Dual Utilization of Waste Crude Glycerol for Sustainable Electrocatalyst Development and Energy Applications

Abstract

The transition to renewable energy is paramount for addressing the global energy crisis and mitigating the environmental impact of fossil fuels. Fuel cells, particularly hydrogen fuel cells, have emerged as a promising solution due to their high efficiency and ability to convert chemical energy directly into electricity. Hydrogen, produced through water electrolysis, offers a zero-carbon emission energy system but is constrained by the slow oxygen evolution reaction (OER) accompanying the hydrogen evolution reaction (HER). Simultaneously, the biodiesel industry generates substantial amounts of crude glycerol as a byproduct expected to increase significantly over the years. This unrefined surplus presents challenges in direct utilization, prompting research into its conversion into value-added products and energy sources. Replacing OER with the glycerol electrooxidation reaction (GEOR) in water splitting has enhanced energy efficiency and yielded valuable chemicals. However, the crude glycerol electrooxidation reaction (CGEOR) requires efficient, cost-effective catalysts, as the presence of impurities necessitates the utilization of expensive noble metals.

One of the aims of this work was to develop efficient metal-based electrocatalysts using transition metals, particularly copper (Cu), nickel (Ni), and iron (Fe), supported on sulfur doped carbon materials. These materials were derived from crude glycerol, as mentioned above. The study also explored using elemental sulfur, another waste product from the petroleum industry, to further enhance sulfur doping and metal sulfide synthesis. This work contributes to sustainable development goals (SDGs) by converting waste into valuable resources for energy applications. The developed catalysts exhibited strong performance for CGEOR. Ni and Cu catalysts outperformed their Fe-based counterparts. Sulfur doping significantly enhanced the catalytic activity by modifying the carbon structure and creating more active sites. Additionally, the use of persulfate as an oxidant was explored, and reaction conditions were optimized using response surface methodology (RSM). These findings underscore the potential of sulfur-doped, transition metal-based catalysts in improving the efficiency of CGEOR and advancing the commercialization of crude glycerol and hydrogen fuel cells.

Date of Award	8 Jan 2025
Original language	American English
Supervisor	Mirella El-Kadi (Supervisor)