Synthesis And Modification Of Transition Metal Chalcogenide And Application In Electrocatalytic Water Splitting

Since the revolution of traditional fossil energy in the industrial society,human life quality has made a qualitative leap.However,together with the social progress and rapid development of science and technology,the pollutants that emitted by traditional fossil fuel consumption have caused severe damage to our living environment.Because traditional fossil energy resources are limited and difficult to recycle,therefore environmentally friendly energy resources are need to be explored.Thus,the biggest challenge which human beings are facing after entering into the 21st century is the sustainable use and development of new green energy resources.Fortunately,many researchers around the world are working on the development of new clean energy to replace the current traditional fossil energy and achieving a sustainable development of energy in the future.With the development of nanotechnology,the nanomaterial has many functional applications those are not available for which with the large sizes of similar materials due its small size and large specific surface area merits.In view of the controllable preparation of functional nanomaterials,we gradually found that these functional nanomaterials with different morphologies show good application prospects in optoelectronic devices,electrocatalysts and energy reservation material,which are suitable for the development of new energy resources.Designing both efficient and selective electrocatalysts is critical and gains an increasing attention.This thesis aims to control the preparation of transition metal chalcogenide functional nanomaterials?TMCFNs?and explore its application in electrocatalytic water splitting.Through a series of control methods,the shape of TMCFNs can be controlled during the preparation,and its performance in electrocatalytic water splitting can be further improved by structural modification.At the same time,we utilize X-ray photoelectron spectroscopy and other characterization techniques to understand the relationship between the fine structure of the material itself and the performance regulation,which demonstrate that the TMCFNs have a good catalytic activity and stability as electrocatalysts.Our work not only broadens the research field for the scientific research and accelerates development of new energy,but also provides new ideas in response of energy conversion.The specific research contents are as follows:1.The NiCo₂O₄ nanowires can be successful synthesized by control the solvothermal reaction and its surface metal valence is regulated via MOF precursor's organic ligands.The HER tests show that its exhibits a remarkable catalytic activity and stability under alkaline conditions.Particularly,the HER has an overpotential of 83 mV at a current density of 10 mA cm^-2 and a stability up to 80 hours.For the OER,when the current density is 10 mA cm^-2,the corresponding overpotential is 280 mV.Later on,the NiCo₂O₄ nanowires are used as electrodes material for both the positive and negative electrodes,and they have good water total decomposition performance.When the current density is 100 mA cm^-2,the driving voltage is only 1.8 V,and it can be stably used for up to 15 hours.It is worth noting that the modified nanowires also have a good performance in energy conversion,and they are assembled as a positive electrode material of a zinc-air battery into a liquid zinc-air battery with a high specific energy(800 mAh g^-1)and a good long-range stability?100 hours?.In this section,we have successfully prepared functional nanomaterials that can be applied to electrocatalytic water total decomposition and have certain zinc-air applications.2.The selenium-doped bimetal oxide Mn₃O₄/NiSe₂ nanosheets with a thickness of only 3 to 5 nm were designed and synthesized by the solvothermal reaction.XRD tests showed that the content of NiSe₂ in the material was very low and the bulk of this material was Mn₃O₄.According to the performance test of electrocatalytic water splitting,the result shows that the material exhibits a good catalytic performance.During the OER,the overpotential is about 228 mV,and the current density is 10 mA cm^-2.The overpotential is about 59.4 mV in the HER process given the current density is 10 mA cm^-2,and the stability of the alternating current test with the same piece of material can be more than 10 hours.Above all,we have successfully prepared a dual-function electrolyzed water catalyst with controlled morphology,and it has a low catalytic overpotential,which can broaden new catalytic materials for the development of overall water splitting.3.A CoSe₂/MoO₂ nanorod with high chaos and surface roughness is prepared.HRTEM proves that the lattice fringe is clear and exists two-phase interfaces.Exposuring more active sites can enhance the catalytic performance of the material caused by the defects between the interfaces.In the meantime,the rough surface helps to increase the surface area,and the relative active specific surface area test further confirms that the electrochemical active area is greatly improved after selenization.The nanorods exhibit a good catalytic performance and stability under alkaline conditions.Under alkaline conditions,the HER process has an overpotential of about 45.8 mV at a current density of 10 mA cm^-2 and a stability up to 36 hours.In summary,we have increased the internal chaos of the material by means of selenization,which can expose more defects,increase the number of active sites,and increase the electrochemical active area.This work broadens the way of building new catalytic material for the new energy research.