First-principles Study Of Binary And Ternary Alloys Based On PdCu As Oxygen Reduction Catalysts

Proton exchange membrane fuel cells(PEMFC)are one of the most likely alternative energy sources for replacing traditional energy sources in the future due to their high efficiency,cleanliness and greenness.It is well known that the slow kinetics of fuel cell cathodes is the main problem for the development of fuel cells.Metal Pt is the catalyst with the highest catalytic activity,but its low abundance lead to extremely high price.In addition,large-scale commercialization of fuel cell catalysts has been difficult to develop due to poor long-term duration.The development of ORR catalysts with low precious metals,high activity and stability has become a breakthrough technical obstacle to the large-scale practical application of PEMFC.So from the theoretical point of view,not only rational designed of the catalyst will save a lot of research funding and time,also the mechanism of the oxygen reduction catalyst has an important supporting role for the experiment.With the development of computational chemistry theory and technology,the density functional theory and high-performance computer technology provide the basis for us to study the theory of ORR.In this paper,the kinetic and thermodynamic properties of fcc-PdCu(111),bcc-PdCu(110)and its Nidoped S-PdCuNi(110)surface were studied by DFT,and the optimal reaction mechanism was determined.At the same time,the catalytic activity and stability of MPdCuCo(110)and M-PdCuNi(110)catalysts were also discussed in detail,and the experimental results of the previous experiments were verified theoretically,and the Pd-based series alloy catalysts were summarized.The main work and results of this paper are as follows:Firstly,the fcc-PdCu(111)and bcc-PdCu(110)surface plate models were established by DFT method.By comparing the adsorption energy,the most stable adsorption configuration of surface and ORR intermediates was determined.The thermodynamic and dynamic properties were also investigated.The optimal reaction pathway was determined by calculation and analysis.According to the ORR free energy step diagram,we have clarified the speed control steps on the surface of fcc-PdCu(111)and bcc-PdCu(110),and the overpotential platform is 0.59 eV and 0.64 eV respectively,which shows that ORR is more likely to occur on the fcc-PdCu(111)surface.Secondly,a plate model of a small amount of atomic Ni-doped bcc-PdCu(110)was calculated by DFT method,this model abbreviated as S-PdCuNi(110).The theoretical calculation results show that the adsorption energy of ORR intermediates is smaller than that of bcc-PdCu(110).The comparative analysis of kinetics and thermodynamic properties proves that the doped S-PdCuNi(110)has a lower activation energy barrier,its reaction pathway is consistent with bcc-PdCu(110)surface,and the overpotential platform for the best reaction pathway is only 0.58 eV.Finally,a multi-doped plate model of Co/Ni atoms was studied by DFT calculation.The M-PdCuCo(110)and M-PdCuNi(110)catalyst systems were used to compare and analyze the d-band center,adsorption energy and segregation energy,the results show that both M-PdCuCo(110)and M-PdCuNi(110)structures have good stability and catalytic activity.Among them,M-PdCuCo(110)is the best performance of Pd-based alloy series catalysts.