(123f) Electrochemical Biomass Upgrading: Degradation of Glucose to Lactic Acid on a Copper (II) Electrode

Biomass upgrading, the conversion of biomass waste into value-added products, provides a method to reduce global dependency on nonrenewable resources. Among value-added products of biomass upgrading, lactic acid has garnered much attention due to its large market – 1.2 billion kg in 2016 (Grand View Research). The majority of studies on lactic acid production from biomass have employed thermally-driven systems with catalysts aimed at controlling glucose oxidation products. Significant progress has been made in thermocatalytic studies for selective lactic acid production, but the systems still suffer from high temperatures (120-400°C), high pressures (up to 50 MPa), high catalyst loadings, or requiring anaerobic conditions. In search of a green process, our group evaluated lactic acid production from glucose in an electrochemical system, and preliminary optimization of this reaction led to a reaction yield of 23.3±1.2% and a selectivity of 31.1±1.9% - yield and selectivity appear to be limited by slow kinetics and over-oxidation of glucose. Further improvement of the reaction requires mechanistic understanding; however, most studies of glucose oxidation on a CuO electrode are performed by the glucose sensor field, where studies are focused on improving response linearity and detection limits and are not inherently concerned with mechanisms. This talk will first present results from electrochemical studies on glucose oxidation, in which we suggest a correction in nomenclature on the third oxidation state of copper, along with the preliminary optimization attempts. We will then discuss our studies designed to understand the mechanism of glucose oxidation at a CuO electrode, mainly consisting of in situ spectroelectrochemistry supported by density functional theory calculations. These combined techniques showed evidence for changes to CuO surface chemistry as well as specific reaction intermediate and by-products.