Study On The In-situ Growth Of Three-dimensional Porous Nickel Foam Nickel-iron-based Water Electrolysis Catalyst

At present,the search for clean and renewable new energy has become a pressing challenge.Hydrogen production methods mainly include methane reforming,coal gasification and electrolytic water to produce hydrogen.In these ways,fossil fuels are still being used in methane reforming and coal gasification,which contrary to the search for clean energy.As an efficient and clean technology,the advantages of electrolyzing water to produce hydrogen are obvious that it can easily be combined with other renewable energy sources,such as wind,tidal and solar energy.These energy sources from nature are the good solution to avoid the problems caused by burning fossil fuels.Therefore,electrolytic water to produce hydrogen in recent years has attracted much attention.It is well known that electrolytic water for hydrogen production is composed of oxygen evolution reaction?OER?and hydrogen evolution reaction?HER?.However,due to the low energy efficiency caused by the high overpotential required by the OER at the anode and the HER at the cathode,the practical application of electrolytic water for hydrogen production is greatly limited.Therefore,it is necessary to develop a stable and efficient electrolytic water catalyst to reduce the overpotential of OER and HER.At present,noble metal Ru-based materials and Pt-based materials are the most effective catalysts for OER and HER.However,precious metals are scarce on earth,so their prices are very expensive.These problems have seriously hindered the commercial application of electrolytic water for hydrogen production.In addition,because OER prefers to occur in alkaline electrolyte and HER in acidic electrolyte,the catalytic efficiency of electrolytic water tends to decrease further when they are in the same electrolytic system.In addition to the above problems,the stability of the catalyst is another important factor in the commercial application of electrolytic water.Therefore,the design of catalysts with high activity,low cost,strong tolerance of electrolyte pH and long-term stability to replace noble metal-based catalysts has become an important challenge to the commercialization of hydrogen production.Recently,transition metal?Mn,Ni,Co and Fe?have been widely studied for electrolytic water.In addition,it is found that the combination of the two metals tends to bring higher electrochemical performance to OER and HER.Compared with other electrocatalysts?NiCo,NiMn,CoFe,etc.?.The catalysts based on NiFe tend to show excellent performance in OER and HER.What is more interesting is that Ni and Fe are always found together on the earth,and the reserves of Ni and Fe on the earth are very rich,and their application in electrolytic water catalysts can greatly reduce the commercialization cost.In terms of stability,combining the catalyst with the conductive substrate is a very effective method.In particular,the Ni foam substrate with porous structure,and the unique 3D structure of nickel foam can not only increase the contact area between catalyst and electrolyte,but also play a good supporting effect.In this paper,the applications of NiFe based materials and nickel foamed substrates in OER and HER have been studied.The(Fe_xNi_1-x)₂P electrocatalysts on Ni foam for HER and the NiFe₂O₄electrocatalysts on Ni foam for OER are prepared.Firstly,FeNi-LDH precursor?FeNi-LDH@Ni foam?was synthesized on nickel foam by hydrothermal method.FeNi-LDH@Ni foam and NaH₂PO₂ were then placed in a tube furnace,and NaH₂PO₂ was decomposed in the atmosphere of 450?and Ar to produce PH₃ to make FeNi-LDH@Ni foam phosphating.After the HER test,it was found that(Fe_0.048Ni_0.952)₂P@Ni foam exhibited excellent HER performance and long-time stability at high current density in different pH electrolytes.On the other hand,density functional theory?DFT?calculations were used to explain the superior catalytic performance of the catalyst.The results show that proper doping of Fe can effectively regulate the charge distribution around the active sites.By increasing the number of charge transfer at active sites,the reactive barrier of HER is reduced.Using the amphoteric nature of Fe?OH?₃,a certain amount of Fe?OH?₃ and Ni foam were put into high concentration NaOH solution,and the octahedral NiFe₂O₄@Ni foam.was successfully prepared by hydrothermal reaction at high temperature and high pressure.Then the NiFe₂O₄@Ni foam was etched with plasma,resulting in defects on the NiFe₂O₄@Ni foam surface.Then the treated catalyst was tested and analyzed.The results showed that the NiFe₂O₄@Ni foam after etch has better OER initial potential and higher current density.The catalytic performance of the obtained catalysts is comparable to that of the leading OER catalysts at home and abroad,and the stability at high current density is also verified.