Theoretical Calculation Research Of Reducyion Reacyion Of Oxygen-containing Small Molecules On Inorganic Metal Composite Catalysts Surface

The earth environment contains a large number of oxygen-containing small molecules,such as SO2,NO2,N2O,CO2,O2,etc.The main sources are the respiration of animals and plants,photosynthesis,and the burning of fossil energy in industrial development.With the gradual consumption of fossil energy,human are facing the dual problems of resource shortage and environmental destruction.Therefore,researchers hope to degrade and eliminate oxygen-containing small molecules through catalytic reactions or convert them into new substances for recycling.With the deepening of scientific research,traditional experimental methods are faced with problems such as difficulty in studying the specific reaction mechanism and difficulty in predicting the reaction trend.Therefore,with the rapid development of software technology,based on density functional theory,the use of related modeling and calculation software for oxygen-containing small molecules is very necessary,it aims to conduct theoretical calculation research on the catalytic reaction process,such as energy change,electron distribution,etc.,for in-depth exploration of the microscopic nature of related reactions.This work will also be based on density functional theory(DFT),using Materials Studio,VASP and other modeling calculation software to study the catalytic reduction reaction process about some small oxygen molecules(N2O,CO2,O2)on the surface of the corresponding catalyst materials to prediction reaction performance trends and give reasonable interpretation of related experimental results and provide strong theoretical data support.First,in the catalytic reduction reaction of N2O molecules(N2ORR),this work selects three typical perovskite catalysts as the main research objects(LaMnO3,LaCoO3,LaNiO3),and studies the two-step decomposition of N2O molecules to produce O2 molecules and N2 molecules.Theoretical calculation results show that these three perovskite catalysts have good catalytic effects on the decomposition reaction of N2O molecules.From the overall energy change,the decomposition process of N2O molecules shows a downward trend as a whole.The process of degrading N2O molecules into N2 molecules in the reaction is a rate control step,and the reaction energy barriers(TS)of N2O decomposition on(001)planes of LaMnO3,LaCoO3 and LaNiO3 are close to 1.00eV,1.70eV and 2.20eV,respectively,so LaMnO3 has the highest decomposition activity of N2O molecules.In addition,the results of the d-band center shows that the d-band center positions(relative to Ef)of the Mn,Co and Ni atoms in the system are-4.17 eV,-3.25 eV,and-3.46 eV,respectively.In addition,in the study of the desorption process of O2 molecules,it is found that the desorption energy of O2 molecules is in the range of 0.20eV-0.50eV as a whole,which indicates that the desorption process of O2 molecules can occur more easily,thereby avoiding O poisoning.This will expose the original active sites for the next new reaction cycle process.The results of kinetic analysis show that the reaction rate constant of LaMnO3 catalyst is the largest,which is positively correlated with temperature,and the reaction rate coefficient of O2 desorption process also indicates that O2 is easy to desorb.Secondly,in the catalytic reduction reaction of CO2 molecules(CO2RR),this work takes Cu2O and modified Cu0 and Cu+ mixed Cu2O-Cu catalyst materials as the main research objects,and studies the reaction process of CO2 molecules reduction to C2H4 molecules in detail.The calculated gibbs free energy curve shows that the adsorption process of CO2 molecules is spontaneous,and the adsorption energy of CO2 molecules is higher on the(100)planes in Cu2O-Cu,it has higher chemical activity,which is beneficial to the dissociation process in the next step occurs.And the coupling process of the CO intermediate is a rate control step.Next,the transition state study of the CO coupling process found that the energy barrier of the reaction decrease from 2.81 eV of the Cu2O catalyst to 1.13eV,so the Cu2O-Cu catalyst has obvious chemical catalytic activity for the coupling reaction of intermediate CO.In addition,because the source of H+is mainly the cracking reaction of H2O molecules in the solution,this work supplements Cu catalysts and studies the cracking reaction process of H2O molecules in Cu,Cu2O and Cu2O-Cu in detail.The calculation results shows that the cracking energy barriers of H2O molecules on the surface of Cu,Cu2O and Cu2O-Cu are 2.33eV,2.15eV and 1.64eV,respectively.It is found by comparison that H2O molecules have the highest cracking activity on Cu2O-Cu catalysts.Finally,in the catalytic reduction reaction of O2 molecules(ORR),based on experimental results,this work selects the f-FeNC/f-FePNC catalyst material as the main research object,and studies the four-step reduction reaction process of O2 molecules under acidic conditions.The calculated results show that under 0V conditions,compared with the f-FeNC catalyst,the doping of P atoms makes the f-FePNC catalyst have higher catalytic activity,and reaction overpotential(η)of f-FeNC,f-FePNC-1,f-FePNC-2 are 0.72V,0.27V,0.88V,respectively.And f-FePNC-1 has the highest chemical catalytic activity.Since the adsorption of H3PO4 molecules will inhibit the progress of the reaction and reduce the catalytic activity,this work studies the adsorption process of H3PO4 molecules on their respective surfaces.The calculation results show that the adsorption energies(E)of H3PO4 molecules on f-FeNC,f-FePNC-1,and f-FePNC-2 are 0.36eV,0.74eV,and 0.69eV,respectively.The difficulty of adsorption increases and the chemical catalytic activity is improved.Therefore,the possibility that the doping position of P atoms is located at the a position is the highest,that is,the f-FePNC-1 structure formed.