Hydrothermal Synthesis Of Self-supported Co-Ni Bimetallic Telluride And Oxygen Evolution Performance Of Electrolytic Water

With the deterioration of natural environment and the growth of energy demand,people need to develop clean and alternative sustainable energy.Hydrogen energy is regarded as an effective potential energy to replace non-renewable energy among all kinds of energy sources,water splitting is one of the core technologies for the preparation of green hydrogen,which is of great significance for the realization of"carbon neutralization"strategic plan,and it is also one of the key technologies for the economic development of hydrogen energy.Water splitting involves two and a half reactions:hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）.Due to the kinetics of OER is relatively slow,restricting the hydrogen efficiency.Therefore,developing OER catalysts with high activity and good stability is the key point in the field of water splitting.In recent years,transition metal telluride has been widely used as functional materials for energy storage,environment and catalysis,which has been regarded as a potential material to replace traditional noble-metal catalysts for its unique and adjustable electronic structure.What’s more,the self-supported electrode can be used not only as a conductive substrate to provide hydrothermal reaction sources,but also directly as the electrode.There are no additional polymer binder in the process of the preparation,which increases the stability of the electrode.Hence,Co foam,Ni foam and Co Ni alloy foam were used as the substrate materials in this paper.In suit growth of Co/Ni metal telluride on these substrate by one-step hydrothermal method,and then Co-Ni bimetallic telluride was synthesized by introducing other transition metal Ni/Co.Self-supported Co-Ni based bimetallic telluride catalyst materials with controllable morphology and excellent electrocatalytic OER performance were successfully prepared by optimizing the hydrothermal synthesis process parameters.The main research results are as follows:（1）Co@CoTe₂nanocrystalline was synthesized on Co foam（CF）and applied to the field of alkaline medium（1.0 M KOH;p H=13.5）electrocatalytic OER.When the hydrothermal reaction temperature was 240°C,Co@Co Te₂-240 electrode shows excellent electrocatalytic performance,which needs the overpotential of 286m V attaining the current density of 10 m A cm^-2,the Tafel slope is 42 m V dec^-1.Ni doped Co Te₂nanocrystalline catalyst（Co@Ni Co Te₂）was prepared by introducing transition metal Ni,which further improved the catalytic performance of Co-Ni based bimetallic telluride catalyst.The optimizing Co@0.2g Ni Co Te₂-240 electrode required a low overpotential of 280 m V to attain an current density of 10 m A cm^-2,with the Tafel slope as 34 m V dec^-1,and has excellent electrochemical stability.（2）The samples of Ni-Te（no Co）、CoNiLDH（no Te）and CoNiLDH-Ni_10.35Te_7.9-NiTe（denoted as CoNiLDH@Te）was synthesized in situ on the surface of Ni foam（NF）by a similar hydrothermal method.Analyzing the crystal phase,morphology and alkaline electrocatalytic OER performance of these electrocatalysts.Compared with bare Ni foam,When the hydrothermal reaction temperature is180°C and the amount of Co（NO₃）₂·6H₂O is 0.40 g,the 0.4Ni Co LDH@Te-180C electrode exhibits an impressive electrocatalytic activity,which requires the overpotential of 360 m V,producing a current density of 10 m A cm^-2,and the Tafel slope is 56.6 m V dec^-1.Due to the heterostructure not only has the high specific surface area and abundant active sites of LDH,but also has the high conductivity of transition metal telluride.（3）CoTe₂-NiTe₂heterojunction was synthesized by one-step hydrothermal method using Co Ni alloy foam designed for 10%Ni（atomic percent）as substrate.When the hydrothermal reaction temperature is 240°C and the amount of hydrazine hydrate（N₂H₄·H₂O）is 3.0 m L,the 3CNT/CNF-240C electrode has the best OER performance.The 3CNT/CNF-240C electrode only needs a low overpotential of 280m V to attain an anodic current density of 10 m A cm^-2,with a small Tafel slope of19.4 m V dec^-1.The excellent OER performance of the sample can be attributed to the interaction between Co Te₂and NiTe₂,which promotes the charge transfer process.In addition,the Co Te₂-NiTe₂heterojunction nanosheets were synthesized by the Co Ni alloy foam with different Ni（10%Ni,20%Ni and 30%Ni）.The results show that the Co Te₂-NiTe₂heterojunction prepared by the Co Ni alloy foam with10% Ni has the best OER performance.