A Scalable, Biopolymer-Based Microenvironment for Electrochemical CO2 Conversion to Multicarbon Products with Current Densities Over 2 A/cm2

Abstract

<p>The electrochemical CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) offers a sustainable approach for converting CO<sub>2</sub> into valuable fuels and chemicals. CO<sub>2</sub>RR relies on copper (Cu) catalysts to produce desirable multicarbon (C<sub>2+</sub>) products, but C<sub>2+</sub> yields rely heavily on the surrounding microenvironment. Moreover, controlling the microenvironment to achieve high C<sub>2+</sub> yields at industrially-relevant current densities remains a persistent challenge. To address this challenge, we show that biopolymer coatings on the Cu electrodes can tune the microenvironment, enabling a new strategy to achieve high yields of C<sub>2+</sub> products at ultra-high current densities. This approach achieves remarkable C<sub>2+</sub> Faradaic efficiencies (FE<sub>C2+</sub>) of 90±1.7% at 1.6 A cm<sup>-2</sup> and FE<sub>C2+</sub>=83±3.2% at 2.2 A cm<sup>-2</sup> with a formation rate of 5925.9 μmol h<sup>−1 </sup>cm<sup>−2</sup>. Furthermore, these biopolymers can even fully substitute traditional ionomers and binders, such as Nafion, within the cathode. Our findings challenge previous assumptions about the non-viability of hydrophilic materials for CO<sub>2</sub>RR and provide critical new insights into microenvironment design to enhance C-C coupling. Several complementary investigations reveal that biopolymer coatings increase local CO<sub>2</sub>/CO concentration, lower local water activity, and provide suitable ion conductivity and local pH. We anticipate that these molecular-level insights represent a paradigm shift in catalyst design to unlock new approaches to optimize the microenvironment for CO<sub>2</sub>RR to enable high rates of C-C coupling without the typical unwanted increase in hydrogen evolution. These abundant biopolymer coatings are environmentally benign, solution-processable, and highly accessible, which is expected to provide researchers with a facile route towards high-performance CO<sub>2</sub>RR at both laboratory and industrial scales.</p&gt