Highly Active and Stable Fe-N-C Catalyst for Oxygen Depolarized Cathode Applications.

Area of Science:

• Electrocatalysis
• Materials Science
• Energy Storage

Background:

• Anion immunity is crucial for oxygen reduction reaction (ORR) catalysts in applications like fuel cells and batteries.
• Platinum group metal (PGM) catalysts are expensive and susceptible to halide poisoning, limiting their use.
• Developing robust, cost-effective ORR catalysts is essential for advancing electrochemical technologies.

Purpose of the Study:

• To develop and evaluate a metal-organic framework (MOF)-derived Fe-N-C catalyst with enhanced anion immunity for ORR.
• To compare the performance of the Fe-N-C catalyst against state-of-the-art catalysts (RhₓSᵧ/C and Pt/C) in the presence of chloride ions.
• To demonstrate the practical viability of the Fe-N-C catalyst in hydrochloric acid electrolyzers for oxygen depolarized cathode (ODC) applications.

Main Methods:

• Synthesis of a MOF-derived Fe-N-C catalyst.
• Electrochemical characterization using rotating disk electrode (RDE) voltammetry in the presence of Cl⁻.
• Performance evaluation in a hydrochloric acid electrolyzer under simulated industrial conditions.

Main Results:

• The Fe-N-C catalyst exhibited a significantly improved half-wave potential (240 mV higher) compared to RhₓSᵧ/C in the presence of Cl⁻.
• The Fe-N-C catalyst demonstrated intrinsic immunity to Cl⁻ poisoning due to its Fe-N₄ active sites, unlike Pt/C.
• The Fe-N-C catalyst showed only marginal activity decrease in Cl⁻-containing electrolytes and superior performance in HCl electrolyzers.

Conclusions:

• MOF-derived Fe-N-C catalysts offer a cost-effective and highly stable alternative to PGM catalysts for ORR, especially in anion-rich environments.
• The intrinsic anion immunity of Fe-N-C catalysts overcomes the limitations of current state-of-the-art materials.
• These findings pave the way for advanced ODCs and other electrochemical devices requiring robust anion-tolerant ORR electrocatalysts.