纳米异质结光催化剂制氢研究进展（英文）

发布时间：2018-05-31 14:16

本文选题：异质结 + 导带　；参考：《催化学报》2017年08期

【摘要】：随着世界经济的迅猛发展,人们生活水平飞速提高的同时,能源短缺和环境污染成为当前人类可持续发展过程中的两大严峻问题.氢作为一种能源载体,能量密度高,可储可运,且燃烧后唯一产物是水,不污染环境,被认为是今后理想的无污染可再生替代能源.20世纪60年代末,日本学者Fujishima和Honda发现光照n-型半导体TiO_2电极可导致水分解,使人们认识到了利用半导体光催化分解水制氢可直接将太阳能转化为氢能的可行性,利用半导体光催化分解水制氢逐渐成为能源领域的研究热点之一.然而,单相光催化材料的光生电子和空穴复合仍然严重,光催化制氢效率低,无法满足实际生产需要;另外,单相光催化材料不能同时具备较窄的禁带、较负的导带和较正的价带.近年来,国内外学者在新型光催化材料的探索、合成和改性以及光催化理论等领域开展了大量研究工作.不断有不同种类的半导体材料被研究和发展为光催化分解水制氢催化材料.例如,具有可见光催化活性的阴、阳离子掺杂TiO_2,具有可见光下光解纯水能力的In_(0.9)Ni_(0.1)TaO_4,在256 nm紫外光辐照下量子效率达到56%的镧掺杂NaTaO_3,CdS以及(AgIn)_xZn_(2(1-x))S_2等.在现有的光催化材料中,单相光催化材料可以通过掺杂、形貌控制合成、晶面控制合成、染料敏化和表面修饰等提高其光催化活性.复合型光催化材料则能通过组合不同电子结构的半导体材料并调控其光生载流子迁移获得优异的光催化制氢性能,大幅拓展了光催化制氢材料的研究范围和提升了光催化制氢性能.构建异质结能够有效提高光生电子-空穴分离效率,促使更多的光生电子参与光催化制氢反应,提高其氧化还原能力,从而提高其光催化制氢效率.在I-型纳米异质结中,半导体A的价带高于半导体B,而导带则是前者高于后者,光照时,光生电子-空穴对的迁移速率是不同的,延长了光生电子的寿命,从而提高了材料的光催化活性.但是在I-型异质结中,电子和空穴都集中在B半导体上,这样光生电子-空穴对的复合几率仍然很高.II-型异质结中电子和空穴的富集处各不相同,因此使用范围也更广泛一些.光辐照激发时,光生电子从半导体B的导带迁移到半导体A的导带上,而空穴则从半导体A的价带向半导体B的价带上转移,从而形成了载流子的空间隔离,有效抑制其复合.但是,在这个类型的异质结中,光生电子转移到了相对位置较低的导带,而空穴则转移到相对位置较高的价带,这样就降低了光生电子的还原能力和空穴的氧化能力.pn型异质结中,在两种半导体相互接触时,由于电子-空穴对的扩散作用,两种半导体的能带发生漂移,其中p型上移,n型下移.而且在两种半导体异质结的界面处会产生空间电荷层,在这个电荷层的作用下,在异质结界面上形成内建电场.在合适波长的光源辐照的条件下,两种半导体同时被激发,光生电子在内建电场的作用下,从p型半导体快速迁移到n型半导体上,而n型半导体中留在价带上的空穴则快速迁移到p型半导体上,这样光生电子-空穴对就得到了有效的分离.在以Z型载流子迁移为主导的异质结构材料中摈弃了中间媒介,通过控制界面的载流子迁移使低能量的光生电子与空穴直接复合保留高能量的光生电子-空穴,从而提高了材料的光催化效率.本文介绍了纳米异质结光催化剂在设计合成方面的研究进展,总结了几种纳米异质结(I-型、II-型、pn-型及Z-型)的光催化原理及其在制取氢气方面的研究进展,并展望了研究发展方向.期望本文能够加深研究者对该领域的理解,为今后高效光催化材料的设计提供帮助和指导.
[Abstract]:With the rapid development of the world economy and the rapid improvement of people's living standards, energy shortage and environmental pollution have become the two major problems in the process of sustainable development of human beings. As a carrier of energy, hydrogen is high in energy density and can be stored and transported, and the only product after combustion is water, not polluting the environment, and is considered to be ideal for the future. In the late 60s of.20 century, pollution of renewable alternative energy sources, Japanese scholars Fujishima and Honda found that light n- semiconductor TiO_2 electrode could cause water decomposition. People realized the feasibility of converting solar energy into hydrogen by using semiconductor photocatalyst to decompose water from hydrogen to hydrogen, and gradually become energy by using semiconductor photocatalytic decomposition of water to produce hydrogen. However, the photoelectron and hole recombination of single-phase photocatalytic material is still serious, the efficiency of photocatalytic hydrogen production is low, and it can not meet the actual production needs. In addition, the single-phase photocatalytic material can not have a narrow band, negative guide band and more positive valence band. In recent years, domestic and foreign scholars have been in the new photocatalytic material. A lot of research work has been carried out in the fields of material exploration, synthesis and modification, and the theory of photocatalytic catalysis. Various kinds of semiconductor materials have been studied and developed as photocatalytic materials for the photocatalytic decomposition of water for hydrogen production. For example, the visible photocatalytic activity of the cathode, cation doped TiO_2, and the ability to photolysis of pure water under visible light, In_ (0.9) Ni_ (0.1) TaO_4, the quantum efficiency reaches 56% of the lanthanum doped NaTaO_3, CdS and (AgIn) _xZn_ (2 (1-x)) S_2 under 256 nm UV irradiation. In the existing photocatalytic materials, the single-phase photocatalytic materials can be doped, morphology controlled synthesis, crystal surface control synthesis, dyestuff sensitization and surface modification to improve their photocatalytic activity. The excellent photocatalytic hydrogen production performance can be obtained by combining semiconductor materials with different electronic structures and controlling their photoinduced carrier migration, which greatly expands the scope of photocatalytic hydrogen production and improves the performance of photocatalytic hydrogen production. The construction of heterojunction can effectively improve the efficiency of photoelectron hole separation and promote more light generation. In the I- type nano heterojunction, the valence band of semiconductor A is higher than that of the semiconductor B, while the conduction band is higher than the latter in the guide band, and the migration rate of the photoelectron hole pair is different, thus prolonging the lifetime of the photoelectron and thus increasing the lifetime of the photoelectron. Photocatalytic activity of the material, but in the I- type heterojunction, the electrons and holes are concentrated on the B semiconductor, so the recombination probability of the photoelectron hole pair is still very high in the concentration of electrons and holes in the.II- type heterojunction, so the use range is more extensive. It is migrated to the guide band of the semiconductor A, while the hole is transferred from the valence band of the semiconductor A to the valence band of the semiconductor B, thus forming the space isolation of the carrier and effectively inhibiting its recombination. However, in this type of heterojunction, the photoelectron transfer to a relatively low relative position leads and the hole is transferred to a relatively higher valence band, In this way, the reduction ability of the photoelectrons and the oxidation capacity of the cavity are reduced in the.Pn type heterojunction. When the two semiconductors contact each other, the energy band of the two semiconductors is drifting due to the diffusion of the electron hole pair, in which the P type is moved up and the N type is moved down. And the space charge layer will be produced at the interface of the two kinds of half conductor heterojunction. Under the action of this charge layer, an internal electric field is formed at the heterojunction interface. Under the condition of radiation of the suitable wavelength light source, two kinds of semiconductors are excited simultaneously. Under the action of the internal electric field, the photogenerated electrons migrate from the P type semiconductor to the N type semiconductor rapidly, while the holes in the valence band in the N type semi conductors are rapidly migrated to the P type half. On the conductor, the photoelectron hole pair is effectively separated. The intermediate medium is abandoned in the heterostructure material which is dominated by the Z carrier migration. By controlling the carrier migration of the interface, the low energy photoelectrons and holes are directly combined with the cavity to retain the high energy photoelectron hole, thus increasing the light of the material. In this paper, the research progress in the design and synthesis of nano heterojunction photocatalyst is introduced. The photocatalytic principle of several nano heterostructures (I-, II-, pn- and Z-) and the research progress in the production of hydrogen are summarized, and the prospect of the research is also prospected. This paper hopes to deepen the understanding of the researchers in this field. In the future, the design of efficient photocatalytic materials will help and guide.
【作者单位】：中国科学技术大学合肥微尺度物质科学国家实验室纳米材料与化学研究部;新疆师范大学化学化工学院;
【基金】：supported by the National Natural Science Foundation of China (51572253,21271165) Scientific Research Grant of Hefei Science Center of CAS (2015SRG-HSC048) Cooperation between NSFC and Netherlands Organization for Scientific Research (51561135011)~~
【分类号】：O643.36;TQ116.2

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