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 Nb4N5 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‐N1/5, Nb‐N2/5, Mo‐N1/3, and Mo‐N1/6 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.

High‐Density Lewis Acid Sites in Porous Single‐Crystalline Monoliths to Enhance Propane Dehydrogenation at Reduced Temperatures

“…Porous single‐crystalline transition‐metal nitride monoliths combining the ordered lattice structures and disordered interconnected pores would create well‐defined surface structures [21] . The single‐crystalline property of the monoliths therefore delivers higher stability similar to bulk single crystals and higher activity similar to nanocrystals in catalysis.…”

“…In contrast, traditional monolithic catalysts are in polycrystalline states and they are mainly prepared from catalyst particles by mechanical forming and sintering. Transition‐metal nitrides like Mo 2 N and MoN are typical interstitial compounds with metal atoms closely packing to stabilize the lattice structures in which the top‐layer elements are mainly metal atoms at surface [21] . In this case, the unsaturated metal‐nitrogen coordination structures would be therefore confined at the well‐defined surfaces of porous single‐crystalline nitride monoliths, leading to the generation of high‐density Lewis acid sites at the electron‐deficient surfaces [22] .…”

Activating Lattice Oxygen at the Twisted Surface in a Mesoporous CeO2Single Crystal for Efficient and Durable Catalytic CO Oxidation

“…Mesoporous single crystals can create continuously twisted surfaces that are kinetically trapped in high‐energy states by synergistically incorporating ordered crystal lattice and disordered interconnected pores [3, 4] . Activating lattice oxygen would be therefore achieved with the well‐defined active sites at the surfaces.…”

“…Mesoporous single crystals can create continuously twisted surfaces that are kinetically trapped in high-energy states by synergistically incorporating ordered crystal lattice and disordered interconnected pores. [3,4] Activating lattice oxygen would be therefore achieved with the well-defined active sites at the surfaces. CeO 2 is a key catalyst with a broad range of oxygen storage capacity and the redox behaviors originate from the reversible switch of Ce 3+ $Ce 4+ that gives rise to the change of oxygen coordination of centered Ce ion and the generation of oxygen vacancy in lattice.…”

Dry Reforming of CH4/CO2by Stable Ni Nanocrystals on Porous Single‐Crystalline MgO Monoliths at Reduced Temperature

“…Porous single‐crystalline (PSC) MgO monoliths which combine the ordered lattice structures and the disordered interconnected pores would create well‐defined surface structures [15] . The single‐crystalline property of the monoliths therefore delivers higher thermal stability similar to bulk single crystals and higher catalytic activity similar to nanocrystals in the reforming reactions [16] . The highly crystalline MgO scaffold with negligible defects in the form of amorphous surface could alter the expected redox reaction between methyl anions (CH 3 − ) and CO 2 , leading to a more efficient dry reforming catalyst based on the PSC MgO monolith.…”