Theoretical Study On The Structure And Catalytic Performance Of Titanium Doped Boron Nitride Nanocages

Since Takeo Oku et al.successfully synthesized boron nitride(BN)fullerenes and metal-doped BN fullerenes,the BN fullerenes have attracted extensive attention due to its excellent thermal and chemical stability.However,due to lack of crystal structure determination,the unambiguous,atomically resolved structures of metal-doped BN fullerenes remain unclear.Previously,it was generally believed that metal-doped BN fullerenes behave the same as metal-doped carbon fullerenes.The metal atom is confined inside the fullerene cage.Although unproven in experiment,it has even become a commonly accepted premise upon which many studies on metal-doped BN fullerenes are based,so it is urgent to determine the structure of metal-doped BN fullerenes.In section three,by using density functional theory(DFT),we determined the structure of Ti(BN)n(n=12-24)complexes.In Ti-doped BN fullerenes,the metal is located outside the BN cage instead of being confined inside the cage.It can be verified by collision-induced dissociation experiments.The predicted global minimum structures have some common bonding features,which make them very stable.In addition,we also found that these global minimum structures are very likely to be synthesized experimentally.The Ti doping BN fullerene not only changes the topological structure of the cage,but also changes the arrangement of N and B atoms,making the BN complexes have the potential to nitrogen fixation and capture CO2.These results may expand or alter the understanding of BN nanostructures functionalized with other transition metals.There is only one Ti atom in Ti(BN)n,so these complexes can be used as single atom catalyst(SAC).SAC has been widely studied because of their excellent catalytic activity and 100%atom utilization.The Ti(BN)n can avoid the aggregation of Ti atom in the reaction process,because the single Ti atom forms four very strong chemical bonds with four N atoms,which makes the Ti atom firmly embedded in the BN cage.In section four and five,we present a detailed study on the catalytic activity of Ti(BN)14 as a SAC for carbon monoxide(CO)oxidation and the selective hydrogenation reaction of 1,3-butadiene,by means of DFT calculations.In section four,we found that the single Ti site in Ti(BN)14 has a good catalytic activity,which can catalyze the oxidation reaction of CO.The energy barrier of the rate determining step in the optimal pathway for the catalysis of CO oxidation is only 23.0 kcal/mol,which indicates that Ti(BN)14 is a good SAC.In section five,we found that the single Ti site can catalyze the cracking of H2 very efficiently.However,the energy barrier of the H atom transfer to 1,3-butadiene is high,which leads to the poor catalytic performance of Ti(BN)14 on the selective hydrogenation of 1,3-butadiene.Based on our results,we believe that Ti(BN)14 can be used as SAC to catalyze important chemical reactions such as CO oxidation.