Sponge-inspired catalyst design for durable acidic CO₂ reduction at low K⁺ concentration

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Acidic CO2 reduction (CO2RR) often requires K+ ions to suppress hydrogen evolution reaction (HER).
• High K+ concentrations can lead to salt precipitation, reducing electrolysis stability.
• Developing stable CO2RR catalysts for acidic media with low K+ is challenging.

Purpose of the Study:

• To design a durable electrocatalyst for efficient acidic CO2RR with low K+ concentrations.
• To overcome the limitations of salt precipitation and HER in acidic CO2RR.
• To achieve high Faradaic efficiency (FE) for formic acid production.

Main Methods:

• Fabrication of a three-dimensional interconnected porous cubic SnO2 electrocatalyst (SnO2 sponge).
• Utilizing the sponge's structure to confine OH- and consume protons, creating a local H+-depleted microenvironment.
• Experimental and theoretical studies to analyze catalyst performance and mechanism.

Main Results:

• The SnO2 sponge demonstrated sustained high OH- concentration, outperforming dispersed SnO2 nanoparticles.
• Achieved 94.5% FEHCOOH at 800 mA cm-2 at pH 1.82.
• Maintained 95.2% FEHCOOH at 400 mA cm-2 with only 0.075 M K+.
• Demonstrated continuous HCOOH production at 400 mA cm-2 with 97.7% FEHCOOH for over 390 hours.

Conclusions:

• The SnO2 sponge provides a promising strategy for durable and efficient acidic CO2RR.
• The sponge structure effectively manages proton influx and suppresses HER.
• This approach enables high-performance CO2RR in acidic media with low K+ concentrations, mitigating stability issues.