Zero-Gap Bipolar Membrane Electrolyzer for Carbon DioxideReduction Using Acid-Tolerant Molecular Electrocatalysts

The scaling-up of electrochemical CO2reduction requires circumventing the CO2loss as carbonates under alkalineconditions. Zero-gap cell configurations with a reverse-bias bipolar membrane (BPM) represent a possible solution, but the catalystlayer in direct contact with the acidic environment of a BPM usually leads to H2evolution dominating. Here we show that usingacid-tolerant Ni molecular electrocatalysts selective (>60%) CO2reduction can be achieved in a zero-gap BPM device using a purewater and CO2feed. At a higher current density (100 mA cm-2), CO selectivity decreases, but was still >30%, due to reversibleproduct inhibition. This study demonstrates the importance of developing acid-tolerant catalysts for use in large-scale CO2reductiondevices.