Study On Preparation,Characerization,and Hydrogen Evolution Reaction Electrochemical Properties Of Ni-P Nanoparticles

As a kind of highly effective and cost-effective catalyst for hydrogen evolution reaction?HER?,Ni-P alloys possessing nanostructure have attracted great attention from academia.HER–an efficient method for preparing hydrogen–is worth researching under the backdrop of global warming and the appeal for alternatives of fossil fuels.When the electric power is on,Ni-P alloys are expected to greatly lower the overpotenital required for HER.By far,Ni-P alloys have served as a potential alternative for Pt.Additionally,Ni-P alloys can not only serve as cataysts for HER,but can also be catalyst for other half-reaction of water-splitting–oxygen evolution reaction?OER?.Despite the progress made in research of Ni-P alloys,however,there still remains some basic questions unsolved.This thesis focuses on preparation of Ni-P nanomaterials,a research hotspot of HER catalysts and made a series of explorations of their preparation process,characterization and electrochemical properties.Capitalizing on nickel's auto-catalytic property and sodium hypophosphite as reducing agent,a range of yolk-in-shell Ni-P nanoparticles and Ni-P nanospheres have been successfully prepared and the different reaction parameters leading to these morphologies have been studied.Electrochemical workstation was applied to test Ni-P alloys'catalytic properties and preparation process and heat treatment process,which are closely related with electrochemical properties,have also been discussed.The main content of this thesis is on the points below:?1?By taking advantage of the auto-catalytic property,a range of yolk-in-shell Ni-P nanoparticles,Ni-P nanospheres have been successfully prepared.The nickel sulfate was the nickel source and the corresponding precursor was prepared at first.Then nanoparticles of 50¹00 nm as mean size were prepared by taking sodium hypophosphite as reducing agent and palladium chloride as nucleate agent.For those acid-and alkali-soaked Ni-P nanospheres,an extra step was needed,which made use of ammonia water and a kind of acid comprised by chloric acid and sulfuric acid to rinse the nanospheres'surface.?2?A string of means of characterization were adopted to analyze the abovementioned nanomaterials'preparation method,surface morphology,microstructure and element ratio.Main conclusions of the means of characterization are:1)the first step to prepare yolk-in-shell nanoparticles was to obtain uniform and stable Ni-P nanoparticles which requires 80?as reaction temperature and SDBS as surfactant.The next step was to get the yolk-in-shell surface morphology by the sacrificial template method;2)the method to prepare Ni-P solid nanospheres was comparatively easy.The reaction temperature was90?,but this course should also be accompanied with strong stir,which would be helpful in making the materials grow into sphere-like form.3)surface morphology of the alkali-and acid-soaked Ni-P nanospheres will almost make no change;however,after this procedure of being soaked in alkali and acid,atomic percentage of nickel would decrease with a little increase of nickel.What's more,the original amorphous Ni-P alloy phase would convert in to a mixture of Ni₁₂P₅ and Ni₂P phases.4)heat treatment procedure will not cast much influence on surface morphology of materials and the molar ratio of nickel to phosphorus,but will induce phase transformation of the primitive Ni-P phases to other corresponding phases.5)due to the fact that the chemical reaction did not happen in an airtight environment,there exists some amounts of oxides on materials'surface.?3?Among all the samples,the 8-hour-heat-treated Ni-P nanospheres bear the best catalytic properties.To achieve-100 mA/cm² output current density,only 251 mV overpotential is required.By contrast,the yolk-in-shell nanoparticles,despite their novel morphology which may be useful in other applications,have comparatively inferior catalytic property.Ni-P alloys prepared in this thesis all have favorable durability.Among them,the 8-hour annealed smaple is able to secure high current density?259 mA/cm²?after long-term stability tests.Additionally,samples tested in alkaline condition need a period of time to achieve their best catalytic property.This is concerned with the removal of the oxide film on the materials surface.