Preparation Of Ni Coated Graphite Powders Composites And The Electrocatalytic Performance Of Hydrogen Evolution

As a metal–coated composite powders of a new material,Ni coated graphite powders possess both the advantages of metal nickel,such as strong conductivity,excellent magnetic properties and good performance of hydrogen evolution,and the characteristics of graphite powders,such as soft texture,strong plasticity and low coefficient of friction.Ni coated graphite powders can not only maintain the basic characteristics of metal nickel and graphite powders,but also can make up for their own shortcomings,so as to obtain excellent comprehensive performance.Therefore,as a new material,Ni coated graphite powders possess the crucial research value.Firstly,on the basis of consulting literature,we summarized preparation,basic properties and application of Ni coated graphite powder composites.Secondly,Ni coated graphite powders were prepared by electroless plating and electrodeposition technology.The morphology and surface composition of the Ni coated graphite powders have been obtained by scanning electron microscopy,X–ray energy dispersive spectrometer and X–ray powder diffractometer.The preparation of Ni coated graphite powders were discussed,such as time,temperature,bath pH,type of complexing agent and so on.Thirdly,the electrochemical behavior of Ni coated graphite powders composites electrode in H₂SO₄ solution and NaOH solution was studied by electrochemical workstation.Ni coated graphite powders were researched by means of electrochemical measurements including cyclic voltammetry,Tafel polarization,LSV polarization and electrochemical impedance spectroscopy?EIS?.The electrochemical properties of Ni coated graphite powders,reagent graphite powder and pure nickel electrode were compared.Then Ni coated graphite powders electrode was analyzed by means of hydrogen evolution reaction in water.The relationship between current density,electrolysis time,electrode materials and hydrogen production by electrolyzing water were discussed.Finally,the paper summarized.Through experimental exploration,we reached the following important conclusions:?1?Sub-micron level Ni–P coated graphite powders composites?Ni–P–C?were prepared by electroless plating technique.Morphologies of Ni–P–C?graphite?powders composites have a close relationship with time,temperature,bath pH and complexing agent and other factors.The optimal technics conditions for preparing Ni–P–C?graphite?composites:electroless plating time 4.5 h,temperature 90?,bath pH 4.8,citric acid as the complexing agent.Coating of Ni–P–C?graphite?composites is continuous,uniform and compact.?2?Ni–coated graphite powders were prepared by electrodeposition technique and were named Ni?shell?–C?core?composites.Powders electrodeposition technics are very complex,Ni²⁺can not be reduced completely on the surface of the graphite powders.Ni?shell?–C?core?composites are related to current density,plating time and bath temperature.The plating process was carried out under cathodic current density of 7.84 A/dm²,plating time of 60 min,the temperature of 55?,and a portion of the nickel coating was coated on the surface of the graphite powders by using scanning electron microscope.?3?By analysing cyclic voltammetry,Tafel polarization,LSV polarization and electrochemical impedance spectroscopy?EIS?,it could be found that Ni–P–C?graphite?powders electrode compared with the reagent graphite powders and pure nickel electrode,then showed lower potential and larger current for hydrogen evolution,lower resistivity,better conductivity,excellent electrochemical activity,higher hydrogen evolution catalytic activity.?4?In this experiment of hydrogen production by electrolyzing water,under the conditions of changing the electrolysis time and current density,Ni–P–C?graphite?powders electrode showed higher hydrogen production than the reagent graphite powders electrode.At the same time and current density,Ni–P–C?graphite?powders electrode exhibited good hydrogen evolution ability.