Important progress has been made in theoretical calculation and Simulation of chemical properties and catalytic activity of functional groups on the surface of carbon nanomaterials catalysts

As a kind of important non-metallic catalysts, nano carbon materials such as carbon nanotubes, nano diamond and graphene have shown comparable or superior catalytic performance to traditional metal catalysts in many catalytic reactions Oxygen, nitrogen, boron and sulfur are common surface functional groups on carbon nanomaterials, and they are also important factors to control catalytic performance Understanding and summarizing the chemical properties and catalytic activity of surface functional groups is a key scientific issue for further optimization and development of catalysts for carbon nanomaterials Li Bo, associate researcher, catalytic materials research department, Institute of metals, Chinese Academy of Sciences, and Su dangsheng, researcher In the past five years, starting from the chemical properties of various surface functional groups, the catalysis of oxygen, nitrogen, boron, sulfur and other functional groups in the dehydrogenation of alkanes, oxidation of carbon monoxide, reduction of oxygen, selective hydrogenation and other catalytic reactions has been explained in detail by using the first principle calculation and quantum chemistry method, and the general rules and mechanism of the regulation of surface functional groups have been summarized The gain and loss of electron ability and acidity and basicity of oxygen and nitrogen functional groups can be successfully introduced into nano carbon materials by nitric acid oxidation How to quantitatively and accurately describe the activity difference between different oxygen functional groups and the activity change of the same oxygen functional group in different chemical environment is a difficult problem Due to the coexistence of various oxygen functional groups on the catalyst, it is difficult to give an accurate description by experimental means By using the Fukui function and density functional theory, the researchers first gave a quantitative characterization of the electronic gain and loss ability of oxygen functional groups The calculated results can help the experimental work to distinguish the chemical activities of different oxygen functional groups and determine the active sites in the reaction (Chemistry - a European Journal 2014, 20, 7890-7894) The introduction of nitrogen functional groups into carbon nanomaterials can effectively enhance the basicity of the catalyst Pyridine, pyrrole, fourth-order nitrogen and graphite nitrogen are common nitrogen functional groups How to distinguish the basicity of different nitrogen functional groups is the key to optimize the catalytic performance Based on the calculation of proton adsorption and acid dissociation constants, the researchers have successfully quantified the basicity of four different nitrogen functional groups The calculation results show that pyridine nitrogen is the most basic functional group, which lays a solid foundation for the determination of active sites in alkali catalysis (Phys Chem Chem Phys 2015, 17, 6691-6694) Figure 1 (a) common oxygen functional groups on nano carbon materials (b) the order of affinity of oxygen functional groups low chain alkane oxidative dehydrogenation reaction active site, reaction path and mechanism research oxidative dehydrogenation reaction is the most successful chemical reaction using nano carbon materials catalyst The first principle for the first time revealed the oxidative dehydrogenation of ethane in the presence of dicarbonyl activity (J mater Chem A 2014, 2, 5287-5294), and revealed the reaction process different from the previously widely reported active site regeneration mechanism Through calculation, the researchers proposed that oxygen removal energy is an active parameter that can characterize the catalytic activity of nano carbon materials in oxidative dehydrogenation Further calculation results show that the catalytic activity of the carbon atom connected with the oxygen functional group which has not been noticed in the previous experiments can also be verified as the active site in the oxidative dehydrogenation reaction (chem Commun 2014, 50, 11016-11019) By analyzing the aromaticity of carbon nanomaterials, it is shown that the catalytic ability of carbon atom active sites is due to the reduction of aromaticity (Chemistry - an Asian Journal 2016, 11, 1668-1671) Fig 2 Oxidative dehydrogenation of propane in mono carbonyl group Fig 3 Kinetic parameters of oxidative dehydrogenation of ethane calculated by micro reaction kinetics (a) Pre exponential factor (b) reaction equilibrium constant (c) reaction conversion frequency low chain alkane direct dehydrogenation reaction mechanism nano diamond shows excellent catalytic effect in alkane direct dehydrogenation reaction, not only surpasses the traditional metal catalyst, but also has better stability and selectivity compared with other nano carbon material catalysts such as carbon nanotubes Through the first principle calculation, the researchers revealed the structure-activity relationship between the unique core-shell structure and catalytic performance of nano diamond from the aspects of catalyst structure, activation energy barrier of hydrocarbon bond, charge transfer and size effect, which provided theoretical support for further design and optimization of non-metallic nano carbon material catalyst (ACS catalysis 2017, 7, 3779-3785）。 Figure 4 Schematic diagram of structure-activity relationship between core-shell structure and catalytic performance of nanodiamond SP2 @ SP3 (ACS catalysis 2017, 7, 3779-3785) The design hydrogen molecule of new hydrogenation catalyst is an important reactant in chemical reaction Traditionally, noble metals have been used as catalysts to activate hydrogen molecules Using the concept of "blocked Lewis pair (FLP)" as catalyst, we designed the boron nitrogen Co doped double-layer graphene catalyst system by theoretical calculation The results show that the catalyst of carbon material has similar catalytic effect with noble metal catalyst (Phys Chem Chem Phys 2016, 18, 11120-11124) Further more, the researchers tried to test the catalytic reaction of selective hydrogenation of cinnamaldehyde, which showed the method to improve the selectivity of cinnamyl alcohol and achieved good selectivity of cinnamyl alcohol (chemcatchem 2014, 6, 3246-3253) Figure 5 Hydrogen molecular activation mechanism (Phys Chem Chem Phys 2016, 18, 11120-11124) the structural configuration of boron and nitrogen atoms on several different carbon nanomaterials was constructed by the researchers of the regulatory effect of support functional groups on metal catalysts Due to the difference of electronegativity, boron and nitrogen atoms have the opposite regulatory effect on the supported single atom gold catalyst Charge analysis shows that the electron transfer is from gold atom to the carrier on the nitrogen doped carrier, and the direction of electron transfer is just the opposite on the boron doped carrier Therefore, gold atoms show different valence states, which directly lead to different forces and mechanisms between carbon monoxide and oxygen molecules The interaction between gold atom and carbon monoxide molecule is stronger on the nitrogen doped carrier, and between gold atom and oxygen molecule is stronger on the boron doped carrier Different forces with reactants lead to different oxidation mechanism of carbon monoxide on different supports In addition to the traditional reaction mechanism of LH and ER, a tri molecular reaction mechanism was also found, which deepened the understanding of the regulatory role of carriers (J mater Chem A 2017, 5, 16653-16662) In addition, we also studied the effects of single hole, double hole and stone Wales defect sites on the support of graphene and carbon nanotube on the regulation of supported nitrogen atom gold catalyst, and compared the curvature effect of carbon nanotube (Phys Chem Chem Phys 2017, 19, 22344-22354) The calculation of the general regulation and mechanism of the function group shows that the introduction of nitrogen atom into the nano carbon material in the dehydrogenation reaction can improve the electron delivery ability of the oxygen function group, further enhance the olefin desorption and improve the catalyst selectivity (chem Asian J 2013, 82605-2608) Compared with nitrogen atom doping, boron atom has one valence electron less than carbon atom, so a hole is generated The calculation results show that the hole generated by boron atom can activate oxygen molecule, generate active oxygen species, and catalyze partial oxidation of methane to formaldehyde (Journal of Physical Chemistry C 2013, 117, 17485-17492) Through large-scale calculation and selection, the researchers found that the functional groups on the carbon material catalyst followed the BEP rule in the dehydrogenation reaction, and there was a linear relationship between the hydrocarbon bond breaking distance and the energy barrier (nanoscale 2015, 7, 16597-16600) Figure 6 The oxidative dehydrogenation process (chem Commun Doi: 10.1039 / c7cc06941c) on nano carbon materials has published 29 articles in SCI journals such as ACS catalysis, nanoscale, J mater Chem A, chem Comm since 2013 Among them, the properties of heteroatom regulated metal catalysts in carbon monoxide oxidation (J mater Chem A 2017, 5, 16653-16662) were rated as 2017 "hot article" by the editorial department Recently, some research results have been published on Chemical Communications (DOI: 10.1039 / c7cc06941c) under the title of "optimistic dehydrogenation reaction of short alkanes on the nanostructured carbon catalysts: accounting account" This work is supported by NSFC, outstanding scholars, Sinopec and Guangzhou supercomputing Brief introduction of Li Bo: http://sourcedb.imr.cas.cn/zw/rck/fyjy/imr/201408/t2014821.html brief introduction of Li Bo: http://210.72.142.130:8080/web/26380/37