Catalytic Activities of Transition Metal Phosphides for NO Dissociation and Reduction With CO

Transition metal phosphides are a group of compounds with interesting chemical/physical properties and potential applications in various fields, such as electronics, magnetism, photonics, catalysis, and so on1–4. In particular, metal phosphides (e.g. MoP, Ni2P, WP, Fe2P and Co2P) have been used as catalysts and extensively studied for hydrotreating reactions5–8. Among these phosphides, MoP, Ni2P and WP catalysts have shown significant promise in this regard because of their high activities and resistance to poisoning9–10. Therefore, they have been gradually explored as catalysts in many reactions, including N2H4 decomposition 11,12, carbon dioxide reforming of methane13, hydrogen evolution reaction2,14 and hydrogen oxidation reaction15. However, compared with phosphides of metals (Ni, Mo and W), Fe2P has received far less attention due to its poor activity in hydrotreating reactions6. Recently, it has been found that a highly dispersed Fe2P catalyst on activated carbon showed better performance and stability than an iron catalyst16. Yet its general catalytic properties have not been explored, and this remains an area of considerable challenge. In this study, we firstly report that Fe2P has a much higher catalytic activity for NO dissociation than phosphides of Ni, Mo, W and Co. In view of this unprecedented activity, Fe2P was selected as the representative of phosphides to investigate the genuine nature of these catalysts for catalytic removal of NO. Although the activity and reaction mechanism of Fe2P catalyst for NO reduction with H2 had been studied in our previous letter17, some important details were still missing about the development of a catalytic cycle in phosphide-catalyzed NO reduction reaction. Currently, the NO/CO reaction was used as a probe reaction to study the catalytic nature of Fe2P catalyst. The route for keeping the catalyst stable and active was further perfected.