Highly Stable and Active RuO2/TiOx Electrode for Kolbe Electrolysis of Acetic Acid: An Investigation to Valorize the Pyroligneous Acid

Abstract

The efficient utilization of renewable sources based on the simultaneous production of energy fuels and value-added chemicals is an essential tactic of achieving the targets of the circular economy as well as carbon neutrality. As an abundant by-product during the pyrolysis of biomass, pyroligneous acid is rich in acetic acid (AA, CH3COOH) that has been proven to be converted into valuable chemicals and fuels (e.g. methane, ethane, propane). Herein, we fabricate a highly stable and effective ruthenium oxide electrocatalyst (RuO2/TiOx) via using available titanium sheet as the substrate, to highly selectively transform AA to ethane by electrochemical conversion with ~82 (±5)% selectivity. The obtained results demonstrate that RuO2/TiOx exhibits an efficient electrochemical performance at low temperatures (5℃), and can convert AA at various pH, current density, and different concentrations. The catalytic ability of RuO2/TiOx could be maintained even after 200 hours of Kolbe electrolysis. Moreover, we mimicked the complex chemical environment of the pyroligneous acid by adding diverse hydrocarbons (e.g., phenols, aldehydes) in acid solution to evaluate the stability of RuO2/TiOx. The electrolysis was also conducted in original pyroligneous acid solution, in which the RuO2/TiOx exhibits a considerable performance to convert AA to ethane. This work, based on the selective production of ethane from AA by a RuO2/TiOx electrode as an alternative to bulk metals as anodes for oxidative upgrading of carboxylic acids, making it promise to directly turn biomass residual into fuel thus improve the biomass utilization.