光解水催化剂介绍photocatalysts
光解水催化剂介绍photocatalysts
major developing history
well-known as the Honda-Fujishima effect
first discovery and basic principles
energy band theory
different energy levels correspond with different bands
special electronic structures—mixed-configuration metal oxides
2、migrate without recombination 3、inhibit the backward reaction
example: Pt-TiO2 at 1980 with NaOH loaded on the cocatalyst
K. Maeda / Journal of Photochemistry and Photobiology C: Photochemistry Reviews 12 (2011) 237–268
major developing history
special structures—perovskites
Aurivillius phases
Dion-Jacobson phases
Ruddleson-Popper phases
major developing history
Science 2015 光催化电解水 Metal-free efficient photocatalyst for stable visible water splitting
ACKNOWLEDGMENTSSupported by U.S.Department of Energy award DE-EE0006709(solar cell)and Defense Threat Reduction Agency award HDTRA1-14-1-0030(radiation detector).J.H.conceived the idea and supervised the project;Q.D.grew thesingle crystals and fabricated the devices;Q.D.,Y.F.,and Y.S.P.M.,J.Q.,and L.C.measured the devices under gamma ray irradiation and did the simulation;and J.H.wrote the paper.SUPPLEMENTARY MATERIALS/content/347/6225/967/suppl/DC1Figs.S1to S11Tables S1and S2References (17–21)27December 2014;accepted 20January 2015Published online 29January 2015;water is a promising means of storing solar energy in a way that compensates for the intermittency of sunlight as a primary source of power (1,2).It can be realized by apply-ing a hybrid system in which a solar cell powers an electrolyzer [photovoltaic (PV)electrolysis].Pho-toelectrolysis (PE)uses photocatalyst electrodes with additional electrical power provided by a photovoltaic element.Photocatalysis (PC)involves light-irradiated catalysts (typically catalyst pow-ders suspended in water)for water splitting (3).Recently reported “solar-to-hydrogen ”(STH)ef-ficiencies for PV electrolysis systems exceed 10%(4–6).State-of-the-art PE systems yield STH values of 2to 3%(7)but are believed to provide a cheaper solution for H 2production.PC is the simplest water-splitting approach,more ame-nable to cheap,large-scale applications of H 2generation.Unfortunately,despite intense efforts during the past 40years (8–15),current direct photocatalysts for water splitting still face several challenging issues:(i)Currently reported cata-lysts suffer from low quantum efficiency (QE)in the visible range,with STH efficiencies less thanof rare and expensive materials;(iii)various pho-tocatalysts show poor stability [e.g.,inorganic sulfide and (oxy)nitride-based photocatalysts are less stable and more susceptible to oxida-tion than water];(iv)O 2release from semi-conductor catalysts is difficult,so that the use of sacrificial reagents is required;(v)the overall four-electron water oxidation to O 2encounters a large overpotential;and (vi)the kinetically com-peting two-electron reaction to H 2O 2often poisons the photocatalysts (19).Overall water splitting to H 2and O 2requires a high free energy of 113.38kcal/mol (20,21).The challenge lies mainly in the release of diatomic O 2,which involves four electron and four pro-ton transfers for the eventual formation of an O-O bond.The concerted four-electron process for oxygen evolution (1.23eV)is thermodyna-mically more favorable than the two-electron process for H 2O 2formation (1.78eV).However,detailed analysis (see supplementary text)shows that a higher reaction rate may be achieved in a system where water is first oxidized via a two-electron reaction to H 2O 2and H 2,followed by H 2O 2decomposition to O 2and H 2O.For this stepwise two-electron/two-electron water splitting to H 2and O 2to be viable and practical,the photo-catalyst applied should be capable of promoting generation as well as subsequent decomposition of H 2O 2with high efficiencies and low overpo-tentials,so as to allow considerable reduction in the energy cost for production of H 2and O 2overall water splitting.Here,we report that nanocomposites of carbon nanodots embedded a C 3N 4matrix perform as an excellent photo-fulfilling the above requirements.C 3N 4is commercially available (e.g.,from Carbo-and can be easily fabricated (e.g.,from urea)19).It is an Earth-abundant and low-cost photo-capable of generating H 2and H 2O 2from even in the absence of catalytic metals,with a low QE (19,22–26).C 3N 4belongs to oldest reported polymer materials prepared chemists (by Berzelius in ~1830)and first “Melon ”(27).In 2006it was determined the visible light activity of TiO 2after treat-with urea was due to “Melon ”(28).In 2009,and colleagues described in detail the properties,electronic structure,and photo-activity of C 3N 4(29).Following this work,groups attempted to optimize the catalytic of C 3N 4,motivated by its relatively low gap energy E g of 2.7eV,and high valence and conduction band positions (29)[1.8–0.9eV versus reversible hydrogen electrode Many heterojunction composites with semiconductors as well as photocatalyst were investigated.The latter included systems with a variety of oxides (30)and sulfides (31)along with pure metals (19)and even graphene (32)and carbon nanotubes (33).Different prep-aration methods were studied in an effort to increase the surface area of C 3N 4and to improve its catalytic activity.The QE values obtained using C 3N 4as a catalyst for water splitting to H 2and O 2have been low (maximum 3.75%at 420nm and less than 0.5%for 500nm),and generally the use of a sacrificial reagent has been necessary (19,24,26,30–32,34).The efficiency at 700nm can be largely increased by applying dye mol-ecules,but again a sacrificial reagent is a must (35).During water splitting C 3N 4suffers from poi-soning by the produced H 2O 2,which is difficult to remove from the C 3N 4surface (19).Different methods including stirring,bubbling,and/or ad-dition of chemical agents have been attempted for regeneration of the poisoned C 3N 4catalyst (19).Carbon nanodots (CDots;monodisperse graph-ite particles less than 10nm in diameter)exhibit unique photo-induced electron transfer,photo-luminescence,and electron reservoir properties (36).In particular,CDots possess high catalytic activity (by chemical catalysis;no light is needed)for H 2O 2decomposition (37).Given the photo-catalytic properties of CDots and C 3N 4,we hypoth-esized that a combination of CDots and C 3N 4could constitute a high-performance composite photocatalyst for water splitting via the stepwise two-electron/two-electron process:(i)2H 2O →H 2O 2+H 2;(ii)2H 2O 2→2H 2O +O 2.97027FEBRUARY 2015•VOL 347ISSUE SCIENCE1Jiangsu Key Laboratory for Carbon-based FunctionalMaterials and Devices,Institute of Functional Nano and Soft Materials (FUNSOM),Soochow University,Suzhou 215123,China.2Department of Materials Science and Engineering,Technion,Israel Institute of Technology,Haifa 3200003,Israel.*Corresponding authors.E-mail:zhkang@ (Z.K.);apannale@ (S.-T.L.);shayli@tx.technion.ac.il (Y.L.)RESEARCH |REPORTSo n F e b r u a r y 28, 2015w w w .s c i e n c e m a g .o r g D o w n l o a d e d f r o mCDots were synthesized by a typical electro-chemical method followed by hydrothermal treat-ment with ammonia (37).CDots-C 3N 4composites were then prepared by heating a mixture of ammonia-treated CDots and urea powder at 550°C for 3hours (see supplementary material).Characterization of the as-produced CDots-C 3N 4composites by transmission electron microscopy (TEM)showed highly porous grains (Fig.1A)consisting of CDots (2to 10nm in diameter)embedded in a porous C 3N 4matrix (Fig.1B).The CDots were non-uniformly distributed,with apparent regions of dots denser by one order of magnitude than the average concentration in the C 3N 4matrix.A high-resolution TEM (HRTEM)image of a CDot crys-tallite (Fig.1C)showed an interplanar spacing of 0.202nm,which corresponds to the 〈101〉spacing of graphitic carbon.The corresponding 2D fast Fourier transform (FFT)pattern (Fig.1D)exhibits the hexagonal crystalline structure of the CDots.Linewidth analysis of x-ray powder diffraction patterns (fig.S1)of the grains of the CDots-C 3N 4composite suggests that the C 3N 4matrix comprises nanocrystallites with an average diameter of ~4nm (29,38,39).The diameter of the grains of the CDots-C 3N 4composite deduced from atomic force microscopy (fig.S2)ranges between 90and 400nm (fig.S3).The incorporation of CDots into the C 3N 4matrix leads to an increase in the ultraviolet-visible (UV-vis)absorption over the entire wave-length range investigated (Fig.2A).The optical band gap of a semiconductor can be estimated from the Tauc plot [i.e.,the curve of converted (a h n )r versus h n from the UV-vis spectrum,in which a ,h ,and n are the absorption coefficient,Planck constant,and light frequency,respectively,and r =2for a direct band gap material and r =1/2for an indirect band gap material].Figure 2B shows a good linear fit when using r =2,in accord with previous work (25)claiming C 3N 4to be a direct band gap material (no good lin-ear fit is obtained for r =1/2).The E g value of CDots-C 3N 4(CDots concentration of 1.6×10−5g CDots /g catalyst )was thus determined to be 2.77eV by measuring the x -axis intercept of an extrapolated line from the linear regime of the curve (Fig.2B,red curve),which is almost identical to that of pure C 3N 4(Fig.2B,2.75eV,black curve)within experimental error.The Tauc plot curve (Fig.2B,red curve)of CDots-C 3N 4shows an apparent tail between 2.0and 2.7eV,which is helpful for improving the light absorb-ance and the photocatalytic efficiency.Aside from an appropriate band gap,the proper matching of conduction band and valence band levels of a photocatalyst with the redox potentials of the photocatalytic reactions is also important for water splitting.We used ultraviolet photo-electron spectroscopy (UPS)to determine the ionization potential [equivalent to the valence band energy (E v )]of CDots-C 3N 4,which was calculated to be 6.96eV by subtracting the width of the He I UPS spectra (Fig.2C)from the excitation energy (21.22eV).The con-duction band energy E c is thus estimated at 4.19eV from E v –E g .The E g ,E v ,and E c values ofSCIENCE 27FEBRUARY 2015•VOL 347ISSUE 6225971Fig.2.Characterization of the electronic structure of the composite catalyst.(A )UV-vis absorption spectra of C 3N 4(black curve)and CDots-C 3N 4(red curve)catalysts.Inset:Digital photograph of catalyst grains.The actual size of the digital photo is 4cm ×4.3cm.(B )(a h n )2versus h n curve of C 3N 4(black curve)and CDots-C 3N 4(red curve).The horizontal dashed black line marks the baseline;the other dashed lines are the tangents of the curves.The intersection value is the band gap.(C )UPS spectra of CDots-C 3N 4(black curve).The dashed red lines mark the baseline and the tangents of the curve.The intersections of the tangents with the baseline give the edges of the UPS spectra from which the UPS width is determined.(D )Band structure diagram for CDots-C 3N 4.In all panels,the CDots concentration in the CDots-C 3N 4sample analyzed was 1.6×10−5g CDots /g catalyst .VB,valence band;CB,conduction band.Fig.1.Characterization of the physical structure of the composite catalyst.(A )TEM image of a grain of the CDots-C 3N 4composite.(B )A magnified TEM image of the CDots-C 3N 4region of (A)marked in red.(C )HRTEM image of a single CDot embedded in C 3N 4.(D )Corresponding FFT pattern of the crys-tallite in (C),indicating hexagonal symmetry.In all panels,the CDots concentration of the sample was 1.6×10−5g CDots /g catalyst .RESEARCH |REPORTSCDots-C 3N 4in electron volts are converted to electro-chemical energy potentials in volts according to the reference standard for which 0V versus RHE (reversible hydrogen electrode)equals –4.44eV versus evac (vacuum level).Figure 2D further shows that the reduction level for H 2is posi-tioned below the conduction band of CDots-C 3N 4,and the oxidation level for H 2O to H 2O 2or O 2is above the valence band;these bands are properly positioned to permit transfer of electrons and holes,respectively,for water splitting,thus corroborating the potential of CDots-C 3N 4as a photocatalyst for overall water splitting.Additional characterization of the CDots-C 3N 4composites included Raman spectroscopy (fig.S4),Fourier transform infrared spectroscopy (FTIR,fig.S5),energy-dispersive spectra (EDS,fig.S6),x-ray photoelectron spectroscopy (XPS,fig.S7),and x-ray absorption near edge structure (XANES,fig.S8).Figure 3A shows the evolution of H 2and O 2from 150ml of water containing 0.08g of non-optimized CDots-C 3N 4composite under visible light irradiation.H 2and O 2were both quantified by gas chromatography (GC);a typical sample curve (GC signal)is shown in fig.S9.H 2and O 2evolution proceeded continuously in a molar ratio of H 2/O 2of 2.02,effectively identical to the the-oretical value of 2for overall water splitting,but ceased immediately when the light was turned off.The constant H 2evolution rate was ~8.4m mol/hour and that of O 2~4.1m mol/hour,and no other gases than H 2and O 2(e.g.,CO 2or N 2)were detected by GC.Control experiments showed that no O 2evolution was detected by gas chromatography when pure CDots,pure C 3N 4,or a macroscopic mixture of the two was used as photocatalyst over a 24-hour reaction period.This indicates (see supple-mentary material)that proximity between the CDots and the generation sites of H 2O 2(achieved in the composite CDots-C 3N 4structure)is nec-essary for the CDots to decompose H 2O 2and generate O 2.We further verified that the detected O 2was indeed generated by water splitting.When we used H 218O as reagent under the same water-splitting conditions described earlier,18O 2(mass 36)was the only product detected by GC-MS (gas chromatography –mass spectrometry).We next measured the QE of overall water splitting by CDots-C 3N 4as a function of the incident light wavelength l 0(Fig.3B).QE decreased with in-creasing wavelength,and the longest wavelength capable of inducing water-splitting coincided with the red absorption edge of the CDots-C 3N 4com-posite,suggesting the reaction proceeds via pho-toabsorption by the catalyst.We proceeded to optimize the catalyst composition by measuring QE for different concentrations of CDots in a fixed mass of composite (Fig.3C).With increasing CDots concentration,the QE increased to a max-imum value of 16%around 4.8×10−3g CDots /g catalyst ,after which it decreased upon addition of more CDots.Next,we optimized the amount of composite catalyst added to water at the op-timum CDots/C 3N 4ratio of 4.8×10−3g CDots /g catalyst (Fig.3D).We found that the QE increased to a maximum value of 16%as the catalyst wasadded,and then stayed the same upon further addition.We interpret the dependence of QE on CDots concentration to an enhancement of the decom-position rate of H 2O 2until the rate is sufficient to remove all the generated H 2O 2(by the photo-catalytic effect of C 3N 4).Afterward,further in-crease of the CDots concentration could enhance the light absorption by introducing subband states,thus raising the QE to a maximum,after which addition of more CDots seems to increase energy losses (light absorbed in CDots and not in C 3N 4,e –/h +recombination,lower catalytic ef-ficiency of C 3N 4due to CDots,etc.),thus decreas-ing the QE.On the other hand,the initial increase (Fig.3D)of the composite catalyst load (keeping the CDots concentration constant)increases the generation rate of H 2(more catalyst →more light absorbance)until reaching a maximum.Addi-tional increase of the composite CDots-C 3N 4load cannot further increase the light absorb-ance (all incident light is absorbed),so that theQE remains unchanged (Fig.3D).We believe that the large values of QE obtained by the CDots-C 3N 4composite relate to the highly porous struc-ture of the C 3N 4grains (resulting from the preparation method of the catalyst),which yields a large water-catalyst interface area [97m 2/g as measured by the Brunauer-Emmett-Teller (BET)method].Our further studies systematically confirmed that water-splitting photocatalysis by CDots-C 3N 4indeed proceeds via the stepwise 2e –/2e –two-step process,in which H 2O oxidation to H 2O 2is the first and rate-limiting step,fol-lowed by the second and fast step of H 2O 2dispro-portionation to O 2,which is chemically catalyzed by CDots (detailed experiments and analysis are given in the supplementary material).The experiments above focused on catalytic properties at l =420nm;however,solar water splitting in the vicinity of the solar spectrum peak (l =550to 650nm)region is more relevant to efficient harvesting of solar energy.The QE of the standard CDots-C 3N 4catalyst (i.e.,CDots con-centration of 1.6×10−5g CDots /g catalyst ,catalyst load 0.53g/liter)at l =580nm was relatively low97227FEBRUARY 2015•VOL 347ISSUE 6225 SCIENCEFig.3.Photocatalytic water-splitting performance of the composite catalyst.(A )T ypical time course of H 2and O 2production from water under visible light irradiation (by a 300-W Xe lamp using a long-pass cutoff filter allowing l >420nm)catalyzed by CDots-C 3N 4(CDots concentration,1.6×10−5g CDots /g catalyst ).(B )Wavelength-dependent QE (red dots)of water splitting by CDots-C 3N 4(irradiated by a 300-W Xe lamp using a bandpass filter of l T 20nm for 420,460,500,540,and 630nm;a bandpass filter of l T 15nm for 580nm;a bandpass filter of l T 10nm for 600nm;a bandpass filter of l T 30nm for 650nm;and a long-pass cutoff filter for l >700nm).The UV-vis absorption spectrum (black)of the CDots-C 3N 4catalyst is superimposed for comparison.The data were derived using a nonoptimized CDots-C 3N 4catalyst (CDots concentration,1.6×10−5g CDots /g catalyst ).(C )QE for different concentrations of CDots (g CDots /g catalyst )in a fixed mass of composite catalyst.Experimental conditions:0.080g of catalyst,150ml of ultrapure water,300-W Xe lamp irradiation for 24hours with a 420T 20nm bandpass filter.The inset shows an enlarged curve of the low CDots concentration in the region marked in the figure.(D )QE for different catalyst loads with a constant CDots concentration of 4.8×10−3g CDots /g catalyst )in 150ml of ultrapure water.The experiments were carried out under the same light irradiation conditions as in (C).For (B),the horizontal bars indicate the width of the wavelength band of the filters used.For (C)and (D),the vertical error bars indicate the maximum and minimum values obtained;the dot represents the average value.RESEARCH |REPORTS(~0.3%).Upon optimization,we succeeded in pre-paring catalysts with a high QE =16%at l =420T 20nm by increasing the quantity of CDots in the C 3N 4.The higher CDots concentration and the associated larger total C fraction in the composite (Fig.4A)concurrently increased the absorbance in the solar spectrum peak region (black versus red curve in Fig.4B).This is most likely due to the effect of C addition leading to the formation of more subband states in the band gap.Figure 4C shows that the H 2generation rate at our standard conditions (80mg of catalyst in 150ml of water;300-W Xe light radiation with a long-pass cutoff filter allowing l >420nm)increased by a factor of 5.4for CDots-C 3N 4with a higher CDots concen-tration.The QE of the catalyst with the optimum amount of CDots (4.8×10−3g CDots /g catalyst )remark-ably increased (Fig.4D,black)relative to the QE of the catalyst with a CDots concentration of 1.6×10−5g CDots /g catalyst (Fig.4D,red).It reached 6.29%at l =580T 15nm (20times the QE for the 1.6×10−5g CDots /g catalyst catalyst)and 4.42%at l =600T 10nm.For irradiation wavelengths l >650nm,both cat-alyst systems showed zero QE (Fig.4D).The solar energy conversion was evaluated in the following studies by using an AM 1.5G (air mass 1.5global conditions)solar simula-tor asthe light source (see fig.S10for ~output spectral distribution)and CDots-C 3N 4(4.8×10−3g CDots /g catalyst )as the catalyst (80mg catalyst in 150ml of water).After 6hours of illumination,the total incident power over the irradiation area of 9cm 2was 0.63W,so that the total input energy was 1.36×104J.During the photocatalytic reaction,1150m mol of H 2was detected by GC,which indicated that the energy generated by water splitting is E F =274J.The STH value of CDots-C 3N 4with the higher concen-tration of CDots was determined to be 2.0%,which is at least one order of magnitude larger than pre-viously reported values (40,41).Indeed,the STH values were very low (0.3%for 1.6×10−5g CDots/g catalyst )for low CDots concentration and reached 2%only at the optimum CDots con-centration (fig.S11).An independent alternative STH calculation based on the CDots-C 3N 4(4.8×10−3g CDots /g catalyst )QE curve (Fig.4D,black curve)and the spectral irradiance of the AM 1.5G solar simulator (fig.S10)was also carried out,yielding a STH value of 1.78%,in good agreement (89%)with the direct solar simu-lator value of 2%(see supplementary material for detailed calculations).A recent work (40)claimed a STH efficiency of 5.1%for CoO nanoparticles,but the catalyst sys-tem was unstable and corroded after 1hour ofoperation.In striking contrast,the CDots-C 3N 4composite of 1.6×10−5g CDots /g catalyst exhibited long-term stability of at least 200days for a cat-alyst dried and reused 200times (Fig.3A),whereas the catalyst with the larger CDots concentration of 4.8×10−3g CDots /g catalyst has shown no obvious de-cay of QE after 501-day cycles of reuse (fig.S12).The stability of the CDots-C 3N 4catalyst system was further studied from several different vantage points:(i)the structural stability of the catalyst over time,(ii)the catalytic functionality (gener-ation rate of H 2and O 2)over time,(iii)the mass loss or gain after long-term operation,and (iv)the gases released during operation (to detect possi-ble degradation by-products).These factors were probed for two CDots concentrations (1.6×10−5and 4.8×10−3g CDots /g catalyst )and two catalyst loads (80mg/150ml and 10mg/150ml).All pho-tocatalytic water-splitting experiments conducted under different conditions for a variety of reac-tion times manifested the same H 2and O 2gen-eration rates and QEs,within experimental error (Fig.3A and figs.S12to S15).These different ex-periments included (i)45days of continuous operation (figs.S13and S14),(ii)200cycles of 24hours each (Fig.3A),(iii)50cycles of 24hours each (fig.S12),and (iv)15cycles of 24hours (fig.S15).Raman,FTIR,and XPS spectra (figs.S16to S18)of CDots-C 3N 4catalysts before and after 5024-hour cycled reactions show no obvious differ-ences,confirming the structural stability of the CDots-C 3N 4catalyst under water-splitting condi-tions.No CO 2or N 2gas could be detected in the reaction system by GC,which suggests that the CDots-C 3N 4catalyst is stable and did not decom-pose during the photocatalytic process.There was only negligible mass loss or gain in all the exper-iments in which the catalyst was weighed before and after use (tables S1and S2).A recent U.S.Department of Energy (DOE)–solicited technoeconomical analysis of H 2gener-ation by solar water splitting (3)suggested that PC systems with STH =5%(not far away from the 2%efficiency reported above)would allow a H 2production cost of $2.30/kg,which meets the DOE target of $2to $4/kg H 2.The cheapest PE configuration with STH =10%,in compar-ison,allows a H 2production cost of $5.60/kg H 2,more than twice the cost of the PC system (although the efficiency of the PE system is twice the efficiency of the PC system).The present PC catalyst thus offers a simpler and cheaper approach to extract H 2from water in large scale.The main disadvantage of PC systems is the generation of a potentially explosive gas mixture of oxygen and hydrogen,which requires sep-aration to ensure safety.Modern industrial tech-nology offers a variety of mature methods for realization of large-scale hydrogen separation and extraction from other gases (nitrogen,argon,oxygen).This point is considered and is part of the above H 2production cost evaluation of the DOE-solicited work.The separation systems eval-uated (3)include pressure swing adsorption (PSA),temperature swing adsorption (TSA),palla-dium membrane separation,nanoporous mem-brane separation,and electrochemical pumps (42).SCIENCE 27FEBRUARY 2015•VOL 347ISSUE 6225973Fig.4.Catalyst optimization for longer-wavelength absorption.(A )Ratio of nitrogen to carbon (N:C)for different concentrations of CDots (g CDots /g catalyst )in the composite catalyst from the average value of the EDS test.(B )Wavelength-dependent absorbance and derived T auc plots of two different concentrations of CDots in the CDots-C 3N 4composite (red:1.6×10−5g CDots /g catalyst ;black:4.8×10−3g CDots /g catalyst ).(C )H 2generation rate from composites with two different concentrations of CDots (300-W Xe lamp,l >420nm),showing considerable rate increase for higher CDots concentration.(D )Wavelength-dependent QE of water splitting by catalysts with two different concentrations of CDots applying several bandpass filters (for l <680nm).A long-pass cutoff filter was used to attain l >700nm light from a 300-W Xe lamp.For (A)and (C),the vertical error bars indicate the maximum and minimum values obtained;the dot represents the average value.For (D),the horizontal bars indicate the width of the wavelength band of the filters used.RESEARCH |REPORTSThe active wavelength region of CDots-C 3N 4,l <620nm,would allow a theoretical STH efficiency of ~15%for sunlight (AM 1.5G),which thus leaves substantial room for technical optimization.Our catalyst is also mildly active for the overall sea-water photocatalytic ing CDots-C 3N 4(4.8×10−3g CDots /g catalyst )in seawater,we obtained QE (420nm)of 3.86%and STH =0.45%(fig.S19).This is a preliminary result,and future studies should probe the reason for the reduction of water-splitting efficiency of sea water versus pure water [QE (420nm)=16%,STH =2%].We have shown that CDots-C 3N 4composites can be made of low-cost,environmentally benign materials and can split water into H 2and O 2with QEs of 16%for l =420T 20nm and 6.3%for l =580T 15nm.The 2.0%STH efficiency obtained is at least one order of magnitude larger than that previously reported for any stable water-splitting photocatalysts (41).It is close to 5%STH,which allows achievement of the DOE price target for H 2generation.In contrast to the conventional one-step four-electron reaction,CDots-C 3N 4cat-alyzes water splitting to hydrogen and oxygen via the stepwise two-electron/two-electron two-step pathway under visible light irradiation.C 3N 4is re-sponsible for the first step (photocatalysis),and CDots are responsible for the second step (chem-ical catalysis).CDots also increase the light absorb-ance and thus the values of QE and STH.The composite nature of the catalyst provides suffi-cient proximity between the H 2O 2generation sites on the C 3N 4surface and the Cdots so that H 2O 2decomposition and O 2generation in the second stage become efficient.Moreover,CDots-C 3N 4maintains a high rate of hydrogen and oxygen production (for l >420nm)with robust stability in 200runs of recycling use over 200days.The results demonstrate CDots-C 3N 4as a highly ef-ficient and stable photocatalyst for visible light –driven water splitting.REFERENCES AND NOTES1. 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A.Kudo,Y.Miseki,Chem.Soc.Rev.38,253–278(2009).10.W.J.Youngblood,S.H.A.Lee,K.Maeda,T.E.Mallouk,Acc.Chem.Res.42,1966–1973(2009).11.K.Maeda,K.Domen,J.Phys.Chem.Lett.1,2655–2661(2010).12.X.Chen,S.Shen,L.Guo,S.S.Mao,Chem.Rev.110,6503–6570(2010).13.K.Maeda,ACS Catal.3,1486–1503(2013).14.K.Maeda et al .,J.Phys.Chem.B 110,13753–13758(2006).15.K.Maeda et al .,Nature 440,295(2006).16.V.Balzani,A.Credi,M.Venturi,ChemSusChem 1,26–58(2008).17.H.B.Gray,Nat.Chem.1,7(2009).18.I.Tsuji,H.Kato,A.Kudo,Angew.Chem.Int.Ed.44,3565–3568(2005).19.J.Liu,Y.Zhang,L.Lu,G.Wu,W.Chen,mun.48,8826–8828(2012).20.F.Rappaport,M.Guergova-Kuras,P.J.Nixon,B.A.Diner,vergne,Biochemistry 41,8518–8527(2002).21.G.Ananyev,G.C.Dismukes,Photosynth.Res.84,355–365(2005).22.D.J.Martin,P.J.Reardon,S.J.Moniz,J.Tang,J.Am.Chem.Soc.136,12568–12571(2014).23.F.He et al .,ACS Appl.Mater.Interfaces 6,7171–7179(2014).24.X.Zhang et al .,ACS Catal.4,162–170(2014).25.K.Schwinghammer et al .,J.Am.Chem.Soc.136,1730–1733(2014).26.R.Marschall,Adv.Mater.24,2421–2440(2014).27.J.Liebig,Ann.Pharm.10,10(1834).28.S.Yin,Y.Aita,M.Komatsu,T.Sato,J.Eur.Ceram.Soc.26,2735–2742(2006).29.X.Wang et al .,Nat.Mater.8,76–80(2009).30.B.Chai,T.Peng,J.Mao,K.Li,L.Zan,Phys.Chem.Chem.Phys.14,16745–16752(2012).31.J.Hong,Y.Wang,Y.Wang,W.Zhang,R.Xu,ChemSusChem 6,2263–2268(2013).32.Q.J.Xiang,J.G.Yu,M.Jaroniec,J.Phys.Chem.C 115,7355–7363(2011).33.A.Suryawanshi et al .,Int.J.Hydrogen Energy 37,9584–9589(2012).34.S.Yang et al .,Adv.Mater.25,2452–2456(2013).35.L.Yu et al .,Phys.Chem.Chem.Phys.16,4106–4114(2014).36.H.T.Li,Z.H.Kang,Y.Liu,S.T.Lee,J.Mater.Chem.22,24230–24253(2012).37.H.Ming et al .,Dalton Trans.41,9526–9531(2012).38.X.Wang et al .,J.Am.Chem.Soc.131,1680–1681(2009).39.M.Yang,Q.Huang,X.Q.Jin,Mater.Sci.Eng.B 177,600–60540.L.Liao et al .,Nat.Nanotechnol.9,69–73(2014).41.S.Mubeen et al .,Nat.Nanotechnol.8,247–251(2013).42.R.W.Baker,Ind.Eng.Chem.Res.41,1393–1411(2002).ACKNOWLEDGMENTSWe thank A.Rothschild for helpful discussions.We thank Beijing and Shanghai synchrotron radiation facility for XANES and EXAFS data collection.Supported by Collaborative Innovation Center of Suzhou Nano Science and Technology,the National Basic Research Program of China (973Program)(2012CB825803,2013CB932702),the National Natural Science Foundation of China (51422207,51132006,21471106),the Specialized Research Fund for the Doctoral Program of Higher Education (20123201110018),a Suzhou Planning Project of Science and Technology (ZXG2012028),and a project funded by the Priority Academic ProgramDevelopment of Jiangsu Higher Education Institutions (PAPD).SUPPLEMENTARY MATERIALS/content/347/6225/970/suppl/DC1Materials and Methods Figs.S1to S36Tables S1to S3References (43–54)17November 2014;accepted 26January 2015fundamental topic in astrophysical,space,and laboratory plasma research.Very high-energy particles are commonly found in astrophysical and planetary shocks (1–3)and in the energy releases of solar flares and terrestrial substorms (4–7).Collisionless shock waves and magnetic reconnection,respectively,have been considered to be the ultimate plasma energization mechanisms responsible for rela-tivistic particles found in such phenomena.Al-though ions can be energized efficiently duringin a localized region must be invoked to explain the observed electron heating and acceleration (8–11).In this Report,we show that efficient elec-tron energization can occur during turbulent magnetic reconnection that arises over an entire region of a strong shock wave.Magnetized collisionless shocks are charac-terized by the Alfvén Mach number M A ,which is the ratio of the flow speed to the Alfvén speed.When the Alfvén Mach number becomes larger than a critical value (M A *∼3),the upstream (low-entropy)plasma cannot be fully dissipated across the shock (12).In such supercritical collisionless shocks,ions are partly reflected by the shock front and then counterflow in the upstream region.The motion of these particles serves to dissipate the plasma further by exciting multiple kinetic instabilities (13).The reflected ions are the key97427FEBRUARY 2015•VOL 347ISSUE 6225 SCIENCE1Department of Physics,Chiba University 1-33Yayoi-cho,Inage-ku,Chiba 263-8522,Japan.2Department of Earth and Planetary Science,The University of Tokyo,7-3-1Hongo,Bunkyo-ku,Tokyo 113-0033,Japan.3Center for Computational Astrophysics,National Astronomical Observatory of Japan,2-21-1Osawa,Mitaka,Tokyo 181-8588,Japan.*Corresponding author.E-mail:ymatumot@chiba-u.jpRESEARCH |REPORTS。
光解水催化剂
无机层状化合物
光生物催化反应体系
PART 3
提高光催化剂性能的途径
主要问题Βιβλιοθήκη 能量转化效 率低可见光利用 率低
易发生逆反 应
催化剂易发 生光腐蚀
提高光催化剂性能的途径
离子 掺杂 掺杂过渡金属离子，使晶体结构发生畸变，产生离子缺陷，成为载流 子的捕获阱，延长其寿命，提高了光生电子-空穴对的分离效果，同 时，过渡金属离子在半导体光催化剂能带中形成杂质能级，缩小了带 隙宽度，从而增大响应波长，使其在可见光区发生激发
PART 2
光解水制氢的催化材料
催化材料
TiO2
良好的化学稳定性，抗磨损性， 低成本和无毒 晶粒尺寸大，比表面积小以及 低分散性等缺点，仅能吸收占 太阳光总能3%~5%的紫外线
联吡啶金属配合物
这类催化剂表现出较强的可见 光吸收，氧化还原可逆，氧化 态稳定性高，是性能优越的光 敏化染料
金属氧化物、硫化物和氮氧化物 廉价易得，效率高，对可 见光有良好吸收和响应
途径
燃料 光敏 化
在可见光下，光活性物质吸附于光催化剂表面有较大的激发因子， 利用这个特性，只要活性物质激发态电势比半导体导带电势更负， 就有可能将光生电子输送到半导体材料的导带上，从而扩大激发波 长范围，增加光催化反应的效率
外场 耦合
通过热场、电场、微波场、超声波场等外场与光场的耦合效应，可 以提高光催化剂的活性。热场通过提高反应体系温度增大反应速率
THANKS!
cloud-based architecture for applications and network functions, the underlying network connectivity
表面螯 合及衍 生作用
Ys＋掺杂Ti02光催化降解亚甲基蓝
Ys＋掺杂Ti02光催化降解亚甲基蓝王建;陈芳【摘要】以Y3＋掺杂二氧化钛为光催化剂，以亚甲基蓝为模拟印染废水进行光催化降解实验，考察了催化剂用量、溶液初始pH值、溶液初始浓度、反应时问等因素对降解反应的影响，结果表明：当催化剂的用量为1。
5g/L，亚甲基蓝洛液pH 值为9．0、初始浓度为20mg／L，反应60rain后，其降解效果最佳。
%y3＋doping titanium dioxide as photocatalyst, methylene blue as simulated printing and dyeing wastewater for photocatalytic degradation experiment, surveying the influence of catalyst dosage, initial pH value, initial concentration, reaction time factors on the degradation reaction, the results show that when the amount of catalyst is 1.5 g/L, pH value is 9.0, the initial concentration is 20 mg/L, react for 60 min, the degradation effect is best.【期刊名称】《上海化工》【年(卷),期】2012(037)003【总页数】3页(P1-3)【关键词】二氧化钛光催化降解亚甲基蓝【作者】王建;陈芳【作者单位】湖北师范学院文理学院湖北黄石435003;湖北师范学院化学与环境工程学院湖北黄石435002【正文语种】中文【中图分类】TQ134.11印染行业是最大的水资源消耗产业之一，据不完全统计，每年大约有 6亿～7亿t 印染废水排入环境中，主要来源于染料及染料中间体生产行业。
光触媒介绍
光触媒介绍产品简介：光触媒[Photocatalyst]是光[Photo=Light]+触媒（催化剂）[catalyst]的合成词。
光触媒是一种以纳米级二氧化钛为代表的具有光催化功能的光半导体材料的总称，是当前国际上治理室内环境污染的最理想材料。
光触媒在光的照射下，会产生类似光合作用的光催化反应，产生出氧化能力极强的自由氢氧基和活性氧，具有很强的光氧化还原功能，可氧化分解各种有机化合物和部分无机物，能破坏细菌的细胞膜和固化病毒的蛋白质，可杀灭细菌和分解有机污染物，把有机污染物分解成无污染的水（H2O）和二氧化碳（CO2），因而具有极强的杀菌、除臭、防霉、防污自洁、净化空气功能。
光触媒的特性为利用空气中的氧分子及水分子将所接触的有机物转换为二氧化碳跟水，自身不起变化，却可以促进化学反应的物质，理论上有效期非常长久，维护费用低。
同时，二氧化钛本身无毒无害，已广泛用于食品、医药、化妆品等各种领域。
反应机理：当纳米级二氧化钛超微粒子接受波长为388 nm以下的紫外线照射时，其内部由于吸收光能而激发产生电子·空穴对，即光生载流子，然后迅速迁移到其表面并激活被吸附的氧和水分，产生活性自由氢氧基(·OH)和活性氧(·O )，当污染物以及细菌吸附其表面时，就会发生链式降解反应。
功能：–净化空气家居或办公楼的家私、装修使用的油漆及木地板等建筑材料以及汽车的内饰材料均会产生大量的有毒气体，使用光触媒可以迅速分解空气中的甲醛、苯、氨及挥发性有机化合物(TVOC)等污染物，从而达到净化空气的效果。
–抗菌防霉对大肠杆菌、金黄色葡萄球菌、铜绿假单胞菌、肺炎克雷伯氏菌等细菌具有极强的杀伤力，光触媒的杀菌能力高达99.99 %，并能有效地抑制肠病毒、流行性感冒、滤过性病毒等病原的传播。
物体发霉是由于滋生霉菌的关系，使用光触媒可以轻易分解霉菌，解决物体发霉的问题。
–抗污除臭使用光触媒可强力分解臭源，加快有机物质、有毒气体的分解，提高空气净化效率。
光解水催化剂课件
提高光催化剂性能的途径
金属负 载
光照产生的电子和空穴分别定域在贵金属和半导体光催化剂 上并发生分离，抑制了电子和空穴的再复合，从而大大提高 了光催化剂的活性和选择性。
途径
复合半 导体
表面螯 合及衍 生作用
复合具有Co不re同In能fo带结构的半导体，利用窄带隙的半导体敏化 宽T带o fu隙lly r的eali半ze th导e p体oten，tial可of a以提高宽带隙半导体的催化活性
热场通过提高反应体系温度增大反应速率在可见光下光活性物质吸附于光催化剂表面有较大的激发因子利用这个特性只要活性物质激发态电势比半导体导带电势更负就有可能将光生电子输送到半导体材料的导带上从而扩大激发波长范围增加光催化反应的效率掺杂过渡金属离子使晶体结构发生畸变产生离子缺陷成为载流子的捕获阱延长其寿命提高了光生电子空穴对的分离效果同时过渡金属离子在半导体光催化剂能带中形成杂质能级缩小了带隙宽度从而增大响应波长使其在可见光区发生激发途径离子掺杂燃料光敏提高光催化剂性能的途径外场耦合fullyrealizecloudbasedarchitecturenetworkfunctionsunderlyingnetworkconnectivitycoreinfo提高光催化剂性能的途径途径光照产生的电子和空穴分别定域在贵金属和半导体光催化剂上并发生分离抑制了电子和空穴的再复合从而大大提高了光催化剂的活性和选择性
PART 2
光解水制氢的催化材料
催化材料
TiO2
联吡啶金属配合物
良好的化学稳定性，抗磨损性， 低成本和无毒 晶粒尺寸大，比表面积小以及 低分散性等缺点，仅能吸收占 太阳光总能3%~5%的紫外线
这类催化剂表现出较强的可见 光吸收，氧化还原可逆，氧化 态稳定性高，是性能优越的光 敏化染料
The Mechanism of Photocatalytic Water Splitting
The Mechanism of Photocatalytic WaterSplitting随着环保意识和可持续发展理念的深入人心，能源与环境问题日益成为全球关注的焦点。
太阳能是一种广泛可利用的清洁能源，但其依赖于昼夜的交替和天气的变化，因此，在太阳能转化和存储方面的研究仍然具有重要意义。
将太阳能转化为氢气是一种先进的储氢技术，也是解决能源和环境问题的有效途径之一。
然而，纯太阳能照射到光催化材料上是无法发生水的分解的，需要通过催化剂来实现。
因此，本文主要探讨光催化水分解的机理。
一、介绍光催化水分解是指利用光催化材料将水分解成氢和氧气的过程。
光催化水分解的机理涉及光电化学和表面化学等多个学科的知识。
其中，光电化学反应是指利用光能激发电子从材料表面跃迁至导带，形成电荷对并导致化学反应发生的过程。
表面化学反应则是指分子在固体表面上的吸附、反应和解离等过程。
二、机理1. 光电化学反应在光照射下，光催化材料的电子受光的能量激发跃迁至导带，形成自由电子和空穴。
如图1所示，半导体TiO2的导带最高点（conduction band，CB）和价带最低点（valence band，VB）之间存在带隙，激光照射可以提供足够的光能使价带上的电子跃迁至导带上，形成自由电子；同时，价带上的空穴也会被光子激发至价带上，形成空穴。
因此，在光照射下，导带上的自由电子和价带上的空穴被激发而产生。
图1. TiO2的带结构示意图2. 内部传输在自由电子和空穴被激发后，它们在材料内部发生传输，直至到达材料的表面。
一般而言，电子和空穴具有不同速度的传输，但总的来看，它们都具有一定的活性，可以在材料中传输一定的距离。
3. 表面化学反应自由电子和空穴到达材料表面后，它们会发生表面化学反应。
如图2所示，当光催化材料表面吸附水分子时，水分子会被部分离解为氢离子和氧离子。
然后，自由电子和水分子形成氢离子和氢氧离子，空穴和水分子形成氧离子和氢离子。
光解水制氢 无机半导体
光解水制氢无机半导体英文回答：Water splitting for hydrogen production using inorganic semiconductors is a promising approach for sustainable energy generation. This process, known as photocatalytic water splitting, involves the use of light energy to drive the chemical reaction that separates water into hydrogenand oxygen. Inorganic semiconductors, such as metal oxidesor sulfides, are used as photocatalysts to facilitate this reaction.One example of an inorganic semiconductor used for photocatalytic water splitting is titanium dioxide (TiO2). TiO2 is a widely studied material due to its excellent stability, low cost, and high efficiency in convertingsolar energy into chemical energy. When TiO2 is exposed to light, it absorbs photons and generates electron-hole pairs. The excited electrons and holes can then participate in redox reactions with water molecules, producing hydrogenand oxygen.Another example is bismuth vanadate (BiVO4), which has attracted significant attention as a potential photocatalyst for water splitting. BiVO4 has a suitable bandgap that allows it to absorb visible light, making it more efficient in utilizing solar energy compared to TiO2. By harnessing the power of sunlight, BiVO4 can generate electron-hole pairs and facilitate the water splitting reaction.In addition to these inorganic semiconductors, there are also efforts to develop hybrid materials that combine the advantages of different components. For example, combining a metal oxide semiconductor with a molecular catalyst can enhance the efficiency and selectivity of the water splitting process. These hybrid materials can provide better charge separation and facilitate the transfer of electrons and holes to the catalytic sites.While photocatalytic water splitting using inorganic semiconductors holds great potential, there are stillchallenges that need to be addressed. One challenge is improving the overall efficiency of the process. Researchers are exploring various strategies, such asdoping the semiconductors with different elements or modifying their surface structures, to enhance their photocatalytic activity. Another challenge is the stability of the photocatalysts, as they can degrade over time due to exposure to harsh reaction conditions. Developing stableand durable materials is crucial for the practical application of photocatalytic water splitting.中文回答：光解水制氢是使用无机半导体制备可持续能源的一种有前景的方法。
Photocatalysis. A multi-faceted concept for green chemistry中文PPT
②CdS光催化作用下，起始物质L-赖 氨酸(5)经过大量的外消旋作用，以及 一个脱氨基-N-环化过程，以较低产率 生成哌啶-2-羧酸(6)。但是，让催化剂 CdS结合少量（＜0.3wt%）Pt或PtO2， 则转换率可提高约2.5倍。
光催化合成
1、光致氧化反应 2、深入氧化生成 C-X和C-N键 3、光致还原作用 4、C-C键的形成
光催化合成
1、光致氧化反应
光致氧化反应： 基于光催化技术，用O2取代有害金属氧化剂，以提高经济效益和环境效益。
①TiO2(锐钛矿)是氧化1-苯基乙醇的有效催化剂，先将 1-苯基乙醇置于干燥乙腈中，然后缓慢通入氧气流对其 进行氧化(示意图右，下)。 ②使用了二氧化硅包被的H3PW12O40，作为可循环利用 的多相光催化剂，进行相关实验(右图，上) 。
B)
C) 通过制备固溶体控制导/价带结构。 所形成的新的导/价带电位，必须符合 H2O的氧化/还原电位，并且催化剂必 须有良好的催化性能。 举例：可见光下，用Y2WO6和Bi2WO6 间的固溶体BiYWO6(BYW)充当光催化 剂，可彻底地分解水。其中Bi(6s)和 Y(4d)轨道分别提供了新的VB和CB，带 隙为2.71eV
05
总实验研究到商业开发 的过程。纵观近期的文献，得知从2000年开始，每年会有 多于1300项（1990年前只有十分之一）关于光催化的国际 性专利发表。重点关注了基于TiO2的污染控制研究。 前面所陈述的各类反应，都基于反应过程中生成的高活性物 质C* ，用于水解制氢、化学合成、污染去除。
光触媒知识
什么是光触媒光触媒[Photocatalyst]是光 [Photo=Light] + 触媒(催化剂)[catalyst]的合成词。
主要成分是二氧化钛（TiO2），二氧化钛本身无毒无害，已广泛用于食品，医药，化妆品等各种领域。
光触媒在光的照射下会产生类似光合作用的光催化反应(氧化坊乖 从?,产生出氧化能力极强的自由氢氧基和活性氧，这些产物可杀灭细菌和分解有机污染物。
并且把有机污染物分解成无污染的水(H2O)和二氧化碳(CO2),同时它具有杀菌、除臭、防污、亲水、防紫外线等功能。
光触媒在微弱的光线下也能做反应，若在紫外线的照射下，光触媒的活性会加强。
近来,光触媒被誉为未来产业之一的纳米技术产品。
光触媒反应原理TiO2光触媒当吸收光能量之后，价带中的电子就会被激发到导带，形成带负电的高活性电子e-,同时在价带上产生带正电的空穴h+。
在电场的作用下，电子与空穴发生分离，迁移到粒子表面的不同位置。
热力学理论表明，分布在表面的h+可以将吸附在TiO2表面OH-和H2O分子氧化成(.OH)自由基,而.OH自由基的氧化能力是水体中存在的氧化剂中最强的，能氧化并分解各种有机污染物（甲醛、苯、TVOC等）和细菌及部分无机污染物（氨、NOX等），并将最终降解为CO2、H2O等无害物质。
由于.OH自由基对反应物几乎无选择性，因而在光催化中起着决定性的作用。
此外，许多有机物的氧化电位较TiO2的价带电位更负一些，能直接为h+所氧化。
而TiO2表面高活性的e-侧具有很强的还原能力，可以还原去除水体中金属离子。
应用以上原理光触媒广泛应用于杀菌、除臭、空气净化、污水处理等领域。
光触媒历史1970年初,Fujishima和Honda在实验中发现TiO2单结晶电极在受到光的照射后能够产生光氧化反应和光还原反应,并将水分解成氢和氧,之后此项研究继续发展至今。
光触媒实际应用到各项领域是在最近几年，并得到迅猛地发展。
以石墨相氮化碳为基础的聚合物光催化剂(4)
以石墨相氮化碳为基础的聚合物光催化剂摘要半导体光催化是一种很吸引大家研究兴趣的方法来解决全世界范围内的能源紧缺和环境污染问题。
自从石墨相C3N4在2009年被用于可见光光催化分解水以来，C3N4光催化已经成为一个非常热门的研究话题。
这篇综述总结了C3N4设计制备方面的一些研究进展，也对其在能源和环境方面的应用做了一个全面的概述。
Polymeric Photocatalysts Based on Graphitic Carbon Nitride Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C 3 N 4 ) for visible-light photocatalytic water splitting, g-C 3 N 4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C 3 N 4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C 3 N 4 , bandgap engineering through atomic-level doping and molecular-level modifi cation, and the preparation of g-C 3 N 4 -based semiconductor composites. Also, the photocatalytic applications of g-C 3 N 4 -based photocatalysts in the fi elds of water splitting, CO 2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, andZ-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C 3 N 4 -based photocatalysts are highlighted.以石墨相氮化碳为基础的聚合物光催化剂1.引言日益严重的能源短缺和环境危机问题正成为人类社会长期发展的严重威胁。
Water splitting by photocatalytic materials
Water splitting by photocatalyticmaterials随着人们对可再生能源的需求日益增长，光催化材料逐渐成为人们关注的焦点。
光催化材料可以利用太阳光等能源，在光照的作用下促进水的分解，产生氧气和氢气，以实现水的可持续利用。
这种技术被称为水的光解。
水的光解可分为传统光解和光催化光解两种。
传统光解技术采用紫外线、可见光、红外线等不同波长的光源将水分解成氢和氧。
但是，这种方法需要大量的能源，效率低，成本高，而且在实际应用中存在许多困难和限制。
光催化技术则不同，其利用太阳光或其他光源免费提供的能量，通过光催化材料和水的光解反应，从而产生氢和氧。
光催化材料是实现光催化分解的关键。
目前，常用的光催化材料主要有氧化钛、各种半导体材料、复合材料等。
其中，氧化钛是应用最广泛的光催化材料，具有较高的光催化活性、稳定性和低毒性等特点，是当前应用最广泛的光催化材料之一。
此外，一些非氧化钛基材料，如氮化硅、碳化硅和氢化锗等，在光催化中也有着很好的催化效果。
光催化水解的过程是一个复杂的反应。
在水的光解反应中，水分子首先被光催化材料吸附，然后吸收光子能量，进而产生电子-空穴对。
电子和空穴分别负责氢和氧的产生。
准确地说，空穴会促进氧气的产生，而电子则促进氢气的产生。
这个过程如下所示：2H2O + hv → 2H2 + O2其中，hv代表注入光催化材料的光能。
要想有效地光催化水解，光催化材料必须满足一些特定的要求。
首先，光催化材料必须具有较高的光吸收率和光催化活性。
其次，它应该有足够的表面积和晶格结构来增加光反应式的发生机会。
此外，材料应该是稳定的，并能够在长时间的使用中保持其催化性质。
当前，研究光催化材料以实现光解水已经成为了科学研究的重点。
许多科学家正在积极寻找高效、可持续、低成本的光催化材料。
在不断尝试中，他们已经取得了一些重要的成果。
例如，一些团队已经开发出了一种基于氧化钛的复合光催化材料，这种材料不仅能够有效地分解水，还能够将CO2转化为燃料。
光催化水解论文
光催化分解水过程摘要：光催化分解水制氢气是解决能源危机的一条途径，有着巨大的研究潜力。
本文主要从光催化水解的原理，催化剂简介和催化剂制备方法简介来介绍光催化水解的过程。
分析了目前面临的挑战并对未来发展做出展望。
关键词：光催化；水分解；催化剂Process of Photocatalytic Decomposition of WaterAbstract: Photocatalytic decomposition of water is a way to solve the energy crisis which owns a bright future. This article mainly introduce the photocatalytic decomposition of water from the aspect of theory of photocatalytic, catalyst of the photocatalytic and catalysts preparation. And analysis of the challenge and the prospection of the future development also have been done. Key words: photocatalytic; decomposition of water; catalysts引言随着社会的发展，人类对能源的需求越来越高，能源问题将是人类未来必须面对的难题。
而化石燃料储量有限，而经济的高速发展带来的能源的快速消耗迟早会使这些有限的资源消耗殆尽。
同时，人们对使用化石燃料产生的环境污染问题和温室效应越来越关注，寻找可替代的能源，如生物质能、风能和太阳能的呼声越来越高[1]。
人们期望通过提高替代能源，包括生物质能、风能和太阳能在内的可再生能源在整个能源结构中的比例，缓解这种危机和压力。
半导体 SiC 光催化分解水制氢研究进展
半导体 SiC 光催化分解水制氢研究进展杨静静;何勇平;彭媛【摘要】简单介绍了半导体光催化分解水制氢的原理，综述了改变SiC的尺寸形貌、负载石墨烯、负载贵金属、半导体复合等方法对SiC的光催化产氢性能的影响，重点讨论了复合半导体的光催化产氢机理及SiC与其他半导体复合的研究进展，并提出前景展望。
%The basic mechanism of photocatalytic water-splitting to hydrogen over semiconductor photocatalyst was introduced.The methods to enhance hydrogen production were reviewed, including changing its morphology, loading graphene, loading noble metal, combining with semiconductors, and their effects on hydrogen production were discussed.The hydrogen-producing mechanism of compound semiconductor materials and the related research progress were focused on.The foreground was also prospected.【期刊名称】《广州化工》【年(卷),期】2015(000)007【总页数】3页(P34-36)【关键词】碳化硅SiC;光催化;氢气【作者】杨静静;何勇平;彭媛【作者单位】重庆化工职业学院环境与质量检测系，重庆 400020;中国航油集团重庆石油有限公司，重庆 401120;北京科技大学化学与生物工程学院化学系，北京 100083【正文语种】中文【中图分类】TQ426.7能源危机和环境污染是人类社会目前所面临的两大严峻问题，利用太阳能制氢是解决能源和环境问题的最有效途径之一。
光催化水氧化机理 水亲核进攻机理和自由基耦合机理
光催化水氧化机理水亲核进攻机理和自由基耦合机理1.光催化水氧化是一种利用光能将水分子分解为氢和氧的化学反应。
Photocatalytic water oxidation is a chemical reactionthat uses light energy to split water molecules into hydrogen and oxygen.2.水亲核进攻机理是指水分子中的氧原子发生亲核进攻，将光生产的活性中心氧化成氧气。
The water nucleophilic attack mechanism refers to the oxygen atom in water molecules undergoes nucleophilic attack, oxidizing the active center produced by light into oxygen.3.在水亲核进攻机理中，水分子的氧原子与活性中心发生短暂的共价结合，形成氧合物中间体。
In the water nucleophilic attack mechanism, the oxygen atom of water molecules temporarily forms a covalent bondwith the active center, forming an oxo complex intermediate.4.这个氧合物中间体随后分解，释放出氧气并再生活性中心，为光催化水氧化反应提供了动力。
The oxo complex intermediate then decomposes, releasing oxygen and regenerating the active center, providing the driving force for the photocatalytic water oxidation reaction.5.另一种光催化水氧化的机理是自由基耦合，包括单电子转移和氧释放。
光催化分解水制氢催化剂和助催化剂
光催化分解水制氢催化剂和助催化剂下载提示：该文档是本店铺精心编制而成的，希望大家下载后，能够帮助大家解决实际问题。
文档下载后可定制修改，请根据实际需要进行调整和使用，谢谢!本店铺为大家提供各种类型的实用资料，如教育随笔、日记赏析、句子摘抄、古诗大全、经典美文、话题作文、工作总结、词语解析、文案摘录、其他资料等等，想了解不同资料格式和写法，敬请关注!Download tips: This document is carefully compiled by this editor. I hope that after you download it, it can help you solve practical problems. The document can be customized and modified after downloading, please adjust and use it according to actual needs, thank you! In addition, this shop provides you with various types of practical materials, such as educational essays, diary appreciation, sentence excerpts, ancient poems, classic articles, topic composition, work summary, word parsing, copy excerpts, other materials and so on, want to know different data formats and writing methods, please pay attention!：研究与应用摘要：光催化分解水制氢技术作为一种清洁能源的制氢方法，受到了广泛的关注。
太阳能光解水产O2半导体催化剂的研究进展
半导体催化剂的研究进展太阳能光解水产O2专业：应化1402姓名：适盛航学号：5120141979指导教师：雷洪太阳能光解水产O2半导体催化剂的研究进展适盛航（5120141979）（西南科技大学材料科学与工程学院应用化学1402,绵阳621000）摘要：太阳能光解水产O2效率低是目前限制水光解作为新能源运用的主要原因，半导体光催化剂由于其稳定性和简单性近来成为研究热点，因此半导体水氧化催化剂具有很好的研究前景。
概述述了半导体不同的改性方法对光解水产O2效率的影响，并对未来半导体水氧化催化剂发展趋势进行了展望。
关键词：光解水、半导体水氧化催化剂、半导体改性、研究进展、综述The Development of Solar energy photolysis aquatic O2 semiconductor catalystShenghang SHI（5120141979）（Applied chemistry1402 School of materials science and engineering, Southwest University of Science and Technology, Mianyang 621000）Abstract: Solar energy is currently restricted to aquatic O2 low efficiency water solution as the main reason for the new energy use of the semiconductor photocatalyst because of its simplicity and stability has become a hot research topic, so the semiconductor water oxidation catalyst has good prospects, In this paper, the effects of different modification methods on the O2 efficiency of photo degradation of aquatic products were reviewed, and the development trend of semiconductor water oxidation catalysts was also discussed.Keywords:the photolysis of water; semiconductor water oxidation catalysts; emiconductor modification; research progress; review前言随着科技的不断发展，化石能源的消耗日益增大，全球正面临着严重的能源危机，为了解决能源问题开发清洁高效的可持续能源势在必行。
太阳能光解水制氢催化剂研究进展
太阳能光解水制氢催化剂研究进展张建斌;查飞;左国防;唐慧安【期刊名称】《广东化工》【年(卷),期】2011(038)010【摘要】Hydrogen production from water decomposition on photocatalysts with solar energy is an efficient way to transform solar energy to hydrogen energy.Photocatalysts developed in recent years for water decomposition are metal complexes,metal oxide,inorganicla layered compounds,Z-type photocatalytic hydrogen production reaction system,photocatalytic biological reaction system.The following method can improve photocatalytic activities effectively： metal loading,ion doping,composite semiconductor,dye sensitization,electron trapers,surface chelation and derivatives and external field coupling.To discovery new photocatalysts with peculiar construction and without precious metal loading and to recycle sacrificial agent will be the future direction of development.%利用太阳能制氢是将太阳能转换成氢能的有效方式。
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major developing history
metal-free photocatalysts
electron transitions from the valence band populated by N2p orbitals to the conduction band formed by C2p orbitals
This high activity appears to be due to the thin walls of the mesopores, which provide a short distance for the excited electrons and holes to travel to the surface, reducing the probability of electron– hole recombination.
the biggest problem is the back electron transfer
major developing history
development of visible light utilization—Spectralsensitization
slow electron transfer from the nanoparticulate IrO2 catalyst to the oxidized dye which does not compete effectively with back electron transfer from the conduction band of TiO2 to the dye
major developing history
development of visible light utilization
provides a discreet energy level
totally new band
major developing history
development of visible light utilization-valence band control
major developing history
Water splitting through two-step photoexcitation (Z-scheme)
controlling the selectivity for the forward reactions on each photocatalyst
major developing history
special structures—the well-known lamellar particle
major developing history
special structures—perovskites
Cubic Perovskites
Double Perovskites
probably from its unique electronic properties
major developing history
special structures：Ruddlesden–Popper type layered perovskites of A2La2Ti3O10
a series of layered perovskites have AQYs higher than 20% under UV irradiation
[32] T.Takata,K.Shinohara,A.Tanaka,M.Hara,J.N.Kondo,K.Domen,J.Photochem. Photobiol. A: Chem. 10
major developing history
special structures—perovskites: tunnel structured BaTi4O9 and Na2Ti6O9
major developing history
Water splitting through two-step photoexcitation (Z-scheme)
Strategy to improve the photocatalytic activity
Ways to improve photocatalytic activity
Photo-catalysts for water splitting
赵宇 黄子健 王宏宇 2016年11月23日
first discovery and basic principles
First discovered at 1972
initiated by the demonstration of photo-electrochemical (PEC)
A Tradeoff
A small size
increases the density of surface catalytic sites
increase the probability of recombination between photogenerated electrons and holes,
pentagonal prism tunnel
built-in polarization field
[26] Y. Inoue, T. Niiyama, Y. Asai, K. Sato, J. Chem. Soc., Chem. Commun. (1992
major developing history
first discovery and basic principles
test reactions for overall water splitting
first discovery and basic principles
generally to be particles
specific needs that must be met
1、the band gap restriction 2、migrate without recombination 3、inhibit the backward reaction
example: Pt-TiO2 at 1980 with NaOH loaded on the cocatalyst
K. Maeda / Journal of Photochemistry and Photobiology C: Photochemistry Reviews 12 (2
special electronic structures—d10-Type metal oxides MGa2 O4
the poor symmetry of octahedral and tetrahedral coordination tends to lead to the formation of isolated orbitals
local internal fields due to the dipole moment inside the distorted units
major developing history
special electronic structures—d10-Type metal oxides Ga2 O3
full-occupied half-occupied unoccupied band gap CB VB
first discovery and basic principles
semi-ห้องสมุดไป่ตู้onductors are very useful in this area
K. Maeda / Journal of Photochemistry and Photobiology C: Photochemistry Reviews 12 (2
Improving the physicochemical properties of the photocatalyst
Refining cocatalysts
Controlling the reaction conditions
Strategy to improve the photocatalytic activity
major developing history
development of visible light utilization—Spectralsensitization
organic dyes or inorganic narrow-gap semiconductors
energy gap sufficiently small to harvest visible photons excited-state potential that is more negative
special electronic structures—mixed-configuration metal oxides
hybridization of the atomic orbitals of the two metal ions show effect on the density of states and energy dispersion in the conduction bands increase the mobility of photoexcited electrons and holes
well-known as the Honda-Fujishima effect
first discovery and basic principles
energy band theory
different energy levels correspond with different bands