Designing Catalyst-Ionomer Formulations for High Energy Efficiency CO₂ Electrolysis

<br/>Electrochemical CO₂ reduction (eCO2R) is an attractive route to mitigate the rise in the global CO₂ concentration while producing value-added chemicals. Ethylene (C₂H₄) is one such product of eCO2R which is an essential industrial precursor with a prominent global market of $230 billion. The large-scale implementation of C₂H₄-selective CO₂ electrolyzers is still challenge due to its low energy efficiency. In this work, we design various formulations ionomers with Cu catalyst to address this challenge. Catalyst layer ionomers serve two purposes within the catalyst layer- to act as a mechanical binder to support catalysts on a gas diffusion layer, and to control the local chemical environment. Specifically, the ionomer can control the local pH, water concentration at the catalyst, and CO₂ concentration that dictates the overall cell voltage, and catalyst selectivity. Herein, we show that by incorporating various ionomers into our catalyst layer and tuning the charged headgroup of the ionomers, we can simultaneously decrease the overall cell of a membrane electrode assembly (MEA) CO₂ electrolyzer voltage to &lt;2.7 V for a Cu based system while controlling the liquid product composition by tuning the ionomer: catalyst (IC) ratio. Understanding the role of ionomers in such systems is crucial to gain insight into developing high energy efficiency CO₂ electrolyzers.<br/> <br/>This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.