Electrochemical CO2 reduction to methane with remarkably high Faradaic efficiency in the presence of a proton permeable membrane

Abstract

Nafion is a widely used fluoropolymer that is often mixed with electrocatalysts to facilitate proton transport. In contrast to these Nafion-catalyst composites, this work studies electrodes covered by Nafion overlayers for the CO₂ reduction reaction. By varying the thickness, substrates, and voltage, we perform a detailed study of the effect of Nafion overlayers on metal and carbon mesh electrodes for CO₂ reduction. Depending on the thickness of the Nafion membrane, CO₂ reduction occurs at either the polymer–electrolyte interface or electrode–polymer interface. A Nafion overlayer of 15 μm on a Cu electrode enables an extraordinarily high yield of CH₄ production (88% Faradaic efficiency) at a low overpotential (540 mV) via the stabilization of metal-bound CO intermediates. To the best of our knowledge, this yield is the highest for electrocatalytic CO₂ reduction to CH₄ production at room temperature reported.