Preparation And Electrocatalytic Properties Of Three Materials Based On Oxygen Vacancy Defect Principle

Since the end of the twentieth century,the world has faced serious environmental pollution and huge energy crisis.It is urgent to control pollution and seek new energy.The in-depth development of electrocatalysis technology can provide solutions to the above problems,in which electrocatalysts play the dominant role.Developing electrocatalysts with rich oxygen vacancies via the defect engineering strategy is one of the research hotspots in recent years.Defect engineering is considered to be an effective strategy to improve the catalyst activity and stability.It is of great significance to investigate the generation of oxygen vacancies in materials and their mechanism in electrocatalytic processes.In this paper,oxygen vacancy defect was introduced to modulate the electronic structure and surface structure of the catalyst,and the obtained oxygen vacancy containing materials were further applied in the fields of electrochemical sensing,energy conversion and storage.Different methods were used to control the oxygen vacancies in the materials.Three kinds of nanomaterials rich in oxygen vacancies were constructed,and their structures,compositions and other properties were explored.Excellent electrocatalytic activity was achieved,and the corresponding electrocatalytic mechanism was speculated.The details are as follows:?1?Cubic fluorite-type CeO₂ with rich oxygen vacancy was firstly prepared by hydrothermal calcination method.X-ray diffraction?XRD?,scanning electron microscope?SEM?,energy dispersive X-ray spectroscopy?EDS?and other analysis techniques were used to study the structure,morphology,and chemical composition of the prepared CeO₂.These results showed that cubic fluorite-type Ce O₂ nanoblocks had been successfully prepared.An electrochemical sensor for bisphenol A?BPA?was constructed based on Ce O₂ nanoblocks and the excellent electrochemical performance was verified by electrochemical impedance spectroscopy?EIS?,cyclic voltammetry?CV?,and differential pulse voltammetry?DPV?.The experimental results showed that the electrical conductivity of CeO₂/CPE and the electrocatalytic activity for BPA have been significantly improved.In DPV,a good linear response was obtained within the BPA concentration range of 0.01?5.97 and 5.97?49.57?mol·L^-1,with a detection limit of 0.0033?mol·L^-1?S/N=3?.CeO₂/CPE showed good stability,repeatability,repeatability and anti-interference performance.At the same time,CeO₂/CPE showed good applicability in the analysis of actual samples.?2?Cerium-doped zinc tungstate?Ce-ZnWO₄?nanomaterial was prepared by doping method.The structure and morphology of Ce-ZnWO₄ samples were observed by XRD,SEM and transmission electron microscope?TEM?.EDS mapping,X-ray photoelectron spectroscopy?XPS?and ultraviolet-visible absorption spectroscopy?UV-vis?instruments were used to verify the content of oxygen vacancies in Ce-ZnWO₄ samples.The results show that the lattice of 2%Ce-ZnWO₄ nanorods shrinks,decreases in size,and had a higher concentration of oxygen vacancies.Based on 2%Ce-ZnWO₄ nanorods,an electrochemical sensor was constructed.The electrochemical performance of the sensor was verified by CV,EIS,and DPV.The experimental results showed that 2%Ce-ZnWO₄/CPE showed excellent electrocatalytic activity against carbendazim?CBZ?,and the detection limit of CBZ was obtained to be0.0033?mol·L^-1?S/N=3?.In the meanwhile,the sensor realized the determination of dopamine?DA?and uric acid?UA?,with the detection limits of 0.0033?mol·L^-1 and 0.17?mol·L^-1 in the wide linear range from 0.01?30?mol·L^-1 and 0.5?100?mol·L^-1 for DA and UA,respectively.?3?A novel defect-rich Co₃O₄/VO₂ NHs was synthesized with zeolitic imidazolate framework-67?ZIF-67?nanocrystals as the templates to anchor VO₂ nanoparticles?NPs?.XPS,TEM,electron paramagnetic resonance?ESR?,and UV-vis confirmed that the interface charge was redistributed and rich oxygen vacancy defects were generated in the composite.CV,linear scanning voltammetry?LSV?,chronopotentiometry?CP?and other electrochemical testing methods were used to analyze its oxygen evolution reaction?OER?reactivity and capacitance performance.A low overpotential of 333mV was obtained at the current density of 10 mA·cm^-2 for OER and a high specific capacitance of 489·F·g^-1 was got at a current density of 5·A·g^-1 as pseudocapacitors.The capacitance retention for the Co₃O₄/VO₂ NHs was 72.9%when increasing the current density from 5 to 50 A·g^-1.The results demonstrated that the introduction of defect not only offered more available catalytic active sites but also stabilized the interfacial structure of the nanohybrids efficiently by depleting the stress.