Water Oxidation Electrocatalysis in Acidic Media with Fe-Containing POMs/Carbon Composites

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Iron-based catalysts are cost-effective but less active for water oxidation than cobalt or nickel oxides.
• Polyoxometalates (POMs) offer tunable catalytic properties through controlled structures.
• Iron-POMs (Fe-POMs) generally exhibit lower oxygen evolution reaction (OER) activity than cobalt-POMs in neutral/basic media.

Purpose of the Study:

• To investigate the electrochemical behavior of a specific iron-polyoxometalate, [Fe4(H2O)2(PW9O34)2]6- (Fe-POM), in highly acidic media.
• To compare the performance of Fe-POMs with cobalt-based analogues for electrochemical reactions.
• To explore the potential of Fe-POMs in catalytic applications beyond traditional OER.

Main Methods:

• Electrochemical measurements using carbon paste electrodes modified with Fe-POMs.
• Comparative analysis with cobalt-based analogues.
• Product analysis to determine reaction selectivity.

Main Results:

• Fe-POMs demonstrated unexpectedly low onset potentials and high current densities in acidic oxidative conditions, outperforming cobalt analogues.
• The Fe-POM catalyst exhibited excellent stability in pH < 1 environments.
• While O2 was produced, CO2 was the dominant product, indicating poor OER selectivity but unique carbon oxidation capability.

Conclusions:

• Fe-POMs are modest OER catalysts in acidic media.
• Fe-POMs display a unique ability to electrochemically oxidize amorphous carbon in acidic conditions, a property not observed in iron oxides or simple iron salts.
• This unique carbon oxidation performance suggests novel applications for Fe-POMs in specific electrochemical processes.