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

Abstract

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 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 CO2 reduction devices.

A Bipolar Membrane-Integrated Electrochlorination Process for Highly Efficient Ammonium Removal in Mature Landfill Leachate: The Importance of ClO• Generation

“…Understanding fundamental mechanisms governing in situ generation of ClO • in the BPM-EC process is thus of great interest. Considering the facts that the BPM has the capability to dissociate water to H + and OH – − and the short distance between the membrane and the electrodes in the sandwich architecture, a reasonable hypothesis is that the localized alkaline pH in the vicinity of the PbO 2 anode has a profound influence on the formation of surface-bound HO • and ClO – , ultimately boosting the abundance of ClO • . To verify this hypothesis, the experimental evidence and theoretical analysis were complemented in elucidating the presence of ClO • .…”

“…With this in mind, we leverage the advantages of a bipolar membrane (BPM) that facilitates heterolytic water dissociation in the interface and induces continuous release of H + and OH – under a reverse bias condition − and accordingly propose an advanced BPM-integrated EC process for ammonium oxidation. Indeed, the unique feature of simultaneous H + and OH – production makes BPM attractive for a variety of environmental applications such as CO 2 capture and reduction, , ammonium recovery, removal of ionic contaminants, , and water softening .…”

CO2 Electroreduction in Water with a Heterogenized C-Substituted Nickel Cyclam Catalyst

“…While the system was less selective for CO 2 reduction, it also enjoyed reversible inactivation during electrolysis, mainly assigned to the formation of a nickel− carbonyl complex. 27 In conclusion, the present study provides a further step forward in the utilization of the molecular [Ni(cyclam)] 2+ complex as a catalyst for CO 2 electroreduction. By an appropriate and original functionalization of the ligand and an immobilization of the modified Ni complex, using the pyrene-CNT approach, an active and selective electrode has been prepared for CO formation in aqueous electrolytes.…”

“…During the course of this study, Siritanaratkul and collaborators reported a zero gap electrolyte-free electrolyzer using a bipolar membrane and a gas diffusion cathode, on which the Ni­(cyclam) complex was deposited. While the system was less selective for CO 2 reduction, it also enjoyed reversible inactivation during electrolysis, mainly assigned to the formation of a nickel–carbonyl complex …”

Heterogeneous Catalysis for CO2 Conversion into Chemicals and Fuels

“…Moreover, carbonate can transfer to the anode through the anion exchange membrane, thereby leading to significant carbon loss and a low CO 2 utilization efficiency [176,177]. Possible strategies for dealing with the carbonate issue are to use a cation exchange membrane, bipolar membrane, and solid electrolyte buffer layer [168, 169,[178][179][180]. This leads to an emerging direction, i.e., acid CO 2 electrolysis that has been demonstrated to suppress carbonate formation [181][182][183][184].…”