Preparation And Catalytic Oxidation Performance Of Fe/N Co-doped Carbon Catalyst

From the perspective of basic research and practical application,the development of novel and high-efficiency catalysts has been an important topic in the research of heterogeneous catalysis.In recent years,transition metal nitrogen-doped carbon catalysts（M-N-C）have attracted great interest and exhibit excellent catalytic performance in heterogeneous catalysis due to their low price,good chemical and thermal stability,and adjustable porosity.However,the preparation of M-N-C catalysts generally requires high temperature pyrolysis,which will inevitably lead to the agglomeration of metal nanoparticles.Therefore,the selection of appropriate metal precursors and the reasonable design of catalyst structure are the key to the preparation of high efficiency M-N-C catalysts.In order to reduce the size of metal nanoparticles and increase the number of accessible active sites,Fe-phenanthroline complex as precursor was used in this study to pre-isolate Fe species.At the same time,in order to improve the mass transfer efficiency in the reaction process,the appropriate support and sacrificial template were selected to prepare Fe/N co-doped catalysts with three-dimensional morphology and rich pore structure,and applied to different catalytic oxidation reactions.The physical and chemical properties of the prepared catalyst were investigated by a series of characterization techniques.The main research contents are as follows:（1）Fe-N/KCC-1-T catalysts with high specific surface area and regular morphology were prepared through impregnating Fe-phenanthroline precursor on fibrous silica nanospheres（KCC-1）and further pyrolysis at high temperature.Free N anchor sites were generated during the pyrolysis process of Fe-phen complex,which realized the uniform and ultrafine distribution of metallic phase and increased the density of active sites.In addition,the unique central radial channel structure of KCC-1 greatly improves the mass transfer efficiency in the reaction process.Using air as a green oxidant,Fe-N/KCC-1-T shows good catalytic activity and stability with>99%yield of benzonitrile for the ammonia oxidation of aldehydes under mild reaction conditions.（2）Based on the above research,in order to further improve the metal dispersion,an elaborate multistep protection strategy were reported for preparation of atomically dispersed Fe atoms on 3D N-doped hollow carbon spheres with uniform Si O₂ nanospheres as a sacrificial template and biocompatible dopamine as N and C precursor（named as Fe-N@HCS-T）.A series of multi-step continuous protective effects,including the pre-separation of 1,10-phenanthroline,the physical isolation of excessive Zn²⁺,the anchoring effect of free N sites generated during high temperature pyrolysis,and the rigid skeleton structure of three-dimensional hollow spheres,successfully realized the atomic distribution of Fe-centered active sites and improved the utilization of Fe atoms.The prepared Fe-N@HCS-T catalyst exhibited excellent catalytic activity and selectivity for oxidation of C-H bond under mild reaction conditions.