Identifying and Engineering Active Sites at the Surface of Porous Single-Crystalline Oxide Monoliths to Enhance Catalytic Activity and Stability

Identifying and engineering active sites play a key role in many catalytic reactions.Herein,we create well-defined surface structures through the growth of porous single-crystalline Mn_(3)O_(4) and Mn_(2)O_(3) monoliths at centimeter scale and confine atomically dispersed Pt ions in the lattice at the twisted surface to construct isolated active sites.The activation of lattice oxygen linked to isolated Pt ions is much more effective than the lattice oxygen linked to Mn ions in local structures,leading to an approximately sevento eightfold enhancement of surface oxygen exchange coefficients for catalytic CO oxidation.The active structures of PtO_(1.5) and PtO_(1.4) confined at the well-defined surfaces contribute to the efficient activation of lattice oxygen linked to Pt ions in local structures in addition to the chemisorption of CO in the oxidation reaction.We demonstrate the complete CO oxidation with air at 65℃ without degradation being observed even after continuous operation of 300 h.

Fabrication of three dimensional SiC@C hybrid for efficient direct dehydrogenation of ethylbenzene to styrene

Synthesis of hybrid carbon materials with core-shell structure and robust catalytic performance is of great research interest,and remains a great challenge in catalytic dehydrogenation of hydrocarbons reaction.In this paper,few-layer sp^(2) carbon decorated SiC nanocrystals with core-shell structure(SiC@C)were fabricated through a dual-confined magnesiothermic method by employing glucose and SiO_(2) as precursors.The SiC@C nanocrystals were further crosslinked to be a three dimensional(3D)mesoporous hybrid by the in situ generated carbon as binders and exhibiting a 410.30 m^(2) g^(−1) large surface area.The as-prepared SiC@C hybrid materials as metal-free catalysts were evaluated in the steam-free direct dehydrogenation of ethylbenzene to styrene.Benefiting from the abundant surface carbonyl groups on the graphite carbon layers,the optimized yield rate of styrene normalized by carbon mass was as high as 11.58 mmol g^(−1) carbon h^(−1),nearly 4 times that of nanodiamonds.Considering the low cost and excellent catalytic activity,the hybrid 3D SiC@C material may be a promising candidate for direct dehydrogenation of hydrocarbons.