Preparation Of Nickel-based Layered Hydroxide Nanomaterials And Research On Its Electrocatalytic Performance

With the continuous success of the development of renewable energy on a global scale,the need to integrate renewable energy into the current energy and industry landscape continues to grow.On account of its high energy density(140 M J kg^-1),environmental friendliness without carbon emissions,hydrogen(H₂)is expected to become a promising energy storage medium or carrier.At present,nearly 95%of H₂is produced by reforming or thermal cracking of hydrocarbons(such as fossil fuels or biomass),but this method will result in the production of high carbon-containing gases and high costs.Electrochemical water splitting provides an efficient,facile,and clean route for the production of high-purity H₂.However,as the half-reaction,the anodic oxygen evolution reaction(OER)is kinetically sluggish and needs a large overpotential to overcome the reaction barrier(1.23 V vs.reversible hydrogen electrode,RHE).Noble-metal-based materials such as IrO₂and Ru O₂are by far the state-of-the-art OER catalysts(WOCs)yet suffering low abundance and high cost.So earth-abundant WOCs are highly attractive.Nickel(Ni)-based hydroxides due to their advantages of low cost,adjustable composition,high Redox activity and excellent electrochemical performance,have attracted extensive attention in the field of energy storage and conversion in recent years,especially in water oxidation reaction.However,due to its inherent shortcomings such as poor electrical conductivity,small specific surface area and other factors hinder its application in water oxidation.In this regard,a series of nickel-base hydroxide nanomaterials were prepared and their OER activity was further investigated.The main work contents are as follows:(1)The combination of strontium(Sr)and nickel(Ni)is used as an LDH material to be electrodeposited on 304 stainless steel(NiSr LDH/SS)with excellent conductivity.Stainless steel has excellent ductility and can be stable for a long time under alkaline conditions.Secondly,it can improve the conductivity of the overall material and facilitate the transfer of electrons.The problem of poor conductivity of LDH is solved.The electrodeposition technology adopted enables LDH to grow steadily on stainless steel,avoiding the problem of large contact impedance caused by traditional use of adhesives,and at the same time expanding the specific surface area of LDH.When tested in 1.0 M KOH,NiSr LDH/SS only needs an overpotential of 256mV to provide superior catalytic activity at a geometric catalytic current density of 20 mAcm^-2,while maintaining catalytic activity for at least 24 hours.(2)Synthesis and electrocatalytic properties of hierarchical CuO@NiCo layered double hydroxide core-shell nanoarrayDeveloping hierarchical electrocatalysts for the oxygen evolution reaction(OER)is of great importance for electrochemical hydrogen production.Here,we describe the development of hierarchical CuO@NiCo layered double hydroxide core-shell nanoarray on copper foil(CuO@NiCo LDH/CF)as a 3D OER electrocatalyst.When tested in 1.0M KOH,this electrocatalyst offers superior catalytic activity with a geometrical catalytic current density of 20 mA cm^-2at an overpotential of only 256 mV.And it also displays strong long-term electrochemical durability to retain its activity for at least 24h.The above research contents not only provide a new idea for the design of metal molybdate as an electrocatalyst,but also find a feasible method for finding new energy sources and solving environmental problems.(3)Synthesis and electrocatalytic properties of La doped CuO@NiCo layered double hydroxide core-shell nanoarrayCation doping may change the morphology of copper-based materials,increase electrical conductivity,and improve kinetics.As a one of the rare earth metal element,La is rich and abundant,but there are few reports on OER.We tried to further dope La element based on the Cu(OH)₂@NiCo LDH core-shell structure.Studies have found that La-doped Cu(OH)₂@NiCo LDH has better catalytic performance than Cu(OH)₂@NiCo LDH,which is mainly due to the synergistic effect of La and Cu(OH)₂@NiCo LDH which can be effectively enhanced the conductivity and stability.In the OER test,the doped Cu(OH)₂@NiCo LDH/CF needs an overpotential of 295 mV to drive the geometric current density of 40 mA cm^-2,and it can be well maintained its stability(at least 25 hours).This study once again proves the great potential of Ni-based nanomaterials as OER catalysts in alkaline media.In conclusion,Ni-based nanomaterials have excellent performances when work as OER catalysts,and provide a new idea for the development of renewable energy.