Study On Photocatalytic Properties Of Nickel Oxide Composites

In this paper,first-principles calculation based on density functional theory was used to explore the geometric structure and electric properites of nickel oxide composites.The geometric model,energy band structure,density of state density,charge distribution were calculated to illustrate the photocatalytic mechanism of nickel oxide combined with two-dimensional layered graphene-like materials?graphene,nitrogen-related graphene,fluorine-related graphene,g-C₃N₄?.Additional,the effect of defects on the surface of Ni?OH?₂ was discussed.The specific work content is as follows:?1?The surface properties of Ni?OH?₂ and defect state Ni?OH?₂ were investigated in this chapter using first-principles calculations.Density of states and structural stability of the pure and defective surfaces of Ni?OH?₂ were calculated.The results showed that three vacancies?nickel vacancy,oxygen vacancy,nickel and oxygen vacancies?could improve the conductivity of nickel hydroxide,which made the system transition from insulator to metal phase.Especially when two nickel vacancies existed,the architecture was thermodynamically most stable,and the conductivity of the system was more excellent.Meanwhile,the adsorption properties to urea molecules on Ni?OH?₂?001?surface and Ni?OH?₂?001?-V_2NiNi surface were compared.The theory proved that the Ni?OH?2?001?-V2Ni surface system exhibited electron-rich states and was more able to adsorb urea molecules.These calculations showed that the electron transport performance could be improved better and the surface activity was significantly enhanced by making various intrinsic defects to Ni?OH?₂.?2?Photocatalytic performances of the GR/NiO,GR-N/NiO and GR-F/NiO composite systems were studied by means of simulation calculation.Firstly,the interface binding energy of these three systems was calculated,and it was found that the composite system had strong binding ability.Secondly,the energy band,density of states,work function and optical properties of the composite system were calculated.The results showed that the band gap of the composite system decreased and the system changed from insulator phase to metal phase,which greatly enhanced the electron migration ability of the whole system.And that the research showed the composite systems of the GR-N/NiO and GR-F/NiO had a strong light absorption ability.Finally,the differential charge density and electron layout analysis of the composite system were calculated.The results showed that the interlayer charge transfer of the composite system lead to a decrease of the d-state energy in the Ni of NiO,which enhanced the binding of the GR-N/NiO and GR-F/Ni O.Meanwhile,the hydrogen evolution reaction?HER?activity of NiO,nitrogen-doped graphene,fluorine-doped graphene and composite system were also calculated.It were found that tpPGhtee?Rr1f-o1Fcr1/o?mN miavnOpac?ole0su.i0e t1Te??h?eshryGyesfdHtore=ro0emg.,e0 int5h saaheddoVs w?o,bre epdttw titehohrinac t h hft rhyesedeh r cooeowgnmeeendrpg o ysemi tv?oeor?lesuGy tsieHtox=enc0me.l 0lah8eca ntdite v sVitht?ryy o.dnw rgaoE sgps ephcnelo octioseaecvl alottylaou l tyitttohhineec performance certainly,which also provided experimental ideas for the experimental synthesis of highly active photocatalytic materials.?3?Based on the first principle calculation of density functional theory,the photocatalytic performance of g-C3N4/NiO composite system was studied.First,the interfacial binding energy,the electronic structure of the system,the optical properties and the performance of photocatalytic decomposition of water for hydrogen production of the NiO?001?/g-C3N4 and Ni O?111?/g-C3N4 composite system were calculated.The results showed that the heterojunction system had good interfacial binding ability,especially for the NiO?111?/g-C₃N₄ composite system,its interfacial binding ability reached-9.74 eV,indicating that the composite had the possibility of experimental synthesis.Secondly,the calculated results of energy band and density of states showed that the composite system could adjust the band gap of single-phase photocatalysis and enhance the ability of light absorption to solar light.Meanwhile,it was also found that both Ni O?001?/g-C₃N₄ and NiO?111?/g-C₃N₄ composite systems had strong ability to decompose water to produce hydrogen.These theoretical studies could provide a theoretical basis for the experimental synthesis of composite photocatalytic materials based on NiO.