Prepartion Of Nickel Oxide Composite And Its Performance Study

With the population growth and the accelerating modernization of industry,energy shortages and environmental pollution are the biggest challenges facing the world in the 21 st century.There is an urgent need to develop clean,environmentally friendly and economical energy sources.Hydrogen is recognized as a clean energy due to its good thermal conductivity,zero carbon emissions,good combustion performance,and non-polluting.At the present stage,there are a lot of methods to produce hydrogen,among them the photocatalytic water splitting is the most environmental friendly method,since it just needs light,water,and photocatalyst.Nickel oxide?NiO?is a very important p-type semiconductor.Under the light excitation,it can quickly produce electronic-hole pairs,and the position of the conduction band is lower than the H⁺/H₂ reduction potential,thus water can be decomposed to produce hydrogen.However,due to its wide bandgap,NiO only absorbs ultraviolet light,and the recombination rate of photo-generated electrons and holes is high,its practical application is thus limited.Therefore,it is significantly important to modify NiO to make full use of solar energy.In this thesis,composites of Ni O-g-C₃N₄ and NiO-Au have been synthesized and the corresponding photocatalytic activities have been investgated.Meanwhile,the adsorption of Ni O nanobelts for anionic dyes has been studied.The main work is summarized as follows:1.Porous N and O doping g-C₃N₄?as: N-O-g-CN?was first synthesized by calcining the mixture of thiourea and urea at 550 °C,then load NiO nanoparticles.Both through the close formation on the surface of N-O-g-CN/NiO organic-inorganic composite was obtained by calcining the mixture of N-O-g-CN and Ni?CH₃COO?₂·4H₂O at 290 °C.We found that the porous of N-O-g-CN/NiO composite can stably produce hydrogen from triethanolamine under visible light irradiation?? > 420 nm?.The hydrogen generation rate depends on the NiO content in the N-O-g-CN/NiO composite.The highest rate of hydrogen generation reaches 601 ?mol/h/g,which is 5.7 times higher than that of pure N-O-g-CN and 2.7 times higher than that of 0.5 %N-O-g-CN/Pt.The improved performance may be due to porous structure and the heterostructure bentween N-O-g-CN and NiO.2.NiO/Au porous nanobelts have been prepared by the hydrothermal reaction and subsequent calcination.The photocatalytic activity and stability of Ni O/Au porous nanobelts forhydrogen production from 0.35 M Na₂ S and 0.25 M Na₂SO₃ aqueous solution have been studied under visible light irradiation?? > 420 nm?.Pure NiO can not produce hydrogen under visible light irradiation.When the mole ratio of Au to NiO is 1 %,the photocatalytic performance is the best,and the highest rate of hydrogen generation reaches 153 ?mol/h/g.The improvement in the photocatalytic performance may be due to the large specific surface area,surface plasmon resonance effect of Au nanoparticles,and heterojunction between NiO and Au.3.NiO nanobelts with 40-90 nm in width and several tens of micrometer in length are synthesized by a hydrothermal reaction and subsequent calcination.They possess high specific surface area of 102.4 m2/g and behave as an efficient adsorbent for removal of anionic dyes including methyl blue?MB??1996 mg/g?,methyl orange?MO??1291 mg/g?,and Congo red?CR??331mg/g?.The adsorption kinetics and adsorption mechanism are investigated systematically.The adsorption for MB is well represented by Langmuir isotherm model,while the adsorption kinetics is well described by the pseudo-second-order model.The FT-IR studies revealed that the good adsorption capacity for anionic dyes could be largely attributed to the electrostatic attraction between SO₃-group in dye molecule and positively charged surface of NiO.Our NiO nanobelts show much higher adsorption capacity for MO and CR compared with other transition metal oxides and Ni O nanosheets reported previously.Our product is expected to be promising material for wastewater treatment.