Influence of Operating Conditions and Cell Design on the Performance of Low-Temperature Direct Ammonia Fuel Cells

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Direct ammonia fuel cells (DAFCs) offer a promising alternative energy conversion technology.
• Anion exchange membranes (AEMs) are crucial components in DAFC design.
• Limited data exists on optimizing DAFC performance through operating and design parameters.

Purpose of the Study:

• To investigate the impact of operating conditions and cell design on DAFC performance.
• To identify key parameters influencing electrochemical kinetics and membrane conductivity.
• To guide the development of efficient and high-performing DAFCs.

Main Methods:

• Systematic evaluation of temperature, reactant concentrations (ammonia, KOH), flow rates, and air humidity in a 5 cm² DAFC.
• Testing of various anion exchange membranes (AEMs) including FAS-30 and Sustainion X37-50.
• Assessment of anode catalyst performance (Pt, PtIr/C) and loading effects.
• Measurement of peak power density under optimized conditions.

Main Results:

• Temperature is the most critical operating parameter, enhancing kinetics and conductivity.
• Optimal performance achieved at 5 M NH₄OH and 2 M KOH concentrations.
• FAS-30 membrane showed superior performance; Sustainion X37-50 was limited by ammonia permeability.
• PtIr/C catalysts outperformed Pt-based catalysts, with increased loading improving activity.
• A peak power density of 12.2 mW·cm⁻² was achieved at 80 °C using PtIr/C electrodes and FAA-3-PK-130 membrane.

Conclusions:

• DAFC performance is highly sensitive to temperature and reactant concentrations.
• Membrane selection and catalyst choice are critical for maximizing power output.
• This research provides essential data for the advancement of low-temperature DAFC technology.