Twisted Surfaces in Porous Single Crystals to Deliver Enhanced Catalytic Activity and Stability

Abstract

Porous single crystals which combine ordered lattice structures and disordered inter-connected pores would provide an alternative to create twisted surface in porous microstructures. Now, transition-metal nitride Nb₄ N₅ and MoN single crystals are grown on a 2 cm scale to create well-defined active structures at twisted surfaces. High catalytic activity and stability toward non-oxidative dehydrogenation of ethane to ethylene is observed. Unsaturated metal-nitrogen coordination structures including Nb-N_1/5 , Nb-N_2/5 , Mo-N_1/3 , and Mo-N_1/6 at the twisted surface mainly account for the C-H activation with chemisorption of H in molecular ethane at the twisted surface, which not only improves dehydrogenation performance but also avoids the deep cracking of ethane to enhance coking resistance. 11-25 % ethane conversion and 98-99 % ethylene selectivity is demonstrated without degradation being observed even after the operation of 50 hours.