Enhancing Carbon Monoxide Tolerance in Low-Temperature PEM Fuel Cells through Carbon Nitride Surface Modification.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Low-temperature proton exchange membrane fuel cells (PEMFCs) demand high-purity hydrogen due to extreme sensitivity to carbon monoxide (CO) poisoning.
• Using cost-effective reformed hydrogen sources is challenging due to CO contamination.
• Platinum-Ruthenium (PtRu) catalysts are susceptible to CO inhibition.

Purpose of the Study:

• To develop a surface modification strategy to mitigate CO poisoning in PEMFCs.
• To enhance the tolerance of PtRu/C catalysts to CO contamination.
• To enable the use of less pure hydrogen feedstocks for fuel cell applications.

Main Methods:

• Application of a 0.5-0.91 nm amorphous carbon nitride layer onto PtRu/C substrates.
• Electrochemical measurements, including rotating disk electrode (RDE) experiments.
• Kinetic studies of CO adsorption on modified and conventional catalysts.

Main Results:

• The amorphous carbon nitride layer selectively facilitates hydrogen transport while inhibiting CO diffusion.
• CO adsorption rate was significantly reduced by approximately 50% compared to conventional catalysts.
• Modified catalysts maintained stable operation for over 20 hours with 1000 ppm CO/H2 and supported stable discharge at 1 A cm-2 in PEMFCs with up to 10 ppm CO.

Conclusions:

• Surface modification with amorphous carbon nitride effectively protects PtRu/C catalysts from CO poisoning.
• The modified catalyst demonstrates unprecedented CO tolerance, exceeding the standard by a significant margin.
• This strategy offers a viable pathway for utilizing reformed hydrogen in low-temperature PEMFCs, improving practicality and cost-efficiency.