| The excessive consumption of fossil fuels and the serious environmental problems promote the research and development of clean energy.Electrolysis of water is a potential technology to alleviate energy crisis and environmental problems.However,the slow kinetic process of water splitting hinders its practical application,so it is imperative to develop efficient electrocatalysts.Layered transition metal hydroxide is a promising electrocatalyst in alkaline solution because of its abundant earth resources,good catalytic performance and excellent stability.Morphology control and introduction of heteroatoms can further optimize the electronic structure,enhance the electrical conductivity and improve the electrocatalytic performance of layered hydroxide.In this thesis,ruthenium（Ru）was introduced to layered cobalt-based hydroxide nanocones and then converted into corresponding derivatives by means of topological transformation.The main research contents are as follows:（1）Layered Co Ru hydroxide nanocones with different Ru contents were synthesized by coprecipitation method in one step,where Ru partially replaced Co.It is found that the Ru doping can increase the layer spacing of hydroxide nanocones and promote the performance of oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）.However,when the addition amount of Ru is too high,the conical morphology is destroyed,the OER performance decreases.Co-10%Ru hydroxide nanocones show the best OER performance,with an overpotential of 260 m V at the current density of 10 m A cm-2.In order to ensure excellent OER and HER performance,the content of Ru should be increased as much as possible while maintaining the morphology.（2）Based on the above conclusion,Co Ni Ru hydroxide nanocones were synthesized by adsorption method,which could maintain the morphology and have high content of Ru.Based on the topological transformation rules of Co Ni Ru hydroxide nanocones,a series of metal,oxide and phosphide derivatives were synthesized by calcination.Electrocatalytic tests show that topological transformation can improve the HER performance of hydroxide.However,only oxide has excellent OER performance.At the current density of 10 m A cm-2,the OER and HER overpotentials of the oxide are 188 m V and 90 m V,respectively.（3）By adsorption method and subsequent calcination,the composite NCO@Ru O2-NCs were synthesized,and the NCO@Ru O2 nanosheets（NSs）were synthesized for comparison.The introduction of Ru led to the disordered orientation of the crystal lattice at the interface,which caused the poor crystallinity and the increase of oxygen vacancies on the surface.NCO@Ru O2-NCs have more oxygen vacancies than NCO@Ru O2-NSs because of the structure difference.The increase of oxygen vacancies and the interfacial synergistic effect of NCO and Ru O2 improve the electrocatalytic performance of the material.As a bifunctional catalyst,the NCO@Ru O2-NCs electrode exhibits a low cell voltage of 1.5 V and 2.0 V at the current density of 10 m A cm-2 and 500 m A cm-2 respectively,and has a long stability of 45 h,which is superior to the benchmark Pt/C-Ru O2electrode.The Faraday efficiency of 96.2%demonstrates the feasibility in practical application.The adsorption method proposed in this thesis can be applied to other materials with different morphology and composition,providing a new idea for the introduction of heteroatoms.Heteroatoms can lead to the disordered crystal plane orientation,which can contribute to the generation of oxygen vacancies and reduce the energy barrier in the electrocatalytic reaction process,and accelerate the reaction rate.Heterogeneous interfaces provide more active sites for catalytic reactions and have broad application prospects in the design of high-performance catalysts. |
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