Enhanced Ethylene Selectivity during CO2 Reduction Using Polymers with Intrinsic Microporosity at Copper Gas Diffusion Electrodes

Abstract

CO2 reduction is a rapidly expanding area, and a key part of the global mission to reduce carbon emissions and reduce our impact on our environment. The CO2 reduction reaction (CO2RR) presents a synthetic route to a number of industrially relevant materials, such as methane, ethylene, formate and CO.1 This provides a two-fold environmental benefit; CO2 can be captured from industrial processes before being released into the environment and produce a material usually sourced from fossil fuels.Much work has been dedicated to CO2RR at copper electrodes thanks to its ability to produce C2 species such ethylene with reasonable selectivity. However, the currently attainable selectivity is not sufficient for practical applications. The outflow contains mixtures of CO2RR products, along with a substantial amount of H2 from water reduction at the same potentials.This work improves the selectivity of copper gas diffusion electrodes (GDEs) towards ethylene using Polymers with Intrinsic Microporosity (PIMs). PIMs are easily drop-cast onto the GDE, forming a microporous layer at the catalyst – electrolyte interface. The microporous structure stores gases in a triphasic interface at the electrode surface,2 which has previously been shown to improve catalyst activity towards oxygen reduction.3 We show that the introduction of a PIMs triphasic interface to copper GDEs improves the CO2RR towards ethylene, evidenced by an increased Faradaic efficiency, improved GDE stability and shift in the reduction wave to lower overpotentials.4 The impact of the PIMs is significantly dependent on the loading, with thin layers enhancing performance, but thicker layers having a surprisingly detrimental effect. This work is a proof of concept, showing the potential of triphasic interfaces for enhancing the activity of GDEs for CO2RR towards ethylene production.