Electrochemical Properties of Hydrogen Absorbing Zintl Phases
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Date
2018-05
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Publisher
The Ohio State University
Abstract
Novel, low-cost catalysts are needed for electrocatalysis for a wide variety of applications in order to move towards a renewable energy economy based on clean production and conversion of hydrogen. To date, most common catalysts have depended on pure precious metals or alloying some amount of a precious metals, restricting the commercialization of hydrogen fuel cell technologies. Here, we propose and explore the possibility of using Zintl phase catalysts as potential low-cost electrocatalysts, and using these measurements to understand the electrochemical mechanisms of this family of materials. Known Zintl phases GdGa and BaGa2, each of which are known to be capable of hydrogenation to hydride phases, were synthesized using traditional solid state methods for this study, and confirmed by X-Ray Diffraction. Electrochemical measurements were taken using cyclic voltammetry. Platinum was measured at several pHs as a standard for hydrogen evolution reaction (HER) catalysis. As expected, platinum catalysis revealed high activity and low overpotential, but these properties rapidly decrease as a function of proton concentration. GdGa was measured at pH = 3, and was found to have the same slope as BaGa2 at both pH = 5 and pH = 7, although these trends were distinct from the electrochemistry in the same region of the carbon substrate they were measured on (at pH = 3). This led to an investigation of the interaction of BaGa2 in organic solvent with trimethylamine (TEA), a sacrificial hydrogen donor for possible electrochemical hydrogenation routes. BaGa2 was revealed to reduce the irreversible oxidation potential of TEA from ~0.6 V vs. Ag/AgNO3 to ~0.1 V vs. AgAgNO3. Our results suggest that while the Zintl phases studied thus far do not have HER or OER catalysis ability, they may be useful for the electrochemical catalysis of organic reactions and may be able to be manipulated electrochemically.
Description
Honors Arts & Sciences Undergraduate Research Scholarship (2017-2018)
Keywords
electrochemistry, solid state chemistry, catalysis, materials