Highly dispersed Pt boosts active FeXN formation in ammonia decomposition

Ammonia decomposition plays an important role in hydrogen production, especially in the context of a hydrogen economy. Febased catalysts are a popular choice due to their affordability and moderate activity, making them attractive for large-scale applications. However, the transformation of Fe-based catalysts into more active FexN species can be slow, resulting in a prolonged induction period. To address this issue, we investigated the effects of Pt addition on FexN formation in ammonia decomposition. Our results show that even a slight Pt addition significantly enhances the FexN formation rate, increasing it over threefold. Pt aids in H2 desorption via reverse spillover, which, in turn, exposes more Fe surface sites where nitridation occurs, leading to the formation of iron nitride. Characterization via High-angle annular dark-field imaging scanning transmission electron microscopy, X-ray diffraction, and in situ X-ray absorption spectroscopy (XAS) revealed the formation of Fe2N as active species, whereas temperature-programmed hydrogen desorption, temperature-programmed reduction by hydrogen, and in situ XAS supported the existence of H reverse spillover and spillover effects. Overall, our study provides an improved understanding of the active species formation mechanism of Fe catalysts in ammonia decomposition and offers a simple strategy for improving their catalytic performance.& COPY; 2023, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

Ammonia decomposition is important in hydrogen production, and Fe-based catalysts are commonly used due to their affordability and moderate activity. However, the transformation of Fe-based catalysts into more active FexN species can be slow. Addition of Pt significantly enhances the FexN formation rate by aiding in H2 desorption via reverse spillover and exposing more Fe surface sites. The study provides insights into the formation mechanism of active species in ammonia decomposition and offers a simple strategy for improving catalytic performance.