gC3N4 Based Photocatalysts for Hydrogen Generation

gC3N4 Based Photocatalysts for Hydrogen Generation
gC3N4 Based Photocatalysts for Hydrogen Generation

g ?C 3N 4?Based Photocatalysts for Hydrogen Generation

Shaowen Cao ?and Jiaguo Yu *,?,?

?State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology,122Luoshi Road,Wuhan 430070,People ’s Republic of China

?Faculty of Science,King Abdulaziz University,Jeddah 21589,Saudi Arabia

he development of clean and renewable energy is the key way to satisfy the increasing global energy demands and to resolve the environmental issues caused by the overuse of fossil fuels.One of the most attractive options is the conversion of solar energy into hydrogen through a water splitting process,with the help of semiconductor-based photocatalysts.1?4The design of semiconductor-based photocatalytic systems must take the following requirements into account:5,6(1)The semiconductor should have a narrow band gap to absorb as much light as possible;meanwhile,the bottom of its conduction band has to be more negative than the reduction potential of water to produce H 2.If for overall water splitting,the top of its valence band must be more positive than the oxidation potential of water to produce O 2.(2)E ?cient charge separation and fast charge transport simultaneously avoiding the bulk and surface charge recombi-nation are essentially required to migrate the photogenerated charge carries to the surface reaction sites.(3)Kinetically feasible surface chemical reactions must take place between these carries and water or other molecules;meanwhile,the surface backward reaction of H 2and O 2to water can be successfully suppressed.Therefore,scientists are trying to develop photocatalysts with speci ?c bulk and surface properties as well as energy band structures to satisfy these requirements.Metal oxides such as TiO 2,SrTiO 3,and so forth have been widely investigated for photocatalytic hydrogen generation,but they are not ideal due to the poor solar energy utilization.7,8They are only active in the UV region because of their wide band gaps.Some other oxides including WO 3,BiVO 4,and so forth are visible-light-responsive but cannot conduct water reduction to produce H 2because their conduction bands are lower than the reduction potential of water.9CdS has also been considered,and it indeed possesses a narrow band gap with appropriate band levels for water splitting,whereas it is toxic and usually unstable due to the photocorrosion or self-oxidation.10In recent years,special attention has been paid to graphitic carbon nitride (g-C 3N 4),since the pioneering study in 2009by Wang et al.11on the visible-light photocatalytic water splitting over g-C 3N 4.g-C 3N 4is considered to be the most stable allotrope among various carbon nitrides under ambient conditions.The proposed structure of g-C 3N 4is two-dimensional frameworks of tri-s -triazine connected via tertiary amines (see Figure 1),which makes it possess high stable thermal (up to 600°C in air)and chemical stability (against acid,base,and organic solvents).12It is identi ?ed to be a visible-light-active

polymeric semiconductor with a band gap of ~2.7eV,corresponding to an optical wavelength of ~460nm,as

well as an appropriate band structure for both water reduction and oxidation.12,13As such,g-C 3N 4promptly becomes the

shining star in the ?eld of photocatalysis.g-C 3N 4is generally synthesized by the thermal condensation of nitrogen-rich precursors such as cyanamide,dicyandiamide,

melamine,and so forth.14However,the photocatalytic activity of

the as-obtained g-C

3N 4is usually restricted by low e ?ciency due to the fast recombination of photoinduced electron ?hole pairs.Protocols such as texture modi ?cation,elemental doping,and

copolymerization are subsequently applied to improve the

Received:March 18,2014

Accepted:May 29,2014

Published:May 29,2014

Dramatically increasing attention is paid to g-C 3N 4-based photo-

catalysts due to their unique physicochemical property and electronic band structure.

photocatalytic performance of g-C 3N 4.15?18Besides the fast development of these ameliorating strategies on intrinsic g-C 3N 4,the investigation of g-C 3N 4-based composite photocatalysts was highly stimulated in the past several years.In this Perspective,we give a short overview of the recent signi ?cant progress on designing e ?cient g-C 3N 4-based photocatalysts for hydrogen generation under visible-light irradiation.Design of High-Performance g-C 3N 4for Hydrogen Generation.

The photocatalytic H 2generation that occurred at the g-C 3N 4/water interface is highly dependent on the size,morphology,and defects of g-C 3N 4.The control of the g-C 3N 4mirco/nanostructure can endow it with large surface areas,abundant surface states,and even extended light harvesting,all of which are bene ?cial for the photocatalytic H 2generation.Because g-C 3N 4has a similar layered structure with graphite,the speci ?c surface area could theoretically be increased up to 2500m 2g ?1for perfect monolayer g-C 3N 4,19whereas it is normally below 10m 2

g ?1for the bulk g-C 3N 4powder due to the stacking of polymeric nanosheets.There are several works highlighting the bene ?t for photocatalytic hydrogen generation by reducing the thickness of g-C 3N 4.It has been reported that g-C 3N 4nanosheets with a thickness of ~3nm,corresponding to ~9stacked layers,can be prepared by using urea as the pyrolysis precursor.20A speci ?c surface area of 84.2m 2g ?1is obtained for the ~3nm g-C 3N 4

nanosheets,which is much higher than that of those g-C 3N 4

prepared using cyanamide,dicyandiamide,and melamine.The resultant sheet-like structure also favors the charge transfer.Thus,a more e ?cient hydrogen production is achieved.Thinner free-standing g-C 3N 4nanosheets are prepared by Yang et al.21via a simple liquid-phase exfoliation method.Particularly,the g-C 3N 4nanosheets exfoliated in 2-propanol by sonication has a thickness of ~2nm,high surface area of 384m 2g ?1,and large aspect ratios,which not only provide abundant reactive sites but also promote the charge transport.Signi ?cantly,the average hydrogen evolution rate of these g-C 3N 4nanosheets is more than 9times higher as compared to that of bulk g-C 3N 4under visible-light irradiation.In another work,Xu et al.22obtained g-C 3N 4

nanosheets with a single atomic layer structure (~0.4nm)by a concentrated H 2SO 4involved chemical exfoliation method,although the yield was only 60%.The photocurrent and the hydrogen evolution rate of the single-layer g-C 3N 4

are ~4and ~2.6times as high as those of the bulk g-C 3N 4,respectively.On the other hand,the morphology modulation of g-C 3N 4has been further demonstrated as a successful way to enhance the photocatalytic performance for hydrogen generation by facilitating the light absorption,charge separation and migration,and mass di ?usion during photocatalytic reactions.For example,Zhang et al.23have fabricated ordered mesoporous g-C 3N 4using an innovative template method.Before thermal treatment,su ?cient inclusion of the precursor (cyanamide)in the SBA-15mesozeolite template can be facilitated by the surface acid-

i ?cation of silica and sonication-promoted insertion.The thus-

obtained g-C

3N 4possesses ordered mesopores and cylindrical

channels,with a surface area up to 517m 2g ?1.A better

photocatalytic hydrogen generation activity with an apparent quantum yield of 6.77%at 455nm is achieved by the improved order of mesochannels,the presence of fewer textural structure

defects,and the larger surface area.Furthermore,the ordered

mesoporous frameworks can also serve as a “highway ”for free-charge transport to decrease the electron ?hole recombination.Sun et al.24report an impressive work in regard to the silica template synthesis of g-C 3N 4hollow nanospheres sized in the

optical range as both light-harvesting antennae and nano-structured sca ?olds that improve the photocatalytic e ?ciency.The prepared g-C

3N 4nanospheres have a wavelength-scale size within ~430nm,and the shell thickness can be well tuned from

56to 85nm without deformation against thermal treatment;thus,it can maximize the light harvesting through inner re ?ections and photonic e ?ects (see Figure 2).The resulting

initial visible-light hydrogen evolution rate can reach ~25-fold

higher than that of bulk g-C

3N 4,with an apparent quantum yield of 7.5%at 420.5nm.The performance of the robust g-C 3N 4hollow nanospheres is also competitive and superior to that of TiO 2(P25)and N-doped TiO 2under UV and visible-light irradiation in the presence of the same reaction solution.Very recently,it has been shown that by supramolecular chemistry

of

Figure 1.Tri-s -triazine-based two-dimensional structure of g-C 3N 4.Color scheme:C,gray;N,

blue.

Figure 2.Schematic illustration showing the light-harvesting behavior of

g-C 3N 4hollow nanospheres.

triazine molecules,it is facile to get ordered structures of g-C 3N 4such as hollow boxes,25spherical macroscopic assemblies,26hollow spheres,27and so forth without any additional modi ?cations.This method allows for synthesizing g-C 3N 4with high photocatalytic performance without using any hazard materials by mainly preserving the initial morphologies of the hydrogen-bonded supramolecular network precursors during the thermal polycondensation process.Heteroatom doping can e ?ectively monitor the electronic band structure of g-C 3N 4to extend the light absorption and adjust the redox potentials to further promote the photocatalytic hydrogen generation in the visible-light range.Carbon self-doping of g-C 3N 4is actualized by Dong et al.28via calcinating of solvothermally treated melamine with absolute alcohol.This carbon self-doping can cause the intrinsic electronic band structure change through the formation of delocalized big πbonds originating from the substitution of bridging N atoms with C atoms,thus to increase the visible-light absorption and electric conductivity.UV ?vis spectra indicate that the carbon doping gives rise to a decrease in the band gap from 2.72to 2.65eV.The visible-light hydrogen evolution rate on carbon-doped g-C 3N 4is 1.42times that on pure g-C 3N 4.Hong et al.29synthesize the in situ sulfur-doped mesoporous g-C 3N 4by thermal decomposition of thiourea in the presence of silica nanoparticles.The doped sulfur is proposed to substitute carbon in g-C 3N 4,leading to a downshift of 0.25eV in the conduction band and a narrower band gap of 2.61eV.Optical studies reveal that the sulfur-doped mesoporous g-C 3N 4shows extended and stronger visible-light absorption and a much lower density of defects compared to the native g-C 3N 4prepared from melamine.Simultaneously boosted by the e ?cient mass and charge transfer in the mesoporous structure,a 30times higher photocatalytic activity for hydrogen evolution is observed in comparison with that of native g-C 3N 4,corresponding to a quantum e ?ciency of 5.8%at 440nm.Very recently,Zhang et al.30employed the in situ iodine doping to g-C 3N 4using dicyandiamide and an iodine ion as the precursor and dopant.The I atoms tend to substitute the sp 2-bonded N as an n-type doping modi ?cation,e ?ectively extending the aromatic carbon nitride heterocycle and generating impurity energy levels above the valence band edge (see Figure 3).The optimal I doping can extend the light absorption to 600nm,while pristine g-C 3N 4is inactive at just 500nm,and attain a 2times higher hydrogen evolution rate than that of pristine g-C 3N 4.Another approach for modi ?cation of the electronic band structure of g-C 3N 4is the introduction of other organic additives during the polymerization process of the nitrogen precursor to form modi ?ed tri-s -triazine rings with speci ?c anchoring https://www.360docs.net/doc/5010404626.html,ing a facile bottom-up strategy,Chu et al.31incorporated an electron-de ?cient pyromellitic dianhydride (PMDA)constituent into the network of g-C 3N 4through copolymerizing melem with PMDA,which lowers both the conduction and valence bands.As a result,the photoreactivity of hydrogen evolution was ~3times as high as that of pristine g-C 3N 4under visible light.Similarly,Schwinghammer et al.32fabricated an amorphous variant of poly(triazine imide)doped with 4-amino-2,6-dihydroxypyrimi-dine,exhibiting an extended light absorption up to 800nm and thus a better hydrogen evolution activity.Zhang et al.33also report that the band gap of carbon nitride prepared from urea can be narrowed from 2.83to 2.61eV by simple copolymerization of urea with phenylurea,along with the extension of the delocalized π-conjugation system.Consequently,the rate of H 2evolution in the visible light increases nearly 9times.Therefore,heteroatom doping and copolymerization are pretty good strategies for tuning the electronic band structure of g-C 3N 4to extend the visible-light absorption and adjust the redox potentials for high-performance photocatalytic hydrogen generation.Exploration of g-C

3N 4-Based Composite Photocatalysts for Hydrogen Generation.Recently,much interest has been dedicated

to the construction of g-C 3N 4-based composite photocatalysts

and their application for hydrogen generation under visible light.

In a tentative work,we have prepared a graphene/g-C 3N 4composite photocatalyst in which graphene sheets can serve as electronic conductive channels to e ?ciently separate the photogenerated electron ?hole pairs and further to enhance the visible-light photocatalytic H 2production activity of g-C 3N 4.34This work demonstrates the superiority to utilize conductive graphene to accumulate abundant electrons for the water reduction reaction.An e ?ective strategy for populating the conduction band of g-C 3N 4with abundant electrons is coupling with suitable organic dyes,the excitation of which enables the energy conversion of light at longer wavelengths.Min et al.35report that the light absorption of mesoporous g-C 3N 4(<460nm)can be signi ?cantly extended to a longer wavelength in the visible-light region (up to 600nm)by Eosin Y (EY)sensitization,which allows for electron transfer from the excited states of EY to the conduction band of g-C 3N 4(see Figure 4).In aqueous solution,EY molecules absorb light to form singlet excited states of EY (1

*EY)and subsequently generate the triplet

excited states (3*EY)via an intercrossing transition.The 3*EY is reduced to EY ??by triethanolamine (TEOA),followed by the electron migration from EY ??to the conduction band of g-C 3N 4and then to the Pt cocatalyst for the water reduction reaction.Meanwhile,the reduced dye species return to the ground state,completing the water reduction reaction process.At the same time,g-C 3N 4can also be excited by absorbing photons with energy exceeding its band gap and subsequently transfer the photoinduced electrons directly to the Pt cocatalyst to generate H 2.As a result,the sensitized photocatalyst shows a high hydrogen

evolution

Figure 3.(a)Con ?guration of I-doped g-C 3N 4.Color scheme:C,gray;N,blue;I,red.(b)Photoexciting process of I-doped g-C 3N 4with impurity energy levels above the valence band edge.Heteroatom doping and copoly-merization are pretty good strat-

egies for tuning the electronic

band structure of g-C 3N

4to

extend the visible-light absorp-tion and adjust the redox poten-

tials for high-performance photo-catalytic hydrogen generation.

activity under irradiation of visible light longer than the absorption edge of g-C 3N 4and achieves an apparent quantum e ?ciency of 19.4%even at 550nm.Similarly,Wang et al.20also obtained a high apparent quantum e ?ciency of 33.4%at 460nm by sensitizing the thin-layer g-C 3N 4with low-cost dye Erythrosin B,which is higher than that of CdS-cluster-decorated graphene nanosheets 36and comparable to that of CdS quantum dots/graphene/ZnIn 2S 4heterostructures.37Semiconductor hybridization is another e ?ective strategy to broaden the utilization of g-C 3N 4for visible-light photocatalytic hydrogen generation.This strategy is based on the band alignment between g-C 3N 4and the other semiconductors (such as CdS),driving the photogenerated electrons and holes to migrate in the opposite directions.It subsequently leads to a spatial separation of the electrons and holes on di ?erent sides of the heterojunction,thus to suppress the charge recombination to gain an improved photocatalytic e ?ciency.For example,we have obtained two kinds of CdS/g-C 3N 4heterojunctions;one is g-C 3N 4nanosheets in situ grown with well-dispersed CdS quantum dots,38and the other is CdS/g-C 3N 4core/shell nanowires.39

Both CdS/g-C 3N 4heterojunctions can e ?ectively promote the charge separation and transfer corrosive holes from CdS to g-C 3N 4(see Figure 5),thus reinforcing the stability of CdS and achieving a much higher hydrogen evolution rate under visible-light irradiation as compared to that for pure CdS and pure g-C 3N 4.Similarly,the in situ growth of In 2O 3nanocrystals onto the surface of g-C 3N 4nanosheets is also achieved.The resulting In 2O 3?g-C 3N 4hybrid structures exhibit remarkable improve-ment on the photocatalytic activity for H 2generation,which is attributed to the e ?ective interfacial transfer of photogenerated electrons and holes between g-C 3N 4and In 2O 3.40The improved charge-transfer e ?ciency is further con ?rmed by transient photoluminescence spectroscopy.In another report,Sui et al.41loaded the highly dispersed nanoparticles of an organic semiconductor,polypyrrole,on the surface of g-C 3N 4at a very low mass ratio;the resultant hydrogen evolution rate from pure water was ~50times higher than that of pure g-C 3N 4.A novel approach is to construct isotype heterojunctions of g-C 3N 4,considering the fact that the band structures of g-C 3N 4prepared from di ?erent precursors vary in some cases.In this regard,constructing a g-C 3N 4/g-C 3N 4isotype heterojunction by coupling two components of g-C 3N 4with a well-matched band structure is proved to be an alternative to address the intrinsic drawbacks of g-C 3N 4for enhanced photocatalysis rather than coupling with extra semiconductors.42Stimulated by this

concept,Zhang et al.43created two types of host ?guest heterojunctions of g-C

3N 4(CN)and sulfur-mediated g-C 3N 4(CNS)with close interconnection between CN and CNS by surface-assisted polymerization rather than simply mixing CN

and CNS.One was CNS ?CN (CN serving as the host),and the

other was CN ?CNS (CNS serving as the host).The visible-light

hydrogen evolution activity of the best isotype heterojunctions

was ~11and ~2.3times higher than that of CN and CNS,respectively.The photogenerated electrons were transferred from CN (?1.42V)to CNS (?1.21V),driven by the conduction band o ?set,and the valence band o ?set between CNS (+1.46V)and CN (+1.28V)could induce the migration of photoinduced holes from CNS to CN,giving rise to the redistribution of electrons on the CNS side and holes on the

opposite CN side of the junction,which greatly reduced the

energy-wasteful electron ?hole recombination and,conse-

quently,improved the photocatalytic activity.Therefore,the creation of heterojunctions between g-C 3N 4and appropriate semiconductors has proven to be remarkably e ?ective to achieve a better photogenerated charge separation e ?ciency to promote the hydrogen generation.Note that the previously reported studies on photocatalytic hydrogen generation over g-C 3N 4are mostly assisted by noble

metal cocatalysts such as Pt and Au,which capture conduction -band electrons to reduce the electron ?hole recombination and transfer the electrons to surface water molecules to reduce the activation energy of water reduction.While researchers are

trying

Figure 4.Photocatalytic mechanism for H 2evolution over the EY-g-C 3N 4/Pt photocatalyst under visible

light.

Figure 5.Schematic illustration of a heterojunction formed between g-C 3N 4and CdS.The creation of heterojunctions

between g-C

3N 4and appropriate semiconductors has proven to be remarkably e ?ective to achieve a better photogenerated charge separation e ?ciency to promote the hydrogen generation.

to develop a low-cost noble-metal-free photocatalytic system for hydrogen production,44recent work has successfully introduced non-noble-metal cocatalysts into the g-C 3N 4-based photo-catalytic systems,showing a competitive e ?ciency as compared to that of noble metal cocatalysts.Hou et al.45prepared a thin-layered heterogeneous nanojunction of MoS 2and g-C 3N 4,taking advantage of the similar layered structures of MoS 2and g-C 3N 4(see Figure 6).This MoS 2/g-C 3N 4heterojunction can increase the accessible area around the planar interface of the MoS 2and g-C 3N 4layers and decrease the barriers for electron transport,thus promoting the electron transfer across the interface.It can also minimize the light-shielding e ?ect of MoS 2to improve the light

utilization of g-C 3N 4.Moreover,the e ?ective band alignment between MoS 2and g-C 3N 4enables the directional transfer of photoinduced electrons from the conduction band of g-C 3N 4to MoS 2,while still with enough chemical potential to reduce H +to H 2molecules at the surface of MoS 2.As a result,the MoS 2/g-C 3N 4layered nanojunction makes a signi ?cant contribution to improve the photocatalytic activity,and the highest H 2production rate with an apparent quantum e ?ciency of 2.1%at 420nm is achieved for the 0.2wt %MoS 2/g-C 3N 4,even much higher than that of Pt/g-C 3N 4.We have also successfully introduced Ni(OH)2as a good cocatalyst to enhance the photocatalytic H 2production activity of g-C 3N 4.46The H 2production rate of the optimal 0.5mol %Ni(OH)2modi ?ed g-C 3N 4can approach that of optimal 1.0wt %Pt/g-C 3N 4.This is because the potential of Ni 2+/Ni is lower than the conduction band of g-C 3N 4but still more negative than the reduction potential of H +/H 2,which not only promotes the electron migration from the conduction band of g-C 3N 4to Ni(OH)2but also favors the reduction of H +,further to enhance the photocatalytic H 2production activity.In addition,other nickel and cobalt compounds such as Ni(TEOA)2Cl 2,47NiS,48and cobaloxime 49are also successfully coupled with g-C 3N 4and serve as cocatalysts,generating e ?cient noble-metal-free photo-catalytic systems for hydrogen evolution under visible light.To sum up,this Perspective summarized the recent signi ?cant advances related to the g-C 3N 4-based photocatalysts for e ?cient hydrogen generation under visible-light irradiation.The visible-light photocatalytic performance of g-C 3N 4can be largely enhanced by nanostructure design,band gap engineering,dye sensitization,and heterojunction construction.Although some signi ?cant progress has been achieved in this area,further e ?orts are still required in various aspects to further advance the utilization of g-C 3N 4for visible-light photocatalytic hydrogen generation.For instance,unlike graphene that usually has many oxygen-containing groups,the surface of g-C 3N 4is relatively inert.Thus,further studies on surface activation of g-C 3N 4for the purpose of the speci ?c binding of functional groups,as well as the growth and well dispersion of nanoparticles,can help to prepare more e ?cient g-C 3N 4/semiconductor heterostructures and g-

C 3N 4/cocatalyst hybrids with improved interfacial contact for

photocatalytic hydrogen generation.Also,although the energy band engineering of g-C

3N

4has been widely applied,high

quantum e ?ciency cannot be achieved by simply tuning the band

gap to extend light absorption.Therefore,the combination of

band gap engineering with other modi ?cation strategies is highly

encouraged in order to ?nd better ways for improving the performance of g-C 3N 4.Moreover,the mechanisms of g-C

3N

4-

based photocatalytic systems were not very clear until now.It is necessary to understand the dynamic behavior of photo-generated carriers on the surface and interface of g-C 3N 4with reactants.To gain a signi ?cant breakthrough in photocatalytic performance requires a deep comprehension of the surface/interface processes,especially at the atom level.In this regard,high-quality in situ observations as well as rational fundamental calculations and simulations would be bene ?cial for the design of

e ?cient g-C 3N 4-based photocatalysts.Alongside the photo-catalytic hydrogen evolution,the utilization o

f g-C 3N

4in many photoelectronic devices such as solar cells and fuel cells has also attracted increasing attention.13,14,50Also,very recently,it was

found that

g-C 3N 4is active in the electroreduction of water to hydrogen.51Therefore,it is undoubted that there is an exciting and brightening future for g-C 3N 4-based materials.■AUTHOR INFORMATION Corresponding Author

*E-mail:jiaguoyu@https://www.360docs.net/doc/5010404626.html,.Tel:0086-27-87871029.Fax:0086-27-87879468.Notes The authors declare no competing ?nancial interest.Biographies

Shaowen Cao received his B.S.in 2005from the University of Science

and Technology of China and his Ph.D.in 2010from the Shanghai Institute of Ceramics,Chinese Academy of Sciences.He is now a

Professor at the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology.His current research interests include the design and fabrication of

photocatalytic materials for energy and environmental applications.See

more details on https://www.360docs.net/doc/5010404626.html,/rid/I-8050-2013.Jiaguo Yu received his B.S.and M.S.in chemistry from Huazhong Normal University and Xi ’an Jiaotong University,respectively,and his Ph.D.in Materials Science in 2000from Wuhan University of

Technology.In 2000,he became a Professor at Wuhan University of

Technology.His current research interests include semiconductor photocatalysis,photocatalytic hydrogen production,CO 2reduction to hydrocarbon fuels,dye-sensitized solar cells,and so on.See more details on https://www.360docs.net/doc/5010404626.html,/rid/G-4317-2010.■ACKNOWLEDGMENTS This work was supported by the 973program (2013CB632402),and NSFC (51272199,51320105001,51372190,and 21177100).Also,this work was ?nancially supported by the General Financial Grant from the China Postdoctoral Science Foundation (2014M552101),the Fundamental Research Funds for the Central Universities (WUT:2014-VII-010,2014-IV-

058),Self-determined and Innovative Research Funds of

SKLWUT (2013-ZD-1),and a WUT Start-Up

Grant.

Figure 6.Schematic illustration for the charge transfer and separation in the MoS 2/g-C 3N 4heterostructures under visible-light irradiation.

REFERENCES

(1)Tachibana,Y.;Vayssieres,L.;Durrant,J.R.Artificial Photosyn-thesis for Solar Water-Splitting.Nat.Photonics2012,6,511?518. (2)Tran,P.D.;Wong,L.H.;Barber,J.;Loo,J.S.C.Recent Advances in Hybrid Photocatalysts for Solar Fuel Production.Energy Environ.Sci. 2012,5,5902?5918.

(3)Xiang,Q.;Yu,J.;Jaroniec,M.Graphene-Based Semiconductor Photocatalysts.Chem.Soc.Rev.2012,41,782?796.

(4)Xiang,Q.;Yu,J.Graphene-Based Photocatalysts for Hydrogen Generation.J.Phys.Chem.Lett.2013,4,753?759.

(5)Kudo,A.;Miseki,Y.Heterogeneous Photocatalyst Materials for Water Splitting.Chem.Soc.Rev.2009,38,253?278.

(6)Chen,X.B.;Shen,S.H.;Guo,L.J.;Mao,S.S.Semiconductor-Based Photocatalytic Hydrogen Generation.Chem.Rev.2010,110, 6503?6570.

(7)Tong,H.;Ouyang,S.;Bi,Y.;Umezawa,N.;Oshikiri,M.;Ye,J. Nano-Photocatalytic Materials:Possibilities and Challenges.Adv.Mater. 2012,24,229?251.

(8)Wang,Y.;Wang,Q.;Zhan,X.;Wang,F.;Safdar,M.;He,J.Visible Light Driven Type II Heterostructures and Their Enhanced Photo-catalysis Properties:A Review.Nanoscale2013,5,8326?8339. (9)Navarro Yerga,R.M.;Alvarez Galvan,M.C.;del Valle,F.;Villoria de la Mano,J.A.;Fierro,J.L.Water Splitting on Semiconductor Catalysts under Visible-Light Irradiation.ChemSusChem2009,2,471?485.

(10)Abe,R.Recent Progress on Photocatalytic and Photo-electrochemical Water Splitting under Visible Light Irradiation.J. Photochem.Photobiol.,C2010,11,179?209.

(11)Wang,X.C.;Maeda,K.;Thomas,A.;Takanabe,K.;Xin,G.; Carlsson,J.M.;Domen,K.;Antonietti,M.A Metal-Free Polymeric Photocatalyst for Hydrogen Production from Water under Visible Light. Nat.Mater.2009,8,76?80.

(12)Wang,Y.;Wang,X.;Antonietti,M.Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst:From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry.Angew.Chem.,Int.Ed. 2012,51,68?89.

(13)Zhang,Y.;Mori,T.;Ye,J.Polymeric Carbon Nitrides: Semiconducting Properties and Emerging Applications in Photo-catalysis and Photoelectrochemical Energy Conversion.Sci.Adv. Mater.2012,4,282?291.

(14)Zheng,Y.;Liu,J.;Liang,J.;Jaroniec,M.;Qiao,S.Z.Graphitic Carbon Nitride Materials:Controllable Synthesis and Applications in Fuel Cells and Photocatalysis.Energy Environ.Sci.2012,5,6717?6731.

(15)Wang,X.;Maeda,K.;Chen,X.;Takanabe,K.;Domen,K.;Hou, Y.;Fu,X.;Antonietti,M.Polymer Semiconductors for Artificial Photosynthesis:Hydrogen Evolution by Mesoporous Graphitic Carbon Nitride with Visible Light.J.Am.Chem.Soc.2009,131,1680?1681.

(16)Liu,G.;Niu,P.;Sun,C.;Smith,S.C.;Chen,Z.;Lu,G.Q.M.; Cheng,H.-M.Unique Electronic Structure Induced High Photo-reactivity of Sulfur-Doped Graphitic C3N4.J.Am.Chem.Soc.2010,132, 11642?11648.

(17)Zhang,J.;Zhang,G.;Chen,X.;Lin,S.;Mohlmann,L.;Dolega,G.; Lipner,G.;Antonietti,M.;Blechert,S.;Wang,X.Co-Monomer Control of Carbon Nitride Semiconductors to Optimize Hydrogen Evolution with Visible Light.Angew.Chem.,Int.Ed.2012,51,3183?3187. (18)Wang,X.;Blechert,S.;Antonietti,M.Polymeric Graphitic Carbon Nitride for Heterogeneous Photocatalysis.ACS Catal.2012,2, 1596?1606.

(19)Sano,T.;Tsutsui,S.;Koike,K.;Hirakawa,T.;Teramoto,Y.; Negishi,N.;Takeuchi,K.Activation of Graphitic Carbon Nitride(g-C3N4)by Alkaline Hydrothermal Treatment for Photocatalytic NO Oxidation in Gas Phase.J.Mater.Chem.A2013,1,6489?6496. (20)Wang,Y.;Hong,J.;Zhang,W.;Xu,R.Carbon Nitride Nanosheets for Photocatalytic Hydrogen Evolution:Remarkably Enhanced Activity by Dye Sensitization.Catal.Sci.Technol.2013,3,1703?1711. (21)Yang,S.;Gong,Y.;Zhang,J.;Zhan,L.;Ma,L.;Fang,Z.;Vajtai,R.; Wang,X.;Ajayan,P.M.Exfoliated Graphitic Carbon Nitride Nanosheets as Efficient Catalysts for Hydrogen Evolution under Visible Light.Adv.Mater.2013,25,2452?2456.

(22)Xu,J.;Zhang,L.;Shi,R.;Zhu,Y.Chemical Exfoliation of Graphitic Carbon Nitride for Efficient Heterogeneous Photocatalysis.J. Mater.Chem.A2013,1,14766?14772.

(23)Zhang,J.;Guo,F.;Wang,X.An Optimized and General Synthetic Strategy for Fabrication of Polymeric Carbon Nitride Nanoarchitec-tures.Adv.Funct.Mater.2013,23,3008?3014.

(24)Sun,J.;Zhang,J.;Zhang,M.;Antonietti,M.;Fu,X.;Wang,X. Bioinspired Hollow Semiconductor Nanospheres as Photosynthetic https://www.360docs.net/doc/5010404626.html,mun.2012,3,1139.

(25)Shalom,M.;Inal,S.;Fettkenhauer,C.;Neher,D.;Antonietti,M. Improving Carbon Nitride Photocatalysis by Supramolecular Preorga-nization of Monomers.J.Am.Chem.Soc.2013,135,7118?7121.

(26)Jun,Y.-S.;Park,J.;Lee,S.U.;Thomas,A.;Hong,W.H.;Stucky,G.

D.Three-Dimensional Macroscopic Assemblies of Low-Dimensional Carbon Nitrides for Enhanced Hydrogen Evolution.Angew.Chem.,Int. Ed.2013,52,11083?11087.

(27)Jun,Y.-S.;Lee,E.Z.;Wang,X.C.;Hong,W.H.;Stucky,G.D.; Thomas,A.From Melamine-Cyanuric Acid Supramolecular Aggregates to Carbon Nitride Hollow Spheres.Adv.Funct.Mater.2013,23,3661?3667.

(28)Dong,G.;Zhao,K.;Zhang,L.Carbon Self-Doping Induced High Electronic Conductivity and Photoreactivity of https://www.360docs.net/doc/5010404626.html,mun. 2012,48,6178?6180.

(29)Hong,J.;Xia,X.;Wang,Y.;Xu,R.Mesoporous Carbon Nitride with In Situ Sulfur Doping for Enhanced Photocatalytic Hydrogen Evolution from Water under Visible Light.J.Mater.Chem.2012,22, 15006?15012.

(30)Zhang,G.;Zhang,M.;Ye,X.;Qiu,X.;Lin,S.;Wang,X.Iodine Modified Carbon Nitride Semiconductors as Visible Light Photo-catalysts for Hydrogen Evolution.Adv.Mater.2014,26,805?809. (31)Chu,S.;Wang,Y.;Guo,Y.;Feng,J.;Wang,C.;Luo,W.;Fan,X.; Zou,Z.Band Structure Engineering of Carbon Nitride:In Search of a Polymer Photocatalyst with High Photooxidation Property.ACS Catal. 2013,3,912?919.

(32)Schwinghammer,K.;Tuffy,B.;Mesch,M.B.;Wirnhier,E.; Martineau,C.;Taulelle,F.;Schnick,W.;Senker,J.;Lotsch,B.V. Triazine-Based Carbon Nitrides for Visible-Light-Driven Hydrogen Evolution.Angew.Chem.,Int.Ed.2013,52,2435?2439.

(33)Zhang,G.;Wang,X.A Facile Synthesis of Covalent Carbon Nitride Photocatalysts by Co-Polymerization of Urea and Phenylurea for Hydrogen Evolution.J.Catal.2013,307,246?253.

(34)Xiang,Q.;Yu,J.;Jaroniec,M.Preparation and Enhanced Visible-Light Photocatalytic H2-Production Activity of Graphene/C3N4 Composites.J.Phys.Chem.C2011,115,7355?7363.

(35)Min,S.;Lu,G.Enhanced Electron Transfer from the Excited Eosin Y to mpg-C3N4for Highly Efficient Hydrogen Evolution under 550nm Irradiation.J.Phys.Chem.C2012,116,19644?19652. (36)Li,Q.;Guo,B.D.;Yu,J.G.;Ran,J.R.;Zhang,B.H.;Yan,H.J.; Gong,J.R.Highly Efficient Visible-Light-Driven Photocatalytic Hydrogen Production of CdS-Cluster-Decorated Graphene Nano-sheets.J.Am.Chem.Soc.2011,133,10878?10884.

(37)Hou,J.G.;Yang,C.;Cheng,H.J.;Wang,Z.;Jiao,S.Q.;Zhu,H. M.Ternary3D Architectures of CdS QDs/Graphene/ZnIn2S4 Heterostructures for Efficient Photocatalytic H2Production.Phys. Chem.Chem.Phys.2013,15,15660?15668.

(38)Cao,S.W.;Yuan,Y.P.;Fang,J.;Shahjamali,M.M.;Boey,F.Y.C.; Barber,J.;Loo,S.C.J.;Xue,C.In-Situ Growth of CdS Quantum Dots on g-C3N4Nanosheets for Highly Efficient Photocatalytic Hydrogen Generation under Visible Light Irradiation.Int.J.Hydrogen Energy2013, 38,1258?1266.

(39)Zhang,J.;Wang,Y.;Jin,J.;Lin,Z.;Huang,F.;Yu,J.Efficient Visible-Light Photocatalytic Hydrogen Evolution and Enhanced Photostability of Core/Shell CdS/g-C3N4Nanowires.ACS Appl. Mater.Interfaces2013,5,10317?10324.

(40)Cao,S.W.;Liu,X.F.;Yuan,Y.P.;Zhang,Z.Y.;Liao,Y.S.;Fang, J.;Loo,S.C.J.;Sum,T.C.;Xue,C.Solar-to-Fuels Conversion over In2O3/g-C3N4Hybrid Photocatalysts.Appl.Catal.,B2014,147,940?946.

(41)Sui,Y.;Liu,J.;Zhang,Y.;Tian,X.;Chen,W.Dispersed Conductive Polymer Nanoparticles on Graphitic Carbon Nitride for Enhanced Solar-Driven Hydrogen Evolution from Pure Water. Nanoscale2013,5,9150?9155.

(42)Dong,F.;Zhao,Z.;Xiong,T.;Ni,Z.;Zhang,W.;Sun,Y.;Ho,W. K.In Situ Construction of g-C3N4/g-C3N4Metal-Free Heterojunction for Enhanced Visible-Light Photocatalysis.ACS.Appl.Mater.Interfaces. 2013,5,11392?11401.

(43)Zhang,J.;Zhang,M.;Sun,R.Q.;Wang,X.A Facile Band Alignment of Polymeric Carbon Nitride Semiconductors to Construct Isotype Heterojunctions.Angew.Chem.,Int.Ed.2012,51,10145?10149.

(44)Ran,J.R.;Zhang,J.;Yu,J.G.;Jaroniec,M.;Qiao,S.Z.Earth-Abundant Cocatalysts for Semiconductor-Based Photocatalytic Water Splitting.Chem.Soc.Rev.2014,DOI:10.1039/C3CS60425J.

(45)Hou,Y.;Laursen,A.B.;Zhang,J.;Zhang,G.;Zhu,Y.;Wang,X.; Dahl,S.;Chorkendorff,https://www.360docs.net/doc/5010404626.html,yered Nanojunctions for Hydrogen-Evolution Catalysis.Angew.Chem.,Int.Ed.2013,52,3621?3625. (46)Yu,J.;Wang,S.;Cheng,B.;Lin,Z.;Huang,F.Noble Metal-Free Ni(OH)2?g-C3N4Composite Photocatalyst with Enhanced Visible-Light Photocatalytic H2-Production Activity.Catal.Sci.Technol.2013,3, 1782?1789.

(47)Dong,J.;Wang,M.;Li,X.;Chen,L.;He,Y.;Sun,L.Simple Nickel-Based Catalyst Systems Combined with Graphitic Carbon Nitride for Stable Photocatalytic Hydrogen Production in Water. ChemSusChem2012,5,2133?2138.

(48)Hong,J.;Wang,Y.;Zhang,W.;Xu,R.Noble-Metal-Free NiS/ C3N4for Efficient Photocatalytic Hydrogen Evolution from Water. ChemSusChem2013,6,2263?2268.

(49)Cao,S.W.;Liu,X.F.;Yuan,Y.P.;Zhang,Z.Y.;Fang,J.;Loo,S.C. J.;Barber,J.;Sum,T.C.;Xue,C.Artificial Photosynthetic Hydrogen Evolution over g-C3N4Nanosheets Coupled with Cobaloxime.Phys. Chem.Chem.Phys.2013,15,18363?18366.

(50)Yang,F.;Lublow,M.;Orthmann,S.;Merschjann,C.;Tyborski, T.;Rusu,M.;Kubala,S.;Thomas,A.;Arrigo,R.;Ha v ecker,M.;Schedel-Niedrig,T.Metal-Free Photocatalytic Graphitic Carbon Nitride on p-Type Chalcopyrite as a Composite Photocathode for Light-Induced Hydrogen Evolution.ChemSusChem2012,5,1227?1232.

(51)Shalom,M.;Gimenez,S.;Schipper,F.;Herraiz-Cardona,I.; Bisquert,J.;Antonietti,M.Controlled Carbon Nitride Growth on Surfaces for Hydrogen Evolution Electrodes.Angew.Chem.,Int.Ed.

2014,53,3654?3658.

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