Controllable Preparation And Electrocatalytic Properties Of Ni-Based Nanomaterials

Until now,with the increasing consumption of traditional fossil fuels,energy problem has become one of the main reasons restricting social development.At the same time,the environmental problems caused by the burning of large amount of fossil fuels have also attracted extensive attention.Therefore,the search for new clean energy has become main solutions to energy and environmental problems.Hydrogen has attracted the attention of researchers because of its advantages of pollution-free combustion,renewable energy and high combustion heat.But conventional industrial methods of producing hydrogen still rely on fossil fuels and purity is unlikely to be as high as expected.The electrolytic water decomposition process only produces hydrogen and oxygen without other reaction products,with no pollution,low energy consumption.Electrolytic water has two half reactions,hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?.Compared with HER,OER involves more complex kinetic process,such as mass and charge transfer,which leads to the occurrence of the reaction is much more difficult,and is the main restriction factor of water electrolysis.Catalyst can great improve the efficiency of this process,so it is the key to solve the energy problem to find a suitable catalyst and improve the efficiency of oxygen evolution reaction.The traditional noble metal oxide catalysts are currently known to be the most catalytic active OER catalysts,such as RuO₂ and IrO₂.However,they have fewer reserves and are more expensive to use as hydrogen-producing catalysts for large-scale industrial applications.Therefore,it is stringent to develop non-noble metal OER catalysts.Transition metal compounds have been widely studied because of their low cost and low toxicity.Especially,transition metal oxides and hydroxides have high electrocatalytic activity.As a typical transition metal,Nickel has attracted wide attention because of its abundant storage in the earth,high stability,good corrosion and other advantages.Nickle-based nanomaterials have shown excellent performance in electrochemical catalysts.In this paper,the electrocatalytic properties of nickel-based nanomaterials are studied in relation to their composition,morphology and microstructure.The main research contents of this article are divided into the following three aspects:1.The?-Ni?OH?₂ microspheres assembled by ultrathin nanosheets were prepared by solvothermal method.Specific surface test?BET?showed that the specific surface area of the sample was up to 169.94 m²g^-1,which could provide a large number of active sites in the electrolytic water process.Electrochemical tests showed that OER overpotential was 320 mV at 10 mAcm^-2 and the corresponding Tafel slope was98.7mV/dec.This method of preparing nickel hydroxide is simple,low-cost and environmentally friendly.Therefore,this material provides a new idea for the development of OER catalyst.2.NiFe layered double hydroxides?Ni-Fe LDH?microspheres with different Ni-Fe ratios were prepared by solvothermal method.OER tests showed that electrocatalytic activity was affected by the Ni-Fe ratios.The Ni-Fe LDH with a Ni-Fe ratio of 7:3 had the highest OER activity.BET test showed that its specific surface area could reach 79.374m²g^-1.Compared with Ni?OH?₂ and Fe?OH?₃,the overpotential was found to be as low as 290 mV at 10 mAcm^-2 and Tafel slope was significantly reduced,which was related to the change of surface electronic structure and the increase of conductivity caused by the introduction of Fe.3.Nanometer spinous Ni_xCo_1-x?OH?₂ was prepared by solvothermal method on nickel foam substrate,and then amorphous NiFe compound was deposited on its surface by electrodeposition to abtain Ni_xCo_1-x?OH?₂@NiFe-AM composite.Electrochemical tests showed that the catalyst had good catalytic activity and stability for OER and HER.The electrocatalytic activity was strongest when the electrodeposition time was 30 seconds.We attribute this high activity to the synergistic effect of Ni_xCo_1-x?OH?₂ and NiFe-AM.At the same time,its unique three-dimensional interconnection structure also facilitates rapid charge transfer and proton transmission.