本文選題：光催化還原CO_2 + 二氧化鈦�。� 參考：《南京大學(xué)》2015年碩士論文

【摘要】：隨著人口的增加和現(xiàn)代化與工業(yè)化進(jìn)程的加快,世界各國(guó)對(duì)能源的需求愈來(lái)愈大,而經(jīng)過(guò)數(shù)百年的過(guò)度開(kāi)采和巨大消耗,作為人類社會(huì)主要能量來(lái)源的煤炭、石油和天然氣等化石能源已經(jīng)不可逆轉(zhuǎn)地走向枯竭。而且,化石能源的大量燃燒造成大氣中以CO2為主的溫室氣體急劇增加,破壞了自然界碳循環(huán)的平衡,導(dǎo)致全球氣候變暖。近年來(lái),受自然界綠色植物光合作用的啟發(fā),以CO：為原料,半導(dǎo)體材料為催化劑,在太陽(yáng)光的照射下利用還原劑將CO2轉(zhuǎn)化為含碳化合物的技術(shù)備受關(guān)注。該技術(shù)在降低大氣中溫室氣體CO2的濃度的同時(shí),生成的含碳化合物又能夠緩解日益緊張的能源危機(jī),實(shí)現(xiàn)了能源與環(huán)境的“雙贏”。Ti02具有廉價(jià)、無(wú)毒、光穩(wěn)定性好、容易制備等優(yōu)點(diǎn),被廣泛地應(yīng)用于光催化分解H20、光催化還原CO2和有機(jī)污染物降解。對(duì)C02的選擇吸附性能差、光生電子-空穴復(fù)合幾率高和光譜響應(yīng)范圍窄等因素限制了Ti02光催化CO2還原性能的提高。源于自然界綠色植物的光合作用的靈感,基于孔隙結(jié)構(gòu)傳統(tǒng)的硬模板和軟模板合成方法,本文合成了分級(jí)多孔結(jié)構(gòu)的Ti02海綿和MgO-TiO2復(fù)合材料,并應(yīng)用于光催化還原CO2。主要研究?jī)?nèi)容如下：(1)以多孔藕粉凝膠為模板,將藕粉和Ti02的前驅(qū)物混合與水共熱,共凝膠化形成多孔結(jié)構(gòu),在空氣氛中煅燒將藕粉凝膠移除,合成了3D交聯(lián)大孔/介孔結(jié)構(gòu)的Ti02海綿。此方法將傳統(tǒng)的硬模板法和軟模板法有機(jī)地結(jié)合在一起,在獲得模板的既定大孔結(jié)構(gòu)的同時(shí),交聯(lián)圍成大孔的薄壁表面形成大量的介孔。與同等條件下,不采用模板制得的參比Ti02樣品相比,3D交聯(lián)大孔/介孔結(jié)構(gòu)的Ti02海綿光催化CO2還原為CH4的效率提升了2.6倍,原因?yàn)椋?1)大孔結(jié)構(gòu)有利于氣體反應(yīng)物和生成物的自由擴(kuò)散；(2)入射光在孔隙結(jié)構(gòu)中發(fā)生多步折射和散射,延長(zhǎng)了光的傳播路程,從而增強(qiáng)了樣品的光吸收；(3)介孔結(jié)構(gòu)增加了CO2在催化劑表面的吸附和反應(yīng)活性位點(diǎn)。(2)以空心菜桿為模板,應(yīng)用溶膠凝膠的方法,調(diào)節(jié)MgO的含量合成了系列仿生多孔結(jié)構(gòu)的MgO-TiO2復(fù)合物。通過(guò)探究、比較不同含量MgO對(duì)復(fù)合物光催化C02還原為CH4效率的影響,結(jié)合催化劑的物理和化學(xué)性質(zhì)的表征,證明MgO能夠提高催化劑表面C02的化學(xué)吸附,活化C02分子,從而提高C02的光催化轉(zhuǎn)化活性。雖然MgO的加入能夠提高活性C02分子的含量,由于MgO為絕緣體材料,并且覆蓋在Ti02顆粒表面,阻礙了光生電子向催化劑表面的遷移,一定程度上降低了催化劑的活性。因此,設(shè)計(jì)合成復(fù)合MgO的光催化劑時(shí),要選擇最佳復(fù)合量,本文實(shí)驗(yàn)結(jié)果證明：TiO2的MgO為最佳復(fù)合量為0.2 wt%。
[Abstract]:With the increase of population and the acceleration of modernization and industrialization, the demand for energy is increasing in all countries of the world. After hundreds of years of overexploitation and huge consumption, coal is the main source of energy for human society. Fossil fuels such as oil and natural gas have been irreversibly depleted. Moreover, the combustion of fossil energy causes a sharp increase of greenhouse gases dominated by CO2 in the atmosphere, which destroys the balance of the natural carbon cycle and results in global warming. In recent years, inspired by the photosynthesis of green plants in nature, the technology of conversion of CO2 to carbohydrates by reducing agent under the irradiation of sunlight, using CO: as raw material and semiconductor material as catalyst, has attracted much attention. While reducing the concentration of greenhouse gas CO2 in the atmosphere, the technology can also produce carbohydrates to alleviate the increasingly tense energy crisis and achieve a "win-win" between energy and the environment. Ti02 is cheap, non-toxic, and has good light stability. It is widely used in photocatalytic decomposition of H20, photocatalytic reduction of CO2 and degradation of organic pollutants. The poor selective adsorption of CO2, high photoelectron hole recombination probability and narrow spectral response limit the improvement of Ti02 photocatalytic CO2 reduction performance. Based on the traditional hard template and soft template synthesis method of pore structure, Ti02 sponge and MgO-TiO2 composite with graded porous structure were synthesized and applied to photocatalytic reduction of CO _ 2. The main research contents are as follows: (1) the porous lotus root powder gel is used as template, the precursor of lotus root powder and Ti02 is mixed with water to co-heat, the porous structure is formed by co-gelation, and the lotus root powder gel is removed by calcination in empty atmosphere. A 3D crosslinked Ti02 sponge with macroporous / mesoporous structure was synthesized. This method combines the traditional hard template method and the soft template method organically. While obtaining the established macroporous structure of the template, a large number of mesoporous cells are formed on the thin-walled surface of the cross-linked macroporous. Under the same conditions, the photocatalytic reduction of CO2 to CH4 by Ti02 sponge with 3D crosslinking macroporous / mesoporous structure was 2.6 times higher than that of the reference Ti02 without template. The reason is that the macroporous structure is advantageous to the free diffusion of gas reactants and products. The incident light refracts and scatters in the pore structure, which prolongs the distance of light propagation. Thus, the mesoporous structure of the sample was enhanced, and the adsorption and reaction activity sites of CO2 on the catalyst surface were increased. A series of bionic MgO-TiO2 complexes with porous structure were synthesized by adjusting the content of MgO. The effects of different MgO content on the efficiency of photocatalytic reduction of CO2 to CH4 were compared. It was proved that MgO could enhance the chemisorption of CO2 on the surface of the catalyst and activate CO2 molecule by combining with the characterization of the physical and chemical properties of the catalyst. Thus, the photocatalytic conversion activity of CO2 was improved. Although the addition of MgO can increase the content of active C02 molecule, because MgO is an insulator material and is covered on the surface of Ti02 particles, it hinders the migration of photogenerated electrons to the surface of the catalyst, thus reducing the activity of the catalyst to some extent. Therefore, when designing the photocatalyst for synthesizing composite MgO, we should choose the optimum compound amount. The experimental results show that the optimum compound amount of MgO is 0.2 wt.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ134.11;TQ426

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