Use of Chitosan as Copper Binder in the Continuous Electrochemical Reduction of CO 2 to Ethylene in Alkaline Medium.

This work explores the potential of novel renewable materials in electrode fabrication for the electrochemical conversion of carbon dioxide (CO 2 ) to ethylene in alkaline media. In this regard, the use of the renewable chitosan (CS) biopolymer as ion-exchange binder of the copper (Cu) electrocatalyst nanoparticles (NPs) is compared with commercial anion-exchange binders Sustainion and Fumion on the fabrication of gas diffusion electrodes (GDEs) for the electrochemical reduction of carbon dioxide (CO 2 R) in an alkaline medium. They were tested in membrane electrode assemblies (MEAs), where selectivity to ethylene (C 2 H 4 ) increased when using the Cu:CS GDE compared to the Cu:Sustainion and Cu:Fumion GDEs, respectively, with a Faradaic efficiency (FE) of 93.7% at 10 mA cm -2 and a cell potential of -1.9 V, with a C 2 H 4 production rate of 420 µmol m -2 s -1 for the Cu:CS GDE. Upon increasing current density to 90 mA cm -2 , however, the production rate of the Cu:CS GDE rose to 509 µmol/m 2 s but the FE dropped to 69% due to increasing hydrogen evolution reaction (HER) competition. The control of mass transport limitations by tuning up the membrane overlayer properties in membrane coated electrodes (MCE) prepared by coating a CS-based membrane over the Cu:CS GDE enhanced its selectivity to C 2 H 4 to a FE of 98% at 10 mA cm -2 with negligible competing HER. The concentration of carbon monoxide was below the experimental detection limit irrespective of the current density, with no CO 2 crossover to the anodic compartment. This study suggests there may be potential in sustainable alernatives to fossil-based or perfluorinated materials in ion-exchange membrane and electrode fabrication, which constitute a step forward towards decarbonization in the circular economy perspective.