Theoratical Study On Noble Metal Single-atom With Oxyhydroxide Supports As Efficient Electrocatalyst Towards Oxygen Evolution Reaction

The preparation of hydrogen and oxygen products by electrolysis of water plays an important role in clean energy conversion and renewable energy production.Oxygen evolution reaction（OER）,as the anode reaction of the electrolytic water process,is considered as the rate-limiting step of the overall water decomposition because of the four-electron transfer involved.Noble metal single-atom with oxyhydroxide supports as OER electrocatalysts has been found to be excellent,but the relationships of structure and effect and mechanisms of OER remain unclear.In this thesis,the OER electrocatalied by different kinds of hydroxyl oxides loaded or doped with different noble metal single atoms are investigated using the density functional theory（DFT）method,and the highly efficient OER catalysts are screened and the relationships of structure and effect are revealed.The research contents and conclusions of this paper are as below:（1）The OER mechanisms over 50 hydroxyl oxide-nobel metal single-atom loaded（M/M₁M₂OOH）and doped（M@M₁M₂OOH）systems（M=Ru,Rh,Pd,Ir,Pt;M₁M₂=CoCr-,CoFe-,NiV-,Ni Mn-,NiFe-,M₁/M₂=11:1）are studied.The binding energy calculation shows that M to M₁M₂OOH is more easily influenced by the noble metal M species and the doped system is more stable than M@M₁M₂OOH.It is found that the M site of M/M₁M₂OOH has the lowest OER overpotential,and the lowest OER overpotential of M@M₁M₂OOH is M₂most,thus identifying the M and M₂sites as their active sites,respectively.Comparing with the OER overpotential of the corresponding M₁M₂OOH,it is found that among calculation system the OER overpotential over CoFeOOH and NiMnOOH decreased most by 0.02V-1.39 V after supporting or doping with single atoms,thus the catalytic activity is improved mostly.Except for Ru/NiVOOH,Ir/NiMnOOH,Rh,Ir,and Pt/NiFeOOH,the OER overpotential over M@M₁M₂OOH is lower than that of M/M₁M₂OOH when the same noble metal single atoms are introduced,indicating that the OER catalytic activity of M@M₁M₂OOH is higher than M/M₁M₂OOH.Most potential energy determining steps of OER over M/M₁M₂OOH and M@M₁M₂OOH are OH^*→O^*+H⁺+e^-and O^*+H₂O→OOH^*+H⁺+e^-.Ir/NiFeOOH(η^OER=0.37 V),Ru@CoFeOOH(η^OER=0.45 V),and Rh@NiMnOOH(η^OER=0.45 V)have the lowest overpotentials,presenting their excellent catalytic performance.The relationship between adsorption free energy change of oxygen-containing intermediates(ΔG_^*OH-ΔG_^*O)and the overpotential show a volcano curve,and the above three catalysts with excellent performance are located at the top of the volcano curve,which have moderate adsorption capacity for oxygen-containing intermediates（^*OH,^*O,^*OOH）with moderate values of d-band centers.This is favorable for the adsorption and desorption of reaction intermediates and thus have excellent OER activity.（2）15 hydroxy oxide-nobel supported metal monoatomic systems M/NiFe_xOOH with different Ni/Fe ratios（x=0.09,0.26,0.33,0.41,0.50,M=Ru,Ir,Pt）are investigated by DFT,and the binding energy,electrocatalytic OER mechanism,electronic density of states,and d-band centers are calculated.The results show that with the increase of Fe,the OER activity of Ru/NiFe_xOOH and Pt/NiFe_xOOH increase and then decrease,while that of Ir/NiFe_xOOH show a trend of decreasing then increasing.Comparison of the adsorption free energy of oxygen-containing intermediates（^*OH,^*O,^*OOH）and d-band centers of different catalysts revealed that the adsorption capacity of the catalysts is enhanced in the order of Ru,Pt,and Ir.The potential energy determination steps of OER are similar to the 50 catalysts mentioned above.Pt/NiFe_0.26OOH with the lowest OER overpotential ofη^OER=0.28 V is located at the top of the volcano curve thus has the most excellent electrocatalytic OER performance,which has moderate adsorption capacity for oxygen-containing intermediates（^*OH,^*O,^*OOH）with moderate values of d-band centers.This thesis extends the theoretical construction and screening methods for OER electrocatalysts,and provides theoretical information and guidance for the design of highly efficient catalysts with hydroxyl oxides and noble metal single atoms for OER.