Preparation Of NiO Loaded NaNbO₃/KNbO₃Nanowires And Their Photocatalyst Property

In this paper, hydrothermal method was used to prepare NaNbO₃nanowires, andresearch the influence of reaction temperature, reaction time and the concentration ofNaOH, at the same time, its’ growth mechanism can be studied. Then a two-step methodwas used which combine molten-salt method and hydrothermal method together toprepare KNbO₃nanowires, and research the influence of reaction temperature, reactiontime and the concentration of KOH, at the same time, its’ growth mechanism can bestudied. Then the products’ component, morphology, structure and property was studiedby XRD, SEM, TEM, UV-vis. Considering that loading a suitable co-catalyst on thesurface of raw material can form a PN junction, and this may improve the raw material’sphotocatalytic, so impregnation method was used to load NiO on the raw material andtest its’ property in photocatalytic degradation of organic materials and photocatalyticdecomposes water to hydrogenFirst hydrothermal method was used to prepare Na2Nb2O6H₂O nanowires as aprecursor, and then calcine it to form NaNbO₃nanowires. Nb powder is the reactant,add it into the NaOH solution with a concentration of10mol/L, then the reaction wastaken place through a hydrothermal method at150oC for8h, thus can successfully gotthe Na2Nb2O6H₂O nanowires as a precursor, the nanowires have a diameter of70nm,and tens of micron long. Reaction temperature, reaction time and the concentration ofNaOH do great influence to the product’s morphology and component. When thetemperature is as low as130oC, the products is mostly bulks, and with some nanowiressurrounded. The bulks are in scale of micron, this show that the reaction is incomplete.When the temperature is170oC, the products are small NaNbO₃cubes. When theconcentration of NaOH is lower than10mol/L, products are also NaNbO₃cubes, but ifthe concentration of NaOH is too high, the nanowires will have a higher diameter.Reactant keep decomposing with the reaction time increase, and when the reaction timeis8h, the products are uniformity Na2Nb2O6H₂O nanowires. Calcine theNa2Nb2O6H₂O nanowires precursor in600oC for6h, Na2Nb2O6H₂O nanowires willturn to NaNbO₃nanowires which remain the precursor’s morphology.K₂Nb₈O₂₁nanowires was prepared as a precursor through a molten salt method,then use it to react with KOH in hydrothermal condition, thus can prepare KNbO₃nanowires. Use KCl as the molten salt and as the same time a reactant to provide K, andchoose Nb₂O₅as a reactant to provide Nb, then use molten method to prepare K₂Nb₈O₂₁nanowires. Research the influence of ratio of reactants and the reaction temperature, andthen find out that ratio of reactants do little influence to the reaction if the salt is excessive. the expect products can got only under1000oC, and if the temperature is tolow, the reaction can not complete, and too high will drive products to form blocks.Then use hydrothermal method to prepare KNbO₃, the reactants are K₂Nb₈O₂₁nanowires and KOH. Research the influence of reaction temperature, reaction time andthe concentration of KOH, and finally parameter of200°C,24h and5mol/L waschoosen, through the research, a brief look of the mechanism of this reaction can beobserverd.Ni（NO₃）26H₂O was used as the impregnate agent. Put the raw material into theimpregnate solution with corresponding concentration and mix by continuous stirringuntil it’s uniformity, then react in200°C for10h, NiO can be loaded. This method canform a good surface combine between raw material and the co-catalyst, the average sizeof co-catalyst is about10nm,d and its’ distribution is uniformity. After the impregnation,the raw material’s property in photocatalytic degradation of organic materials andphotocatalytic decomposes water to hydrogen both increased, and the property have atrend of first increase to a extreme value and then decrease. For the NaNbO₃nanowires,when the mass ratio of NiO is5%, the property is the highest, it almost has a2timesincrease. For the NaNbO₃cubes, when the mass ratio of NiO is7%, the property is thehighest, but in a relative low degree. For the KNbO₃nanowires, when the mass ratio ofNiO is3%, the property is the highest, it almost has a2.5times increase.