Ammonia with a hydrogen content of 17.6 wt % is viewed as a promising hydrogen carrier because the infrastructures for its production, storage, and transportation have been well established. The challenge is that currently the straight production of H2 from NH3 only works at high temperatures. To date, various metal-based catalysts have been developed for NH3 decomposition, among which the Ru-based ones are the most superior due to the suitable Ru–N binding energy. In the past decade, efforts have been put in to improve the performance of Ru-based catalysts, and the target is to lower Ru loading and reaction temperature. A large variety of support and promoter materials were studied, and advanced techniques were employed to disclose the relationship between catalytic performance and catalyst structure. In this paper, we conduct a review on the materials that are used as supports and/or promoters, focusing specifically on the carbon (CNTs, CNFs, and graphene) and metal oxide (Al2O3, MgO, SiO2, and others) materials. Moreover, the reaction mechanism for ammonia decomposition over Ru-based catalysts is described, and future works on designing novel catalysts and unravelling the catalyst structure–activity relationship are proposed.

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CeO 2 was employed to modify the Cu/SiO 2 catalyst for water−gas shift (WGS) reaction, and two different ways to introduce CeO 2 were applied, i.e., ammonia evaporation hydrothermal (AEH) and impregnation (IM) methods. The sizes of Cu nanoparticles and strength of Cu−SiO 2 synergetic interaction were analyzed by HRTEM and H 2 -TPR characterizations. The Cu + /Cu 0 ratio and strength of Cu−CeO 2 synergetic interaction were evaluated via XPS and XAES techniques. It was revealed that more Cu 0 leads to higher CO conversion, based on its pronounced effect on water dissociation. The strength of the Cu−SiO 2 synergetic interaction in the Cu/SiO 2 catalyst varies with altering the state of CuO species. Cu−CeO 2 synergetic interaction is associated with oxygen vacancies in CeO 2 , which also act as active sites for H 2 O dissociation. The Cu/SiO 2 −CeO 2 -AEH catalyst exhibits the best activity and stability among the three catalysts toward the WGS reaction, because it has a large number of Cu 0 and strong synergetic interaction of Cu with SiO 2 and CeO 2 .

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