本文選題：光電催化 + 二氧化鈦納米線陣列　； 參考：《西南大學》2017年碩士論文

【摘要】：進入21世紀以來,日益枯竭的能源儲備和日漸嚴峻的環(huán)境污染是世界各國人民所要面臨的兩大挑戰(zhàn)。由于太陽能資源豐富并且清潔無污染,因此人們對于探索利用太陽能的步伐從來都沒有停止過。通過水裂解將太陽能轉(zhuǎn)化為氫氣形式的化學能可能是解決當今能源和環(huán)境危機的終極策略。光電化學(PEC)水分解是太陽能水分解中一種非常有潛力的方式,因為它的成本低、效率高、清潔環(huán)保且具有可工業(yè)化生產(chǎn)的潛能等優(yōu)點。然而,其性能受到非常緩慢的水氧化反應的限制。因此,大量研究集中于改善催化水氧化反應的光陽極。在各種光陽極材料中,二氧化鈦(TiO_2)由于其有利的能帶邊緣位置、強的光學吸收、優(yōu)異的化學穩(wěn)定性、耐光腐蝕性以及低成本受到了廣泛關(guān)注。然而,TiO_2的STH效率在本質(zhì)上受其大的禁帶寬度和快速電子-空穴復合的限制。一方面,大量的研究集中于增強寬帶隙金屬氧化物半導體的可見光吸收。例如,利用窄禁帶半導體的敏化或通過元素摻雜使帶隙變窄是兩種普遍使用的方法,以達到改變金屬氧化物光電極的光吸收系數(shù)和吸收波長范圍從而改善金屬氧化物光電極的轉(zhuǎn)換效率。另一方面,同樣重要的是從根本上改善TiO_2的形貌和電子結(jié)構(gòu)以有效分離和傳遞光生載流子。本論文將分別采用Cu_2O和CoO_x對TiO_2納米線陣列光電極進行表面修飾,所形成的復合異質(zhì)結(jié)均有效地提高了納米線陣列的光電解水性能,并進一步探討了材料的合成機理以及光生載流子在這些異質(zhì)結(jié)光電極中的轉(zhuǎn)移機理。本論文具體內(nèi)容分為三個部分:1.我國2016年的能源生產(chǎn)消耗現(xiàn)狀,表明了清潔能源研發(fā)生產(chǎn)的重要性,簡要回顧了光解水、光催化劑以及PEC光催化系統(tǒng)的發(fā)展和目前所面臨的困境,系統(tǒng)介紹了二氧化鈦用于光解水體系的現(xiàn)狀,二氧化鈦的晶體結(jié)構(gòu)、能帶結(jié)構(gòu)和催化機制,以及提升二氧化鈦在PEC系統(tǒng)中催化活性的途徑。自組裝在構(gòu)建納米材料方面有著廣闊的應用前景,特別是在模板上利用自組裝的方式構(gòu)建納米級復合材料,主要介紹了在軟模板如小分子、線性聚合物、生物分子等和硬模板如碳納米管上的自組裝,而后介紹了影響自組裝的幾大因素,最后介紹了本論文所涉及實驗的實驗用品,材料表征方法及電化學性能測試方法。2.聚合物介導自組裝的TiO_2@Cu_2O核殼納米線陣列用于高效光電化學水氧化。我們利用新型、簡便、經(jīng)濟以及易于工業(yè)化生產(chǎn)的聚合物調(diào)節(jié)自組裝的方法在TiO_2納米線陣列(NWA)上有規(guī)律地生長Cu_2O的超薄連續(xù)薄層以形成真正的核殼結(jié)構(gòu)TiO_2@Cu_2O NWA光電極,在此過程中聚合物作為穩(wěn)定劑、還原劑和連接劑。將該異質(zhì)結(jié)直接作為PEC水分解的光陽極,在0.5 M Na_2SO_4溶液中顯示出(在相對于RHE為1.23 V時)的光電流密度為4.66 mA cm~(-2),最大光轉(zhuǎn)化效率為0.71%,兩者都是在相同條件(中性條件和沒有任何犧牲劑)下以TiO_2作基底的光陽極測量報道的最高值。TiO_2@Cu_2O NWA對水氧化優(yōu)異的PEC性能主要是由于它大大增強了電極對可見光的吸收并促進了電荷分離使得光生載流子密度增大、轉(zhuǎn)移和傳遞速度增加。這項工作不僅制備了一種新穎的TiO_2@Cu_2O核殼NWA光陽極材料用于高效PEC水氧化過程,并深入研究了其增強機制,科學探討了聚合物調(diào)節(jié)的自組裝合成材料的機理,使其能拓展應用到制造各種其他的核-殼納米架構(gòu)。3.聚合物調(diào)節(jié)自組裝CoO_x納米顆粒于TiO_2納米線陣列上顯著促進光電化學水氧化過程。助催化劑在以TiO_2為基底的光陽極的光電化學(PEC)水分解性能改進上起著重要的作用,但它的合成和組裝仍面臨著很大的挑戰(zhàn)。在這個工作中,我們研究了在TiO_2 NWA上通過聚合物調(diào)節(jié)自組裝的方式直接生長超小尺寸、均勻分散和高度密集的CoO_x NP_s,聚合物使CoO_x NP_s強烈地與TiO_2相互作用,這有效地穩(wěn)定了納米線陣列上的CoO_x NP_s及其前驅(qū)體,并在高溫水熱條件下可靠地還原Co~(2+)。將制得的雜化納米陣列作為PEC水氧化的光電極,其中CoO_x NP_s作為TiO_2 NWA的助催化劑,測得的光電流密度為1.67 mA cm~(-2),光轉(zhuǎn)化效率為0.79%,這分別為純TiO_2 NWA(0.54 mA cm~(-2),0.30%)的3.02倍和2.63倍,均高于已報道的在相同條件下發(fā)生水氧化的助催化劑修飾的TiO_2光陽極的最大值。此外,其光電流密度在6900 s衰減?11.81%,而純TiO_2 NWA衰減為54.40%。CoO_x NP_s顯著的助催化效應歸因于其高的自身催化活性、超小的尺寸、良好的分散、高的組裝密度以及其結(jié)構(gòu)的穩(wěn)定帶來的明顯增強的電荷分離、轉(zhuǎn)移、傳輸和減少的載流子復合。這項工作創(chuàng)造了一個新的CoO_x NP_s/TiO_2 NWA光電極,它顯著地提高了TiO_2 NWA的PEC水氧化性能,另外我們深入地研究了其增強機制,并提供了一個可廣泛應用的自組裝各種納米結(jié)構(gòu)光電極的方法。
[Abstract]:Since twenty-first Century, the increasing depletion of energy reserves and the increasingly serious environmental pollution are two major challenges faced by the people all over the world. Because of abundant solar energy resources and clean, so people for exploring the use of solar energy the pace never stopped. By water splitting to convert solar energy into chemical energy may be in the form of hydrogen the ultimate strategy to solve the energy and environmental crisis. Photoelectrochemical (PEC) water decomposition is a promising way of solar water decomposition, because of its low cost, high efficiency, environmental protection and clean industrial production has potential advantages. However, its performance is very slow water oxidation reaction limit light anode. Therefore, many researchers focused on improving water catalytic oxidation. In the light of various anode materials, titanium dioxide (TiO_2) due to its favorable band edge position The strong optical absorption, excellent chemical stability, corrosion resistance and low cost has attracted widespread attention. However, the efficiency of TiO_2 STH by its large band gap and fast electron hole recombination restriction in nature. On the one hand, a large number of studies have focused on enhancement of wide band gap metal oxide semiconductor visible light absorption. For example, the use of narrow gap semiconductor or sensitized by element doping is the two methods commonly used to achieve the change of band gap narrowing, metal oxide photoelectrode light absorption coefficient and wavelength range so as to improve the efficiency of the photoelectric conversion of metal oxide. On the other hand, it is also important to improve the morphology and electronic structure TiO_2 to transfer and effective separation of photogenerated carriers from the root. This paper uses Cu_2O and CoO_x arrays of TiO_2 nanowires photoelectrode surface modification, the formation of the complex He heterojunction effectively raised photoelectric nano wire array solution of water resistance, and further explore the mechanism of synthesis of materials and photo carrier node transfer mechanism in the heterogeneous photo electrode. The main contents of this thesis is divided into three parts: energy production and consumption status of China in 2016 1., shows the importance of clean the energy research and development production, a brief review of the water splitting photocatalyst and photocatalytic PEC system development and are currently facing difficulties, introduces the present situation of the application of titanium dioxide photolysis of water system, the crystal structure of TiO2, the band structure and catalytic mechanism, and the way to enhance the catalytic activity of TiO2 in the PEC system. Self assembly in the construction of nano materials have broad application prospects, especially in the template by self-assembly method to build nano composite materials, mainly introduced in the soft template such as Small molecules, biological molecules and linear polymers, such as hard template self-assembly of carbon nanotubes, and then introduces some factors affecting the self-assembly, finally introduces the activities involved in this paper experiment, test method of material characterization and electrochemical properties of TiO_2@Cu_2O core-shell nanowires.2. polymer mediated self-assembly of array for efficient photoelectrochemical water oxidation. We use a new type, simple, economic and easy industrialized production method to adjust the polymer self-assembled nanowire arrays on TiO_2 (NWA) on the regular growth of Cu_2O thin continuous thin layer to form core-shell structure TiO_2@Cu_2O NWA photoelectrode real, in the process of polymer as stabilizer, reduction agent and connection agent. The heterojunction directly as light anode PEC water decomposition, shown in 0.5 M Na_2SO_4 solution (with respect to RHE for 1.23 V) of the photoelectric current. For 4.66 mA cm~ (-2), the maximum conversion efficiency of 0.71%, both of which are in the same conditions (neutral condition and no sacrificial agent) with TiO_2 as anode substrate measurements reported the highest.TiO_2@Cu_2O NWA on the performance of PEC water is mainly due to its excellent oxidation greatly enhances the absorption of visible electrode light and promote charge separation of the light induced carriers density increases, transfer speed increases. This work not only the preparation of a novel TiO_2@Cu_2O core-shell NWA photo anode materials for efficient PEC water oxidation process, and in-depth study of the mechanism of the enhanced science, discussed the mechanism of self-assembly synthesis of polymer materials regulation the so that it can be applied to manufacture all kinds of other core-shell structure polymer.3. regulation of self-assembled CoO_x nanoparticles in the TiO_2 nanowire array significantly promote the photoelectrochemical water oxidation process. The catalyst as the anode of Photoelectrochemical substrate in TiO_2 (PEC) decomposition of water plays an important role to the performance improvement, but the synthesis and assembly of it is still facing great challenges. In this work, we studied in TiO_2 NWA by adjusting polymer self-assembly approach direct growth of ultra small size. The uniform dispersion and high concentration of CoO_x NP_s, CoO_x polymer NP_s strongly interacted with TiO_2, which effectively stabilizes the CoO_x NP_s and its precursor on nanowire arrays, and reliable reduction of Co~ in high temperature hydrothermal conditions (2+). The hybrid nano array prepared as photoelectrode of PEC water oxidation among them, CoO_x NP_s TiO_2 NWA as cocatalyst, the photocurrent density measured for 1.67 mA cm~ (-2), optical conversion efficiency was 0.79%, which were pure TiO_2 NWA (0.54 mA cm~ (-2), 0.30%) 3.02 times and 2.63 times, were higher than those reported The maximum value of TiO_2 anode catalyst modified water oxidation under the same conditions. In addition, the photocurrent density of 6900 s attenuation? 11.81%, pure TiO_2 NWA and its catalytic activity for catalytic 54.40%.CoO_x NP_s attenuation effect was attributed to its high, ultra small size, good dispersion. High density assembly and stable structure has significantly enhanced the charge separation, transfer, transmission and reduce the carrier recombination. This work has created a new CoO_x NP_s/TiO_2 NWA photoelectrode, it significantly improves the performance of PEC water oxidation of TiO_2 NWA, we also studied the mechanism of the enhanced and, to provide a widely used self assembled nano structure photoelectric electrode method.

【學位授予單位】：西南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O646;TQ116.21

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本文編號：1759454