Preparation And Photo-hydrogenation Of CO₂on Ni/Zn/Cr（Al） Metal Oxides Catalyst

Under the threat of increasingly grim global warming and energycrisis, photocatalytic converting CO2into hydrocarbon fuels withwidespread solar energy as an appealing approach in coping with both ofthe two biggest problems shows great promise though challenging.In this thesis, the feasibility of layered double hydroxides (LDHs) andthe corresponding oxides (LDOs) applied as photocatalyst for reducingCO2to fuels was investigated. A continuous-flow photocatalytic/thermalreaction and detection system was built and optimized. Then thephotocatalysts were obtained through a detailed study on the synthesismethods and conditions. And the correlation between preparation andstructure was revealed via characterizing catalyst by XRD, DRS, TG-DSC,BET, TEM and FT-IR, which established the experimental foundation forfurther catalyst design.A new photo-thermal reactor was developed with the aid of UG, CAD,FLUENT and ANSYS, followed by an impact evaluation for thetranslucent and flow field distribution of differ reactors on the catalyticactivity. Error analysis for the testing system was carried out to determinethe appropriate vapor amount and reacting temperature. Ni/Zn/Cr LDHswere prepared by co-precipitation, hydrothermal and citric acid methodsunder various preparation conditions, among which the pH10Ni3Zn2Cr1LDHs with22h oil bath possessed the optimum structure and the highest activity. By annealing the sample at different temperatures could obtain aseries of Ni3Zn2Cr1composed metal oxides. Along with TEM and othercharacterizations, photocatalytic activity of CO2reduction indicated thatthe existance of highly dispersed, tiny and uniform NiO particles after500oC calcination helped to dramatically improve the photoreductionactivity. Also, the activity increased with appropriate amount ofCu-loading.0.2wt%Cu-loaded Ni3Zn2Cr1LDOs showed the maximumCH4and CO yields, respectively70nmol·h-1·gcat-1and1900nmol·h-1·gcat-1.Methods to Load Ni on Zn/Al LDHs without destroying the layeredstructure based on the memory effect of LDHs was also studied. Theresearch on the synthesized2wt%Ni/Zn2Al1LDHs suggested that theworse photocatalytic activity than the undoped ones might be attributedto the oxidation of Ni0to Ni2+or excessive loading amount.