Research On Preparation And Performances Of Nickel Based Electrocatalysts For Oxygen Evolution Reaction

With the rapid development of society,the exploitation of fossil fuels is increasing day by day,and all kinds of environmental problems have spread all over the world.Nowadays,it is urgent to explore clean and efficient new energies to replace the traditional fuels,to relieve the consumption of resources,to protect the ecological environment,and more importantly,to continue the human civilization.Water splitting is one of the many new energy technologies and famous for the simple preparation,low cost,high efficiency and clean output of hydrogen production.However,the development of water splitting is restricted by the sluggish kinetic process of oxygen evolution,which needs to be carried out at a higher potential to achieve the formation of O=O bond.As a result,it is difficult to make the water splitting come to commercial application at a large scale.In this thesis,nickel-based ternary Ni-Co-B alloys,Ni foam co-growth dendritic-like Co-Ni₃S₂/NF,NiSe₂ nanoparticles anchored NiSe₂/g-C₃N₄ nanocoral-like composite and MWCNTs content-dependent MWCNTs/NiHCF composite have been prepared by facile electroless deposition,chemical precipitation or hydrothermal method.The morphology,structure,composition and oxygen evolution performances of as-prepared catalysts have been characterized by a series of physical and electrochemical methods.The main contents are as follows:?1?Based on the special electronegativity of boron element,Ni-Co-B?NCB?ternary amorphous alloys have been prepared by the electroless deposition method,and further discussed the effect of the molar ratio of Ni/Co on the oxygen evolution reaction.The results show that ternary NCB catalysts exhibit favorable oxygen evolution performances than those of binary Ni-B and Co-B catalysts.When the molar ratio of Ni/Co is 3:7,NCB-1 catalyst shows the lowest overpotential of only 300 mV at current density of 10 mA cm^-2.At the potential of 2.0 V?vs.RHE?,ternary NCB-1 can reach the current density of191 mA cm^-2,while the current densities of binary CB and NB are 137 mA cm^-2 and 131 mA cm^-2,respectively.In addition,the polarization curves of NCB-1 catalyst remain almost the same before and after 55 h stability test,showing a strong electrochemical stability.?2?Nanocoral-like NiSe₂/g-C₃N₄ has been successfully prepared by anchoring NiSe₂nanoparticles on multi-layered g-C₃N₄ substrates through hydrothermal method.NiSe₂/g-C₃N₄ catalyst exhibits lower onset potential of 1.38 V?vs.RHE?.Comparing with single component of NiSe₂ nanoparticles,NiSe₂/g-C₃N₄ composite exhibits lower overpotential of only 290 mV at high current density of 40 mA cm^-2.At the potential of 2.0V?vs.RHE?,NiSe₂/g-C₃N₄ can reach the current density of 199 mA cm^-2,while the current density of single component of NiSe₂ is only 142 mA cm^-2.In addition,NiSe₂/g-C₃N₄exhibits excellent stability in 1.0 mol L^-1 KOH solution.?3?Based on the 3D structure and high conductivity of Ni foam,cobalt-nickel co-grown dendritic-like Co-Ni₃S₂/NF catalyst has been prepared by one-step hydrothermal method.Comparing with Ni₃S₂/NF,Co-Ni₃S₂/NF shows the overpotential of only 274 mV at the current density of 10 mA cm^-2,while Ni₃S₂/NF catalyst needs an additional potential of 70mV to exhibit the same current density,resulting in the overpotential of 344 mV.At the potential of 2.0 V?vs.RHE?,Co-Ni₃S₂/NF can reach the current density of 191 mA cm^-2,while the current density of Ni₃S₂/NF is only 135 mA cm^-2.In addition,Co-Ni₃S₂/NF maintains a stable oxygen evolution current density during the stability test for 10 h.?4?NiHCF/MWCNTs composite catalyst has been prepared by chemical precipitation method.The effect of content of MWCNTs on electrocatalytic oxygen evolution has been discussed.When the content of MWCNTs is 14.29 wt%,as-prepared NFM-2 catalyst exhibits the lowest overpotential of only 360 mV at the current density of 10 mA cm^-2.In addition,at higher current density of 40 mA cm^-2,the overpotentials of bare NiHCF and NFM-2 catalysts are 540 mV and 440 mV,respectively.The results show that the overpotential of NFM-2 is 100 mV lower than that of single component of NiHCF,revealing its outstanding electrochemical performance of OER.At the potential of 2.0 V?vs.RHE?,NFM-2 can reach the current density of 206 mA cm^-2,while the current density of single component of NiHCF is only 97 mA cm^-2.In addition,NFM-2 catalyst exhibits long-term stability for 10 h in 1.0 mol L^-1 KOH solution.