Facet dependence forCeO2as a potential Ammonia oxidation electrocatalyst studied by DFT

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Transitioning to a carbon-free energy system necessitates scalable and sustainable energy carriers.
• Ammonia is a viable energy carrier due to its energy density and existing infrastructure.
• Direct ammonia fuel cells require efficient, cost-effective, and stable anode catalysts for the ammonia oxidation reaction (AOR).

Purpose of the Study:

• To establish a comprehensive mechanistic understanding of the ammonia oxidation reaction (AOR) on pristine ceria surfaces.
• To investigate the activity of different ceria crystal facets ((111), (110), and (100)) for AOR using density functional theory.

Main Methods:

• Density functional theory (DFT) calculations were employed to study the AOR mechanism on ceria surfaces.
• Analysis of reaction pathways and determination of the potential-determining step (PDS) for each mechanism (Gerischer-Mauerer and Oswin-Salomon).

Main Results:

• Ceria (100) exhibited the highest activity for AOR, with the lowest limiting potential of 1.16 V via the Gerischer-Mauerer mechanism.
• Ceria (111) and (110) surfaces showed lower activity with higher limiting potentials (1.38 V and 1.33 V, respectively).
• The (100) facet's AOR activity surpasses that of NiO, suggesting its potential as an improved oxide catalyst.

Conclusions:

• Ceria (100) is identified as a highly promising anode catalyst surface for direct ammonia fuel cells.
• The findings provide crucial mechanistic insights into AOR on ceria, guiding future catalyst design.
• Introducing vacancies into ceria may further enhance its catalytic performance for AOR.