吸收光譜拓展對光催化氧化NO的性能影響研究
發(fā)布時間：2019-04-17 19:20
【摘要】：氮氧化物(NO_x)是大氣主要污染物之一,煙氣中的NO_x濃度較高,主要采用選擇性催化還原脫硝(SCR)技術(shù)脫除,但隧道、地下車庫等場所的NO_x濃度較低,SCR技術(shù)并不適用。光催化氧化NO是一種反應(yīng)條件溫和且成本低的處理技術(shù),在低濃度NO_x治理方面具有良好的應(yīng)用前景。為提高NO光催化氧化的效率,本文通過引入光熱劑Fe_3O_4@SiO_2、制備Bi/BiOI/black TiO_2異質(zhì)結(jié)和La/BiOI等,拓展光催化劑的吸收光譜范圍,從而提高光催化劑對太陽光譜的利用率和NO光催化氧化性能,并在此基礎(chǔ)上對催化劑光催化性能提升的機(jī)理進(jìn)行了探索。首先,通過固混法制備了P25/Fe_3O_4@SiO_2,考察了SiO_2包裹層、Fe_3O_4@SiO_2用量、Fe_3O_4@SiO_2對近紅外光的吸收以及光熱效應(yīng)對光催化活性的影響。研究發(fā)現(xiàn),優(yōu)化后的P25/Fe_3O_4@SiO_2活性比P25提高36%;SiO_2包裹層可在光催化反應(yīng)過程中對Fe_3O_4起到保護(hù)作用�；诒碚鞣治鼋Y(jié)果,提出了光熱效應(yīng)促進(jìn)光催化的機(jī)理:Fe_3O_4@SiO_2吸收近紅外光,通過光熱效應(yīng)產(chǎn)生熱量以促進(jìn)P25的光催化性能。此外,Fe_3O_4@SiO_2光熱效應(yīng)的性能提升作用還可推廣到ZnO、g-C_3N_4和BiOI等典型光催化劑。其次,通過煅燒還原的方法制備了Bi/BiOI/black TiO_2異質(zhì)結(jié),優(yōu)化了前驅(qū)體P25和BiOI的用量。研究顯示,在模擬太陽光照射下,優(yōu)化后的Bi/BiOI/black TiO_2光催化氧化NO效率可達(dá)到70%,且穩(wěn)定性測試結(jié)果顯示催化劑性能穩(wěn)定。從表征分析可知:由于Bi的SPR效應(yīng)和異質(zhì)結(jié)結(jié)構(gòu),Bi/BiOI/black TiO_2的吸收光譜得到有效拓展且其光生電子和空穴能夠有效分離;同時,Bi/BiOI/black TiO_2可產(chǎn)生·O_2-和·OH兩種自由基參與NO的光催化氧化過程,從而提高光催化性能。最后,用一步溶劑熱法和浸漬法制備了La摻雜的3D BiOI,考察了制備方法和鑭源類型的影響,并優(yōu)化了La的用量。研究表明,一步溶劑熱法制備的La/BiOI活性優(yōu)于浸漬法;硝酸鑭為鑭源優(yōu)于醋酸鑭和氯化鑭;優(yōu)化后的0.3%La/BiOI在可見光下的光催化活性高達(dá)74%,穩(wěn)定性測試結(jié)果顯示催化劑性能穩(wěn)定。從分析結(jié)果看,La的摻雜促使光催化劑的吸收光譜紅移,同時促進(jìn)光生電子和空穴的分離,并產(chǎn)生大量·OH參與NO光催化氧化,從而提高光催化活性。
[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.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X701
本文編號：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.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X701
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