The Preparation Of Novel Visible Catalyst BiVO₄and Its Photocatalytic Reduction Of CO₂

In recent years, the global greenhouse gas emissions have been increased, and the fixation in recycling technology of CO2is more concerned about capture and storage (CCS) technology of CO2, Including three systems of CO2that capture, transport and sequestration, but the technology will not only consume extra energy, but there are also ecological damage and safety risks, making the technology challenged. And photocatalytic reduction of CO2technology is considered to be the most promising method in solving the problem of greenhouse gas, and realize the recycling of carbon resource. In this paper, using the BiVO4as new catalyst in visible light in homemade reaction system, making the photocatalytic reduction reaction of CO2/H2O to methanol.Using the method of precipitation to prepare new BiVO4catalyst and then characterized by TG-DTA, XRD, FT-IR, SEM, GC-MS. Experiments show that the BiVO4catalyst has the highest catalyst activity when pH=7and roasted in600℃; Then catalyst dosage is0.6g/L, reaction time is7h, flow rate of CO2is200mL/min, reaction temperature is80℃and the concentration of NaOH and Na2SO3reaction liquid is0.10mol/L. Under this condition, the yield of methanol is as high as249.18umol/g. Using the method of precipitation to prepare La-BiVO4nano composite catalyst and characterized by TG-DTA, FT-IR, UV-Vis, XRD, the results show that the La doping BiVO4can inhibit the BiVO4crystal phase transition, and improve the crystallinity of monoclinic crystal phase, effectively broaden the catalyst visible light response range, and improve the photocatalytic performance; The optimal condition of photocatalytic reduction of CO2is:calcination temperature is800℃, dosage of catalyst is1g/L, reaction time is8h, and flow rate of CO2is200mL/min, reaction temperature is70℃, the concentration of NaOH and Na2SO3reaction liquid is0.10mol/L. Under this condition, the yield of methanol is as high as310.25μmol/g.Experimental study on the influence of reaction conditions to light catalytic redu-ction reaction. Research showed that the calcination temperature of catalyst, catalyst dosage, reaction temperature, solution time, and flow rate of CO2, all have an impact on response, we should strictly control the various factors in the process of experi-ment. Comprehensive studies show that the photocatalyst preparation method of preci-pitation has the advantage of simple, high yield, uniform particle dispersion, and high catalytic activity, so the preparation methods are widely used in the synthesis of catalyst materials. This experiment specific process is as follows the Bi(Ⅲ)-V(V)-oxide-hydroxide-gel-heat treatment. The rare earth metals La after doped effect-tivly expanding light response range, improving the phase transition temperature, increasing crystallinity of monoclinic crystal phase, and reducing the carrier recom-bination rate, improving the photocatalytic activity.