Precise Synthesis Of Single Atom Catalysts And Its Function In Small Molecule Activation

The purpose of this thesis is to develop novel synthetic methods to create single atom catalysts and investigate their activity in hydrogenation of unsaturated hydrocarbons and oxidation of silanes.We describe two efficient and facile strategies for the construction of single atom catalysts,namely the electrostatic adsorption and defect engineering strategies.The as-prepared catalysts exhibited excellent catalytic activity,selectivity,and stability in the hydrogenation of unsaturated hydrocarbons and the oxidation of silanes.This thesis mainly includes the following aspects:1.The SBA-15 supported palladium single atoms and clusters catalyst(Pd1+C/SBA-15@N-C)was prepared by the electrostatic attraction strategy.The palladium species were loaded on SBA-15 by adjusting the acid-base environment of the solution.By means of High-angle annular dark-field scanning transmission electron microscopy,X-ray photoelectron spectroscopy,and near edge X-ray absorption fine structure spectroscopy,the uniform and fully exposed palladium atoms were evidenced.This plays an important role for the effective interaction between the reactant and the active metal sites.2.Defect engineering strategy was applied to construct palladium single atoms dispersed over Ti N.Acid treatment was initially used to create Ti vacancies,followed by the self-reduction to reduce the palladium species at the Ti vacancies.High resolution electron transmission electron microscopy(HR-TEM),X-ray photoelectron spectroscopy(XPS)and electron paramagnetic resonance(EPR)were used to demonstrate the presence of singly and evenly dispersed palladium atoms over the support.3.Both catalysts were applied in the hydrogenation of unsaturated hydrocarbons and oxidation of silanes.In the selective hydrogenation reaction of 1-chloro-4-ethynylbenzene by Pd_1+C/SBA-15@N-C,the conversion was 99%and the selectivity was 95%at 30 min,along with turnover frequency(TOF)up to 25000 h^-1.In the case of 1-bromo-4-ethynylbenzene,the conversion was 99%and the selectivity was 95%at 30 min,and the TOF was up to 19355 h^-1.For Pd₁/Ti N,it showed 99%conversion and 99%selectivity within 15 min in the oxidation of diphenylmethyl silane.For other types of silanes,this catalyst has shown exceptional catalytic activity:1)triethyl silicane,99%conversion and 99%selectivity within 5 min;2)dimethylphenylsilane,99%conversion and 99%selectivity within 40 min;3)diphenylsilane,99%conversion and 99%selectivity within 60 min.Both catalysts showed excellent catalytic activity and stability.