PHOTOCATALYSIS:FUNDAMENTALS AND APPLICATIONS IN JEP 2011,BORDEAUX
Design of graphene-bad TiO 2photocatalysts —a review
朗文英语语法Sergio Morales-Torres &Luisa M.Pastrana-Martínez &JoséL.Figueiredo &Joaquim L.Faria &Adrián M.T.Silva
Received:21October 2011/Accepted:17April 2012/Published online:11July 2012#Springer-Verlag 2012
Environ Sci Pollut Res (2012)19:3676–3687DOI 10.1007/s11356-012-0939-4中国民法
Abstract There is a recent increa in the interest of de-signing high-performance photocatalysts using graphene-bad materials.This review gathers some important aspects of graphene –TiO 2,graphene oxide –TiO 2,and reduced gra-phene oxide –TiO 2composites,which are of especial rele-vance as next generation photocatalysts.The methods ud for the preparation of the materials,the associated mech-anistic fundamentals,and the application of graphene-bad composites on the photocatalytic degradation of pollutants are reviewed.Some structural,textural,and chemical prop-erties of the materials and other photo-assisted applica-tions,such as hydrogen pro
duction from water splitting and dye-nsitized solar cells,are also briefly included.Keywords Environment .Photocatalyst .Graphene .TiO 2.Composite .Synthesis .Mechanistic fundamentals .Application
Introduction
There has been a long lasting and recently increasing scien-tific interest on photocatalysis due to the need of effective photocatalysts and photocatalytic reactor designs for solar applications,the treatment/disinfection of water and air be-ing one of the main rearch areas (Zhang et al.2011b ;Du et
al.2011b ;Pastrana-Martínez et al.2012a )together with hydrogen production from water splitting (Silva et al.2011;Kudo and Miki 2009;Yu et al.2011b ;Li et al.2011d ;Qi et al.2011).Other related applications of the materials are also receiving incread attention,such as solar cells (Roy et al.2010;Zhu et al.2011;Yu et al.2011a ),lithium ion batteries (Yang et al.2011;Li et al.2011c ;Chen et al.2011),nsors (Fan et al.2011b ;2011c ;2011d ;Wang et al.2011a ),photocatalytic reduction of CO 2(Liang et al.2011)and development of substrates with lf-cleaning properties (Zhao et al.2008)and antibacterial or anticancer activity (Akhavan and Ghaderi 2009;Hu et al.2012).
TiO 2has been broadly ud as a standard photocatalyst due to its high stability,low cost,relatively low toxicity,and excellent photocatalytic performance in comparison to other miconductor materials (Leary and Westwood 2011).How-ever,TiO 2usage prents some drawbacks,namely a limited photoactivity in the visible range of Earth ’s solar spectrum.In this context,typical photocatalysts have been modified in order to enhance their solar photocatalytic activity,by dop-ing,metal particle deposition or even by their combination with other materials to produce highly photoactive compo-sites (Wang et al.2011b ;Liu et al.2010a ).
Among different materials that can be lected to prepare composites with TiO 2,carbon materials offer unique advan-tages,such as chemical inertness and stability,in both acid and basic media,and tunable textural and chemical proper-ties.Recently,nanostructured carbon materials (carbon nanotubes,fullerenes,graphene nanosheets)have claimed increasing attention in this context due to their unusual structural and electronic properties (Sampaio et al.2011;Yu et al.2011c ;Wang and Zhang 2012).In particular,graphene has emerged as one of the most promising materi-als in the next generation of photocatalysts,due to its excel-lent mobility of charge carriers,large specific surface area,
Responsible editor:Philippe Garrigues
S.Morales-Torres :L.M.Pastrana-Martínez :J.L.Figueiredo :J.L.Faria (*):A.M.T.Silva
LCM –Laboratory of Catalysis and Materials Associate
Laboratory LSRE/LCM Departamento de Engenharia Química,Faculdade de Engenharia da Universidade do Porto,Rua Dr.Roberto Frias,4200-465Porto,Portugal e-mail:jlfaria@fe.up.pt
flexible structure,high transparency,and good electrical and thermal conduction.Even so,graphene sheets have a certain tendency to form aggregates in solution by strong van der Waals interactions or hydrogen bonds(in the ca of polar solvents).Electrostatic stabilization(Li et al.2008)and chemical functionalization(Niyogi et al.2006)are some of the methods employed to avoid such aggregation.
The possibility to obtain graphene(G)or reduced graphene oxide(RGO)by reduction of graphene oxide(GO)using simple chemical methods facilitates its application in the syn-thesis of composite materials at affordable production costs and scalable approaches.By the way,GO can be prepared by strong chemical oxidation of graphite,for instance by using the method developed by Hummers and Offeman(1958),fol-lowed by the sonicated-assisted exfoliation of the obtained graphite oxide.For this reason,large-scale synthesis of the graphene precursor(GO)is reliable and,as conquence,the
中国故事entire cycle of graphene production is estimated to result in low-cost technologies in comparison to tho ud for the preparation of carbon nanotubes(CNT).
General reviews have been published in the field of photocatalysis(Liu et al.2011c;Chong et al.2010; Bhatkhande et al.2002;Han et al.2009;Thiruvenkatachari et al.2008)and a specific one dedicated to CNT–TiO2 composites(Woan et al.2009).Taking into account the growing interest to design graphene-bad photocatalysts (Xiang et al.2012;An and Yu2011),it ems now appro-priate to prent an overview on some important aspects of graphene-bad composites,in particular when applied to photocatalysis.The methods of synthesis and the mecha-nisms propod so far involving the composites are reviewed.Some structural,textural,and chemical insights are also prented.Finally,publications on the photocata-lytic degradation of pollutants are collected,as well as some additional applications where the materials are having a strong impact.
榜眼
Mechanistic fundamentals of graphene-bad photocatalysts
Different terminologies can be found in the literature(G–TiO2,GO–TiO2,and RGO–TiO2)for graphene-bad com-posites prepared with TiO2.The term RGO is explicitly ud with reference to reduced graphene oxide,meaning that the surface of GO,containing various types of oxygenated surf
ace poxy,hydroxyl,ether,and carboxylic acids)situated in the basal planes and edges(Stankovich et al.2006),was reduced by a thermal or chemical treatment. Some authors refer G–TiO2,even when this material is obtained from GO(formed during an intermediate step from graphite oxide exfoliation)and,therefore,it is more appro-priate to define the resulting composite as RGO–TiO2,since it is very unlikely that complete reduction of GO to pure graphene might occur(oxygenated surface groups usually remain on the graphene sheets after reduction of GO).In this review,we will u the term G–TiO2only for composites prepared with pure graphene,and RGO–TiO2for tho where a reduction of GO is involved.
The first work found in the literature about the prepara-tion of RGO–TiO2composites by UV-assisted photocata-lytic reduction was prented by Williams et al.(2008). They obrved how GO was reduced due to the acceptance of generated electrons from UV-irradiated TiO2suspensions, and propod a graphene–miconductor mechanism (Fig.1)that was also valid for ZnO(Williams and Kamat 2009).Briefly,in the prence of ethanol,the photogener-ated holes in TiO2are scavenged to yield ethoxy radicals, leaving the electrons to accumulate within TiO2particles (Eq.1).When GO is prent,the accumulated electrons interact with the GO sheets,leading to the reduction of certain surface groups–RGO(Eq.2).
TiO2þh n!TiO2hþþeÀ
ðÞ!
婚姻古今异义
C2H5OH
TiO2eÀ
ðÞþHþ
þC2H4OH
ð1ÞTiO2eÀ
ðÞþGO!TiO2þRGOð2ÞThus,a fraction of electrons is ud in the reduction of GO (to obtain RGO)and the remaining electrons(estimated in ca. 16%)are delocalized throughout the basal planes of GO sheets (Kamat2010;Lightcap et al.2010).The reduction of GO can be detected simply by the change of the suspension color,from light brown(GO)to dark black(RGO),as shown in Fig.1.The color change is related with the partial restoration of the sp2 hybrid network within the carbon structure(Becerril et al. 2008),which has a beneficial effect becau the conductivity loss for GO is recovered upon reduction of the GO sheets.
Different mechanistic pathways have been propod for the photodegradation of pollutants in the prence of the composites.Liu et al.(2010b)suggested that the electrons can be transported along the GO sheets and then react with adsorbed O2to form HO●radicals(Fig.1),which in turn oxidize the pollutant molecules.This interpretation was bad on the similar structure of both GO and CNT materi-als,and considering the work reported by Yu et al.(2005)on CNT and their reactivity with adsorbed O2to form HO●radicals.Therefore,it is suggested that this effective charge transfer could reduce the charge recombination and increa the photocatalytic activity of TiO2in GO–TiO2composites. In a subquent publication,Liu et al.(2011b)studied the pathway for the photocatalytic degradation of methylene blue(MB)in aqueous solutions using RGO wrapped TiO2 hybrid photocatalysts.They indicated also that RGO acts by
Environ Sci Pollut Res(2012)19:3676–36873677
capturing photoinduced electrons and MB molecules through an irreversible adsorption process.The MB mol-ecules can be oxidized by the superoxide anion radicals (O 2●−)that are produced by the reaction involving dissolved O 2and electrons contained in the RGO surface (Eq.3).The holes created in the conduction band of TiO 2could also originate the highly reactive HO ●radicals (Eq.4;Fig.1).
e ÀCB þO 2!O À
2
ð3Þh þVB þH 2O !HO þH
þð4Þ
Other models have been postulated to explain the role of graphene,GO,or RGO in graphene-bad TiO 2composites.Chen et al.(2010)obrved clearly a p/n heterojunction for RGO –TiO 2composites with p-type miconductor behav-ior,GO acting as a nsitizer and enhancing the visible light photocatalytic performance.The role of GO as nsitizer was also demonstrated by studying the interface between graphene and rutile TiO 2using density functional calcula-tions (Du et al.2011a ).A significant charge was transferred from graphene to TiO 2,generating a hole doping in the graphene layer.Thus,under this postulate,electrons can be directly excited from graphene to the conduction band of TiO 2under visible light irradiation.
To design a catalyst combining the properties of a mi-conductor material (typically TiO 2)and a noble metal (e.g.,Au,Pt,or Ag)on the same kind of support is a topic of current rearch interest,grap
hene-bad materials being ud not only in the field of photocatalysis but also as catalyst supports in other applications.The scheme prented in Fig.2a has been propod as an example of a “photocatalyst mat ”with tailored reactive sites for the hydrogen production from water splitting (Kamat 2010;2011),although it has also a general applicability for other photocatalytic process (Lightcap et al.2010).The TiO 2(or other miconductor)nanoparticle absorbs light and induces the oxidation reaction.Then,RGO
captures the electrons and shuttles them across the π–πnet-work to the noble metal site,facilitating hydrogen production.
The lective anchoring of noble metal particles and TiO 2at parate sites on the surface of RGO,as well the ability of RGO to capture and shuttle electrons,have been also reported by other authors (Lightcap et al.2010).Therefore,a graphene-bad support acts by capturing photoinduced electrons —due to its excellent electronic properties,the electrons could be shuttled to produce active oxygenated radicals —or simply by storing them —this being of particular interest for energy applications.
Methods of synthesis to prepare graphene-bad TiO 2composites
According to the literature,composites of TiO 2,or other inorganic oxides,with graphene-bad nanosheets can be prepared by different methods:simple mixing and/or sonica-tion (Guo et al.2011;Bell et al.2011),sol –gel process (Mishra and Ramaprabhu 2011),liquid-pha deposition (Jiang et al.2011b ),hydrothermal and solvothermal methods (Fan et al.2011e ;Wang and Zhang 2011;Ding et al.2011).More infor-mation about the methods is prented in the following ctions.In addition,a ction emphasizing the deposition of metals (e.g.Pt,Ag,and Fe)on the composite is also included.In order to offer a uful tool for the reader,Table 1collects a summary of experimental details regarding the preparation of the composites together with some data on their structural,textural,and chemical properties.Mixing and sonication
The simplest route for the preparation of GO –TiO 2compo-sites involves mixing and sonication steps,becau GO has to be exfoliated when added to an aqueous or organic solution.The method is very common due to its
simplicity,
Fig.1TiO 2nanoparticles
attached onto a graphene-bad sheet and generation of HO ●radicals from adsorbed oxygen and H 2O.Illustration of the color change between GO and RGO by UV-assisted reduction
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but in most cas the interaction between the two phas is weak,since chemical bonding is not expected.In fact,the first reported GO –TiO 2composite was prepared by this method,although a UV-assisted photocatalytic reduction step was also included to obtain RGO-TiO 2(Williams et al.2008).In the work of Zhang and Pan (2011),a heat treatment under inert atmosphere was also applied after mixing and sonication,which doped carbon atoms into the TiO 2structure and,conquently,improved the visible light photocatalytic activity.In their work,Degussa P25(now from Evonik)was ud to prepare the RGO –TiO 2compo-sites,hereafter referred as RGO –P25.Other visible light-active composite photocatalysts were prepared by mixing/sonication but using ZnO (Williams and Kamat 2009)or SnO 2(Paek et al.2008)nanoparticles,or even WO 3,or BiVO 4(Ng et al.2011),which have a lower conduction band energy than TiO 2.Sol –gel process
The most widely applied method to obtain an intimate mixing and chemical interaction between GO and TiO 2is the sol –gel technique.The surface of GO nanosheets is generally avail-able to blend with titanium alkoxide precursors,due to the water solubility and hydrogen bonding ability of GO and
becau the hydroxyl surface groups of GO can establish oxo-or hydroxo-bridges with metal centers.The formation of TiO 2in sol –gel process involves oxo-or hydroxo-bridges during the hydrolysis of the alkoxides,and finally dispersion by hydroxo-connected GO sheets to form a sol,which evolves into a gel-like biphasic structure with increasing amount of added GO (Manga et al.2010).Some of the titanium alkoxide species ud in the preparation of GO –TiO 2composites were TiCl 4(Akhavan and Ghaderi 2009),TiCl 3(Wang et al.2009),TiF 4(Lambert et al.2009),(NH 4)2TiF 6(Zhang et al.2011a ),
Ti(SO 4)2(Zhang et al.2011c ),Ti(OPri)4(Peng et al.2008),Ti (OBu)4(Wojtoniszak et al.2012)and titanium peroxo com-plexes (Štengl et al.2011;Zou et al.2011).
However,GO containing aqueous solutions are inadequate for some of the titanium species that are only dissolved in ethanol,the addition of the aqueous GO solution thereby inducing faster hydrolysis and resulting in the rapid precipi-tation of TiO 2.Even so,some precursors such as Ti(OBu)4could decrea the rate of hydrolysis,increasing the interac-tion between GO and the TiO 2materials (Li et al.2011b ).Some modifications to the sol –gel method have been introduced,including the u of surfactants with the aim to improve the asmbly of hydrophobic graphene with hydro-philic TiO 2and to control the nucleation and growth of the resulting nanostructu
re.Wang et al.(2009)prepared G –TiO 2composites using an anionic sulfate surfactant (sodium dodecyl sulfate)as template.Chen et al.(2010)ud the same methodology to prepare RGO –TiO 2composites that yields different kinds of miconductors depending on the GO content of the starting solution.Manga et al.(2010)propod the u of an ionic salt,titanium (IV)bis(ammo-nium lactate)dihydroxide,which has good water solubility and mixes well with GO solutions.
GO –TiO 2composites with more complex structures were also obtained by the sol –gel method when TiO 2nanotubes (Peng et al.2008)were ud.Films have been also produced (Manga et al.2009).Some authors (Jiang et al.2011b ;Zhang et al.2011a )have ud process bad on the sol –gel method but referred as liquid pha deposition,for preparation of TiO 2nanoparticles asmbled on GO.Hydrothermal and solvothermal methods
Both hydrothermal and solvothermal methods involve reac-tions under controlled temperature and/or pressure,and
are
Fig.2Electron shuttling on a graphene-bad sheet with dif-ferent active metals supported (Pt,Ag)or doped (Fe)in dif-ferent catalytic sites:a Pt (Pt/GO –TiO 2)for hydrogen evolu-tion from water splitting,b Ag for transfer charge in Ag/G –TiO 2films and c Fe (Fe doped G –TiO 2)for enhancement of the visible photocatalytic reactivity
Environ Sci Pollut Res (2012)19:3676–36873679
T a b l e 1E x p e r i m e n t a l p r o c e d u r e s a n d a p p l i c a t i o n s o f g r a p h e n e -b a s e d T i O 2c o m p o s i t e s i n t h e l i t e r a t u r e
M e t h o d o f s y n t h e s i s
P r e c u r s o r s
P r e p a r a t i o n d e t a i l s R e l e v a n t c h a r a c t e r i s t i c s (m o r p h o l o g y ,S B E T a ,c r y s t a l l i n e p h a s e )
A p p l i c a t i o n t e s t e d R e f e r e n c e s M i x i n g
T i (O P r i )4
G O s o l i d
G O w a s a d d e d t o a T i O 2s u s p e n s i o n i n e t h a n o l a n d t h e n s o n i c a t e d f o r 30m i n .R G O –T i O 2w a s o b t a i n e d b y U V -a s s i s t e d p h o t o c a t a l y t i c r e d u c t i o n ,u n d e r c o n t i n u o u s s t i r r i n g a n d N 2f l o w H e i g h t o f ~2n m f o r R G O s h e e t a n d a p a r t i c l e d i a m e t e r f o r T i O 2
o f 2–7n m –W i l l i a m s e t a l .(2008)
M i x i n g
T i (O P r i )4
G O d i s p e r s i o n T i O 2n a n o r o d s w e r e s y n t h e t i z e d u s i n g o l e i c a c i d a s s u r f a c t a n t b y a h y d r o t h e r m a l m e t h o d (180°C ,6h ).T h e n ,t h e y w e r e d i s p e r s e d i n t o l u e n e a n d m i x e d w i t h a G O a q u e o u s d i s p e r s i o n f o r 24h .F i n a l l y ,t h e c o m p o s i t e w a s p u r i f i e d a n d w a s h e d w i t h a c e t o n e ,T H F a n d f r e e z e –d r i e d a t −50°C f o r 48h A n a t a s e T i O 2n a n o r o d s o f 2–4n m d i a m e t e r a n d 20–30n m l e n g t h P h o t o d e g r a d a t i o n o f M B (2g T i O 2L −1,10p p m M B )
u n d e r U V l i g h t i r r a d i a t i o n (254n m ,11W )
L i u e t a l .(2010b )
M i x i n g
P 25G O d i s p e r s i o n
P 25w a s a d d e d t o t h e G O d i s p e r s i o n .T h e m i x t u r e w a s s o n i c a t e d f o r 1h a n d t r e a t e d i n A r f l o w a t 300°C f o r 2h
T i O 2p a r t i c l e s w i t h a n a t a s e a n d r u t i l e p h a s e s .S B E T 079m 2g −1
P h o t o d e g r a d a t i o n o f M B (1g c a t L −1,12p p m M B )u n d e r V i s l i g h t i r r a d i a t i o n (250W ,h i g h p r e s s u r e H g l a m p a n d c u t o f f f i l t e r ,λ>400n m )Z h a n g a n d P a n (2011)
S o l –g e l
T i C l 4
人防工程施工方案
G O d i s p e r s i o n
T i O 2f i l m s w e r e p r e p a r e d a n d t r e a t e d a t 450°C f o r 1h .A G O d i s p e r s i o n w a s s p r e a d o n t h e T i O 2f i l m a n d t h e n d r i e d a t 60°C f o r 24h a n d p o s t -a n n e a l e d i n a i r a t 400°C f o r 30m i n a n d U V -a s s i s t e d p h o t o c a t a l y t i c r e d u c t i o n T i O 2f i l m s w i t h a n a t a s e p h a s e
P h o t o d e g r a d a t i o n o f E .c o l i b a c t e r i a (~108C F U m L −1)i n a s a l i n e s o l u t i o n u n d e r s o l a r l i g h t i r r a d i a t i o n
A k h a v a n a n d G h a d e r i (2009)
S o l –g e l
(N H 4)2T i F 6
G O d i s p e r s i o n
(N H 4)2T i F 6a n d H 3B O 3w e r e a d d e d t o a G O d i s p e r s i o n a n d t h e m i x t u r e w a s h e a t e d a t 60°C f o r 2h .T h e s o l i d w a s t h e r m a l l y t r e a t e d i n a i r f l o w a t 200°C f o r 1h T i O 2p a r t i c l e s w i t h a n a t a s e p h a s e .S B E T 080m 2g −1
P h o t o d e g r a d a t i o n o f M O (0.5g c a t L −1,10p p m M O )u n d e r U V l i g h t i r r a d i a t i o n (20W ,U V l a m p )J i a n g e t a l .(2011b )
S o l –g e l
T i C l 3
G r a p h e n e s h e e t s
A n a n i o n i c s u r f a c t a n t (S D S )w a s a d d e d d u r i n g s o l –g e l m e t h o d .C o m p o s i t e s w e r e t r e a t e d i n a i r f l o w a t 400°C f o r 2h .T h e f o r m a t i o n o f a n a t a s e T i O 2p a r t i c l e s i s f a v o r e d b y a d d i n g s o d i u m s u l f a t e t o g e t h e r w i t h S D S A n a t a s e a n d r u t i l e G O -T i O 2
c o m p o s i t e s
L i -i o n b a t t e r i e s
W a n g e t a l .(2009)
S o l –g e l
T i C l 3
G O d i s p e r s i o n
M e t h o d o l o g y s i m i l a r t o (W a n g e t a l .2009)b u t G O i s u s e d i n s t e a d o f g r a p h
e n e .T h e c o m p o s i t e s w e r e p u r i f i e d b y c e n t r i f u g a t i o n –w a s h i n g –r e d i s p e r s i o n c y c l e s A n a t a s e T i O 2p a r t i c l e s w i t h a c r y s t a l s i z e o f 6–8n m .B a n d g a p <2.43e V
P h o t o d e g r a d a t i o n o f M O (1g c a t L −1,12p p m M O )u n d e r V i s l i g h t i r r a d i a t i o n (1000W X e n o n l a m p )a n d c u t o f f f i l t e r ,λ>400n m C h e n e t a l .(2010)
S o l –g e l
T i F 4
G O d i s p e r s i o n
T i F 4w a s a d d e d t o G O a q u e o u s d i s p e r s i o n a n d t h e m i x t u r e w a s h e a t e d a t 60°C f o r 24h t o p r e p a r e G O –T i O 2
c o m p o s i t e s .R G O –T i O 2c o m p o s i t e s w e r e a l s o p r e p a r e
d b y h
e a t i n g G O –T i O 2
(1,000°C )a n d c h e m i c a l r e d u c t i o n u s i n g h y d r a z i n e h y d r a t e a t 100°C A n a t a s e T i O 2n a n o c r y s t a l s a n d S B E T 0121m 2g −1.R G O –T i O 2
c h e m i c a l l y r e
d u c
e d p r e s e n t e d h i g h e r S B E T a n d a n a n a t a s e –r u t i l e p h a s e
f o r T i O 2p a r t i c l e s
–
L a m b e r t e t a l .(2009)
S o l –g e l
T i (S O 4)2
G O d i s p e r s i o n
G O d i s p e r s i o n w a s a d d e d t o a n a q u e o u s s o l u t i o n f o r m e d b y a d d i n g T i (S O 4)2
P h o t o d e g r a d a t i o n o f M O (1g c a t L −1,20p p m M O )
Z h a n g e t a l .(2011c )
3680
Environ Sci Pollut Res (2012)19:3676–3687
T a b l e 1(c o n t i n u e d )
M e t h o d o f s y n t h e s i s
P r e c u r s o r s
P r e p a r a t i o n d e t a i l s R e l e v a n t c h a r a c t e r i s t i c s (m o r p h o l o g y ,S B E T a ,c r y s t a l l i n e p h a s e )
A p p l i c a t i o n t e s t e d R e f e r e n c e s a n d H 2S O 4.T h e m i x t u r e w a s h e a t e d a t 8
0°C f o r 2h
T i O 2c r y s t a l l i t e s o f m i x e d a n t a s e a n d r u t i l e p h a s e s .A v e r a g e c r y s t a l s i z e o f T i O 2w a s a b o u t 9n m u n d e r U V l i g h t i r r a d i a t i o n (250W ,h i g h p r e s s u r e l a m p )
S o l –g e l
T i (B u O )4
G r a p h e n e d i s p e r s i o n
T i (B u O )4w a s a d d e d t o a G O e t h a n o l i c d i s p e r s i o n .A f t e r c u r i n g f o r 2d a y s a c e t i c a c i d w a s a d d e d a n d t h e c u r e w a s p r o l o n g e d f o r o t h e r 2d a y s a n d t h e n t h e m i x t u r e w a s d r i e d a t 80°C f o r 10h .C o m p o s i t e s w e r e t r e a t e d i n a i r f l o w a t 450°C f o r 2h A n a t a s e T i O 2n a n o p a r t i c l e s w i t h a s i z e c a .10–15n m .S B E T 037m 2g −1
H y d r o g e n e v o l u t i o n f r o m w a t e r s p l i t t i n g u n d e r U V –v i s l i g h t i r r a d i a t i o n (500W X e l a m p ),N a 2S a n d N a 2S O 3s o l u t i o n s w e r e u s e d t o g e t h e r w i t h 0.5g
c a t L −1.Z h a n g e t a l .(2010b )
H y d r o t h e r m a l
P 25G O d i s p e r s i o n
G O d i s p e r s i o n (1w t %)i n w a t e r –e t h a n o l (2:1)w a s s o n i c a t e d f o r 1h .P 25w a s a d d e d t o t h e G O d i s p e r s i o n a n d t h e n a d d e d i n a n a u t o c l a v e a t 120°C f o r 3h小朋友故事
A n a t a s e –r u t i l e p h a s e s (80−20%)f o r T i O 2p a r t i c l e s .S
B E T 050m 2g −1创意抽奖
P h o t o d e g r a d a t i o n o f M B (0.75g c a t L −1,10p m m M B )u n d e r U V (100W h i g h p r e s s u r e H g l a m p )o r V i s l i g h t i r r a d i a t i o n (500W X e l a m p a n d c u t o f f f i l t e r ,λ>400n m )Z h a n g e t a l .(2010a )
H y d r o t h e r m a l T i (B u O )4
G O d i s p e r s i o n
T i (B u O )4,G O a n d H 2S O 4w e r e a d d e d t o a E t O H –H 2O s o l u t i o n (15:1v /v ),h e a t e d a t 80°C a n d d r i e d .T h e c o m p o s i t e w a s a d d e d t o a H 2O –D M F s o l u t i o n a n d a d d e d i n a n a u t o c l a v e a t 200°C A n a t a s e T i O 2n a n o c r y s t a l s .S B E T 0190m 2g −1
P h o t o d e g r a d a t i o n o f R B (0.06g T i O 2
L −1
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L −1,9.6p p m )u n d e r U V l i g h t i r r a d i a t i o n (100W h i g h p r e s s u r e H g l a m p ).
L i a n g e t a l .(2010)
H y d r o t h e r m a l T i (B u O )4
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T i (B u O )4a n d N H 4C l w e r e a d d e d t o a n e t h a n o l –H 2O s o l u t i o n .G l u c o s e a n
d N H 4O H w e r e a d d e d t o a G O a q u e o u s d i s p e r s i o n .B o t h s o l u t i o n s w e r e m i x e d i n t o a n a u t o c l a v e a n d h e a t e d a t 160°C f o r 4h A n a t a s e T i O 2n a n o p a r t i c l e s w i t h 9n m s i z e .G O w a s p a r t i a l l y r e d u c e d ,y i e l d i n g R G O
–
S h e n e t a l .(2011)
H y d r o t h e r m a l
P 25G O s o l i d
T i O 2n a n o t u b e s w e r e p r e p a r e d b y a d d i n g P 25t o a N a O H (10M )a q u e o u s s o l u t i o n ,t r e a t e d i n a n a u t o c l a v e a t 150°C f o r 12h a n d w a s h e d w i t h 0.1M H C l a q u e o u s s o l u t i o n .T i O 2s p i n d l e s w e r e p r o d u c e d b y a d d i n g T i O 2n a n o t u b e s t o a w a t e r –E t O H –e t h y l e n e g l y c o l s o l u t i o n ,a d d i t i o n o f d i m e t h y l a m i n e a n d h e a t i n g i n a n a u t o c l a v e a t 180°C f o r 12h .T h e G O –T i O 2s p i n d l e s w e r e o b t a i n e d b y a d d i n g G O d u r i n g t h e p r e p a r a t i o n s t e p o f T i O 2s p i n d l e s A n a t a s e T i O 2s p i n d l e s w i t h a d i a m e t e r s a s l o w a s 5n m a n d l e n g t h s o f c a .15n m
L i -i o n b a t t e r i e s Q i u e t a l .(2010)
H y d r o t h e r m a l
T i C l 4
G O d i s p e r s i o n
T i C l 4a n d G O a q u e o u s s o l u t i o n w e r e a d d e d i n t o a n a u t o c l a v e a n d h e a t e d a t 180°C f o r 6h .T h e c o m p o s i t e s w e r e w a s h e d w i t h w a t e r a t 50°C f o r 2d a y s
A n a t a s e o r r u t i l e c r y s t a l l i t e s w e r e o b t a i n e d f o r c o m p o s i t e s w i t h 0.8–2.0w t %o r 5.0–10.0w t %G O c o n t e n t ,r e s p e c t i v e l y
H y d r o g e n e v o l u t i o n f r o m w a t e r s p l i t t i n g u n d e r U V –v i s l i g h t i l l u m i n a t i o n (500W X e l a m p ).N a 2S a n d N a 2S O 3
s o l u t i o n s w e r e u s e d t o g e t h e r w i t h 0.25g c a t L −1
Z h a n g e t a l .(2012)
S o l v o t h e m a l
T i (B u O )4
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G O w a s s o n i c a t e d i n a n i s o p r o p a n o l s o l u t i o n .T i (B u O )4w a s a d d e d t o t h e G O d i s p e r s i o n a n d t h e n w a t e r d r o p w i s e .T h e m i x t u r e w a s k e p t i n a n a u t o c l a v e a n d h e a t e d a t 180°C f o r 8h
A n a t a s e T i O 2p a r t i c l e s w i t h a n a r r o w s i z e d i s t r i b u t i o n P h o t o d e g r a d a t i o n o f M
B (1g c a t L ,−110−5M M B )u n d e r s u n l i g h t i r r a d i a t i o n (150W h i g h p r e s s u r e X e l a m p )
Z h o u e t a l .(2011)
a
T h e r e f e r r e d S B E T v a l u e i s t h e h i g h e s t a m o n g t h e g r a p h e n e -b a s e d T i O 2c o m p o s i t e p r e s e n t e d i n t h e r e s p e c t i v e w o r k
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