Zero-gap bipolar membrane electrolyzer for carbon dioxide reduction using acid-tolerant molecular electrocatalysts

The scaling-up of electrochemical CO2 reduction requires circumventing the CO2 loss as carbonates under alkaline conditions. Zero-gap cell configurations with a reverse-bias bipolar membrane (BPM) represent a possible solution, but the catalyst layer in direct contact with the acidic environment of a BPM usually leads to H2 evolution dominating. Here we show that using acid-tolerant Ni molecular electrocatalysts selective (> 60%) CO2 reduction can be achieved in a zero-gap BPM device using a pure water and CO2 feed. At higher current density (100 mA cm-2), CO selectivity de-creases, but was still >30%, due to reversible product inhibition. This study demonstrates the importance of developing acid-tolerant catalysts for use in large-scale CO2 reduction devices.