Hydrophilic Single-Atom Interface Empowered Pure Formic Acid Fuel Cells.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Single-atom catalysts (SACs) offer high activity for direct formic acid fuel cells (DFAFCs).
• Current SACs struggle with concentrated formic acid, limiting their application.
• Understanding the reaction mechanism in concentrated formic acid is crucial.

Purpose of the Study:

• To investigate the role of interfacial hydrophilicity in SACs for DFAFCs.
• To enable stable DFAFC operation using highly concentrated formic acid.
• To elucidate the reaction mechanism of formic acid oxidation on SACs.

Main Methods:

• Incorporation of transition metal single atoms (Co, Fe, Ni, Ru) into Ir/NC catalysts.
• Interface engineering to enhance hydrophilicity.
• Molecular dynamics simulations and experimental validation.
• In situ spectroscopy and isotope kinetic analyses.

Main Results:

• Engineered hydrophilic interfaces on SACs.
• Stable DFAFC operation achieved with pure formic acid (>99%).
• Optimized IrCo/NC anode showed 342x higher mass activity than nanoparticle catalysts.
• Achieved a peak power density of 107.7 mW cm⁻².
• Revealed CO as a reactive intermediate and identified water involvement in the rate-determining step.

Conclusions:

• Interfacial hydrophilicity is critical for high-performance DFAFCs.
• Hydrophilic interface engineering enables stable operation with pure formic acid.
• A new reaction mechanism involving CO as an intermediate and water involvement was proposed.