Design And Oxygen Evolution Performance Of Hetero-Interface NiFe₂O₄/NiMoO₄ Electrocatalyst

Due to the rapid consumption of fossil fuel resources and global warming,the development of clean renewable energy becomes critical.Water electrolysis to produce hydrogen is an effective method to solve the above problems.The key to reduce the cost of water electrolysis is to design an efficient oxygen evolution reaction（OER）electrocatalyst.At present,most electrochemical oxygen evolution catalysts suffer from insufficient activity and stability.Hetero-interface engineering is one of the most effective strategies for enhancing OER activity by regulating local electronic structure of active site,and increasing the number of active sites by adding other metal elements is also an effective method to improve catalytic activity.Based on the above,NiFe₂O₄/NiMoO₄hetero-interface and higher-valence iron were obtained by oxygen plasma to achieve excellent electrocatalytic oxygen evolution reaction activity and stability in this thesis.Through various ex-situ and in-situ characterization,the irreversible reconstruction process of NiFe₂O₄/NiMoO₄in the oxygen evolution reaction process was demonstrated.At the same time,the true active species were identified.The main research contents of this paper are as follows:（1）NiMoO₄nanowires with NiFe PBA（NiFe prussian blue analogue）nanoparticals（NPs）were obtained by hydrothermal method and ion exchange.The transformation of NiFe PBA NPs to NiFe₂O₄NPs on NiMoO₄nanowires was completed by oxygen plasma treatment,and the hetero-interface between NiFe₂O₄NPs and NiMoO₄nanowires was characterized by high resolution transmission electron microscope.（2）By comparing the X-ray photoelectron spectroscopy of the samples before and after oxygen plasma treatment,it was found that the NiFe₂O₄/NiMoO₄hetero-interface produced electron transfer effect,the binding energy of iron increased,and the content of Fe³⁺relative to Fe²⁺increased through semi-quantitative analysis.The high-valence iron contributes to the excellent OER performance of NiFe₂O₄/NiMoO₄.Overpotential of 270 mV is required to reach a current density of50 m A cm^-2,while the overpotential is only 309 m V at 500 m A cm^-2.Meanwhile,NiFe₂O₄/NiMoO₄showed excellent oxygen evolution reaction stability at a constant current density of 50 m A cm^-2.（3）Through in-situ Raman characterization of OER activation process,it was determined that the Fe site of NiFe₂O₄/NiMoO₄was reconstructed into Fe OOH and the Ni site was transformed intoγ-Ni OOH.In combination with ex-situ X-ray photoelectron spectroscopy and ex-situ high-resolution transmission electron microscopy,the above results indicated the irreversible reconstruction process of NiFe₂O₄/NiMoO₄and the true active species in OER were FeOOH and NiOOH.