Date on Master's Thesis/Doctoral Dissertation

12-2021

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Chemical Engineering

Degree Program

Chemical Engineering, MS

Committee Chair

Gupta, Gautam

Committee Member

Bhatia, Bikram

Committee Member

Ghorbanian, Mahyar

Committee Member

Jasinski, Jacek

Author's Keywords

HER; TMD; Molybdenum Disulfide'; Solvent Engineering

Abstract

Energy is at an exponentially growing demand, and to keep up with these demands new technologies for renewable energy have received increased attention. Hydrogen plays a vital role in water electrolysis and fuel cells, as the hydrogen evolution reaction (HER) is the main step water splitting process. Most of the current electrocatalysts for HER are dominated by platinum and other precious metals due to their low over-potential and small Tafel slope, however, they are extremely costly. For this reason, cost-effective non-precious metal catalysts must be developed. Transition metal dichalcogenides, such as molybdenum disulfide (MoS2), are abundant and have recently shown promising results for HER. The challenge facing the commercialization of MoS2 is the synthesis process. Hydrothermal synthesis using a precursor, ammonium tetrathiomolybdate, with hydrazine as a solvent is a common route for obtaining MoS2. Despite successful obtainment of MoS2, hydrazine is not favored due to high combustibility and toxicity. For this reason, we have investigated the electrochemical performance of MoS2 obtained by using different solvents. Electrochemical studies reveal best onset potentials of -116 mV for ethylene glycol followed by - 126 mV and -129 mV for water and diethyl glycol solvents, respectively. MoS2 synthesized in 1- methyl pyrilidone exhibit best Tafel slope of 51 mV/dec, followed by ethylene glycol and water at 54.9 mV/dec and 55.2 mV/dec, respectively. In comparison, hydrazine shows Tafel slope of 41 mV/dec and onset potential of -100 mV. Scanning electron microscopy reveals MoS2 catalysts synthesized in dimethylformamide and ethylene glycol produce more active edge sites allowing for better hydrogen proton adsorption. This study’s results found Ethylene Glycol to show most promising to replace hydrazine as a current solvent for synthesis of MoS2 catalysts with a possible link to higher solvent densities improving catalysts performance.

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