On-purpose design of dual active sites in single V atom anchored C2N nanosheets for propane dehydrogenation catalysis

Abstract

As an emerging propylene production technology, propane dehydrogenation (PDH) has attracted much attention of researchers. In this work, we designed single transition metal atom anchored C₂N nanosheets (TM₁/C₂N) with dual active sites as PDH catalysts. Through first-principles calculations and analysis, we unveiled that V₁/C₂N exhibits the highest performance as a single-atom catalyst (SAC) for PDH among the TM₁/C₂N, with propylene and H₂ as the main products. The V/N dual active sites provide separate adsorption sites for intermediates and H atoms, which inhibit both the deep dehydrogenation and reverse reactions. The overall activation barrier for PDH catalyzed by V₁/C₂N is determined as 1.12 eV (the cleavage of the first C–H bond). Due to the occupation of para-N sites, the H atoms dissociated from propylene can only bond to meta-N sites, making propylene desorption more favorable than further dehydrogenation. The activation barriers of other side reactions in PDH have been checked to be much higher than those of the corresponding dehydrogenation reactions, endowing V₁/C₂N with excellent C–C coking resistance and propylene selectivity. Moreover, the favorable activation barrier of the regeneration of active sites facilitates the closure of the catalytic cycle and the production of hydrogen. The large d band center of V in V₁/C₂N and reasonable C_α–H/N–H bond lengths during PDH steps account for its high catalytic activity. The on-purpose design of TM–N dual active sites efficiently promotes the catalytic activity and selectivity, which provides rationales behind the design of catalysts for the selective dehydrogenation of propane.