Efficient anion exchange membrane direct ammonia fuel cells anode catalysts: PtIr nanocubes on carbon and CeO2 composites supports

Abstract

Direct ammonia fuel cells (DAFCs) have emerged as promising alternatives to hydrogen fuel cells for transportation applications, owing to ammonia's low source-to-tank energy cost and its inherent advantages in storage and distribution. However, current DAFC technologies are significantly limited by the kinetically sluggish ammonia oxidation reaction (AOR) at the anode. In this work, the PtIr nanocubes supported on carbon and CeO_2-δ composite supports have been successfully synthesized. The catalyst demonstrates excellent AOR activity in alkaline media. The structural and compositional properties are characterized using high-angle annular dark-field scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The rotating disk electrode (RDE) measurements reveal a lower activation energy of AOR for the catalyst compared to commercial PtIr/C (19.6 vs. 22.0 kJ mol⁻¹). The DAFC employing Pt₅Ir₁/CeO_2-δ-NCs as the anode catalyst reaches a peak power density of 335 mW cm⁻². All the results manifest that both support material and particle morphology play a critical role in improving the activity of anode catalyst for DAFCs.