Selective Kolbe Electrolysis of Medium Size Carboxylic Acid to Alkane Dimer in an Aqueous Environment with an Amorphous Ruo2 Catalyst

The catalytic transformation of biomass-derived volatile carboxylic acids in an aqueous environment is crucial to developing a sustainable biorefinery. To date, Kolbe electrolysis remains the only effective means to convert energy-diluted carboxylic acids (carboxylate) to alkane for biofuel production. This paper reports the use of a structurally disordered amorphous RuO2 (a-RuO2) that is synthesized facilely in a hydrothermal method. The a-RuO2 is highly effective towards electrocatalytic oxidative decarboxylation of hexanoic acid and was able to produce the Kolbe product, decane, with a selectively 5.4 and 7.8-times greater than that of commercial RuO2 and Pt/C, respectively. A systematic study of the reaction temperature, current density, and electrolyte concentration revealed the enhanced Kolbe product yield was attributable to the more efficient oxidation of the carboxylate anions for the alkane dimer formation. Our work highlights a new electrocatalyst that is catalytically comparable to Pt, but only at a fraction of the cost.