Integration of biomass valorization and bicarbonate electrolysis for low-voltage production of value-added chemicals

Abstract

Bicarbonate electrolysis (BCE) utilizing captured CO₂ holds promise for the production of carbon-based chemicals and fuels but exhibits a low energy efficiency due to the high theoretical voltage required to drive the anodic oxygen evolution reaction (OER). Herein, BCE is coupled with the glycerol electrochemical oxidation reaction (GEOR) instead of the OER to decrease the operation voltage and obtain glycolic acid (GCA) and other valuable products. The mechanism of the GEOR, which is catalyzed by a gold nanoparticles embedded nickel oxides combined with multi-walled carbon nanotube (Au-NiO-CNT), is probed by examining the effects of electrolyte alkalinity, with further insights provided by in situ Raman and electrochemical impedance spectroscopic analyses. The incorporated carbon nanotubes increase the catalyst's conductivity, promoting the formation of α-Ni(OH)₂ on the NiO support during the GEOR and thus facilitating the establishment of Ni–OH moieties and their reaction with the primary hydroxyl groups of glycerol to increase GCA selectivity at low applied potentials. Compared with OER-coupled BCE, our process features an ∼890 mV lower operation voltage at 150 mA cm^–2, high CO (86.7 % in 3 M KHCO₃) and GCA (25.5 % in 0.1 M glycerol and 3 M KOH) selectivities, and a 16 % lower energy consumption at 150 mA cm^–2 (76.76 vs. 91.38 MWh per ton CO).