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

[Image: see text] 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

Selective conversion of CO2 to CO using earth abundant tin modified copper gas diffusion electrodes

Earth-abundant copper-tin (CuSn) electrocatalysts are potential candidates for cost-effective and sustainable production of CO from electrochemical carbon dioxide reduction (eCO2R). However, the requirement of high-overpotential for obtaining reasonable current, low Faradaic efficiencies (FE) and low intrinsic catalytic activities require the optimisation of the CuSn nanoarchitecture for the further advancement in the field. In the current work, we have optimised Sn loading on Cu gas diffusion electrodes (GDEs) by electrochemical spontaneous precipitation. Samples with various Sn loadings were tested in a three-chamber GDE reactor to evaluate their CO2 reduction performances. The best performance of 92% CO Faradaic efficiency at a cathodic current density of 120 mA cm−2 was obtained from the 20 min Sn deposited Cu2O sample operated at −1.13 V vs. RHE. The electrocatalyst had ∼13% surface coverage of Sn on Cu GDE surface, and had Sn in oxide form and copper in metallic form. The catalyst also showed stable performance and was operable for >3 h under chronoamperometric conditions. The surface of the GDE reduces from Cu2O to Cu during eCO2R and goes further reconstruction during the eCO2R. This study demonstrates the potential of Cu–Sn for selective CO production at high current densities

Pulsed Electrolysis with a Nickel Molecular Catalyst Improves Selectivity for Carbon Dioxide Reduction.

Pulsed electrolysis can significantly improve carbon dioxide reduction on metal electrodes, but the effect of short (millisecond to seconds) voltage steps on molecular electrocatalysts is largely unstudied. In this work, we investigate the effect pulse electrolysis has on the selectivity and stability of the homogeneous electrocatalyst [Ni(cyclam)]2+ at a carbon electrode. By tuning the potential and pulse duration, we achieve a significant improvement in CO Faradaic efficiencies (85%) after 3 h, double that of the system under potentiostatic conditions. The improved activity is due to in situ catalyst regeneration from an intermediate that occurs as part of the catalyst's degradation pathway. This study demonstrates the wider opportunity to apply pulsed electrolysis to molecular electrocatalysts to control activity and improve selectivity

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