Proton Activity as a Promoter for the CO₂ Electroreduction to Formic Acid in Acidic Media

Area of Science:

• Electrochemistry
• Catalysis
• Green Chemistry

Background:

• Electrochemical carbon dioxide reduction reaction (CO₂RR) in acidic media faces challenges from the competing hydrogen evolution reaction (HER).
• Current strategies to suppress HER by lowering interfacial proton concentration can hinder the formation of proton-dependent products like formic acid (FA).

Purpose of the Study:

• To investigate the role of interfacial proton activity in the electrosynthesis of formic acid via CO₂RR in acidic electrolytes.
• To determine if high proton availability is essential for enhancing FA formation rates.

Main Methods:

• Electrochemical experiments in acidic electrolytes.
• Analysis of reaction kinetics and product selectivity.
• Investigation of interfacial proton concentration effects on CO₂RR and HER.

Main Results:

• Formic acid (FA) electrosynthesis is directly coupled to proton availability, with higher FA formation rates observed at increased proton activities.
• Contrary to prevailing strategies, suppressing the competing HER is not the primary driver for efficient FA synthesis.
• Maintaining high interfacial proton activity is crucial for enhancing FA production rates.

Conclusions:

• Efficient acidic CO₂RR to FA necessitates a paradigm shift, focusing on ensuring sufficient proton flux rather than solely suppressing HER.
• The design of catalysts and electrolytes should balance the kinetic competition between HER and CO₂RR while promoting proton availability for FA formation.