吸收光谱拓展对光催化氧化NO的性能影响研究
发布时间：2019-04-17 19:20
【摘要】：氮氧化物(NO_x)是大气主要污染物之一,烟气中的NO_x浓度较高,主要采用选择性催化还原脱硝(SCR)技术脱除,但隧道、地下车库等场所的NO_x浓度较低,SCR技术并不适用。光催化氧化NO是一种反应条件温和且成本低的处理技术,在低浓度NO_x治理方面具有良好的应用前景。为提高NO光催化氧化的效率,本文通过引入光热剂Fe_3O_4@SiO_2、制备Bi/BiOI/black TiO_2异质结和La/BiOI等,拓展光催化剂的吸收光谱范围,从而提高光催化剂对太阳光谱的利用率和NO光催化氧化性能,并在此基础上对催化剂光催化性能提升的机理进行了探索。首先,通过固混法制备了P25/Fe_3O_4@SiO_2,考察了SiO_2包裹层、Fe_3O_4@SiO_2用量、Fe_3O_4@SiO_2对近红外光的吸收以及光热效应对光催化活性的影响。研究发现,优化后的P25/Fe_3O_4@SiO_2活性比P25提高36%;SiO_2包裹层可在光催化反应过程中对Fe_3O_4起到保护作用。基于表征分析结果,提出了光热效应促进光催化的机理:Fe_3O_4@SiO_2吸收近红外光,通过光热效应产生热量以促进P25的光催化性能。此外,Fe_3O_4@SiO_2光热效应的性能提升作用还可推广到ZnO、g-C_3N_4和BiOI等典型光催化剂。其次,通过煅烧还原的方法制备了Bi/BiOI/black TiO_2异质结,优化了前驱体P25和BiOI的用量。研究显示,在模拟太阳光照射下,优化后的Bi/BiOI/black TiO_2光催化氧化NO效率可达到70%,且稳定性测试结果显示催化剂性能稳定。从表征分析可知:由于Bi的SPR效应和异质结结构,Bi/BiOI/black TiO_2的吸收光谱得到有效拓展且其光生电子和空穴能够有效分离;同时,Bi/BiOI/black TiO_2可产生·O_2-和·OH两种自由基参与NO的光催化氧化过程,从而提高光催化性能。最后,用一步溶剂热法和浸渍法制备了La掺杂的3D BiOI,考察了制备方法和镧源类型的影响,并优化了La的用量。研究表明,一步溶剂热法制备的La/BiOI活性优于浸渍法;硝酸镧为镧源优于醋酸镧和氯化镧;优化后的0.3%La/BiOI在可见光下的光催化活性高达74%,稳定性测试结果显示催化剂性能稳定。从分析结果看,La的掺杂促使光催化剂的吸收光谱红移,同时促进光生电子和空穴的分离,并产生大量·OH参与NO光催化氧化,从而提高光催化活性。
[Abstract]:Nitrogen oxide (NO_x) is one of the main pollutants in the atmosphere. The concentration of NO_x in flue gas is relatively high. The selective catalytic reduction and denitrification (SCR) technology is mainly used to remove the NOx, but the NO_x concentration in tunnels and underground garages is relatively low. SCR technology is not applicable. Photocatalytic oxidation of NO is a kind of treatment technology with mild reaction conditions and low cost. It has a good application prospect in the treatment of low concentration NO_x. In order to improve the efficiency of photocatalytic oxidation of no, the Bi/BiOI/black TiO_2 heterojunction and La/BiOI were prepared by the introduction of photothermal agent Fe_3O_4@SiO_2, and the absorption spectrum of the photocatalyst was extended. Therefore, the utilization rate of solar spectrum and the photocatalytic oxidation performance of no were improved, and the mechanism of the improvement of photocatalytic activity of the catalyst was explored. Firstly, P25 Fe _ 2O _ 3 / 4 / Sio _ 2 was prepared by solid mixing method. The inclusion of SiO_2 and the dosage of Fe_3O_4@SiO_2 were investigated. The absorption of near-infrared light by Fe_3O_4@SiO_2 and the effect of photothermal effect on photocatalytic activity were investigated. It was found that the optimized P25/Fe_3O_4@SiO_2 activity was 36% higher than that of P25, which could protect Fe_3O_4 from photocatalysis. Based on the results of characterization analysis, the mechanism of photocatalysis promoted by photothermal effect is proposed: Fe_3O_4@SiO_2 absorbs near-infrared light and generates heat through photothermal effect to promote the photocatalytic activity of P25. In addition, the performance enhancement of Fe_3O_4@SiO_2 photothermal effect can be extended to typical photocatalysts such as ZnO,g-C_3N_4 and BiOI. Secondly, the Bi/BiOI/black TiO_2 heterojunction was prepared by calcination reduction method, and the dosage of precursor P25 and BiOI was optimized. The results show that the NO oxidation efficiency of the optimized Bi/BiOI/black TiO_2 photocatalyst can reach 70% under simulated sunlight irradiation, and the stability test results show that the performance of the catalyst is stable. From the characterization analysis, we can see that due to the SPR effect and heterojunction structure of Bi, the absorption spectrum of Bi/BiOI/black TiO_2 is effectively expanded and the photogenerated electrons and holes can be separated effectively. At the same time, Bi/BiOI/black TiO_2 can produce two kinds of free radicals, O ~ (2 -) and 路OH, which participate in the photocatalytic oxidation process of NO, and thus improve the photocatalytic performance. Finally, La-doped 3D BiOI, was prepared by one-step solvothermal method and impregnation method. The effects of preparation method and lanthanum source type were investigated, and the dosage of La was optimized. The results show that the activity of La/BiOI prepared by one-step solvothermal method is superior to that of impregnation method, and lanthanum nitrate is superior to lanthanum acetate and lanthanum chloride as lanthanum nitrate. The photocatalytic activity of the optimized 0.3%La/BiOI was up to 74% in visible light, and the stability test results showed that the catalyst was stable. The results showed that the doping of La promoted the red shift of the absorption spectrum and the separation of photogenerated electrons and holes, and produced a large amount of OH to participate in the photocatalytic oxidation of no, thus improving the photocatalytic activity of the photocatalyst.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701
本文编号：2459721
[Abstract]:Nitrogen oxide (NO_x) is one of the main pollutants in the atmosphere. The concentration of NO_x in flue gas is relatively high. The selective catalytic reduction and denitrification (SCR) technology is mainly used to remove the NOx, but the NO_x concentration in tunnels and underground garages is relatively low. SCR technology is not applicable. Photocatalytic oxidation of NO is a kind of treatment technology with mild reaction conditions and low cost. It has a good application prospect in the treatment of low concentration NO_x. In order to improve the efficiency of photocatalytic oxidation of no, the Bi/BiOI/black TiO_2 heterojunction and La/BiOI were prepared by the introduction of photothermal agent Fe_3O_4@SiO_2, and the absorption spectrum of the photocatalyst was extended. Therefore, the utilization rate of solar spectrum and the photocatalytic oxidation performance of no were improved, and the mechanism of the improvement of photocatalytic activity of the catalyst was explored. Firstly, P25 Fe _ 2O _ 3 / 4 / Sio _ 2 was prepared by solid mixing method. The inclusion of SiO_2 and the dosage of Fe_3O_4@SiO_2 were investigated. The absorption of near-infrared light by Fe_3O_4@SiO_2 and the effect of photothermal effect on photocatalytic activity were investigated. It was found that the optimized P25/Fe_3O_4@SiO_2 activity was 36% higher than that of P25, which could protect Fe_3O_4 from photocatalysis. Based on the results of characterization analysis, the mechanism of photocatalysis promoted by photothermal effect is proposed: Fe_3O_4@SiO_2 absorbs near-infrared light and generates heat through photothermal effect to promote the photocatalytic activity of P25. In addition, the performance enhancement of Fe_3O_4@SiO_2 photothermal effect can be extended to typical photocatalysts such as ZnO,g-C_3N_4 and BiOI. Secondly, the Bi/BiOI/black TiO_2 heterojunction was prepared by calcination reduction method, and the dosage of precursor P25 and BiOI was optimized. The results show that the NO oxidation efficiency of the optimized Bi/BiOI/black TiO_2 photocatalyst can reach 70% under simulated sunlight irradiation, and the stability test results show that the performance of the catalyst is stable. From the characterization analysis, we can see that due to the SPR effect and heterojunction structure of Bi, the absorption spectrum of Bi/BiOI/black TiO_2 is effectively expanded and the photogenerated electrons and holes can be separated effectively. At the same time, Bi/BiOI/black TiO_2 can produce two kinds of free radicals, O ~ (2 -) and 路OH, which participate in the photocatalytic oxidation process of NO, and thus improve the photocatalytic performance. Finally, La-doped 3D BiOI, was prepared by one-step solvothermal method and impregnation method. The effects of preparation method and lanthanum source type were investigated, and the dosage of La was optimized. The results show that the activity of La/BiOI prepared by one-step solvothermal method is superior to that of impregnation method, and lanthanum nitrate is superior to lanthanum acetate and lanthanum chloride as lanthanum nitrate. The photocatalytic activity of the optimized 0.3%La/BiOI was up to 74% in visible light, and the stability test results showed that the catalyst was stable. The results showed that the doping of La promoted the red shift of the absorption spectrum and the separation of photogenerated electrons and holes, and produced a large amount of OH to participate in the photocatalytic oxidation of no, thus improving the photocatalytic activity of the photocatalyst.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X701
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