Study On The Photocatalytic Materials Based On BaZr_0.5Ce_0.3Y_0.2O_3-δ For CO₂ Reduction

Using catalyst to reduce CO₂ into hydrocarbons can partially eliminate the excessive CO₂ in atmosphere,meanwhile,this reaction can be used as a sustainable fuel resource.It is effective to alleviates the current status of greenhouse effect and the energy shortage.BaZr_0.5Ce_0.3Y_0.2O_3-δ（BZCY）was perovskite-type material with excellent chemical stability and proton conduction,which may provide a possibility for proton transport.In this study,to get improved photocatalytic performance,we focus on the perovskite BZCY materials modified by doping with transition metals and forming semiconductor composite compounds with other perovskites.The main conclusions can be summarized as follows:（1）We have synthesized BZCY materials by high temperature solid state reaction method.The prepared samples were characterized by XRD,SEM,BET,UV-vis,XPS.Then,the photocatalytic activities of BZCY for CO₂ reduction were investigated in detail.It was found that the best photocatalytic performance was achieved when ultraviolet light irradiation and elevated reaction temperature of 350^oC were implemented.The accumulated yield of methane,ethane and propane can reach 39.13,8.64 and 3.22μmol g^-11 in 5h respectively.The overall carbon dioxide conversion rate is 0.11%.It was worthwhile to be noted,for the first time,not only methane but also other multi-carbon alkanes like ethane and propane were produced at ambient pressure.BZCY was a promising photocatalyst for the reduction of CO₂ and H₂O.（2）BZCY perovskites with different Co-doping levels were also successfully synthesized by high temperature solid state reaction method.The prepared samples were characterized by XRD,SEM,BET,UV-vis,PL,XPS.The photocatalytic activity is investigated at 350℃under ultraviolet light irradiation.It is efficient to convert CO₂ and H₂O into methane,ethane and propane.The results showed that the cobalt elements can increase the light absorptivity,carrier lifetime and the concentration of oxygen vacancy of BZCY materials.When the doping amount of Co is 0.05,the sample exhibits the best photothermal catalytic performance.The experimental results showed that the accumulated yield of methane,ethane and propane can reach 266.8,123.2 and 21.6μmol g^-11 in 5h respectively.The overall carbon dioxide conversion rate is 0.95%.Similarly,BZCY perovskites with different Ni-doping levels were also studied with similar characterization methods.The results showed that when the doping amount of Ni is 0.05,the sample exhibits the best photothermal catalytic performance.The accumulated yield of methane,ethane and propane can reach 219.9,83.2 and 12.7μmol g^-11 in5h respectively.The overall carbon dioxide conversion rate is 0.7%.The relatively lower yield of alkanes with Ni-doped BZCY should be the result of the extreme low BET surface area.However,it can be expected that Ni-doping can be a better option if the surface area can be increased by appropriate method.（3）Semiconductor composite design was realized by mixing BZCY with BaSrCo_1.6Fe_0.4O_6-δ（BSCF）and LaSrCoFeO_6-δ（LSCF）respectively.The photocatalytic performance of the composite materials were characterized in detail.The main product is methanol when BZCY and BSCF were used together.The possible heterojunctions formed between BZCY and BSCF should be the key reason for the formation of methanol when the photocatalysis reaction was implemented with visible light irradiation at 250℃.The highest yield of 30.3μmol g^-11 methanol was achieved when the ratio between BZCY and BSCF was 2:8 in weight.The overall carbon dioxide conversion rate is 0.05%.For the composite of BZCY/LSCF,it was confirmed that the highest yield of 696.2μmol g^-11 of CH₄ was achieved when BZCY/LSCF=4:6 when the reaction was implemented with visible light irradiation at 350℃.The overall carbon dioxide conversion rate is 1.14%.