Enhanced electrocatalytic CO₂ reduction via field-induced reagent concentration

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical reduction of carbon dioxide (CO₂) to carbon monoxide (CO) is crucial for synthesizing fuels and feedstocks using renewable energy.
• Slow reaction kinetics due to low CO₂ concentration around catalysts limit efficiency.
• Alkali metal cations and high potentials can enhance CO₂ concentration but have drawbacks like limited solubility and increased hydrogen evolution.

Purpose of the Study:

• To investigate nanostructured electrodes for enhancing CO₂ concentration at low overpotentials.
• To demonstrate a method for improving CO₂ reduction reaction (CO₂RR) kinetics and selectivity.
• To explore the wider applicability of field-induced reagent concentration in electrocatalysis.

Main Methods:

• Utilized nanostructured electrodes, specifically metallic nanometre-sized tips (e.g., gold nanoneedles).
• Employed simulations to quantify electric field enhancement at nanostructure tips.
• Conducted electrochemical measurements to assess CO₂ reduction performance and Faradaic efficiency.

Main Results:

• Nanostructured electrodes generated local high electric fields, concentrating electrolyte cations and CO₂.
• Gold nanoneedles achieved a geometric current density for CO of 22 mA/cm² at -0.35 V, surpassing existing catalysts by an order of magnitude.
• Palladium nanoneedles yielded formate with >90% Faradaic efficiency and a geometric current density of 10 mA/cm² at -0.2 V.

Conclusions:

• Field-induced reagent concentration using nanostructured electrodes is an effective strategy to overcome CO₂RR kinetic limitations.
• This approach enables efficient CO₂ conversion to CO and formate at low overpotentials.
• The concept of field-induced concentration is broadly applicable to various electrocatalytic reactions.