Glycerol, a major byproduct of biodiesel production, is one of the top twelve biomass-derived platform chemicals identified by the U.S. Department of Energy and can be transformed into various value-added oxygenated commodity chemicals upon oxidation. Among the oxidation products of glycerol, formic acid is of particular interest to the hydrogen economy as it is an attractive choice of liquid hydrogen carrier with high volumetric energy capacity and can be used as the fuel for indirect hydrogen fuel cells. In this context, electrochemical, rather than chemical, oxidation of glycerol offers unique opportunities towards more affordable and scalable production of value-added oxygenated commodity chemicals under milder conditions, yet nearly all the established electrocatalysts for glycerol oxidation are based on noble metals. Here we systematically studied cobalt-based spinel oxides (MCo<sub>2</sub>O<sub>4</sub>, M = Mn, Fe, Co, Ni, Cu, Zn) as new and active earth-abundant electrocatalysts for glycerol oxidation in alkaline solutions, and found that their intrinsic catalytic activities follow an interesting volcano trend. Bulk electrolysis using the most active catalyst followed by high performance liquid chromatography (HPLC) analysis show selective glycerol oxidation to formic acid at 1.26 V vs. RHE in 1 M KOH with excellent overall Faradaic efficiency (98.1%) and formic acid selectivity (93.6%) under high glycerol conversion (96.4%). This work will guide future search for more active and selective earth-abundant electrocatalysts for glycerol oxidation to formic acid and other value-added chemicals.

Selective electrocatalytic oxidation of glycerol to formic acid by Earth-abundant spinel oxides

2019 Fall National Meeting

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