Electro-oxidative valorization of biomass: design strategies for selective and stable catalysis
Adam Holewinski, University of Colorado (Principal Investigator)
Michael Janik, Penn State University (Co-Investigator)
Electrocatalytic reactions are a possible means to process distributed feedstocks, such as biomass derivatives, for synthesis of fuels and commodity chemicals. This project aims to develop a fundamental understanding of the factors that dictate activity and selectivity during electrochemical partial oxidation of multi-carbon organic molecules derived from biomass. Selective conversions of alcohols to aldehydes, and aldehydes to carboxylic acids will be considered. More specifically we will develop principles for the rational design of catalysts that promote acidic partial oxidations of furfural and 5-hydoxymethyfurfural. These represent biomass-derived platform chemicals for an array of value-added products and serve as proxies for oxidation of alcohol and aldehyde functional groups in general. The basic goal is to understand the requirements for controlling the oxidative progression of the oxygenate functional groups (aldehyde to acid, alcohol to aldehyde vs. acid) while also avoiding undesired pathways that lead to poisoning species—for example, C-C cleavage steps that lead to adsorbed CO or overoxidation of acids to adsorbed carboxylates (R-COO).
Work will center around investigation of three possible mechanisms that can break scaling relations between the adsorption energies of key intermediates and rate determining transition states. These include (i) formation of alloy catalysts that violate common correlations between adsorption energies and the d-electron energy center of the constituent metals; (ii) formation of catalyst heterostructures that interface metals and metal-oxides that obey different scaling relations; and (iii) modification of electrolyte composition with anions that can adsorb to catalysts and selectively influence particular adsorbate interactions. The investigations will involve well- defined material synthesis, comparative kinetics, and in-situ and operando spectroscopies, supported by quantum chemical simulations. Applying these tools to a systematic sampling of materials and operating conditions, mechanistic hypotheses will be tested, and tunable materials design strategies as well as reaction engineering approaches will be developed to circumvent apparent limitations. The ultimate goal is to enable design of viable catalytic systems for a wide range of organic electro-oxidation reactions.