Electrooxidation of biomass sugar alcohols: effect of concentration and catalyst on products and activity

Harris, Lauren

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https://hdl.handle.net/2142/129261 Copy

Description

Title

Electrooxidation of biomass sugar alcohols: effect of concentration and catalyst on products and activity

Author(s)

Harris, Lauren

Issue Date

2025-04-29

Director of Research (if dissertation) or Advisor (if thesis)

Gewirth, Andrew A.

Doctoral Committee Chair(s)

Gewirth, Andrew A.

Committee Member(s)

• Kenis, Paul J. A.
• Rodríguez-López, Joaquín
• Murphy, Catherine J

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Electrocatalysis
• Electrooxidation
• Oxidation
• Glycerol
• Sorbitol
• Xylitol
• Gold
• Nickel
• Flow Cell
• HPLC
• Products
• Cyclic Voltammetry
• Alkaline

Abstract

Achieving the global target of net zero carbon emissions requires replacing current fossil fuel-heavy processes from the chemical industry with more sustainable operations. Electrocatalytic oxidation can sustainably convert renewable biomass materials to value-added products. For this technology to advance to a feasible industrial-scale application, it is essential to expand the arsenal of biomass conversion resources and to address factors that inhibit catalytic reactions. Glycerol electrooxidation (GEOR), sorbitol electrooxidation (SEOR), and xylitol electrooxidation (XEOR) are notable examples of sustainable conversion technologies that require further development and refinement. Chapter 1 details the necessary background information relevant to my work. Chapter 2 reports how changes in substrate concentration influence GEOR activity and products with Au catalyst materials. Increasing the glycerol concentration from 0.1 M to 1 M improves GEOR current density and delays the poisoning of the Au surface to higher potentials. This enhancement of catalytic activity indicates that the formation of poisoning oxide species is delayed in high glycerol concentrations. High performance liquid chromatography (HPLC) analysis was utilized to quantify electrooxidation products. Only high degree oxidation products were observed in low glycerol concentrations for GEOR, and with high glycerol concentrations, low degree oxidation products were additionally observed. High glycerol concentrations change the degree of oxidation of the products, which is hypothesized to arise due to competition between glycerol and Au surface for oxidation with hydroxide, inhibiting the degree of oxidation of both the reagent and the catalyst. Chapter 3 shows how changing substrate concentration has a different effect on GEOR activity for Ni catalysts compared to Au catalysts. Higher glycerol concentrations increased GEOR current on a Ni catalyst. HPLC analysis was used to quantify products. Nickel produces high selectivity for formic acid in both 0.1 M and 1 M glycerol but lower concentrations of formic acid in the higher glycerol concentration. The different effect of glycerol concentration with a Ni catalyst is due to an indirect oxidation mechanism, where the primary role of hydroxide is to regenerate the active nickel oxyhydroxide surface in Ni-catalyzed GEOR. Chapter 4 reports the differences in activity and product formation for SEOR and XEOR. Higher current density and lower peak potential were observed XEOR compared SEOR in 1 M KOH. Higher product concentrations were also observed with xylitol oxidation. The major product species differed between SEOR and XEOR, indicating a difference in the dominant mechanisms for each reaction. Increasing the KOH concentration in SEOR most drastically increased current density up to 2 M KOH, whereas in XEOR current density significantly improved up to 3 M KOH. These results further suggest different processes dominating these reactions as changes in hydroxide availability influenced the rate of SEOR differently than the rate of XEOR. Overall, this work shows that electrooxidation of xylitol is easier than the electrooxidation of sorbitol on Au, evidenced by higher catalytic activity and product concentrations.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129261

Copyright and License Information

Copyright 2025 Lauren Harris

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