A scalable, biopolymer-based microenvironment for electrochemical CO2 conversion to multicarbon products with current densities over 2 A cm−2

Abstract

The electrochemical CO2 reduction reaction (CO2RR) relies heavily on the surrounding microenvironment to promote formation of desirable multicarbon (C2+) products. However, microenvironment control to achieve high C2+ yields at industrially relevant current densities remains a crucial challenge. We report that chitosan, cellulose and chitin biopolymer coatings on CO2RR electrocatalysts enhance the microenvironment by increasing local CO2/CO concentration, reducing local water activity and providing suitable ion conductivity and local pH. This facile approach achieves C2+ Faradaic efficiencies of 90 ± 1.7% at 1.6 A cm−2 and C2+ Faradaic efficiency = 83 ± 3.2% at 2.2 A cm−2 with a formation rate of 5,926 μmol h−1 cm−2. Importantly, within the cathode, these ion-conductive hydrophilic biopolymers can fully substitute traditional hydrophobic ionomers/binders, such as Nafion, challenging previous assumptions about the non-viability of hydrophilic materials for selective CO2RR due to excess interfacial H2O. These findings unveil key insights into microenvironment design to enhance C–C coupling through a simple method.