1、Effects of doping of metal cations on morphology, activity, andvisible light response of photocatalysts参杂金属阳离子对光催化剂的形态，活性，对光的回应的影响Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japanb Core Research Evolutional Science an
2、d Technology, Japan Science and Technology Agency (CREST/JST), Japan应用化学系，理学院，东京大学的科学，1-3 神乐坂，新宿区，东京 162-8601，日本B 核心科学与技术演进的研究，日本科学技术振兴机构（顶/ 日本时间） ，日本Received 23 March 2007; accepted 23 July 2007Available online 28 July 20072007 年 3 月 23 日收到，2007 年 7 月 23 日接受，2007 年 7 月 28 日在网上提供摘要Effects of doping
3、of metal cations into wide band gap semiconductor photocatalysts on morphology, visible light response, and photocatalyticperformance were studied.金属离子对宽带隙半导体光催化剂的形态，可见光感特性和光催化性能的影响的研究Doping of lanthanide and alkaline earth ions improved activity of a NaTaO3 photocatalyst for water splitting.镧系元素和碱土
4、金属离子掺杂提高了 NaTaO3 光催化剂对水的分解的活性Lanthanum was the most effective dopant. The NaTaO3:La with a NiO cocatalyst gave 56% of a quantum yield at 270 nm.镧掺杂剂是最有效的。NaTaO3 与一氧化镍助催化剂在 270 纳米提高了 56的量子产率This remarkable photocatalytic activity was brought by formations of nano-crystalline particle and surface nano
5、-step structure by the doping这显著的光催化活性是由纳米晶体颗粒表面纳米结构的一步编队所带来的On the other hand, metal cation doping into ZnS, TiO2, and SrTiO3 gave visible light responses for H2 or O2 evolution from aqueous solutions containing of sacrificial reagents.另一方面，硫化锌，二氧化钛和钛酸锶的金属阳离子的参杂对包含献祭试剂的水溶液分解成氢气和氧气的响应The visible lig
6、ht responses were due to the electronic transition from donor levels formed with dopants to conduction bands of the host photocatalysts可见光响应的原因是电子跃迁从参杂过的施主能级到光催化剂传导带Codoping was effective to compensate charge unbalance brought by doping of transition metal cations, resulting in the improvement of vi
7、sible light response for photocatalytic reactions.共掺杂对补偿不平衡的过渡金属离子，掺杂是有效的，引起光催化反应的可见光响应改善Among the transition metal-doped photocatalysts, SrTiO3 doped with Rh (SrTiO3:Rh) was the novel metal oxide photocatalyst that produced H2 under visible light irradiation.在过渡金属掺杂的光催化剂，参杂了铑（钛酸锶：铑）的钛酸锶是一种新型金属氧化物型的
8、光催化剂，可以在可见光照射的情况下产生氢气The SrTiO3:Rh photocatalyst was employed with O2 evolution photocatalysts such as BiVO4 and WO3 for construction of Z-scheme systems that were active for water splitting into H2 and O2 under visible light irradiation.钛酸锶：铑光催化剂发展为用于氧气的制备，例如 BiVO4 和 WO3 用于 Z 型计划体制建设，水在可见光照射下分解成氢气和
9、氧气的催化剂2007 Elsevier B.V. All rights reserved.2007 年爱思唯尔 B.诉保留所有权利1. IntroductionPhoton energy conversion reactions using semiconductorelectrodes 17 and powdered photocatalysts 825have been extensively studied since the HondaFujishimaeffect 26 was reported. Efficient water splitting into H2and O2 usi
10、ng a powdered photocatalyst is attractivebecause it can be a clean and simple process for H2 productionusing a natural energy. Water splitting utilizing solarlight, that is called solar hydrogen production, is thefinal target in the present research field.1 简介光子能量转换用半导体反应电极1-7 和粉状催化剂 8-25已被广泛研究，因为本田
11、藤岛效应26的报道。水使用粉末光催化剂高效分解成氢气和 O2 是有吸引力的因为它可以是一个 H2 的清洁生产，工艺简单,使用自然能源。利用太阳能分解水光，这被称为 太阳能产氢，是在目前的研究领域最终的目标。* Corresponding author. Address: Department of Applied Chemistry,Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka,Shinjuku-ku, Tokyo 162-8601, Japan. Tel.: +81 35228 8267; fax: +8135
12、261 4631.E-mail address: a-kudors.kagu.tus.ac.jp (A. Kudo).*通讯作者。地址：应用化学系，理学院，东京理科 1-3 神乐坂大学新宿区，东京 162-8601，日本。电话：。+81 35228 8267 传真：+8135261 4631。E - mail 地址：a-kudors.kagu.tus.ac.jp （答：工藤） 。Many metal oxide photocatalysts have been reported for water splitting so far. The present authors have found
13、 many niobate and tantalate photocatalysts 19,20,25.Some metal oxide photocatalysts such as NaTaO3 show high activities for water splitting although they work only under UV irradiation because of their wide band gaps. Domen and coworkers have reported water splitting using metal (oxy)nitride photoca
14、talysts that are nonoxide materials 21,23,24. Water splitting under visible light irradiation has been achieved by some photocatalyst systems 16,18,21,24. However, the efficiencies are not satisfying. Development of new photocatalyst materials is still animportant topic.至今有分解水方面有许多报道金属氧化物光触媒。本文作者发现有
15、很多钽铌酸和光触媒19,20,25。有些人，如 NaTaO3 光表现出较高的对水的分裂活动尽管它们在紫外光照射下工作，不仅是因为他们的宽带隙金属氧化物催化剂。 Domen 和同事报告了光催化剂分解水制氢是利用氮化物非氧化物材料21,23,24金属（氧） 。在可见光照射下水分也被一些分裂光触媒系统实现16,18,21,24 。但是，效率并不令人满意。 新型光触媒材料开发仍是一个重要的课题。Photocatalytic activities are affected by particle size,crystallinity, surface properties, etc. These fac
16、tors are controlled by changes in a preparation method, loading of acocatalyst, and introducing a foreign element. Doping of a foreign element into a photocatalyst is one of the strategies that can affect the morphology (particle size and surface structure) of photocatalyst particles. On the other h
17、and, doping of transition metal cations into photocatalysts with wide band gaps such as TiO2 and SrTiO3 hasbeen studied for a long time in the research field of photoelectrochemistry and photocatalysis in order to modify electronic structure and develop materials with visible light responses 2734. H
18、owever, doping is regarded as an unsuitable method because photocatalytic efficiencies drastically decrease in many cases, even if visible light absorption bands are obtained. Recently, anion doping of nitrogen, sulfur, and carbon has been extensively investigated 3538.光催化活性受颗粒大小，结晶度，表面特性等影响，这些都是由制备
19、方法引起变化的因素，装载助催化剂，并引入外来因素。使用光催化剂是其中一种策略，可以影响催化剂粒子的形貌（颗粒大小和表面结构）之一。另一方面，过渡金属离子掺杂宽禁带的光催化剂，如二氧化钛和钛酸锶在被研究的光电化学和光催化研究领域有很长一段时间，以便修改电子结构和发展与可见光响应材料27-34。然而，掺杂被认为是一种不适合的方法，因为光催化效率大大降低，在许多情况下，甚至可以吸收可见光波段获得。最近，阴离子掺杂氮，硫，碳被广泛的研究35-38 。The present review paper introduces the improvement of the activity of a NaTa
20、O3 photocatalyst by doping lanthanum and alkaline earth metals. Development of visible light-driven photocatalysts by doping of metal ions into ZnS, TiO2, and SrTiO3 of wide band gap semiconductor photocatalysts is also reported. In the present paper, dopingmeans the substitution of dopants for meta
21、l cations of the host materials at crystal lattice points. The amounts of dopants are quite large (0.14%).本次审查介绍掺杂镧和碱土金属的一 NaTaO3 光催化活性的提高。可见光光驱动发展的催化剂，金属离子进入硫化锌，二氧化钛和宽禁带半导体光催化剂钛酸锶掺杂也有报道。在本文件中，掺杂指掺杂在主体材料为金属离子在晶格点替代。对掺杂的数额是相当大（0.1-4）。2. Highly efficient water splitting using NiO-loaded NaTaO3 photoca
22、talysts doped with lanthanum and alkaline earth metal ions 39,402。高效分解水用镧和碱土金属离子掺杂氧化镍负载 NaTaO3 光催化剂39,40NaTaO3 loaded with a NiO cocatalyst is a highly active photocatalyst for water splitting 41. In general, photocatalytic activities are increased when the particle size becomes small and highly cry
23、stalline 4244. Therefore, the authors tried to reduce the particle size of the NaTaO3 photocatalyst by doping. Fig. 1 shows SEM photographs of nondoped and La-doped NaTaO3. The particle size of Ladoped NaTaO3 was 0.10.7 lm while that of nondoped NaTaO3 was 23 lm. The particle sizes of NaTaO3 also be
24、came small by doping of Ca, Sr, and Ba. The surface of nondoped NaTaO3 was smooth whereas La-doped NaTaO3 particles had surface nanostructure with steps of315 nm. It was also observed for Ca-, Sr-, and Ba-doped NaTaO3. Thus, the doping of La, Ca, Sr, and Ba affected the morphology of the NaTaO3 part
25、icle. This effect wasdue to the difference in ionic radii between dopants and Na cation 45. Ionic radii of La3 , Ca2 , Sr2 , and Ba2 are 1.50, 1.48, 1.58, and 1.75 A in 12-coordination, respectively. Those values are similar to an ionic radius of Na (1.53A ). On the other hand, in six-coordination,
26、ionic radii of La3 , Ca2 , Sr2 , and Ba2 are 1.17, 1.14, 1.32, and 1.49A , respectively. Those values are smaller than the ionic radius of Ta5 (0.78A ). Therefore, Na in NaTaO3, an A site in perovskite structure, is replaced with those dopants. Crystalline and fine particles, and surface nanostep st
27、ructure were formed by suppression of crystal growth due to distortion of local structure. These effects were not observed for Mg-doping一氧化镍是一种助催化剂 NaTaO3 与一氧化镍光分解水的41 高活性催化剂。一般情况下，光催化活动增加时，粒径变小，高度结晶42-44。因此，笔者试图减少兴奋剂方面的 NaTaO3 光催化剂粒子的大小。图。 1 显示 nondoped和 La 掺杂 NaTaO3 光扫描电镜照片。该 Ladoped NaTaO3 光粒径为 0
28、.1-0.7流明的 nondoped NaTaO3 光而为 2-3 流明。 NaTaO3 光粒子的大小也变小了钙，锶，钡和掺杂。对 nondoped NaTaO3 光表面光滑而掺镧 NaTaO3 光颗粒的表面纳米结构的步骤3-15 纳米。另据观察钙，锶，钡和掺杂 NaTaO3 光。因此，镧，钙，锶，钡和影响了 NaTaO3 光粒子形貌掺杂。这种效应是由于在与钠离子之间掺杂离子半径差异45。镧离子半径，钙，锶，钡和是 1.50，1.48，1.58 ，1.75 和 12 -协调，分别。这些价值观是相似的安娜（1.53A）离子半径。另一方面，在六协调，镧，钙，锶，钡离子半径和 1.17，1.14 ，
29、1.32 和 1.49A，分别。这些值均高于 Ta5（0.78A ）的离子半径较小。因此，在 NaTaO3 光钠，钙钛矿结构中A 位，被替换的掺杂剂。晶和细颗粒物和表面 nanostep 结构，形成了由晶体生长的抑制由于局部结构的扭曲。这些影响并没有观察到镁兴奋剂。Table 1 shows photocatalytic activities for water splitting on La-, Ca-, Sr-, and Ba-doped NaTaO3. The activity of NaTaO3 was increased by La-, Ca-, Sr-, and Ba-doping
30、and was drastically improved by NiO-loading. The NiO cocatalyst works as a H2 evolution site. La-doped NaTaO3 with the NiO cocatalyst showed the highest activity. The apparent quantum yield of this photocatalyst was 56% at 270 nm. Vigorous evolution of bubbles of H2 and O2 was observed using a 200-W
31、 XeHg lamp.表 1 显示了水对镧，钙，锶，钡和掺杂 NaTaO3 光催化分裂活动。 NaTaO3 光活性的增加腊，钙，锶，钡和兴奋剂并大幅提高了 NiO 的加载。 而 NiO 助剂工程作为产氢的网站。 镧掺杂的 NiO 助剂NaTaO3 光具有最高的活性。这种光催化剂的表观量子效率为 56，至 270 纳米。氢气和氧气的蓬勃发展，观察气泡用 200 瓦氙汞灯Table 2 shows H2 or O2 evolution from aqueous solutions containing of sacrificial reagents on La-, Ca-, Sr-, and Ba
32、-doped NaTaO3 photocatalysts. The photocatalyticactivities of the H2 and O2 evolution were increased 1.21.3 and 34 times by doping, respectively. This result suggests that the doping mainly affects the formation of O2 evolution sites表 2 显示了氢气或氧气从上镧，钙，锶，钡和掺杂 NaTaO3 光催化剂牺牲试剂含水溶液的演变。光催化氢气和氧气的演化活动分别增加了兴
33、奋剂 1.2-1.3 和 3-4 倍。这一结果表明，掺杂主要影响析氧地盘平整工程。TEM and SEM observation revealed that PbO2 was oxidatively photodeposited on grooves of the surface nanostep structure by the reaction of Pb2+ with photogeneratedholes. This result indicates that the grooves work as oxidation sites for photocatalytic reaction
34、s. On the other hand, EXAFS analyses of nickel indicate that the NiO cocatalystwas loaded on the surface like a cluster. The nickel oxide species were detected on the edge and flat surface by TEMEDS, except for grooves, as shown in Fig. 2. Theedges and grooves on the surface nanostep structure work
35、as reduction and oxidation sites for photocatalytic reactions, respectively. The separation of the reduction sitefrom the oxidation site is important to achieve water splitting of an uphill reaction to suppress a backward reaction to form H2O from H2 and O2. The surface nanostep structure contribute
36、s to the formation of the separated reaction sites.TEM 和 SEM 观察发现，氧化 photodeposited 二氧化铅是对受铅反应槽 +表面 nanostep结构与光生孔。这一结果表明，作为光催化反应槽氧化用地。另一方面，镍的 EXAFS 分析表明，氧化镍助剂像装上了一个群集的表面。氧化镍物种的边缘检测和透射电镜- EDS 的平面上，除槽，如图所示。 2。该沟槽边缘和表面上 nanostep 为减少和光催化氧化反应结构的工作地点分别。 该网站的分离减少从氧化网站重要的是要实现水资源的上坡反应的分裂抑制落后反应，形成水的氢气和氧气。表面
37、nanostep 结构有助于分离反应位点的形成。Thus, the photocatalytic activity for water splitting of NaTaO3 was significantly improved by La-, Ca-, Sr-, and Ba-doping. It is due to the formation of highly crystalline fine particles and surface nanostep structure in which a H2 evolution site is separated from an O2 evol
38、ution site因此，镧，钙，锶，钡和催化剂对水的 NaTaO3 光催化分解活性显着提高了。 这是由于高结晶细颗粒和表面结构，其中一 nanostep H2 的进化是从一个网点的网点分离析氧的形成。3. Visible light response of doping photocatalysts3。可见光响应光催化剂的掺杂3.1. Design of visible light driven photocatalysts by doping of metal ions 193.1。可见光的金属离子掺杂光催化剂驱动设计 19The band structure, in which the
39、bottom of a conduction band level is more negative than a redox potential of H+/H2 (0 V vs. NHE) and the top of a valence band is more positive than a redox potential of O2/H2O (1.23 V vs. NHE), is required for water splitting into H2 and O2 by semiconductor photocatalysts. Valence band levels ofmet
40、al oxide photocatalysts with d0 or d10 configuration are too positive (ca. 3 V vs. NHE) compared with the redox potential of O2/H2O. Therefore, the band gaps of photocatalysts for water splitting are inevitably wider than 3 eV. These photocatalysts respond to only UV. Making new valence bands or ele
41、ctron donor levels above thevalence band consisting of O2p orbitals (band engineering) is indispensable to develop visible light-responsive photocatalysts. If a dopant forms an electron donor level in the band gap of a host semiconductor photocatalyst, the photocatalystmay show visible light respons
42、e as shown in Fig. 3. This idea is also applied to metal sulfide photocatalysts such as ZnS with UV response. Visible-active photocatalystsobtained by doping are presented in the following.该能带结构，其中一个是导带底水平比氧化还原电位负的 H + /氢气（向 0 V 对比 NHE 的）和一价带顶比一个更积极的 O2/H2O 氧化还原电位（1.23 V 对 NHE） ，是需要水为 H2 和O2 分裂的半导体光
43、催化剂。价带水平D10 的配置与 d0 或金属氧化物催化剂是太积极（约 3 伏对 NHE 的） ，而对 O2/H2O 氧化还原电位。因此，光催化剂分解水的带隙宽度大于 3 eV 的必然。这些只紫外线光催化剂反应。使上述新价带或电子施主能级价带 O2p 轨道（带工程）组成的发展是必不可少的可见光响应光催化剂。如果掺杂形式在一台主机带隙的半导体光催化剂的电子供体的水平，光触媒可能会出现明显的光响应，如图所示。 3。这种思想也适用于金属硫化物光催化剂反应，如与紫外线硫化锌。可见光活性光催化剂掺杂，得到的列于下。3.2. Visible light response of ZnS photocatal
44、ysts doped with metal ions 46483.2。可见与金属离子掺杂的 ZnS 光催化剂的光响应46-48Metal ion doping into oxide photocatalysts has beenextensively studied, but not for sulfide photocatalysts. A ZnS photocatalyst with a wide band gap (3.6 eV) has a highconduction band. It shows high activity for H2 evolution without any
45、assistance of cocatalysts such as Pt in the presence of a sacrificial reagent 42. The authors have tried to dope metal cations into the ZnS photocatalyst to make it visible light responsive. Fig. 4 shows diffuse reflectance spectra of Cu-, Ni-, and Pb-doped ZnS. Visible light absorption band tails w
46、ere obtained in addition to the band gap absorption band of the ZnS host. These metal cationdoped ZnS photocatalysts showed activities for H2 evolution from aqueous solutions containing of S2 and/or SO2 3 of electron donors as shown in Table 3. Loading of cocatalysts such as Pt was not necessary for
47、 the H2 evolution, indicating that the high conduction band of the ZnS host was maintained after the doping of metal cations.金属氧化物催化剂离子掺杂进了 beenextensively 研究，但没有硫化物光催化剂。一个有宽禁带的 ZnS 光催化剂（3.6 eV）的具有高 导带。这表明高，如没有任何铂在一个牺牲试剂的存在42 cocatalysts 援助产氢活性。笔者尝试进入到涂料的 ZnS 光催化剂金属离子，使其可见光响应。 图。 4 显示弥漫性铜，镍，铅掺杂的 ZnS
48、 的反射光谱。可见光吸收带尾，获得除带隙的 ZnS 基质吸收带。这些金属的 ZnS 光催化剂 cationdoped 显示，产氢活性的研究 S2 和/ 或电子供体，如表 3 所示，3 个含有二氧化硫的水溶液。如装载的 cocatalysts 铂没有必要的，而 H2 演变，表明了硫化锌举办高导带后的金属离子掺杂维持。Thus, it was found that metal cation doping was effective for visible light response of metal sulfide photocatalysts因此，人们发现，金属离子掺杂的金属硫化物对可见光光催
49、化剂的光反应有效。3.3. Photocatalytic activities of transition metal-dopedSrTiO3:Rh 493.3。光催化活性过渡金属 SrTiO3：铑49Although SrTiO3 with 3.2-eV band gap can not absorb visible light, SrTiO3 powders doped with Rh, Ir, Ru, and Mn possess absorption bands in a visible light region as shown in Fig. 5. These doping photocatalysts showed activities for H2 or O2 evolution from aqueous solutions with sacrificial reagents as shown in Table 3. Rh-doped SrTiO3showed the highest activity among oxide photocatalysts fo
