Catalytic Oxidation On Co Doped CeO₂ And Oxygen Evolution Reaction On Au@Ni₁₂P₅ Nanocluster From First-principles Calculations

At present environmental issues and energy crises are becoming increasingly prominent.Air pollution control and utilization of renewable energy are of great importance due to being two fundmental parts of national sustainable development strategies.Catalytic conversion is usually an effective way to the relieve of urban air pollution and the conversion and utilization of renewable energy.The engineering design of catalysts has been regarded as the most effective way to accomplish the toxicity-free conversion of catalytic oxidation of formaldehyde(HCHO)and carbon monoxide(CO).Converting surplus electricity from renewable energy sources such as solar energy and wind energy into clean,highly efficient,and pollution-free hydrogen fuel via catalytic water-splitting reaction,is widely perceived as one of the promising ways to develop and utilize clean energy in the 21st century.The oxygen evolution reaction(OER)of anodic oxidation in water splitting has become the bottleneck to the efficient conversion from surplus electricity to hydrogen production because of the relatively high overpotential.Therefore,the development and design of an effective OER electrocatalyst with high anode efficiency(i.e.,low-reaction overpotential)is the key to improving the efficiency of hydrogen production from the water-splitting reactions.In the engineering design of catalyst materials,doping can usually improve the catalytic performance of main catalysts.In this paper,we firstly model the single Co-doped and double(Co,Cu)doped CeO2 low-index surface slabs with active surfaces,respectively.Combing first-principles calculations with transition state theory,we exhaustively explore the oxidation process of harmful gases such as HCHO and CO for detoxification and predict that Co or Cu doping can significantly enhance the ability of CeO2 to catalytic oxidation of these harmful gases.Moreover,we artificially model the core-shell Au@Ni12P5 doping structure and reveal the origin of the high-performance core-shell catalyst from the perspective of chemical reaction thermodynamics and kinetics by first-principles and transition-state calculations.Specifically,the extracted research achievements of this paper are listed as follows.(1)We calculate the electronic structure of bulk CeO2 with varying Co doping concentrations and Co-doped CeO2(111)and(110)surface slabs using the DFT+U method.It shows that Co-doped bulk CeO2 induces spin polarization,which promotes the formation of oxygen vacancy.For the Co-doped CeO2 slabs,we find hybridization of electronic orbits between Ce 4f,Co 3d,and O 2p in shell the is the result of the decreasing formation of oxygen vacancy on doped CeO2 surfaces and enhances the redox capacity of the doped slabs.Finally,we went through the effect of Co doping concentration on the formation of surface oxygen vacancy on CeO2(110)and find that the formation of oxygen vacancy is easier for the larger Co doping concentration.(2)We study the oxidation process of HCHO on Co-doped CeO2(111)within Hubbard U DFT theory.At the first,the formation of oxygen vacancies at different equivalent sites relative to the doping Co atom is thoroughly explored.And corresponding physical or chemical adsorption configurations are also given,where the most stable one is in good agreement with previously reported literature on the geometry of dioxymethylene(CH2O2)adsorption configuration.Within the Langmuir Hinshelwood(L-H)mechanism,we explore three possible reaction models for HCHO oxidation on O2-assistant Co-doped CoxCe1-xO2-δ(111)surface.It indicates that the reaction pathway where HCHO is oxidized to CO is the most possible one because of the lowest reaction energy barrier among the three models.It also demonstrates the catalytic activity is linear with an adsorption energy of HCHO on the CoxCe1-xO2(111)surface.To summarize,both Co doping and oxygen vacancy contribute to HCHO oxidation on the CeO2 surface.(3)We investigate the adsorption and dissociation of HCHO at the CoyCe1-yO2γ(110)using the DFT+U method.It shows that Co doping makes its adjacent oxygen vacancy form spontaneously by itself and is accompanied by charge compensation.We further calculate the possible adsorption configurations and their corresponding adsorption energies at the different adsorbed sites on the CoyCe1-yO2γ(110).At last,we explore the dissociation process for HCHO adsorbed on the CoyCe1-yO2-γ(110)with oxygen vacancy.It reveals that catalytic activity is linear with adsorption energy and the presence of active oxygen species helps the oxidation process.(4)Within the L-H mechanism,we study the oxidation process of CO on the surfaces of single Co-doped and double(Co,Cu)doped CeO2(110)and(111)from first-principles calculations.Bader charge analysis shows that doping leads to the transfer of charge on the surface and decreases the difficulty of the formation of oxygen vacancy,which helps to redox capacity.DOS calculation indicates that the formation energy of oxygen vacancy is linear with its bandgap.Adsorption of CO on doped CeO2 is associated with electron localization function(ELF)and stronger ELF reduces adsorbed strength of CO on the doped CeO2.We also find the linear correlation between adsorption and catalytic activity.Finally,it demonstrates that both the lower formation energy of oxygen vacancy and the proper adsorbed strength of CO enhance the efficiency of the CeO2 catalyst.(5)DFT+D3(van der Waals correction)calculations are employed to study the water-splitting oxygen evolution reaction(OER)on～1.5 nm diameter Au13@Ni120P50 core-shell nanocluster.Water splitting to produce oxygen proceeds in four intermediate reaction steps(OH*,O*,OOH*and O2).Adsorption configurations and adsorption energies for species involved in OER on both Au13@Ni120P50 cluster and Ni12P5(001)supported by Au are presented.In addition,thermodynamic free energy diagrams and kinetic potential energy changes have been systematically discussed.We show that the third intermediate reaction(O*reacts with H2O to produce OOH*)in four elementary steps is the reactiondetermining step,which is in accord with previous results.Also,the catalytic performances of OER for Au13@Ni120P50 are better than that for Ni12P5(001)supported by Au in terms of reactive overpotential(0.74<1.58 V)and kinetic energy barrier(2.18<3.17 eV).The optimal kinetic pathway of OER is further explored carefully for the Au13@Ni120P50 cluster.