Elevated temperature photo-electrochemical water splitting
Abstract/Contents
- Abstract
- In order for solar energy to become a major contributor to utility-scale electricity production across the country, it is critical to tackle the inherently intermittent nature and geographically uneven distribution of solar energy. Due to the high energy densities and transportability, solar fuels, such as hydrogen and hydrocarbons, remain the most promising media to store and provide solar energy when and where it is needed. Photo-electrochemical (PEC) water splitting is a particular cost-effective and efficient approach to store solar energy into hydrogen. An overwhelming majority of the work has focused on ambient-temperature PEC cells, as it is believed that the efficiency of photovoltaic devices decreases with increasing temperature. While that the photovoltage generally decreases with temperature due to the rising intrinsic carrier concentration, electrocatalytic activity and minority/majority carrier transport properties in many materials actually improve with temperature. Therefore, it leaves an open question whether it is optimal to operate PEC cells at ambient temperatures. Motivated by that, I have carried out extensive investigation in elevated temperature photo-electrochemical water splitting. In this thesis, I will first discuss the non-trivial effect of temperature on PEC cells in aqueous solutions based on hematite (a-Fe2O3) thin film photoanode, grown by pulsed-laser deposition, as a model system. Building on top of that, I explicitly demonstrate that thermal energy significantly improves the saturation photocurrent in BiVO4 photoanode with only slight loss of the onset potential, the mechanism of which is rigorously attributed to the thermally activated minority carrier hopping. Furthermore, I extend the investigated temperature range even beyond 100 oC where the existing design of PEC cells in aqueous electrolyte are no longer applicable. This is achieved by an innovative design of liquid-free PEC cell with both theoretical analysis and experimental demonstration. Our observation confirms that increasing temperature could be an effective route to activing PEC cells, which contrasts with the prevailing understanding that the decreasing photovoltage dominates the temperature dependence of the energy conversion efficiency.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2016 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Ye, Xiaofei |
|---|---|
| Associated with | Stanford University, Department of Materials Science and Engineering. |
| Primary advisor | Chueh, William |
| Primary advisor | Melosh, Nicholas A |
| Thesis advisor | Chueh, William |
| Thesis advisor | Melosh, Nicholas A |
| Thesis advisor | McIntyre, Paul Cameron |
| Advisor | McIntyre, Paul Cameron |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Xiaofei Ye. |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2016. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2016 by Xiaofei Ye
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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