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130 results on '"Ramaiyan, Kannan"'

1. Phosphoric acid pre-treatment to tailor polybenzimidazole membranes for vanadium redox flow batteries

Author

Maurya, Sandip, Abad, Sergio Diaz, Park, Eun Joo, Ramaiyan, Kannan, Kim, Yu Seung, Davis, Benjamin L, and Mukundan, Rangachary

Subjects
Engineering, Chemical Sciences, Physical Chemistry, Affordable and Clean Energy, Chemical Engineering, Chemical sciences
Abstract

Vanadium redox flow batteries (VRFBs) use ion-selective membranes for transporting ionic species while separating the positive and negative electrolytes. In this paper, we report phosphoric acid doped polybenzimidazole (PBI) membranes that yield high ionic selectivity and conductivity in VRFBs. The phosphoric acid pre-treatment swells the PBI matrix irreversibly and increases its sulfuric acid doping in VRFB electrolytes. The pre-treated membranes show comparable area resistance with Nafion-212 with better selectivity towards vanadium ions. A low resistance was obtained with a reduced membrane thickness, which can reduce the overall cost of materials. The VRFB using an optimized phosphoric acid pre-treated PBI membrane demonstrates coulombic, voltage, and energy efficiencies of 99.7, 90.3, and 90.0%, respectively, at 40 mA cm−2 while achieving ∼40% higher discharge capacity compared to Nafion-212. Furthermore, the VRFB cell shows excellent cycling stability, i.e., only 6.8% or 0.068% per cycle capacity decay for 100 cycles while maintaining coulombic efficiency at >99.9% (98.5% coulombic efficiency for Nafion-212 with a capacity decay of 0.42% per cycle) proving the effectiveness of pre-treatment of phosphoric acid on PBI membranes.

Published
2023

24. Bismuth Oxychloride Nanoflakes Enabled High Sensitivity Colorimetric UV Dosimetry.

Author

Troche, Kyle, Ramaiyan, Kannan, Boyle, Timothy J., and Garzon, Fernando H.

Abstract

Excessive exposure to sunlight's ultraviolet (UV) radiation causes adverse effects such as premature aging, sunburn, and skin cancers. Monitoring daily exposure to sunlight is essential to avoid developing health risks. Colorimetric UV sensors change color as a function of UV exposure, provide onsite information about the level of exposure, and can act as a personal wearable device to assist in making informed decisions on sunlight exposure. These sensors utilize radiation-induced reactions on a dye to produce a color change. Here, BiOCl based UV sensor is reported for monitoring UV exposure where a white-to-black color transformation is induced due to the creation of oxygen vacancies in BiOCl. This color transformation is not quantifiable in bulk BiOCl; hence BiOCl was purposely dispersed on filter paper to form petal-like nanostructures that help quantify the color change. Four different dye molecules, 6-carboxyfluorescein, 5-carboxyfluorescein, rhodamine-B, and Prussian blue were evaluated, where 6-carboxyfluorescein gave the best color contrast. The sensor responds to UVA, UVB, and UVC and with proper UV filters can be made selective for specific UV radiations. This unique colorimetric UV sensor can help manage personal UV exposure and reduce the risk of sun exposure ailments. [ABSTRACT FROM AUTHOR]

Published
2023
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33. Role of phosphate source in improving the proton conductivity of tin pyrophosphate and its composite electrolytes

Author

24775290 - Kerres, Jochen A., Ramaiyan, Kannan P., Kerres, Jochin, Herrera, Sergio, Workman, Michael J., Semelsberger, Troy A., 24775290 - Kerres, Jochen A., Ramaiyan, Kannan P., Kerres, Jochin, Herrera, Sergio, Workman, Michael J., and Semelsberger, Troy A.

Abstract

Metal pyrophosphates (MPPs) in general and tin pyrophosphate (TPP) in particular have received significant interest in the last decade due to their potential as proton conductors for electrolyte application in intermediate temperature (IT)-fuel cells. However, for MPP based electrolytes, despite high reported proton conductivities, achieving good fuel cell performance and high open circuit voltage (OCV) remains a challenge with synthesis methods playing a crucial role in determining the final proton conductivity. Here we report the role of phosphate precursor in determining the TPP proton conductivity by examining five different precursors: (1) phosphoric acid (TPP-PA), (2) ammonium hydroxide + phosphoric acid (TPP-NH4OH), (3) diammonium phosphate (TPP-DAP), (4) tetramethylammonium sulphate + phosphoric acid (TPP-TMAP), and (5) tetrabutylammonium phosphate (TPP-TBAP), where a maximum conductivity of 88 mS cm−1 at 200 °C was obtained for TPP prepared from the TBAP precursor. TPP prepared from all of the different precursors formed the crystalline cubic Pa[3 with combining macron] phase after sintering at 650 °C for 2.5 hours. Furthermore, TPP-TBAP/Nafion® composite membranes prepared with a 90 : 10 ratio exhibited an OCV of 0.98 V and produced a maximum peak power density (PPD) of 630 mW cm−2 at an operating temperature of 220 °C. Our results demonstrate the significant impact of the TPP precursor on proton conductivity and fuel cell performance

Published
2020

36. Solid State Electrochemical Sensor R&D

Author

Brosha, Eric Lanich, primary, Mukundan, Rangachary, additional, Kreller, Cortney, additional, Lujan, Roger W., additional, Ramaiyan, Kannan, additional, and Romero, Christopher Jesse, additional

Published
2016
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42. Selective electrochemical oxidative coupling of methane mediated by Sr2Fe1.5Mo0.5O6-δ and its chemical stability.

Author

Ramaiyan, Kannan P., Denoyer, Luke H., Benavidez, Angelica, and Garzon, Fernando H.

Subjects
*OXIDATIVE coupling, *CHEMICAL stability, *METHANE, *CARBON dioxide in water, *STEAM reforming, *PARTIAL oxidation, *NATURAL gas reserves
Abstract

Efficient conversion of methane to value-added products such as olefins and aromatics has been in pursuit for the past few decades. The demand has increased further due to the recent discoveries of shale gas reserves. Oxidative and non-oxidative coupling of methane (OCM and NOCM) have been actively researched, although catalysts with commercially viable conversion rates are not yet available. Recently, Sr 2 F e 1.5 + 0.075 M o 0.5 O 6 − δ (SFMO-075Fe) has been reported to activate methane in an electrochemical OCM (EC-OCM) set up with a C2 selectivity of 82.2%1. However, alkaline earth metal-based materials are known to suffer chemical instability in carbon-rich environments. Hence, here we evaluated the chemical stability of SFMO in carbon-rich conditions with varying oxygen concentrations at temperatures relevant for EC-OCM. SFMO-075Fe showed good methane activation properties especially at low overpotentials but suffered poor chemical stability as observed via thermogravimetric, powder XRD, and XPS measurements where SrCO3 was observed to be a major decomposition product along with SrMoO3 and MoC. Nevertheless, our study demonstrates that electrochemical methods could be used to selectively activate methane towards partial oxidation products such as ethylene at low overpotentials while higher applied biases result in the complete oxidation of methane to carbon dioxide and water. Catalytic conversion of methane to ethene is limited by poor conversion, selectivity, and catalyst stability. Here a solid oxide electrolysis process is reported as a promising method for selective, partial oxidation of methane with low overpotentials. [ABSTRACT FROM AUTHOR]

Published
2021
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49. Synthesis and characterisation of ceramic proton conducting perovskite-type multi-element-doped Ba0.5Sr0.5Ce1−−−Zr Gd Y O3−δ (0 < x < 0.5; y = 0, 0.1, 0.15; z = 0.1, 0.2)

Author

Kalpana Singh, Ramaiyan Kannan, and Venkataraman Thangadurai

Subjects
Proton, Renewable Energy, Sustainability and the Environment, Chemistry, Doping, Analytical chemistry, Energy Engineering and Power Technology, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Multi element, 0104 chemical sciences, Dielectric spectroscopy, Crystallography, Fuel Technology, visual_art, visual_art.visual_art_medium, Chemical stability, Ceramic, 0210 nano-technology, Perovskite (structure)
Abstract

This study addresses the influence of A-and B-site co-doping on the chemical and electrical properties of perovskite-type Ba0.5Sr0.5Ce1−x−y−zZrxGdyYzO3−δ (0

Published
2016

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