Amorphous RuO₂ Catalyst for Medium Size Carboxylic Acid to Alkane Dimer Selective Kolbe Electrolysis in an Aqueous Environment**

Abstract

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 arguably the most effective means to convert energy‐diluted aliphatic 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 is able to produce the Kolbe product, decane, with a yield 5.4 times greater than that of commercial RuO2. A systematic study of the reaction temperature, current intensity, and electrolyte concentration reveals the enhanced Kolbe product yield is attributable to the more efficient oxidation of the carboxylate anions for the alkane dimer formation. Our work showcases a new design idea for establishing an efficient electrocatalysts for decarboxylation coupling reaction, providing a new electrocatalyst candidate for Kolbe electrolysis.

Organic Chemicals from Wood: Selective Depolymerization and Dearomatization of Lignin via Aqueous Electrocatalysis

“…The 1 H‐ 1 H COSY NMR spectra in Figure 3 clearly show that 4‐hydroxyvalerate and levulinate are present as products in − 175 mA/20 h . No methanol was detected in these experiments, indicating that the depolymerization does not follow the Kolbe pathways [20,21] in our catalyst system.…”

Mechanistic investigation of a Ni-catalyzed electrochemical reductive cleavage of the α-O-4 bond in the lignin model compound benzyl phenyl ether

“…For instance, the phenomenon is commonly observed in Kolbe electrolysis where the dimerization of alkyl radicals benefits from a high concentration of the starting materials. 55–57 For the second experiment, the radical inhibitor butylated hydroxytoluene was added into the system using Ni-CP electrode at the optimized conditions, the reaction still proceeded smoothly with up to 90% conversion. Based on these observations, it is unlikely that the reaction system proceeded via a free radical mechanism.…”

Energy‐Saving Electrochemical Hydrogen Production Coupled with Biomass‐Derived Isobutanol Upgrading

“…Moreover, the current density declined rapidly during potentiostatic electrolysis in 1 M NaOH with 0.1 M IBAc at 1.50 V vs. RHE (Figure S14b), wherein the weak current can be attributed to the possible Kolbe oxidation of IBAc. [51] Consequently, it can be inferred that the oxidative CÀ C cleavage occurs prior to the formation of IBAc.…”