The Structural Regulation And Electrocatalytic Properties Of NiFe Alloy Films

Hydrogen energy is one of the most ideal and clean energy sources to solve the energy crisis and environmental problems caused by excessive use of fossil energy.Among the hydrogen production processes,electrolytic water method is one of the most promising green hydrogen production methods,which is highly dependent on highly active electrocatalysts.Oxygen evolution reaction（OER）is a semi-reaction in electrocatalytic water decomposition,which involves the transfer of four electrons.At the same time,the transfer of multiple electrons is unfavorable in kinetics,which leads to the slow kinetics of OER.Optimizing the anode catalyst and reducing the overpotential of oxygen evolution are the necessary conditions to realize the overall efficient electrolytic water process.At present,Ru/Ir-based materials are considered to be the most effective electrocatalyst materials for oxygen evolution reaction,but the high cost of this precious metal limits its large-scale industrial application.Among the electrocatalyst materials studied at present,many transition metals and their alloys are expected to have high catalytic activity and large-scale application potential because they are easy to donate and obtain electrons from incompletely filled d orbitals and their prices are low.Among them,iron-based and nickel-based alloys,as classical transition metal alloys,and the construction of their nanostructures have attracted the attention of many researchers.Because of their disordered atomic structure,metastable state,rich defects and unique chemical properties,these transition metal amorphous alloys have a good effect in wastewater purification.They are also widely used in catalytic applications in petroleum and chemical industries,and in hydrogen production by electrolysis of water.In this work,a series of NiFealloy films were prepared and doped with elements,and then nano-porous structures and nano-composite structures were constructed.Finally,the catalytic performance of oxygen evolution reaction by electrolytic water was studied.The specific contents and conclusions are as follows:NiFealloy films were prepared by magnetron sputtering,and C-doped NiFe-based alloy films were prepared by co-sputtering.The NiFe-based alloy films prepared and doped under different process parameters were characterized and tested by SEM,EDS,XPS,XRD,step meter and electrochemical workstation.The results showed that:NiFe-2 Pa/ITO shows a thin film structure with uniformly distributed nanoparticles and closely ordered,and the size of nanoparticles varies from 10 to 50nm.NiFe-2 h/ITO obtained by increasing sputtering time shows a completely different"pyramid structure"with a width of about 50nm.The NiFe-150W/ITO prepared by increasing sputtering power presents a film structure which is more closely ordered than NiFe-2 Pa/ITO with similar nanoparticles.The NiFeC-15 W/ITO prepared by doping is"fleshy without bud",and the film’s amorphousness is further strengthened,showing good catalytic activity in alkaline electrolyte,with an overpotential of 393 m V at a current density of 10 m A/cm².Based on the above research results,Zn-doped NiFeC alloy films were prepared by magnetron sputtering and co-sputtering,and Zn was removed by high vacuum physical dealloying to construct NiFeC alloy films with nano-porous structure.Finally,NiFeC alloy films with S-doped surface phase were prepared by chemical vapor deposition.The NiFe-based alloy films prepared and doped under different process parameters were characterized and tested by SEM,EDS,XPS and electrochemical workstation.The results show that:NiFeC（Zn-0.4 V）/Niis dealloyed at moderate heating temperature.The zinc element is detached to a high degree,and the pore size ranges from tens of nanometers to 200nanometers.The whole structure is honeycomb,with the roughest surface and the most voids.NiFeC（Zn）-S/Nishowed a slightly blocked and bloated nano-porous film structure,and showed good catalytic activity in alkaline electrolyte.When the current density was 10 m A/cm²,the overpotential was 272 m V.The current density of NiFeC（Zn）-S/Nicatalyst sample is well preserved after 12 hours of stability test,and the doping of S element improved the catalytic activity and stability of the catalyst.Inspired by the above two works,the amorphous structure is prepared by co-deposition of various elements,the electronic structure of the original elements is adjusted by element doping,and the specific surface area of catalyst materials is increased by the construction of nanostructures.NiFealloy thin films were prepared by electrochemical deposition,and bulk Ce-and S-doped NiFe-based alloy thin films were prepared by electrochemical deposition.Finally,NiFeCeS alloy thin films with nano-composite structure were prepared by compounding with conductive substrates with nano-structures.The NiFe-based alloy thin films prepared and doped under different bath composition conditions were characterized and tested by SEM,TEM,EDS,XPS,XRD and electrochemical workstation.The results showed that NiFeCeS/Cu（OH）₂/Cu F exhibited a nano-composite film structure with nano-particles coated with nanorods,and showed excellent catalytic activity in alkaline electrolyte.The overpotential was 227 m V when the current density was 10 m A/cm².After 12 h stability test,the current density of NiFeCeS/Cu（OH）₂/Cu F catalyst samples increased,showing excellent catalytic stability.To sum up,a series of NiFe-based alloy films prepared by many preparation methods and subsequent treatment methods in this paper have good catalytic performance and stability for electrolytic water oxygen evolution reaction,which is of positive significance for hydrogen energy development and carbon emission reduction.