Achieving Low-Temperature High-Efficient Ammonia Decomposition Over sub-nm Ru Cluster with CeO2– x Support via Photopromoted Hydrogen Spillover and Nitrogen Recombination

Abstract

The low-temperature high-efficient decomposition of ammonia, a carbon-free hydrogen carrier, is essential to the promising hydrogen energy storage. However, the decomposition is hindered by slow reaction kinetics due to dynamically hydrogen poisoning and thermodynamically high nitrogen recombination barrier in ordinary thermocatalysis. Herein, we propose a photothermocatalytic strategy to resolve these kinetic issues and achieve enhanced hydrogen production. Under full-spectrum light irradiance of 20 kW m–2, a hydrogen production rate of 4.2 mmol g–1 min–1 at 300 °C has been achieved over the Ru/CeO2–x catalyst, significantly outperforming conventional thermocatalysis. Insights from in situ characterizations and density functional theory calculations indicate that the enhanced performance is ascribed to photopromoted hydrogen spillover and nitrogen recombination, which are mediated by the strong metal–support interaction. On one hand, the photogenerated electrons promote the H dissociation over sub-nm Ru clusters and migration across the metal–support interface, and the photoinduced oxygen-vacancy-rich CeO2–x surface favors to spread the active H· species. On the other hand, the photogenerated electrons reduce the activation energy for Ru–N bond cleavage, which is beneficial for N–N recombination. This study has demonstrated the distinct advantage of photothermocatalytic hydrogen production as an energy-saving, high-efficient, and carbon-free route.