原位制备Bi2Ti2O7/TiO2异质结构亚微米纤维以增强光催化活性资源-CSDN文库

175 浏览量 2021-03-23 20:41:53 上传评论收藏 3.08MB PDF 举报

本文研究的主题是采用一种便捷的两步法，即静电纺丝技术和水热技术相结合的原位制备工艺，来制备出具有增强光催化活性的Bi2Ti2O7 / TiO2异质结构亚微米纤维。为了深入理解该研究内容，我们需要关注以下几个方面的知识点： 1. Bi2Ti2O7 / TiO2异质结构：异质结构是指由两种或两种以上的材料构成，这些材料在原子尺度上有一个或多个维度是分隔的。在本文中，异质结构是由Bi2Ti2O7和TiO2两种不同的材料组成，这种特殊的结构能够带来许多优异的性质。例如，异质结构中的不同半导体之间能够产生内部电场，从而促进光生电荷的有效分离，提高光催化效率。 2. 静电纺丝技术：这是一种通过在高电压下将聚合物溶液或者熔融体挤出并形成纤维的技术。在本文中，静电纺丝技术用于制备TiO2亚微米纤维，这是一种有效的制备纳米材料的技术，可以通过调整电压、溶液流速、收集距离等参数来控制纤维的直径和形态。 3. 水热技术：这是一种利用溶剂在密闭容器中高温高压下溶解和再结晶材料的方法。文中利用水热技术在TiO2亚微米纤维表面生长出Bi2Ti2O7纳米片。这种方法有利于在较低的温度下制备出结晶性好、形貌可控的无机材料。 4. 光催化活性：光催化是一种利用光能催化化学反应的过程，其中光催化剂吸收光能后激发电子从价带跃迁至导带，产生自由电子和空穴对，从而促进化学反应的进行。TiO2是一种常用的光催化剂，但其主要吸收紫外光，对可见光吸收有限。本文通过构建Bi2Ti2O7 / TiO2异质结构，有效地扩展了TiO2的光吸收范围至可见光区域。 5. 光电化学分析：光电化学分析是研究材料光电化学性能的技术，通过测量材料在外加光源激发下的光电流或电势响应来评估其性能。本文通过光电化学分析证明了Bi2Ti2O7 / TiO2异质结构能够驱动有效的光生载流子分离，是其光催化活性提高的重要原因。 6. 可见光响应：传统的TiO2光催化剂主要吸收紫外光，而紫外光只占太阳光能量的一小部分。因此，提高光催化剂对可见光的吸收能力对于提升光催化效率和实际应用至关重要。通过将Bi2Ti2O7与TiO2结合，成功实现了光吸收范围的扩展。 7. 催化剂的降解活性：研究中使用罗丹明B（Rhodamine B）作为有机污染物模型进行光催化降解实验。结果表明，在可见光照射下，Bi2Ti2O7 / TiO2异质结构表现出比未修饰的TiO2亚微米纤维更高的罗丹明B降解速率。 8. 金属氧化物的光催化研究背景：过去几十年，大量金属氧化物被探索用于光催化降解有害有机物质和水分解制氢。TiO2因其低成本、强氧化能力、无毒性和长期光稳定性而被广泛视为废水中有害污染物光降解的异质光催化剂。但其只吸收紫外光的限制以及光生电子-空穴对的高复合率，使其在实际应用中存在局限。 9. 紫外-可见光漫反射光谱（UV-vis）：这是一种常用来分析材料吸光性质的技术。通过分析Bi2Ti2O7 / TiO2复合材料的紫外-可见漫反射光谱，研究者可以确定其吸光范围是否向可见光区域扩展。这些知识点共同构建了文章中的研究主题和研究内容。通过原位制备技术构建了具有可见光响应的光催化剂，实现了材料性能的优化，为光催化技术的发展提供了新的思路。

资源推荐

资源详情

资源评论

NAN O E X P R E S S Open Access

In Situ Fabrication of Bi

/TiO

Heterostructure Submicron Fibers for

Enhanced Photocatalytic Activity

Di Zhou

, Hu Yang

, Yafang Tu

, Yu Tian

, Yaxuan Cai

, Zhenglong Hu

and Xiaolong Zhu

Abstract

A facile two-step synthesis route combining electrospinning and hydrothermal techniques has been performed to

obtain Bi

/TiO

heterostructured submicron fibers. Bi

nanosheets were grown on the surface of TiO

submicron fibers. The density of the nanosheets increased with higher precursor concentration of the Bi/Ti reaction

raw materials. UV-visible (UV-vis) diffuse reflectance spectroscopy indicated that the absorption spectrum of the

/TiO

composite extended into the visible-light regio n. Photocatalytic tests showed that the Bi

/TiO

heterostructures possess a much higher degradation rate of rhodamine B than the unmodified TiO

submicron

fibers under visible light. The enhanced photocatalytic activity can be attributed to the synergistic effect between

improved visible-light absorption and the internal electric field created by the heterojunctions. The effective

separation of photogenerated carriers driven by the photoinduced potential was demonstrated by the

photoelectrochemical analysis.

Keywords: Bismuth titanate, Heterostructure, Hydrothermal, Visible light, Photocatalyst

Background

Over the past decades, a large number of metal oxides

have been explored for the purpose of photocatalytic

degradation of harmful organic subs tances and hydrogen

production through splitting water. Titanium dioxide

(TiO

) is widely regarded as a heterogeneous photocata-

lyst for the photodegradation of pollutants in wastewater

due to its low-cost, strong oxidizing power, non -toxicity,

and long-term photostability [1–4]. For certain practical

applications, however, pure TiO

is not very suitable be-

cause it only absorbs UV light at wavelengths no longer

than 387.5 nm (anatase phase) or 413.3 nm (rutile

phase). Even complete absorption in that range would

account for less than 5 % of incoming solar light energy.

Additionally, the high recombination rate of photogener-

ated electron-hole pairs is another problem if TiO

used for photocatalysis [4]. A common method used to

overcome these drawbacks is to creat e a heterojunction

composite comprising a TiO

bottom-layer and a

different top-layer semiconductor with a narrow band

gap. That way, the built-in potential gradient at the

interface between the semiconductors facilitates the sep-

aration of electron-hole pairs and reduces the chance of

recombination [5–8]. For effective sensitization of TiO

using another semiconductor to capture a larger part of

the solar spectrum, the second semiconductor should

meet the following conditions [5, 6]: (1) be a narrow

band gap semiconductor; (2) possess a lower anodic con-

duction band (CB) than TiO

; (3) possess high stability

to prevent photocorrosion; and (4) be a visible light-

driven photocatalyst itself. Thus, the development of

suitable methods to fabricate narrow band gap semicon-

ductor/TiO

heterojunction composites will be essential

for the practical application of TiO

as photocatalyst.

Bismuth titanates, a large family that includes several

phases of the Bi-O-Ti system, including Bi

,Bi

TiO

, and Bi

TiO

, are

promising candidates for many technological applica-

tions [9 –14]. Several of these materials have been re-

ported as visible light-driven photocatalysts, for example:

nanorods, Bi

TiO

nanowires, and Bi

TiO

nanosheets [12–14]. Especially, Bi

with its

* Correspondence: zhdijhu@gmail.com

School of Physics and Information Engineering, Jianghan University, Wuhan

430056, China

Full list of author information is available at the end of the article

International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and

reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to

the Creative Commons license, and indicate if changes were made.

Zhou et al. Nanoscale Research Letters (2016) 11:193

DOI 10.1186/s11671-016-1408-7

pyrochlore structure forms a shallow acceptor energy level

in the forbidden band because of a non-stoichiometric ra-

tio of Bi

1.74

6.62

and the Bi vacancy [15]. As a result,

the holes in Bi

can be excited into the valence band

(VB) under irradiation with visible light. Bian and Ren et

al. reported independently that Bi

absorbs well in

the visible region and also possesses enhanced photocata-

lytic activity with regard to the decomposition of rhoda-

mine B (RhB) under visible light [16, 17]. However, the

fast recombination of photogenerated electron-hole pairs

seriously limits energy-conversion efficiency. To promote

the separation of photogenerated carriers in Bi

,de-

signing a composite photocatalyst by coupling Bi

with a semiconductor with matched band potentials is a

sensible strategy. For example, Wang and Hou et al. re-

ported independently that Bi

/TiO

composite pow-

ders and nanowire arrays showed higher photocatalytic

activity than pure TiO

under visible light [18–20]. Based

on the above considerations, the authors constructed a

novel Bi

sensitized TiO

composite system, with

the goal to expand the photocatalytic activity of TiO

into

the visible-light range. However, the photocatalytic per-

formance of common composite films with a dense and

smooth surface is still moderate. This is because the redox

reaction occurs on the surface of catalyst film, and the sur-

face morphology of the catalyst film plays a key role in the

photocatalytic property [20–22]. Therefore, Bi

nanosheets-TiO

submicron fibers heterostructures were

chosen as tested candidates and fabricated by using a

combination of an electrospinning technique and hydro-

thermal method.

In this work, a facile in situ hydrothermal method was

used to grow secondary Bi

nanostructures on TiO

submicron fibers. Electrospun TiO

submicron fibers

were employed because the fiber matrix possesses the fa-

vorable morphology of high surface areas and aspect ra-

tios [23, 24]. Moreover, it can serve as both reactant and

substrate, ensuring close contact between Bi

nano-

structures and TiO

submicron fibers for uniform growth

of a hierarchical configuration. The hydrothermal process

was performed in an alkaline environment where an aque-

ous solution of Bi(NO

)

and submicron TiO

fibers were

used as reactants [25–27]. The characterization results in-

dicated that Bi

nanosheets with high crystallinity

grew successfully on TiO

submicron fibers and well-

defined three-dimensional hierarchical heterostructures of

/TiO

submicron fibers were formed. In contrast

to pure TiO

and Bi

, the composites showed sig-

nificantly improved light absorption at a wavelength above

420 nm, as well as higher photocurrent density under a

visible-light pulse. Photocatalytic tests revealed that the

/TiO

heterostructures have higher visible-light

activity for degrading RhB than the pure Bi

, and

unmodified TiO

Methods

TiO

submicron fibers were fabricated using the well-

known process reported previously in Refs. [20, 23]. In

the following hydrothermal procedure, 5 mg of the elec-

trospun TiO

submicron fibers were placed into an

autoclave containing two different Bi(NO

)

solutions.

The concentration of the Bi(NO

)

solutions was 0.0103

and 0.0412 mmol L

−1

, respectively. The pH value of the

solution was adjusted to 13 using a 1 M KOH solution.

The reaction was carried out at 180 °C for 24 h. The fab-

ricated products were collected, washed with deionized

water, and then dried in an oven at 60 °C for 6 h. Using

this method, two different Bi

/TiO

composites

were produced, which were denoted as BT1 and BT2,

respectively.

The structure and morphology of the prepared sam-

ples was investigated using powder X-ray diffraction

(XRD; Bruker D8 Advance, using Cu Kα radiation), scan-

ning electron microscopy (SEM; Hitachi S-4800), and

transmission electron microscopy (TEM; JEOL 2100).

The optical properties of the samples were analyzed via

UV-visible diffuse reflectance spectroscopy, recorded on

a UV/Vis spectrophotometer (Shimadzu UV-2550) at

room temperature. Photoelectrochemical measurements

of the prepared samples were recorded with a

laboratory-built electrochemical analyzer (CHI660E,

China) consisting of a standard three-electrode system

[20]. The Bi

/TiO

heterojunction composite films

served as working electrodes after coating the produced

samples on Au/SiO

/Si substrates (10 × 10 mm). A 300-

W Xe lamp, equipped with a 420 nm cutoff filter was

used for excitation source.

To measure photocatalytic activity, a 100 ml of rhoda-

mine B (RhB; 1.0 × 10

−5

mol L

−1

) solution with an initial

concentration of 10 mg L

−1

in the presence of solid cata-

lyst was filled into a laboratory-built photoreactor. The

photoreactor was equipped with an internal light source

(150-W Xe lamp and a cutoff filter transmitting

>420 nm) surrounded by a water-cooled quartz barrier

to cool the lamp. The solution with the photocatalysts

was stirred in the dark for 30 min to obtain a good dis-

persion and establish an adsorption-desorption equilib-

rium between the organic molecules and the catalyst

surface. Changes in concentration of the dye solution

were measured with a spectrophotometer at lambda of

553 nm at specified reaction intervals.

Results and Discussion

The crystal structures of Bi

/TiO

composites were

identified via XRD analysis, as shown in Fig. 1. The

strong, sharp peaks indicated that the as-obtained prod-

ucts are highly crystallized. For the sample BT1, diffrac-

tion peaks at about 2θ = 25.1°, 37.4°, 48.2°, 54.1°, and

55.0° could be indexed perfectly to the (101), (004) ,

Zhou et al. Nanoscale Research Letters (2016) 11:193 Page 2 of 8

剩余7页未读，继续阅读

评论收藏

内容反馈

weixin_38663036

粉丝: 4
资源: 928

原位制备Bi2Ti2O7 / TiO2异质结构亚微米纤维以增强光催化活性

最新资源

原位制备Bi2Ti2O7 / TiO2异质结构亚微米纤维以增强光催化活性

NiO/TiO2复合结构的制备及其电化学性能研究

Ru/TiO2/AC催化剂在臭氧光催化过程中的作用

Cu2O/TiO2纳米阵列异质结的制备及其光电化学性能研究

活性炭处理出水的UV/TiO2光催化消毒试验研究

具有三维异质结构的CdSe/TiO2纳米管阵列薄膜制备及性能测试

V2O5-WO3/TiO2催化氧化NO性能研究

蜂窝状Mn-Ce/TiO2催化剂的脱硝催化性能

CuO/TiO2可见光催化亚甲基蓝脱色影响因素研究

碳纳米管修饰V2O5-WO3/TiO2催化剂降解二噁英的研究

介孔Co/TiO2可见光选择性催化性能研究

多孔SO42-/TiO2型固体酸的表征及其催化性能

CuO/TiO2-H2O2自然光催化降解印染废水的影响因素

介孔结构Na4W10O32/TiO2复合光催化剂的制备及其可见光光催化性能的研究 (2006年)

纳米复合材料CdS/TiO2NTs的可见光催化分解水制氢

Fe3+、Ce4+掺杂改性对SO42-/TiO2固体超强酸催化尿囊素催化性能的研究

Pt/TiO2甲醛热催化剂影响因素实验研究

最新资源