Preparation Of In-situ Phosphate Intercalation Ni（OH）₂/NiOOH And Performance Of Elec-catalytic Decomposition Of Water To Produce Oxygen

The energy crisis and environmental pollution are becoming more and more serious,and the development and utilization of renewable clean energy is urgent.Hydrogen is currently the most promising new energy source carrier,and there are many ways to obtain it.Among them,photovoltaic power generation-water electrolysis is one of the most valuable methods.Photovoltaic power generation technology has been industrialized,but electrolyzed water is still limited by problems such as device,solution resistance,and reaction overpotential on the electrode surface.Moreover,Oxygen evolution reaction（OER）for water electrolysis has a bigger obstacle than Hydrogen evolution reaction（HER）,so solving the problem of OER obstacle plays a decisive role in the production of hydrogen from electrolysis of water.Preparation of an excellent OER electro-catalyst is a very important way to solve the obstacle in water electrolysis.In this thesis,amorphous Ni/Ni（OH）₂ nano-sheets was grown on Ni Foam（NF）via electrodeposition.At the same time,the phosphate formed by oxidation is absorb on or intercalated into Ni（OH）₂ layers.In the process of further the electrochemical activation,Ni/Ni（OH）₂ is transformed into Ni（OH）₂/Ni OOH,and the phosphates are also intercalated to Ni（OH）₂/Ni OOH（named as NF-Ni（OH）₂/Ni OOH-Pi（Phosphate ions,Pi））,which is used as OER electro-catalyst.The Ni（OH）₂/Ni OOH intercalated by phosphate shows good oxygen evolution activity and stability.The thesis is divided into the following three parts:（1）Study on the composition and morphology of NF-Ni（OH）₂/Ni OOH-Pi.NF-Ni/Ni（OH）₂-Pi was prepared by electrodeposition method,followed by electrochemical activation to obtain NF-Ni（OH）₂/Ni OOH-Pi under alkaline conditions.And the composition and morphology of the catalyst were studied by XRD,XPS,Raman and SEM.It is proved that there is a phosphate intercalation in NF-Ni（OH）₂/Ni OOH-Pi,and the phosphate intercalation is beneficial to obtain thinner nano-sheets and to expose more active sites.（2）The activity and stability of the catalyst was studied by LSV,CV and current-time curve（I-t）etc.The phosphate intercalation is the main reason for high OER activity and stability of NF-Ni（OH）₂/Ni OOH-Pi.Moreover,the activity of NF-Ni（OH）₂/Ni OOH-Pi obtained via in-situ intercalation is more active than that of NF-Ni（OH）₂/Ni OOH via post-intercalation.When the current density is 10 m A cm^-2and 100 m A cm^-2,OER over-potentials for NF-Ni（OH）₂/Ni OOH-Pi were 90 m V and240 m V,respectively;and the stability is up to 240 h at～60 m A cm^-2.（3）Based on the research of the above two chapters,through ECSA,IR,EIS and ICP-OES testing methods,the influence of phosphate intercalation of catalyst on the catalyst structure was studied,and the possible reaction mechanism was discussed.After phosphate intercalation,the interlayer distance of laminate is increased,which is beneficial to the mass transfer along the interlayers;phosphate,as a proton transfer intermediate,effectively accepts the protons produced by the decomposition of water to improve protons transport along the interlayers to electrolyte solution.The phosphate intercalation promoted the direction adsorption of water molecules at laminates,and the direction protons movement along the layers,which reduces the resistance of the catalyst to only 0.1Ωcm^-2.These factors cooperatively improve OER performance,avoid the dissolution of the laminate metal and thus maintain the stability of the catalyst.