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<td><img alt="Dissertation Defense Announcement at the Cullen College of Engineering" width="600" height="171" src="https://www.egr.uh.edu/sites/www.egr.uh.edu/files/enews/2022/images/dissertation1.png">
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<div style="font-size:24px; color:rgb(200,16,46); line-height:28px"><strong>Bismuth Oxyhalide Nanosheets with Adjustable Band Edge Potentials for Photocatalytic Ammonia generation </strong></div>
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<div style="margin-top:5px; line-height:22px"><strong style="font-size:18px">Mohammadjavad Mohebinia</strong><br>
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November 17th, 2022; 2:00 PM - 4:00 PM (CDT)<br>
Location: Zoom<br>
Zoom: <a href="https://urldefense.com/v3/__https://zoom.us/j/549082551?pwd=WjA4S2p4TmxPclQ1QU9lRnNSbTA1dz09__;!!LkSTlj0I!HtKy-umLHGdKF6BX2qtPZlYynykeMJBe0APeHwkwWQEwR8aZ5VkMQWKs6CVOFaNAd_ErkrRigg97fV83gfrUT6sK$" data-auth="NotApplicable" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:16px; text-align:start">https://zoom.us/j/549082551?pwd=WjA4S2p4TmxPclQ1QU9lRnNSbTA1dz09</a></p>
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<strong>Committee Chair:</strong><br>
Jiming Bao, Ph.D.<br>
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<strong>Committee Members:</strong><br>
Lars Grabow, Ph.D. | Xiaonan Shan, Ph.D. | Zhifeng Ren, Ph.D. | Jae Hyun Ryou, Ph.D.</p>
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<strong>Abstract</strong></p>
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<span style="font-family:"Times New Roman",serif; font-size:12pt; text-align:justify; text-indent:23.75pt; color:rgb(34,34,34)">Ammonia is a crucial compound and precursor in industry and agriculture. It can be easily liquified and transported. Thus, it could
be an exciting way to store intermittent renewable energies. However, the current industrial process is energy demanding and polluting. Recently, photocatalytic nitrogen fixation for ammonia generation attracted much attention to be a promising and sustainable
alternative to the traditional Haber-Bosch process. Although many proposed photocatalysts are shown to work for ammonia generation, there are still several challenges to achieving high production rates and energy conversion efficiency.</span></p>
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<span style="font-family:"Times New Roman",serif; font-size:12pt; text-align:justify; text-indent:23.75pt; color:rgb(34,34,34)">Among the studied photocatalysts, bismuth iodide (BiOI) showed promising properties such as visible light absorption capability,
adjustable band edge potentials, and abundant surface oxygen vacancies to activate nitrogen molecules. In the third chapter, we fabricated ultrathin BiOI nanosheets by a surfactant-assisted hydrothermal method. Unlike bulk BiOI, ultrathin nanosheets were active
for water splitting and nitrogen reduction. It is shown that functional groups (polyvinyl pyrrolidone) on the surface of BiOI induced an electric dipole and upshifted the band edge potentials. Therefore, enhancing redox overpotential, reducing the particle
size, and generating a significant amount of oxygen vacancies could enable the photocatalyst to efficiently reduce nitrogen to ammonia in pure water.</span></p>
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<span style="font-family:"Times New Roman",serif; font-size:12pt; text-align:justify; text-indent:23.75pt; color:rgb(34,34,34)">Another challenge toward efficient ammonia generation is providing a sufficient number of electrons and protons from the water oxidation
half-reaction. However, almost all previous studies focused solely on nitrogen reduction reaction, and its counterpart (OER) was neglected. In chapter 4, a new strategy was employed to eliminate the need for using organic sacrificial reagents for ammonia generation.
We proposed using cobalt oxyhydroxide (CoOOH) as an OER co-catalyst for a well-known nitrogen reduction photocatalyst, bismuth oxychloride (BiOCl). A series of cobalt-doped BiOCl (Co-BiOCl) nano-platelets were synthesized through a combination of co-precipitation
and hydrothermal synthesis with systematic variation in the percentage of added co-catalyst. The formation of CoOOH was verified via X-ray diffraction, X-ray photoelectron spectroscopy, electron microscopy, Raman, and infrared spectroscopy. A 4.6-fold improvement
in the ammonia production rate was realized with 5% Co-BiOCl. The OER performed and correlated well with the ammonia generation. Consequently, improving water oxidation by loading OER co-catalyst points to a promising and applicable method for better N</span><sub style="font-family:"Times New Roman",serif; text-align:justify; text-indent:23.75pt; color:rgb(34,34,34)">2</sub><span style="font-family:"Times New Roman",serif; font-size:12pt; text-align:justify; text-indent:23.75pt; color:rgb(34,34,34)">
fixation photocatalyst design.</span><span style="font-family:"Times New Roman",serif; font-size:12pt; text-align:justify; text-indent:23.75pt; color:rgb(34,34,34)"> </span></p>
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<td><img alt="Engineered For What's Next" width="600" height="82" src="https://www.egr.uh.edu/sites/www.egr.uh.edu/files/enews/2022/images/dissertation2.png"></td>
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