Highly Efficient CO2-Free Hydrogen Production: A Novel Ru/Al2O3 Catalyst for Ammonia Decomposition

In order to promote better environmental protection and enhance energy conversion efficiency, the on-site production of CO2-free hydrogen from ammonia has emerged as a viable solution for power generation and clean energy applications. Ammonia (NH3) has shown promise as a hydrogen carrier due to its ability to overcome challenges associated with hydrogen storage and transportation. However, the thermocatalytic ammonia decomposition reaction (ADR) requires catalysts with high activity and stability.

This study presents a synergistic strategy for the preparation of a highly dispersed Ru/Al2O3 catalyst using an atmosphere-induced method. The catalyst synthesis begins with the preparation of Ru/Al2O3-O in an oxidizing atmosphere, resulting in RuO2 particles larger than 10 nm. Upon reduction, the particle size of Ru increases to 17.5 nm. In contrast, the reducing atmosphere synthesis of Ru/Al2O3-R maintains highly dispersed Ru particles, with sizes less than 2 nm.

The resulting K-Ru/Al2O3-R catalyst exhibits an impressive NH3 conversion efficiency of 97% at 450 oC and gas hourly space velocities of 18,000 mL/gcat/h. The catalyst also demonstrates excellent stability, as it successfully operates in a fixed-bed reactor for 700 hours.

To gain a deeper understanding of the catalyst's characteristics, we employed various analytical techniques. These include high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, and X-ray diffraction patterns to elucidate the morphology and electronic structure of the Ru metal.

Overall, this study presents a novel approach for the synthesis of a highly active and stable Ru/Al2O3 catalyst. The catalyst shows great potential for application in the thermocatalytic ammonia decomposition reaction, facilitating CO2-free hydrogen production and the adoption of clean energy technologies.