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${CsPbBr}_{3} - {MoS}_{2}$ -GO nanocomposites for boosting photocatalytic degradation performance
用于提高光催化降解性能的 ${CsPbBr}_{3} - {MoS}_{2}$ -GO 纳米复合材料

Hongmei Ju, Tingsen Fang, Yun Zhou, Xianbin Feng, Tinghui Song, Feng Lu, Wenchao Liu
鞠红梅、方廷森、周云、冯显斌、宋廷辉、卢锋、刘文超Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), Nanjing, China
南京理工大学柔性电子学重点实验室（KLOFE）和先进材料研究院（IAM），江苏先进材料国家协同创新中心（SICAM），南京，中国

ARTICLE INFO 文章信息

Keywords: 关键词：

Perovskite
Nanocomposites 纳米复合材料

{CsPbBr}_{3}

Photocatalytic 光催化
Degradation 退化

Abstract 摘要

In order to address the main challenge of weak photocatalytic performance of pure metal halide perovskite materials, we innovatively introduced ${MoS}_{2}$ -graphene oxide (GO) composite structure and synthesized ${CsPbBr}_{3}^{-}$ ${MoS}_{2}$ -GO nanocomposites by a two-step method. XRD and Raman results show that the three components are well combined to form a new ${CsPbBr}_{3} - {MoS}_{2}$ -GO nanocomposite. TEM results show that ${MoS}_{2}$ nanoribbons and ${CsPbBr}_{3}$ quantum dots (QDs) are uniformly dispersed on the GO sheet. The photocatalytic activity of nanocomposites was evaluated by studying the photodegradation of Sudan Red III under xenon lamp irradiation. Benefiting from abundant active interfaces, the nanocomposites show much excellent photocatalytic degradation performance compared with pure ${CsPbBr}_{3}$ QDs. The degradation rate of Sudan Red III by ${CsPbBr}_{3} - {MoS}_{2} - GO$ nanocomposites is 3.1 times of that of pure perovskite QDs. Sudan Red III was completely photocatalytic degraded in 100 min . We believe that GO, with suitable band structure, high conductivity and good dispersibility, can bridge well ${MoS}_{2}$ and ${CsPbBr}_{3}$ , act as a good electron transport channel, reduce carrier recombination and ultimately boost photocatalytic performance.
针对纯金属卤化物包晶材料光催化性能弱的主要难题，我们创新性地引入了 ${MoS}_{2}$ -氧化石墨烯（GO）复合结构，并通过两步法合成了 ${CsPbBr}_{3}^{-}$ ${MoS}_{2}$ -GO纳米复合材料。XRD 和拉曼结果表明，三种组分很好地结合在一起，形成了一种新的 ${CsPbBr}_{3} - {MoS}_{2}$ -GO 纳米复合材料。TEM结果表明， ${MoS}_{2}$ 纳米带和 ${CsPbBr}_{3}$ 量子点（QDs）均匀地分散在GO片上。通过研究氙灯照射下苏丹红 III 的光降解，评估了纳米复合材料的光催化活性。与纯 ${CsPbBr}_{3}$ QDs 相比，纳米复合材料得益于丰富的活性界面，表现出更为优异的光催化降解性能。 ${CsPbBr}_{3} - {MoS}_{2} - GO$ 纳米复合材料对苏丹红 III 的降解率是纯包晶体 QDs 的 3.1 倍。苏丹红 III 在 100 分钟内被完全光催化降解。我们认为，GO 具有合适的能带结构、高导电性和良好的分散性，可以很好地桥接 ${MoS}_{2}$ 和 ${CsPbBr}_{3}$ ，成为良好的电子传输通道，减少载流子重组，最终提高光催化性能。

1. Introduction 1.导言

With the rapid development of industry, the pollution caused by organic substances is becoming increasingly serious. Nonionic organic dyes, such as Sudan Red, are widely used in textile, leather, coating and plastic industries, causing serious environmental hazards. Some criminals add them into food. Their metabolites are classified as grade II or III carcinogens. What’s more, Sudan Red dyes are a kind of azo compounds, compared to some widely used photocatalytic degradation dyes such as methyl orange, their chemical structure is extremely stable and difficult to remove. Therefore, most countries prohibit the use of Sudan Red dyes. It is urgent to seek an effective method to solve these problems. Photocatalytic degradation technology is an efficient and clean technology to convert organic pollutants to

{CO}_{2}

, water, and other small molecules under the help of renewable solar energy [1-4]. The traditional photocatalysts, for example,

{TiO}_{2}

has a wide band-gap ( 3.2 eV ) and can only absorb the ultraviolet light which has only about

5 %

of the whole sunlight energy. All-inorganic halide perovskite nanocrystal quantum dots

({CsPbX}_{3} QDs, X = Cl, Br

, and I

)

have attracted much attention due to their excellent opto-electric properties such as high absorption
随着工业的快速发展，有机物造成的污染日益严重。苏丹红等非离子有机染料广泛应用于纺织、皮革、涂料、塑料等行业，对环境造成严重危害。一些不法分子将其添加到食品中。它们的代谢产物被列为二级或三级致癌物。更重要的是，苏丹红染料是一种偶氮化合物，与甲基橙等一些广泛使用的光催化降解染料相比，其化学结构极其稳定，难以去除。因此，大多数国家禁止使用苏丹红染料。寻找一种有效的方法来解决这些问题迫在眉睫。光催化降解技术是一种在可再生太阳能的帮助下，将有机污染物转化为

{CO}_{2}

、水和其他小分子物质的高效清洁技术[1-4]。传统的光催化剂，如

{TiO}_{2}

具有宽带隙（3.2 eV），只能吸收紫外线，而紫外线的能量只占整个太阳光能量的

5 %

左右。全无机卤化物过氧化物纳米晶体量子点

({CsPbX}_{3} QDs, X = Cl, Br

和 I

)

由于具有高吸收等优异的光电特性而备受关注。
coefficient in the visible light range, controllable band-gaps, multi-excitons and high quantum yields [5-8]. They have been widely used in solar cells [9-11], light-emitting diode [12-15], lasers and so on

[16, 17]

. Recent years, halide perovskite QDs are also considered possible candidate materials for photocatalytic applications. The main photocatalytic application fields of halide perovskites include photocatalytic hydrogen evolution, carbon dioxide reduction, pollutant degradation and photocatalytic polymerization reaction [18-20]. Up to now, the published reports focus on photocatalytic hydrogen evolution and carbon dioxide reduction. The reports of halide perovskites nanocomposites for photocatalytic degradation are very limited. The main challenge of halide perovskite materials in application of photocatalytic degradation is that the degradation efficiency is still low [20].
在可见光范围内的系数、可控带隙、多激子和高量子产率 [5-8]。它们已被广泛应用于太阳能电池 [9-11]、发光二极管 [12-15]、激光等领域

[16, 17]

。近年来，卤化物过氧化物 QDs 也被认为是光催化应用的可能候选材料。卤化物类包晶石的主要光催化应用领域包括光催化氢气进化、二氧化碳还原、污染物降解和光催化聚合反应 [18-20]。迄今为止，已发表的报告主要集中在光催化氢进化和二氧化碳还原方面。关于卤化物过氧化物纳米复合材料用于光催化降解的报道非常有限。卤化物包晶材料在光催化降解应用中面临的主要挑战是降解效率仍然较低[20]。

In recent years, two-dimensional

{MoS}_{2}

has been used in the field of photocatalysis. Researchers found that

{MoS}_{2}

as a co-catalyst attached on semiconductor can improve the efficiency of visible light absorption and charge separation [21], and greatly increase the photocatalytic activity of catalyst materials [22,23]. Graphene oxide (GO) has special physical and chemical properties, such as two-dimensional structure, large specific surface area, good conductivity and high mobility [24-27]. It has
近年来，二维

{MoS}_{2}

在光催化领域得到了应用。研究人员发现，

{MoS}_{2}

作为助催化剂附着在半导体上，可以提高可见光吸收和电荷分离的效率[21]，大大提高催化剂材料的光催化活性[22,23]。氧化石墨烯（GO）具有特殊的物理和化学特性，如二维结构、大比表面积、良好的导电性和高迁移率 [24-27]。它具有

Fig. 1. Schematic diagram of (a)

{MoS}_{2} - GO

and (b)

{CsPbBr}_{3} - {MoS}_{2} - GO

nanocomposites forming process.
图 1.(a)

{MoS}_{2} - GO

和 (b)

{CsPbBr}_{3} - {MoS}_{2} - GO

纳米复合材料成型过程示意图。
been proved to be an ideal co-catalyst for enhancing photocatalytic activity. GO can not only prevent the photocatalyst from agglomerating, but also provide a charge transfer channel with high mobility to prevent the recombination of electron hole pairs [28].
已被证明是提高光催化活性的理想助催化剂。GO 不仅能防止光催化剂团聚，还能提供具有高迁移率的电荷转移通道，防止电子空穴对的重组 [28]。

In this paper, we make full use of the respective advantages of two dimensional

{MoS}_{2}

and GO in catalytic field and combine them with

{CsPbBr}_{3}

QDs to form

{CsPbBr}_{3} - {MoS}_{2} - GO

nanocomposites. This structure is expected to solve the main challenge of low photocatalytic efficiency of pure halide perovskite QDs. When

{CsPbBr}_{3}

QDs absorbs solar light, electrons in the valence band are stimulated to the conduction band, and holes are formed in the valence band. Because the redox potential of

GO / {GO}^{∙ -}

is lower than the conduction band of

{CsPbBr}_{3}

, photogenerated electrons can easily be transferred to GO [29]. GO as an electron transport channel can transfer electrons.

{MoS}_{2}

on GO can receive electrons and provide more reaction sites for catalytic reaction. This can further prevent the recombination of electrons and holes and improve the photocatalytic degradation of organic pollutants [30]. Up to our best knowledge, there are no reports about the photocatalytic degradation of

{CsPbBr}_{3} - {MoS}_{2}

-GO nanocomposites.
本文充分利用二维

{MoS}_{2}

和 GO 在催化领域的各自优势，将它们与

{CsPbBr}_{3}

QDs 结合形成

{CsPbBr}_{3} - {MoS}_{2} - GO

纳米复合材料。这种结构有望解决纯卤化物过氧化物 QDs 光催化效率低的主要难题。当

{CsPbBr}_{3}

QDs 吸收太阳光时，价带中的电子被激发到导带，同时在价带中形成空穴。由于

GO / {GO}^{∙ -}

的氧化还原电位低于

{CsPbBr}_{3}

的导带，光生电子很容易转移到 GO 上 [29]。作为电子传输通道，GO 可以传输电子。GO 上的

{MoS}_{2}

可以接收电子，并为催化反应提供更多的反应位点。这可以进一步防止电子和空穴的重组，提高有机污染物的光催化降解能力 [30]。据我们所知，目前还没有关于

{CsPbBr}_{3} - {MoS}_{2}

-GO 纳米复合材料光催化降解的报道。

2. Experimental section 2.实验部分

Fig. 1 shows the synthesis process of

{MoS}_{2}

- GO and

{CsPbBr}_{3} - {MoS}_{2} - GO

nanocomposites. The details of the synthesis are blow.
图 1 显示了

{MoS}_{2}

- GO 和

{CsPbBr}_{3} - {MoS}_{2} - GO

纳米复合材料的合成过程。合成的详细过程如下。

2.1. Synthesis of ${CsPbBr}_{3}$ QDs
2.1. ${CsPbBr}_{3}$ QD 的合成

5 mL octadecene and

0.188 mmol (69 mg) {PbBr}_{2}

were added into a three flask under the protection of

N_{2}

. After heating at

120^{\circ} C

for 1 h , 0.5 mL oleic acid and 0.5 mL oleamine were added. After 30 min , the solution was gradually heated to

180^{\circ} C

and 0.4 mL cesium oleate was rapidly injected. After 5 s , it was cooled by ice-water bath and 20 mL ethyl acetate was added to dissolve completely the synthesized samples. Then the obtained samples were centrifuged for 5 min at

12000 rpm /

min, washed three times with ethyl acetate, and vacuum dried at

70^{\circ} C

for 12 h .
在

N_{2}

的保护下，将 5 mL 十八烯和

0.188 mmol (69 mg) {PbBr}_{2}

加入三口烧瓶中。在

120^{\circ} C

下加热 1 小时后，加入 0.5 mL 油酸和 0.5 mL 油胺。30 分钟后，将溶液逐渐加热至

180^{\circ} C

，并迅速注入 0.4 mL 油酸铯。5 秒后，冰水浴冷却，加入 20 mL 乙酸乙酯使合成样品完全溶解。然后在

12000 rpm /

分钟离心5分钟，用乙酸乙酯洗涤三次，在

70^{\circ} C

真空干燥12小时。

2.2. Synthesis of ${MoS}_{2}$ nanosheets
2.2. ${MoS}_{2}$ 纳米片的合成

0.205 g {Na}_{2} {MoO}_{4}

and 0.38 g thiourea were dissolved in 60 mL deionized water, then were transferred to 100 mL hydrothermal reactor, sealed and reacted at

210^{\circ} C

for 26 h and cooled to room temperature naturally. The solution was centrifuged at

12000 rpm / \min

speed for 5 min, washed alternately with deionized water and ethanol for 3 times, and dried in vacuum at

60^{\circ} C

for 12 h .
将

0.205 g {Na}_{2} {MoO}_{4}

和 0.38 g 硫脲溶于 60 mL 去离子水中，然后转移到 100 mL 水热反应器中，密封并在

210^{\circ} C

下反应 26 h，然后自然冷却到室温。溶液以

12000 rpm / \min

速度离心 5 分钟，用去离子水和乙醇交替洗涤 3 次，在

60^{\circ} C

真空中干燥 12 小时。

2.3. Synthesis of GO
2.3.合成 GO

GO is synthesized by an improved Hummers method [31]. Firstly, 2 g graphite powder and

1 g {NaNO}_{3}

were mixed evenly.

96 mL H_{2} {SO}_{4}

was added into the ice bath slowly and stirred continuously. Then 6 g KMnO 4 was added gradually. Then the mixture was heated to

35^{\circ} C

in water bath for 18 h . During the reaction, the mixture becomes pasty and brown. Then the paste mixture was added slowly into

150 mL H_{2} O

. Since the addition of water into high concentration

H_{2} {SO}_{4}

will release a lot of heat, it is necessary to keep the mixture in an ice bath so that the temperature of the mixture can be kept below

50^{\circ} C .5 mL 30 % H_{2} O_{2}

was diluted with

240 mL H_{2} O

and then slowly added to the mixture. The color of the solution gradually turned bright yellow and bubbles were constantly emerging. After stirring for 2 h , the mixture was filtered and washed with

250 mL 10 % HCl

aqueous solution, deionized water and ethanol to remove other ions. The final sample was vacuum dried at

60^{\circ} C

.
GO 是通过改进的 Hummers 方法合成的[31]。首先，将 2 克石墨粉和

1 g {NaNO}_{3}

混合均匀。将

96 mL H_{2} {SO}_{4}

缓慢加入冰浴中并不断搅拌。然后逐渐加入 6 g KMnO 4。然后将混合物在水浴中加热至

35^{\circ} C

18 小时。在反应过程中，混合物变成糊状和棕色。然后将糊状混合物缓慢加入

150 mL H_{2} O

中。由于向高浓度的

H_{2} {SO}_{4}

中加水会释放大量热量，因此必须将混合物置于冰浴中，使混合物的温度保持在

50^{\circ} C .5 mL 30 % H_{2} O_{2}

以下，用

240 mL H_{2} O

稀释后缓慢加入混合物中。溶液的颜色逐渐变成亮黄色，并不断冒出气泡。搅拌 2 小时后，过滤混合物，用

250 mL 10 % HCl

水溶液、去离子水和乙醇洗涤，除去其他离子。最后的样品在

60^{\circ} C

真空干燥。

2.4. Preparation of ${MoS}_{2}$ -GO nanocomposites
2.4.制备 ${MoS}_{2}$ -GO 纳米复合材料

0.135 g GO was well dispersed in 60 mL deionized water by ultrasonic for 30 min . Then

0.205 g {Na}_{2} {MoO}_{4}

and 0.380 g thiourea were added in the solution. After stirred for 30 min , the mix solution was transferred into 100 mL hydrothermal reactor, sealed and reacted at

210^{\circ} C

for 26 h then cooled naturally to room temperature. The obtained sample was centrifuged at

12000 rpm / \min

for 5 min , washed alternately with deionized water and ethanol for 3 times, and dried in vacuum at
用超声波将 0.135 克 GO 充分分散在 60 毫升去离子水中 30 分钟。然后在溶液中加入

0.205 g {Na}_{2} {MoO}_{4}

和 0.380 克硫脲。搅拌 30 分钟后，将混合溶液转移到 100 mL 水热反应器中，密封并在

210^{\circ} C

温度下反应 26 小时，然后自然冷却至室温。得到的样品在

12000 rpm / \min

下离心 5 分钟，用去离子水和乙醇交替洗涤 3 次，然后在

12000 rpm / \min

下真空干燥。

Fig. 2. (a) XRD patterns of

{CsPbBr}_{3}, {MoS}_{2}, {CsPbBr}_{3} - GO, {CsPbBr}_{3} - {MoS}_{2}, {MoS}_{2} -

GO and

{CsPbBr}_{3} - {MoS}_{2} - GO

, (b) The Raman spectra of

{CsPbBr}_{3}, GO, {CsPbBr}_{3} - GO

{CsPbBr}_{3} - {MoS}_{2}, {MoS}_{2} - GO

and

{CsPbBr}_{3} - {MoS}_{2} - GO

nanocomposites.
图 2：（a）

{CsPbBr}_{3}, {MoS}_{2}, {CsPbBr}_{3} - GO, {CsPbBr}_{3} - {MoS}_{2}, {MoS}_{2} -

GO 和

{CsPbBr}_{3} - {MoS}_{2} - GO

的 XRD 图；（b）

{CsPbBr}_{3}, GO, {CsPbBr}_{3} - GO

、

{CsPbBr}_{3} - {MoS}_{2}, {MoS}_{2} - GO

和

{CsPbBr}_{3} - {MoS}_{2} - GO

纳米复合材料的拉曼光谱。

$60^{\circ} C$ for 12 h. $60^{\circ} C$ 12小时。

2.5. Preparation of ${CsPbBr}_{3} - {MoS}_{2}, {CsPbBr}_{3} - GO$ and ${CsPbBr}_{3} - {MoS}_{2} - GO$ nanocomposites
2.5.制备 ${CsPbBr}_{3} - {MoS}_{2}, {CsPbBr}_{3} - GO$ 和 ${CsPbBr}_{3} - {MoS}_{2} - GO$ 纳米复合材料

5 mL octadecene was added into a 50 mL flask, then

5 mg MoS_{2}

(or 5 mg GO or

5 mg {MoS}_{2}

-GO) was added to the flask and well dispersed under ultrasonic for 30 min . Then

0.188 mmol (69 mg) {PbBr}_{2}

ARTICLE INFO 文章信息

Keywords: 关键词：

Abstract 摘要

1. Introduction 1.导言

2. Experimental section 2.实验部分

2.1. Synthesis of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs2.1. CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QD 的合成

2.2. Synthesis of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanosheets2.2. MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 纳米片的合成

2.3. Synthesis of GO2.3.合成 GO

2.4. Preparation of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO nanocomposites2.4.制备 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} -GO 纳米复合材料

60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} for 12 h. 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 12小时。

2.1. Synthesis of ${CsPbBr}_{3}$ QDs
2.1. ${CsPbBr}_{3}$ QD 的合成

2.2. Synthesis of ${MoS}_{2}$ nanosheets
2.2. ${MoS}_{2}$ 纳米片的合成

2.3. Synthesis of GO
2.3.合成 GO

2.4. Preparation of ${MoS}_{2}$ -GO nanocomposites
2.4.制备 ${MoS}_{2}$ -GO 纳米复合材料

$60^{\circ} C$ for 12 h. $60^{\circ} C$ 12小时。