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

Area of Science:

• Electrochemistry
• Catalysis
• Carbon Capture and Utilization

Background:

• Scaling electrochemical CO2 reduction is hindered by carbonate formation in alkaline media.
• Zero-gap cells with bipolar membranes (BPMs) offer a solution but face challenges with catalyst stability in acidic environments.
• Hydrogen evolution often dominates over CO2 reduction in BPM devices due to catalyst degradation.

Purpose of the Study:

• To develop and evaluate acid-tolerant electrocatalysts for selective CO2 reduction in a zero-gap BPM device.
• To investigate the performance of Ni molecular electrocatalysts under alkaline conditions within a BPM setup.
• To demonstrate efficient CO2 conversion using a pure water and CO2 feed.

Main Methods:

• Utilized zero-gap cell configurations with reverse-bias bipolar membranes (BPMs).
• Employed acid-tolerant Ni molecular electrocatalysts for CO2 reduction.
• Operated the device with a pure water and CO2 feed at various current densities.
• Analyzed product selectivity and identified performance limitations.

Main Results:

• Achieved selective CO2 reduction (>60%) using acid-tolerant Ni molecular electrocatalysts in a zero-gap BPM device.
• Demonstrated successful CO2 conversion with a pure water and CO2 feed, circumventing carbonate loss.
• Observed decreased CO selectivity (>30%) at higher current densities (100 mA cm-2) due to reversible product inhibition.
• Confirmed the viability of Ni molecular catalysts in acidic environments within BPMs.

Conclusions:

• Acid-tolerant catalysts are crucial for efficient electrochemical CO2 reduction in zero-gap BPM devices.
• Ni molecular electrocatalysts show promise for selective CO2 conversion, overcoming challenges of carbonate formation and catalyst degradation.
• Further research into mitigating product inhibition is needed for optimizing performance at higher current densities.