本文選題：碳化硅　切入點：異質(zhì)結(jié)　出處：《北京科技大學》2017年博士論文

【摘要】：隨著人類社會中能源的大量消耗和環(huán)境污染問題的出現(xiàn),探索清潔無污染的可持續(xù)發(fā)展能源成為解決該問題的希望之路。在半導體作用下,利用太陽能催化分解水制備氫能被認為是解決能源危機和環(huán)境問題的有效途徑之一。為更好地利用太陽光,發(fā)展可見光響應(yīng)的半導體則成為研究的焦點。碳化硅(SiC)作為一種重要的無機非金屬半導體材料,具有化學性質(zhì)穩(wěn)定、高電子遷移率等優(yōu)良性質(zhì)。同時,其價帶導帶位置能夠滿足分解水的要求,是一種具有發(fā)展?jié)摿Φ目梢姽夥纸馑拇呋瘎１菊n題以SiC為主體催化劑,致力于研究SiC及其復(fù)合物的可見光催化產(chǎn)氫性能。通過與CdS復(fù)合形成促進載流子順利轉(zhuǎn)移的直接Z型光催化體系,之后通過改變合成方法優(yōu)化異質(zhì)結(jié)的接觸界面,并探討了半導體不同晶格匹配程度對于異質(zhì)結(jié)結(jié)構(gòu)構(gòu)建的影響。在此基礎(chǔ)上,繼續(xù)引入有機偶聯(lián)劑作為載流子轉(zhuǎn)移橋梁促進光生電子空穴的分離。取得的研究結(jié)果如下:(1)采用化學沉淀法用CdS對SiC進行修飾。CdS的負載改變了 SiC表面過電勢較高,不易發(fā)生化學反應(yīng)的問題,與SiC之間形成Z型載流子轉(zhuǎn)移體系促進光生載流子的傳輸。該催化劑在可見光下產(chǎn)氫速率達到555μmol·h-1·g-1,負載3 wt%Pt顆粒作為共催化劑后,產(chǎn)氫效率進一步提高至5460μmol·h-1·g-1,且在420nm處的量子效率達到了 2.1%。該異質(zhì)結(jié)能夠有效促進電子和空穴的分離,提高載流子的利用率。(2)通過理論計算優(yōu)化了 CdS在SiC表面的負載量,并通過水熱控制CdS的異質(zhì)形核過程優(yōu)化了二者的接觸界面及CdS的分散程度。該催化劑的可見光催化產(chǎn)氫效率是普通沉淀法制備復(fù)合物產(chǎn)氫量的兩倍。同時,該催化劑具有更好的結(jié)晶性、均勻的分散性和良好的光吸收性能。其體相也具有較長的光生電子壽命,有利于載流子轉(zhuǎn)移到復(fù)合物的表面產(chǎn)氫,從而促進了光催化效率的提升。(3)通過改變水熱溫度制備了一系列不同晶型匹配的SiC/CdS復(fù)合物異質(zhì)結(jié)光催化劑。六方相CdS(H-CdS)和六方相SiC(H-SiC)具有一致的空間群,且晶格參數(shù)之間存在3aaH-CdS=4aH-SiC的恒比關(guān)系,在水熱環(huán)境中H-CdS以H-SiC為核進行外延式生長,形成的異質(zhì)結(jié)的缺陷較少,從而有更好的接觸界面。其可見光催化產(chǎn)氫性能為259μmol·h-1·g-1,是立方相CdS(C-CdS)負載的晶型不匹配的復(fù)合物C-CdS/H-SiC的四倍,且具有更強的光電流響應(yīng)。H-CdS與H-SiC更為匹配的價帶導帶位置也更有助于電子空穴的分離。(4)將有機硅烷偶聯(lián)劑(3-巰基丙基三甲氧硅烷)引入到SiC/CdS無機復(fù)合體系中作為鏈接鍵橋促進載流子轉(zhuǎn)移。偶聯(lián)劑和SiC之間能夠形成Si-O-Si鍵,使得SiC體相中的載流子易于順利轉(zhuǎn)出,并延長了光生電子的壽命,促進產(chǎn)氫效果相比于未加偶聯(lián)劑的樣品有三倍的提升,為制備新型復(fù)合半導體研究提供了新思路。
[Abstract]:With the large consumption of energy and the emergence of environmental pollution in human society, exploring clean and pollution-free sustainable development energy becomes a promising way to solve this problem. The preparation of hydrogen energy by catalytic decomposition of water from solar energy is considered to be one of the effective ways to solve the energy crisis and environmental problems. The development of visible light responsive semiconductors has become the focus of research. As an important inorganic nonmetallic semiconductor material, sic has many excellent properties, such as chemical stability, high electron mobility and so on. The valence band conduction band position can meet the requirements of water decomposition, and it is a potential catalyst for water decomposition by visible light. In this paper, SiC is used as the main catalyst. In order to study the visible light catalytic hydrogen production of SiC and its complexes, a direct Z-type photocatalytic system was formed by combining with CdS to facilitate the smooth transfer of carriers, and then the contact interface of the heterojunction was optimized by changing the synthesis method. The influence of different lattice matching degree on the structure of heterojunction is discussed. Organic coupling agent was continuously introduced as carrier transfer bridge to promote the separation of photogenerated electron holes. The results obtained are as follows: 1) the loading of SiC modified with CdS by chemical precipitation method changed the surface overpotential of SiC. The formation of Z type carrier transfer system with SiC promotes the transport of photogenerated carriers. The hydrogen production rate of the catalyst reaches 555 渭 mol h-1 g-1 under visible light. The supported 3 wt%Pt particles are used as co-catalysts. The efficiency of hydrogen production was further increased to 5460 渭 mol h-1 g-1, and the quantum efficiency at 420nm reached 2.1. The heterojunction can effectively promote the separation of electrons and holes and improve the carrier utilization. The heterogeneous nucleation process of CdS was controlled by hydrothermal method. The contact interface and the dispersion of CdS were optimized. The hydrogen production efficiency of the catalyst was twice as high as that of the conventional precipitation method. The catalyst has better crystallinity, uniform dispersion and good photoabsorption performance, and its bulk phase also has a longer photoelectron lifetime, which is favorable for the carrier transfer to the surface of the complex to produce hydrogen. Therefore, a series of heterojunction photocatalysts of SiC/CdS complexes with different crystal types were prepared by changing the hydrothermal temperature. The hexagonal and hexagonal SICP H-CdS) and hexagonal SICP H-SiC have a consistent space group. Moreover, there is a constant ratio of 3aaH-CdS=4aH-SiC among lattice parameters. In hydrothermal environment, H-SiC is used as the core for epitaxial growth of H-CdS, and the defects of heterojunction are less. The visible photocatalytic activity of hydrogen production is 259 渭 mol h-1 g-1, which is four times higher than that of cubic CdS- C-CdS- supported complex C-CdS/H-SiC. The valence band position, which has stronger photocurrent-response. H-CdS and H-SiC, is also more helpful for the separation of electron holes. (4) the organic silane coupling agent, 3-mercapto propyl trimethoxysilane, is introduced into the SiC/CdS inorganic composite system as a kind of inorganic compound system. The link bridge facilitates carrier transfer. Si-O-Si bonds can be formed between the coupling agent and the SiC. The carrier in the bulk phase of SiC is easy to be transferred out, and the lifetime of photogenerated electrons is prolonged. The hydrogen production efficiency is three times higher than that of the sample without coupling agent, which provides a new idea for the preparation of new composite semiconductors.
【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O643.36;TQ116.2

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