Open Access Publications
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Open access publications by faculty, postdocs, and graduate students in the Department of Mechanical Engineering.
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Browsing Open Access Publications by Subject "affordable and clean energy"
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Item 3D Computational Model for an Electrochemical Gas Separation and Inerting System(Journal of The Electrochemical Society, 2022-04-25) Aryal, Utsav Raj; Aziz, Majid; Prasad, Ajay K.Aircraft fuel tank inerting is employed to reduce the flammability of the fuel vapor in the ullage (air volume above the fuel) by restricting its oxygen concentration to a safe value—12% for commercial aircraft and 9% for military aircraft. Inerting is typically accomplished by displacing oxygen in the ullage with an inert gas like nitrogen. Electrochemical gas separation and inerting system (EGSIS) is an on-board method to generate and supply nitrogen-enriched air (NEA) to the fuel tank. EGSIS combines a polymer electrolyte membrane (PEM) electrolyzer anode which dissociates water to evolve oxygen, and a PEM fuel cell cathode which reduces oxygen from atmospheric air to produce NEA at its outlet. This paper represents the first attempt to model and simulate EGSIS using a three-dimensional, steady state, isothermal model. Various EGSIS performance indicators such as current density, reactant concentration distribution, and polarization curves are studied as a function of operating conditions and design parameters. The results from the computational model are validated against our previous experimental results for various operating conditions. The simulation results reveal the effects of temperature, reactant flowrates, and material property optimization on EGSIS performance. Different operating strategies are explored with the goal of improving system performance.Item Boosting photocatalytic hydrogen production from water by photothermally induced biphase systems(Nature Communications, 2021-02-26) Guo, Shaohui; Li, Xuanhua; Li, Ju; Wei, BingqingSolar-driven hydrogen production from water using particulate photocatalysts is considered the most economical and effective approach to produce hydrogen fuel with little environmental concern. However, the efficiency of hydrogen production from water in particulate photocatalysis systems is still low. Here, we propose an efficient biphase photocatalytic system composed of integrated photothermal–photocatalytic materials that use charred wood substrates to convert liquid water to water steam, simultaneously splitting hydrogen under light illumination without additional energy. The photothermal–photocatalytic system exhibits biphase interfaces of photothermally-generated steam/photocatalyst/hydrogen, which significantly reduce the interface barrier and drastically lower the transport resistance of the hydrogen gas by nearly two orders of magnitude. In this work, an impressive hydrogen production rate up to 220.74 μmol h−1 cm−2 in the particulate photocatalytic systems has been achieved based on the wood/CoO system, demonstrating that the photothermal–photocatalytic biphase system is cost-effective and greatly advantageous for practical applications.Item Fluoroalkyl phosphonic acid radical scavengers for proton exchange membrane fuel cells(Journal of Materials Chemistry A, 2023-04-06) Agarwal, Tanya; Adhikari, Santosh; Kim, Yu Seung; Babu, Siddharth Komini; Tian, Ding; Bae, Chulsung; Pham, Nguyet N. T.; Lee, Seung Geol; Prasad, Ajay K.; Advani, Suresh G.; Sievert, Allen; Rasika, Wipula Priya Liyanage; Hopkins, Timothy E.; Park, Andrew; Borup, RodRadical-induced degradation of proton exchange membranes limits the durability of proton-exchange membrane fuel cells. Cerium is widely used as a radical scavenger, but the migration of cerium ions to the catalyst layer has been an unresolved issue, reducing its effectiveness over time. Here, we report phosphonic acids as a promising class of radical scavengers, showing competent radical scavenging activity compared to cerium without the migration issue. The ex situ Fenton test shows that the fluoride emission rate for Nafion membrane incorporated with fluoroalkyl phosphonic acid ranged from 0.22 to 0.37 μg F cm−2 h−1, lower than that of the cerium-incorporated Nafion™ membrane (0.39 μg F cm−2 h−1). The in situ open circuit voltage hold test confirmed that a phosphonic acid-incorporated Nafion™ membrane has a 58% lower fluoride emission rate compared to the baseline. Density functional theory calculations indicate that the activation energy of the hydroxyl radical scavenging reaction of an alkyl phosphonic acid is only 0.68 eV, suggesting an effective radical scavenging pathway.Item Plasma-Wind-Assisted In2S3 Preparation with an Amorphous Surface Structure for Enhanced Photocatalytic Hydrogen Production(Nanomaterials, 2022-05-21) Guo, Shaohui; Luo, Hui; Duan, Xiaochuan; Wei, Bingqing; Zhang, XianmingPhotocatalytic production from water is considered an effective solution to fossil fuel-related environmental concerns, and photocatalyst surface science holds a significant interest in balancing photocatalysts’ stability and activity. We propose a plasma-wind method to tune the surface properties of a photocatalyst with an amorphous structure. Theoretical calculation shows that the amorphous surface structure can cause an unsaturated coordination environment to adjust the electron distribution, forming more adsorption sites. Thus, the photocatalyst with a crystal–amorphous (C–A) interface can strengthen light absorption, harvest photo-induced electrons, and enrich the active sites, which help improve hydrogen yield. As a proof of concept, with indium sulfide (In2S3) nanosheets used as the catalyst, an impressive hydrogen production rate up to 457.35 μmol cm−2 h−1 has been achieved. Moreover, after plasma-assisted treatment, In2S3 with a C–A interface can produce hydrogen from water under natural outdoor conditions. Following a six-hour test, the rate of photocatalytic hydrogen evolution is found to be 400.50 μmol cm−2 g−1, which demonstrates that a catalyst prepared through plasma treatment is both effective and highly practical.