Electrochemical Valorization of Glycerol: Catalyst Development and Product Analysis

Abstract

The growing interest in biofuels as a substitute for traditional fossil fuels has raised environmental concerns about the extensive production of their by-products. Among these by-product, Glycerol, which accounts for over 10% of the total by-products, resulted in the production of nearly 4 billion liters in 2020. (1) Glycerol is a polyol organic molecule, viscous, and water-soluble liquid that if not disposed of properly, it can have detrimental impacts on the environment, including soil and water pollution, ultimately contributing to an increase in the carbon footprint. Hence, addressing this growing concern has prompted a surge of interest in developing sustainable and economically viable techniques for converting glycerol into value-added products.The electrochemical glycerol oxidation reaction (GOR) is a cost-effective and reliable method to enable circular economy practices by selectively producing highly value-added products such as dihydroxyacetone, glyceric acid, and glycolic acid from glycerol. However, it requires the development of active, selective, and stable electrocatalysts to steer GOR at low overpotentials. To date, catalysts based on platinum group metals (PGMs) have outperformed other GOR catalysts in terms of activity. However, in addition to the high cost of fabrication, these catalysts are susceptible to surface poisoning by glycerol intermediates, thereby impeding their commercialization due to the absence of long-term stability. (2) As a result, developing electrocatalysts based on earth-abundant element has become the focal point in GOR catalyst research.Here in, we highlight the latest advancements in the development of low-PGM content GOR catalysts. Our discussion focuses on the strategies for understanding how the type and concentration of PGM can influence selectivity, with a particular emphasis on the significance of GOR overpotentials. We also aim to highlight the inconsistencies in GOR product analyses, specifically regarding the use of H-NMR analysis, with an ultimate goal of advancing accurate GOR product quantification. References Nomanbhay S, Hussein R, Ong MY. Sustainability of biodiesel production in Malaysia by production of bio-oil from crude glycerol using microwave pyrolysis: a review. Green Chemistry Letters and Reviews. 2018;11(2):135-57. Li T, Harrington DA. An Overview of Glycerol Electrooxidation Mechanisms on Pt, Pd and Au. ChemSusChem. 2021;14(6):1472-95.