Matching Items (5)
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Description
Microbial fuel cells (MFCs) promote the sustainable conversion of organic matter in black water to electrical current, enabling the production of hydrogen peroxide (H2O2) while making waste water treatment energy neutral or positive. H2O2 is useful in remote locations such as U.S. military forward operating bases (FOBs) for on-site tertiary

Microbial fuel cells (MFCs) promote the sustainable conversion of organic matter in black water to electrical current, enabling the production of hydrogen peroxide (H2O2) while making waste water treatment energy neutral or positive. H2O2 is useful in remote locations such as U.S. military forward operating bases (FOBs) for on-site tertiary water treatment or as a medical disinfectant, among many other uses. Various carbon-based catalysts and binders for use at the cathode of a an MFC for H2O2 production are explored using linear sweep voltammetry (LSV) and rotating ring-disk electrode (RRDE) techniques. The oxygen reduction reaction (ORR) at the cathode has slow kinetics at conditions present in the MFC, making it important to find a catalyst type and loading which promote a 2e- (rather than 4e-) reaction to maximize H2O2 formation. Using LSV methods, I compared the cathodic overpotentials associated with graphite and Vulcan carbon catalysts as well as Nafion and AS-4 binders. Vulcan carbon catalyst with Nafion binder produced the lowest overpotentials of any binder/catalyst combinations. Additionally, I determined that pH control may be required at the cathode due to large potential losses caused by hydroxide (OH-) concentration gradients. Furthermore, RRDE tests indicate that Vulcan carbon catalyst with a Nafion binder has a higher H2O2 production efficiency at lower catalyst loadings, but the trade-off is a greater potential loss due to higher activation energy. Therefore, an intermediate catalyst loading of 0.5 mg/cm2 Vulcan carbon with Nafion binder is recommended for the final MFC design. The chosen catalyst, binder, and loading will maximize H2O2 production, optimize MFC performance, and minimize the need for additional energy input into the system.
ContributorsStadie, Mikaela Johanna (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
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Description
Climate change is one of the biggest challenges facing today's society.Since the late 19th century, the global average temperature has been rising. In order to minimize the temperature increase of the earth, it is necessary to develop alternative energy technologies that do not depend on fossil fuels. Solar fuels are

Climate change is one of the biggest challenges facing today's society.Since the late 19th century, the global average temperature has been rising. In order to minimize the temperature increase of the earth, it is necessary to develop alternative energy technologies that do not depend on fossil fuels. Solar fuels are one potential energy source for the future. Solar fuel technologies use catalysts to convert low energy molecules into fuels via artificial photosynthesis. TiO2, or titania, is an important model photocatalyst for studying these reactions. It is also important to use remaining fossil fuel resources efficiently and with the lowest possible greenhouse gas emissions. Fuel cells are electrochemical devices that aim to accomplish this goal and CeO2, or ceria, is an important material used in these devices. One way to observe the atomic structure of a material is with a transmission electron microscope (TEM). A traditional transmission electron microscope employs a beam of fast electrons to form atomic resolution images of a material. While imaging gives information about the positions of the atoms in the material, spectroscopy gives information about the composition and bonding of the material. A type of spectroscopy that can be performed inside the transmission electron microscope is electron energy loss spectroscopy (EELS), which provides a fundamental understanding of the electronic structure of a material. The energy loss spectrum also contains information on the chemical bonding in the material, and theoretical calculations that model the spectra are essential to correctly interpreting this bonding information. FEFF is a software that performs EELS calculations. Calculations of the oxygen K edges of TiO2 and CeO2 were made using FEFF in order to understand the changes that occur in the spectrum when oxygen vacancies are introduced as well as the changes near a grain boundary.
ContributorsHussaini, Zahra (Author) / Crozier, Peter (Thesis director) / Rez, Peter (Committee member) / Jorissen, Kevin (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Materials Science and Engineering Program (Contributor) / Department of Physics (Contributor)
Created2013-12
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Description隨著全球一體化,社交網絡在國際平台上擁有了相當出色的表現,影響全球人民的生活,特別有助於國際經濟發展,因此引起了各國的關注。雖然如此,它們具體的效果是難以去評估的。本文在前人研究的基礎上探討社交網絡的經營模式以及它對於國際經濟的影響。在微觀層面可以看到社交網的存在對市場有著直接的影響。在宏觀層面上,社交網站通過其網站設計推銷其他公司產品,提高廣告商的知名度,刺激消費。這兩方面,本文討論社交網的影響為何跟傳統公司有差別。
ContributorsLi, Marilyn Yih (Author) / Spring, Madeline (Thesis director) / Zhu, Jie (Committee member) / Barrett, The Honors College (Contributor) / Department of Economics (Contributor)
Created2013-12
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Description
As the global community raises concerns regarding the ever-increasing urgency of climate change, efforts to explore innovative strategies in the fight against this anthropogenic threat is growing. Along with other greenhouse gas mitigation technologies, Direct Air Capture (DAC) or the technology of removing carbon dioxide directly from the air has

As the global community raises concerns regarding the ever-increasing urgency of climate change, efforts to explore innovative strategies in the fight against this anthropogenic threat is growing. Along with other greenhouse gas mitigation technologies, Direct Air Capture (DAC) or the technology of removing carbon dioxide directly from the air has received considerable attention. As an emerging technology, the cost of DAC has been the prime focus not only in scientific society but also between entrepreneurs and policymakers. While skeptics are concerned about the high cost and impact of DAC implementation at scales comparable to the magnitude of climate change, industrial practitioners have demonstrated a pragmatic path to cost reduction. Based on the latest advancements in the field, this dissertation investigates the economic feasibility of DAC and its role in future energy systems. With a focus on the economics of carbon capture, this work compares DAC with other carbon capture technologies from a systemic perspective. Moreover, DAC’s major expenses are investigated to highlight critical improvements necessary for commercialization. In this dissertation, DAC is treated as a backstop mitigation technology that can address carbon dioxide emissions regardless of the source of emission. DAC determines the price of carbon dioxide removal when other mitigation technologies fall short in meeting their goals. The results indicate that DAC, even at its current price, is a reliable backup and is competitive with more mature technologies such as post-combustion capture. To reduce the cost, the most crucial component of a DAC design, i.e., the sorbent material, must be the centerpiece of innovation. In conclusion, DAC demonstrates the potential for not only negative emissions (carbon dioxide removal with the purpose of addressing past emissions), but also for addressing today’s emissions. The results emphasize that by choosing an effective scale-up strategy, DAC can become sufficiently cheap to play a crucial role in decarbonizing the energy system in the near future. Compared to other large-scale decarbonization strategies, DAC can achieve this goal with the least impact on our existing energy infrastructure.
ContributorsAzarabadi, Habib (Author) / Lackner, Klaus S (Thesis advisor) / Allenby, Braden R. (Committee member) / Dirks, Gary W (Committee member) / Reddy, Agami (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Global decarbonization requires a large-scale shift to sustainable energy sources. Innovation will be a key enabler of this global energy transition. Although the energy transition and innovation literatures overwhelmingly focus on the Global North, energy innovation is arguably even more important for the Global South because it can enable them

Global decarbonization requires a large-scale shift to sustainable energy sources. Innovation will be a key enabler of this global energy transition. Although the energy transition and innovation literatures overwhelmingly focus on the Global North, energy innovation is arguably even more important for the Global South because it can enable them to grow their energy demand and power their development with sustainable resources. This dissertation examines three aspects of energy innovation, focusing on Mexico, to advance the understanding of innovation systems and identify policy levers for accelerating energy innovation in emerging economies. The first project utilizes econometric models to assess patenting drivers for renewable energy (wind and solar) and enabling technologies (energy storage, high voltage direct current technologies, hydrogen technologies, and fuel cells) across 34 countries, including Mexico. The examination of enabling technologies is a particular contribution, since most research on energy innovation focuses on renewable generation technologies. This research finds that policies have differential effects on renewable technologies versus enabling technology, with innovation in enabling technologies lagging behind the deployment of renewable energy. Although renewable energy policies have some spillover effects on enabling technologies, this research suggests that targeted policy instruments for enabling technologies may be needed for global decarbonization. The second and third projects apply the innovation systems framework to understand energy innovation in Mexico. The second project analyzes the sectoral innovation system (SIS) for wind and solar technologies, using expert interviews to evaluate SIS structure and functions systemically. It finds that this innovation system is susceptible to changes in its structure, specifically institutional modifications, and encounters cultural and social aspects that reduce its performance. Further, it finds that non-government organizations and local governments are trying to support the SIS, but their efforts are hampered by low participation from the federal government. The third project studies the technology innovation system (TIS) for green hydrogen, an emerging industrial opportunity for Latin America. It evaluates this TIS's functionality and identifies 22 initiatives to improve its performance by interviewing green hydrogen experts in Mexico. The most important initiatives for strengthening the green hydrogen TIS are information campaigns, policy and regulation (taxes, subsidies, standards, and industrial policies), pilot or demonstration projects, and professional training. Overall, this dissertation contributes to the nexus of energy transition and innovation studies by advancing the understanding of energy innovation in an emerging economy.
ContributorsAguiar Hernandez, Carlos Gabriel (Author) / Breetz, Hanna (Thesis advisor) / Parker, Nathan (Committee member) / Solis, Dario (Committee member) / Arizona State University (Publisher)
Created2022