Zero-Gap Bipolar Membrane Electrolyzer for Carbon Dioxide Reduction Using Acid-Tolerant Molecular Electrocatalysts.

The scaling-up of electrochemical CO 2 reduction requires circumventing the CO 2 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 H 2 evolution dominating. Here we show that using acid-tolerant Ni molecular electrocatalysts selective (>60%) CO 2 reduction can be achieved in a zero-gap BPM device using a pure water and CO 2 feed. At a higher current density (100 mA cm -2 ), CO selectivity decreases, but was still >30%, due to reversible product inhibition. This study demonstrates the importance of developing acid-tolerant catalysts for use in large-scale CO 2 reduction devices.