Engineering the catalyst interface enables high carbon efficiency in both cation-exchange and bipolar membrane electrolyzers

Abstract

Abstract The formation of (bi)carbonate in alkaline and neutral membrane-electrode assembly (MEA) electrolyzers poses an unsatisfactorily low upper-bound of CO2 single-pass utilization rate (SPU) and single-pass conversion rate (SPC) in CO2 electrolyzers. Electrolyzing CO2 in acidic MEA has been regarded as an effective strategy to prevent carbonate formation and CO2 loss but poses challenges due to the competitive hydrogen evolution reaction. Here we report the preparation of a hydrogel buffering layer on an Ag-coated gas diffusion electrode (GDE) to prevent the (bi)carbonate formation and break the theoretical limitation of 50% SPU in neutral-media electrolyzers. Through precise control of the porosity within the buffering layer, while maintaining superaerophobicity, we found that the hydrogel enhances the mass transfer of regenerated CO2 at the interface between the buffering layer and the cation-exchange layer. We demonstrate a high energy efficiency of 37% and high SPU of 77% at a total current density of 375 mA cm− 2 when performing acidic electrolysis using an optimal Ag/buffer GDE within a Nafion-based MEA cell.