Study On In-situ Sulfurization Construction Of Bimetal Oxide Composite And Its Electrocatalytic Water Splitting Performance

Currently,humans’ demand for energy has been increasing.However,the current energy supply is still mainly from fossil fuel based non-renewable energy sources,which not only causes serious environment pollution during combustion process,but also limit sustainable development due to its limited reserves.Therefore,it is indispensable to seek a kind of clean and green renewable energy sources to replace fossil energy step by step for future energy development that researchers have been paying attention to.Hydrogen energy has been considered one of the most idea clean energy to replace fossil energy by right of high energy density,high burning heat value,product free-pollution etc.Hydrogen produced by cracking water,one of high-efficiency mean,has zero pollutant emissions during the reaction process,and meets the requirements of the development of green chemistry,which has a bright prospect in the industrial large-scale production.The electrocatalytic water splitting consists of two half-reactions,namely the hydrogen evolution reaction（HER）that occurs at the cathode and the oxygen evolution reaction（OER）that occurs at the anode respectively.The noble metal（Pt、Pd）and corresponding oxide such as RuO2,IrO2 are the most outstanding catalyst for HER and OER,respectively.Nevertheless,these precious metals lack of resources,high price,which limited the use of industrial production.Bimetal oxide is an ideal electrocatalyst to replace noble metal catalyst owing to easy to synthesis,high-activity and low price.However,this material has inherently poor electrical conductivity and insufficient exposure of catalytic active site,which prevent its further employ.Based on this,we put transition metal oxide and conductive substrate together to construct transition metal oxide-based composited material by in-situ growth technique.The transition metal oxide and its composite has achieved electrocatalytic activity improved and improved the active site exposure.After further in-site sulfurization,the electronic structure and interface structure was further modified and modified to regulate the local charge of the active center,improved the charge transfer at the interface,improved the performance of electrocatalytic water splitting,and studied the internal mechanism that affects the activity.the research contents of this paper are as follows:In the first chapter,we are mainly summarizing the background of electrocatalysis water cracking technology and its corresponding research status.The reaction principle of electrocatalytic cracking water and the key factors restricting the efficiency of electrocatalytic cracking will emphatically emphasis.Secondly,the main indicators for evaluating the performance of electrocatalysts are summarized.Finally,Analyzed the research strategy to improve the reactivity and stability of OER,as well as the research progress and existing problems of domestic and foreign researchers,and the topic selection ideas and research content of this article are proposed.In the second chapter,the Ni1-xFe2O4/Ni3S4/Ni（OH）2/NF composite material with heterogeneous structure was constructed in situ on the nickel foamed matrix through Fe3+solution low-temperature hydrothermal corrosion nickel foamed and subsequent in-site treatment.First of all,Ni（OH）2 with hexagonal nanosheet structure and NiFe2O4 nanoparticle with catalytic activity are evenly grew on the nickel foam after Fe3+low-temperature hydrothermal corrosion treatment of nickel foamed.The in-situ attachment of the nanoparticles on the nanosheets exposes more active sites.Meanwhile,the close combination of the nanosheets and the nanoparticles is conducive to accelerating the charge transfer between the substrate and the active site interface.After in-situ sulfurization treatment,Ni3S4 particles of smaller size are grown in-situ around the contact between the Ni（OH）2 nanosheets and the active species NiFe2O4 nanoparticles.The emergence of Ni3S4 particles,on the one hand,further increases the active area and exposes more active sites,which is beneficial to promote the improvement of HER catalytic performance,and at the same time strengthens the interface between the heterostructure NiFe2O4 nanoparticles and Ni（OH）2 nanosheets.The close combination of interface accelerates the charge transfer at the heterogeneous interface and reduces the overpotential of the OER process;on the other hand,sulfidation causes the generation of a large number of nickel vacancies,optimizes the charge distribution of NiFe2O4 metal active center,reduces the energy barrier required for the reaction,and significantly improves the oxygen evolution reaction activity of the material.When used as the electrode to drive the oxygen evolution reaction,it only needed 120 mV overpotential to attain a current density of 10 mA/cm2 and kept stability more than 200h in the 1M KOH solution.When used as a double electrode for the complete hydrolysis reaction,only a potential of 1.494 V is required to attain a current density of 10 mA/cm2.This show that the prepared Ni1-xFe2O4/Ni3S4/Ni（OH）2/NF composite material has excellent OER electrocatalytic activity and stability,which can be used to design efficient and stable OER electrocatalysts for cracking Water provides a new method and idea.In the third chapter,we used nickel foam as substrate and hydrothermal growth of CoMoO4/NF nanoarrays on nickel foam.Then,the heterostructure composite material CoS2/Co1-xMoO4/NF was prepared by in-situ sulfurization.After in-situ sulfurization treatment of CoMoO4/NF nanorods,cobalt ions in CoMoO4 are replaced,and flower-like CoS2 is grown on the surface of the nanorods.The appearance of the nanoflower structure further increases the surface area of the material,exposes more active sites.Meanwhile,in-situ sulfurization produces a large number of Co2+vacancies and regulates the electrons in the catalytic active center.The structure optimizes the transfer of charges between the heterogeneous interface and the substrate,reduces the overpotential of the reaction,and achieves a significant improvement in catalytic performance.It needs only 134 mV to reach a current density of 10 mA/cm2 during the alkaline HER process.Compared with the un-vulcanized material,it reduces the overpotential of 76 mV.And it can perform stable cyclic voltammetry more than 1000 times to show excellent hydrogen evolution reaction activity and stability.This work provides new ideas and directions for the rational use of interface engineering and defect engineering to coordinate catalysts,so as to achieve a significant improvement in the catalytic performance of materials.In the fourth chapter,The research content and innovation points of this paper has been summarized,and the next step has also been prospected.