DOI: 10.1002/cctc.201300874

Effect of TiO2 Surface Structure on the HydrogenProduction Activity of the Pt@CuO/TiO2 Photocatalysts forWater SplittingFei Teng,* Mindong Chen, Na Li, Xia Hua, Kai Wang, and Tongguang Xu[a]

Introduction

Since the first report on photoelectrochemical water splittingover the TiO2 electrode,[1, 2] photocatalytic water splitting hasbeen considered to be a promising approach to hydrogen pro-duction. Among various semiconductors, TiO2 is one of themost widely used photocatalysts because of its nontoxicity,low cost, and high chemical stability against photocorro-sion.[3–5] However, the hydrogen production efficiency of TiO2 isfairly low, owing to the facts: (i) the energy levels of the con-duction bands of TiO2 are not negative enough to effectivelyreduce water; (ii) the photogenerated electrons and holes fastrecombine.[4, 5] Hence, many approaches,[3–5] including iondoping, noble metal deposition, dyes sensitization, and semi-conductor coupling, have been developed to overcome thesedisadvantages. Among these, semiconductor coupling isa simple and effective strategy to compensate for the disad-vantages of the individual components.[6, 7] Furthermore, theCuOx/TiO2 composites are reported to have high hydrogen pro-duction activity, in which CuOx could benefit the charge sepa-ration and provide the photocatalytic active sites.[8–22] For ex-ample, Choi et al.[11] and Xu et al.[15] reported that the hydrogenproduction rates could be markedly enhanced by depositingCuO on TiO2. Furthermore, Sreethawong et al.[10] have reportedthat the hydrogen production rate of Cu-loaded TiO2 is doublethat of the Ni-loaded one. Bandara et al.[9] have reported that

under UV-light irradiation, both TiO2 and CuO can be excitedsimultaneously, and the exited electrons can accumulate in theconduction bands of CuO. Because of the accumulation ofelectrons, a negative shift of the Fermi level of CuO couldresult in the required negative overpotential necessary for thereduction of water. To conclude, CuO could be an electrontank and benefits the charge separation. It is noted that forthe composites photocatalysts, the instability or leaching ofthe deposited secondary component is a big challenge in prac-tice and should be focused.

Recently, the anatase TiO2 nanosheets with the high-percent-age {0 0 1} facets exposed have attracted much attention.[23–29]

It has been demonstrated that the {0 0 1} facets of anatase TiO2

is more reactive than the thermodynamically stable {1 0 1}facets for degradation of rhodamine B.[30, 31] Furthermore, it hasalso been reported that water molecules can chemically disso-ciate on the {0 0 1} facets, whereas they can only physicallyadsorb on the {1 0 1} facets.[30] Many researchers have reportedthat the water splitting activity can be enhanced by the ex-posed {0 0 1} facets of anatase TiO2.[32–36] For example, Amanoet al.[32] have reported that the decahedral anatase TiO2 withthe exposed {0 0 1} facets has a higher hydrogen productionrate than Degussa P25 TiO2 under UV light irradiation. Luet al.[33–35] have also reported that the water-splitting photoac-tivity can be enhanced by the exposed {0 0 1} facets of nitro-gen-doped TiO2 nanosheets. To conclude, most of researchesare focused on the activity improvement of photocatalysts. Tothe best of our knowledge, however, almost no comprehensiveresearch reports the surface effect of TiO2 on the stability ofthe composites photocatalysts. It is noted that the stabilities ofthe composite are significantly important for practical applica-tions. Herein, we mainly investigated the recyclability of thePt@CuO/TiO2 photocatalysts with different surface structures.

Herein, we report, for the first time, the effect of the inter-face structure on the recyclability of Pt@CuO/TiO2, as well asthe hydrogen generation activity. In the study, CuO was depos-

CuO/TiO2 composites were prepared by the impregnationmethod, in which TiO2 nanosheets and nanorods are used asthe precursors, respectively. We investigated the effect of theTiO2 surface structure on the activity and recyclability of thephotocatalysts. The hydrogen production activities were testedin a 3 mol L�1 methanol aqueous solution under UV-light irradi-ation. After deposition of Pt, both Pt@CuO/TiO2 samples dis-played higher hydrogen production activities than the Pt/TiO2

samples. The results reveal that the TiO2 sheet-based samplesdisplay higher hydrogen production activities and stabilitythan the TiO2 rod-based ones. It is proposed that a morestable p–n heterojunction form at the interface between CuOand TiO2 nanosheets owing to the strong interaction of CuOwith the {0 0 1} facets of the TiO2 sheets, which significantly re-frains the recombination rate of electrons and holes.

[a] F. Teng, M. Chen, N. Li, X. Hua, K. Wang, T. XuJiangsu Key Laboratory of Atmospheric EnvironmentMonitoring and Pollution ControlInnovative Laboratory of Environment and EnergySchool of Environmental Science and EngineeringNanjing University of Information Science & Technology219 Ningliu Road, Nanjing 210044 (China)Fax: (+ 86) 25-9882-1090E-mail : tfwd@163.com

Supporting information for this article is available on the WWW underhttp://dx.doi.org/10.1002/cctc.201300874.

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ited on TiO2 nanosheets and nanorods with different exposedfacets, respectively. The samples were characterized by X-raydiffractometry (XRD), scanning electron microscopy (SEM),transmission electron microscopy (TEM), X-ray photoelectronspectroscopy (SPS), UV/Vis diffuse reflectance spectroscopy,photoluminescence spectroscopy (PL), and nitrogen sorptionisotherms. The effect of the TiO2 surface structure on the hy-drogen production activity and recyclability of the Pt@CuO/TiO2 composites was mainly studied. A synergetic effect ofCuO/TiO2 P/N heterojunction and Pt@CuO Schottky barrier wasproposed to understand the photocatalytic performances.

Experimental Section

Sample preparation

All reagents were of analytical grade, purchased from BeijingChemical Reagents Industrial Company of China, and were usedwithout further purification.

Preparation of TiO2 nanosheets. The sample was prepared by thehydrothermal method similar to the report by Yu et al.[24] Typically,Ti(OC4H9)4 (25 mL) was mixed with 40 wt % HF solution (3 mL) ina 120 mL Teflon-lined autoclave. Then the mixture system washeated at 180 8C for 24 h. After reaction, the white precipitate wasseparated, washed, and dried at 80 8C overnight. The fluorine ionsadsorbed were removed by washing in a 2 m NaOH solution.[29] Theproduct was obtained by further calcination at 450 8C for 2 h anddenoted S1.

Preparation of TiO2 nanorods. The TiO2 nanorods were prepared byfollowing the reference[37, 38] but with modifications. Typically, tita-nia powder (2 g) was dispersed in 10 mol L�1 KOH solution (80 mL)under intensive stirring. The mixture was loaded into a 120 mLvolume of a Teflon-lined autoclave and heated at 200 8C for 72 h.The white powders were separated by centrifugation, washed with0.1 mol L�1 HNO3 solution, and washed with deionized water untilthe pH reached 7, respectively. The sample was dried at 80 8C over-night. The powders were also calcined at 450 8C for 2 h under airto obtain the product, denoted S2.

Preparation of CuO/TiO2 heterojunctions. The impregnationmethod was used to prepare the CuO/TiO2 samples. Typically, TiO2

powder (0.2 g) was dispersed in 0.001 m Cu(NO3)2 solution (50 mL)under ultrasonic stirring. The products were vaporized, dried in anoven at 80 8C overnight, and annealed at 400 8C for 2 h. Theweight percent of CuO was 2 %. The as-obtained CuO/TiO2 samplesfrom S1 and S2 precursors were denoted S3 and S4, respectively.

Preparation of Pt-loaded catalysts. Typically, under ultrasonic stir-ring, CuO/TiO2 or TiO2 (0.2 g) the was dispersed in 0.1 mg mL�1

H2PtCl6 solution (20 mL). The samples were separated by centrifu-gation and dried in an oven at 80 8C overnight. The Pt-loaded cata-lyst was obtained by annealing at 450 8C for 2 h under a flowing of5 % hydrogen/argon. The loading amounts of Pt were 0.47 % in allthe samples.

Characterization

The crystal structures of the samples were determined by X-raypowder polycrystalline diffractometry (Rigaku D/max-2550VB),using graphite monochromatized CuKa radiation (l= 0.154 nm),operating at 40 kV and 50 mA. The XRD patterns were obtained inthe range of 20–808 (2q) at a scanning rate of 58min�1. The sam-

ples were characterized on a scanning electron microscope (SEM,Hitachi SU-1510) with an acceleration voltage of 15 keV. The sam-ples were coated with a 5 nm-thick gold layer before observations.The fine surface structures of the samples were determined byhigh-resolution transmission electron microscopy (HRTEM) ona JEOL JEM-2100F equipped with an electron diffraction attach-ment with an acceleration voltage of 200 kV. XPS measurementswere done on a VG ESCALAB MKII XPS system with MgKa sourceand a charge neutralizer. All the binding energies were referencedto the C 1s peak at 284.8 eV of the surface adventitious carbon.UV/Vis diffused reflectance spectra of the samples were obtainedby using a UV/Vis spectrophotometer (UV-2550, Shimadzu, Japan).BaSO4 was used as a reflectance standard in a UV/Vis diffuse reflec-tance experiment. PL spectra were measured on a fluorescencespectrophotometer (Japan, Shimadzu RF-5301PC) with the 340 nmexcitation line of a Xe lamp as the excitation source. Nitrogen sorp-tion isotherms were performed at 77 K and <10�4 bar on a Micro-meritics ASAP2010 gas adsorption analyzer. Each sample was de-gassed at 150 8C for 5 h before measurements. Surface area andthe pore size distribution were calculated by the BET and BJHmethods, respectively.

Photocatalytic hydrogen production

The photocatalytic hydrogen production reactions were performedunder UV-light irradiation. The photocatalyst (0.1 g) was placedinto a 200 mL quartz reactor containing 3 mol L�1 methanol aque-ous solution (100 mL). A 500 W high-pressure Xe lamp (BeijingZhongjiaoJinyuan Science Co. Ltd. China) was used as the lightsource (1 cm distance from the photocatalytic reactor). The gasproducts were analyzed by a gas chromatograph (GC-14C witha 5 � molecular sieve column, Shanghai Tianmei Instrument Com-pany), equipped with a thermal conductivity detector (nitrogen asthe carrier gas).

Leaching experiments

Recovered solids after 5 cycles (10 mg) were dispersed in glycerol(20 mL) under ultrasonic stirring. After centrifuging at 500 rpm for1 min, the solids were obtained and analyzed by inductively cou-pled plasma.

Results and Discussion

Crystal and surface structures of the samples

The XRD patterns of samples S1–S4 are shown in Figure 1. ForS1 and S2, the diffraction peaks at 25.38, 37.58, 48.08, 53.88,54.98, 62.58, 68.78, 70.38, and 75.18 can be ascribed to the(1 0 1), (0 0 4), (2 0 0), (1 0 5), (2 11), (2 0 4), (11 6), (2 2 0), and(2 1 5) planes of anatase TiO2 (JCPDS no. 21-1272, space group:I41/amd (1 4 1)), respectively.[36] It is clear that S1 and S2 arethe pure anatase phases. For S3 and S4, besides the diffractionpeaks of anatase TiO2, the diffraction peaks at 35.58, 38.88, and49.08 can be well indexed to the (0 0 2), (111), and (2 0 2) crystalplanes of monoclinic CuO (a = 4.69 �, b = 3.42 �, c = 5.12 �, b=

99.57 �, JCPDS 48-1548), respectively. In Figure 2, the SEM mi-crographs of the CuO/TiO2 samples are shown. The as-pre-pared TiO2 nanosheets have side sizes of approximately 2 mmand a thickness of approximately 500 nm (Figure 2 a, S1). Afterdeposition, the approximately 100 nm CuO nanoparticles or

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their aggregates were loaded onto the TiO2 surfaces (Fig-ure 2 b, S3). As seen in Figure 2 c, the as-obtained TiO2 nano-rods are 2–3 mm long and 200–500 nm in diameter (S2). FromFigure 2 d it is clear that the CuO nanoparticles were alsoloaded on the TiO2 nanorods (S4). Furthermore, the CuO/TiO2

samples were characterized by HRTEM (Figure S1 of the Sup-porting Information). An HRTEM image of a free standingnanosheet reveals that the lattice spacing is 0.19 nm, corre-sponding to (2 0 0) or (0 2 0) planes of anatase TiO2 (Fig-ure S1 b). As seen in Figure S1 c, the lattice spacing is 0.235 nm,corresponding to (0 0 1) planes of anatase TiO2. Along the[0 0 1] direction, the typical diffraction spots correspond to(0 2 0), (2 2 0), and (2 0 0), respectively (Figure S1 d). Based onthese structural analyses, it can be concluded that the as-pre-pared anatase TiO2 nanosheets are dominated by {0 0 1} facets.Similar results have been reported by the others research-ers.[39–41] The single-crystalline nature of the TiO2 nanosheetscan also be revealed. As confirmed by other authors,[24, 42, 43]

both top and bottom facets can be identified as {0 0 1} facetsaccording to the symmetry of the TiO2 nanosheet. The percent-age of the {0 0 1} facets was calculated to be 67 % from theregular geometry. In Figure 3 a, the CuO nanoparticles can beidentified by the bright/dark contrast resulting from the differ-ent electron densities of CuO and TiO2. The polycrystallinenature of CuO can be revealed by the diffraction rings (inset in

Figure 3 a). Furthermore, the chemical composition of S2 canbe confirmed by its XPS data (Figure S2), and the polycrystal-line nature of anatase TiO2 nanorods (S3) is revealed by Fig-ure S3. In Figure 3 b is also shown that the CuO nanoparticleswere successfully deposited on the TiO2 nanorods. The poly-crystalline nature of CuO is shown in Figure 3 b. Owing to thehigh percentage of {0 0 1} facets of TiO2 nanosheets, it is clearthat most of the CuO mainly deposit on the {0 0 1} facets. Ithas been demonstrated that the {0 0 1} facets of TiO2 havea higher surface energy than the {1 0 1} facets.[24, 25] Hence, itcould be assumed that the interaction between CuO and TiO2

nanosheets is stronger than that between CuO and TiO2 nano-rods. Therefore, more stable p–n heterojunctions can form be-tween CuO nanoparticles and TiO2 nanosheets than betweenCuO nanoparticles and TiO2 nanorods, which favors the effi-cient interparticle electron transfer. As a result, the leaching ofCuO from TiO2 nanosheets can be refrained effectively, whichis important in practical applications.

The textural properties of the samples before deposition ofPt were measured by nitrogen adsorption isotherms (Table 1).Compared with the bare TiO2 (S1, S2), the CuO/TiO2 samples(S3, S4) have smaller surface areas and pore sizes. The BETareas of S3 and S4 are 41.1 and 55.2 m2 g�1, respectively. Thedifference results from the incorporation of CuO on the TiO2

nanosheets or nanorods.

UV/Vis and PL spectra

In Figure 4, the UV/Vis diffuse reflection spectra of the samplesbefore deposition of Pt are shown. S1 and S2 have the sameabsorbing edges at 380 nm. Compared with the bare TiO2 sam-ples (S1, S2), a clear “red shifting” can be observed for bothCuO/TiO2 samples. Both CuO/TiO2 samples (S3, S4) have thesame absorbing edges at 425 nm. Moreover, S3 and S4 have

Figure 1. The XRD patterns of samples S1–S4.

Figure 2. SEM micrographs of the TiO2 and CuO/TiO2 samples: a) S1, b) S3,c) S2, d) S4.

Figure 3. TEM micrographs (inset: electron diffraction patterns) of the CuO/TiO2 samples: a) S3, b) S4. The arrows represent the supported CuO nano-particles on titania.

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a significant absorption in the visible light region of 400–800 nm. It is well known that anatase TiO2 (3.2 eV) can onlyabsorb UV light below 390 nm and CuO (1.7 eV) can absorbsvisible light. According to the formula of l= 1240/Eg (Eg, bandgap; l, excitation wavelength), the red shifting for CuO/TiO2

can be caused by strong metal–support interactions (SMSI),[6, 23]

which is beneficial to the efficient utilization of visible light. PLspectroscopy is a powerful technology to investigate the effi-ciency of carrier separation, trapping, migration, and transfer insemiconductors, because PL emission results from the recom-bination of electrons and holes.[44–48] In Figure 5, the PL spectraof the samples at an excitation wavelength of 340 nm areshown. This excitation wavelength is close to the maximumabsorption of TiO2. Three strong peaks at 411, 445, and 460 nmcorrespond to the band-gap energies of 3.2, 2.7, and 2.6 eV, re-spectively. According to the references,[22, 44, 49] the strong peakat approximately 411 nm may arise from the band–band PLphenomenon, equal to the band-gap energy (3.2 eV) of TiO2.The PL peaks at 445 and 460 nm can be attributed to the freeexcitons, and other two small peaks at 480 and 492 nm are at-tributed to the bound excitons. It is clear that S3 and S4 dis-play much weaker PL peaks than S1 and S2, suggesting thatthe coupled CuO/TiO2 have lower recombination rate of elec-trons and holes than the bare TiO2. The PL quenching indicatesa low recombination rate.

Under UV-light irradiation, the electrons are excited from thevalence band (VB) to the conduction band (CB) of TiO2, andthen are transferred to the CB of CuO, but the photogenerated

holes are remained in the VB of TiO2. As a result, the direct re-combination of electrons and holes can be refrained effectively.Note that CuO does not incorporate into the TiO2 lattice, be-cause of unmatched charges of Ti4+ and Cu2 + ions. The stronginteraction of CuO with TiO2 can effectively promote electrontransfer. A low recombination rate of electrons and holes isoften associated with high photocatalytic activity.[41–46]

Hydrogen production activity and cycling stability

We also measured the hydrogen generation performances ofthe samples before deposition of Pt (Figure S4). The hydrogenproduction amounts followed the order: S3>S4>S1>S2.However, much smaller amounts of hydrogen were producedbefore Pt deposition, indicating the loading of Pt is necessaryas a cocatalyst, which could accept photogenerated electrons.Furthermore, in Figure 6 the photocatalytic H2 production ac-tivities of the samples after deposition of Pt under UV-light illu-mination are shown. After irradiation for 3 h, the produced hy-drogen amounts over Pt/S1 and Pt/S2 after deposition of Ptwere 606 and 454 mL, respectively. Their fairly low photocata-lytic activities can be ascribed to the fast recombination rates

Figure 4. UV/Vis diffuse reflectance spectra of the samples.

Figure 5. PL emission spectra of the samples at an excitation wavelength of340 nm.

Figure 6. H2 production amounts of the samples under UV light irradiationafter deposition of Pt (0.1 g catalyst).

Table 1. The textural properties of the samples.[a]

Samples Surface area[m2 g�1]

Pore volume[cm3 g�1]

Pore size[nm]

S1 46.2 0.26 22.1S2 61.3 0.35 18.6S3 41.1 0.22 27.3S4 55.2 0.29 24.8

[a] S1, TiO2 nanosheets ; S2, TiO2 nanorods; S3, CuO/TiO2 prepared withS1; S4, CuO/TiO2 prepared with S2 ; Surface area calculated by the BETmethod; Pore sizes calculated by the BJH method.

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of electrons and holes. Comparatively, the produced H2

amounts of Pt/S3 and Pt/S4 were 1222 and 1034 mL, respec-tively. The higher photocatalytic activities of the Pt@CuO/TiO2

than of the bare Pt@TiO2 could be ascribed to the effectivecoupling of CuO with TiO2, which significantly reduces the re-combination rates of electrons and holes, as well as to the in-creased light absorption. Most importantly, Pt/S3 displayedhigher activity than Pt/S4, although the BET area (55.2 m2 g�1)of S4 was larger than that (41.1 m2 g�1) of S3, indicating thatthe BET area has little influence on the hydrogen productionactivity. Notably, variations in the activities may be related tothe difference in surface structures of TiO2. As described above,the TiO2 nanosheets expose approximately 67 % of the {0 0 1}facets, but the TiO2 nanorods mainly expose the {1 0 1} facets.Compared with the {1 0 1} facets, the {0 0 1} facets of anataseTiO2 are more active owing to the surface atomic configura-tion.[30, 31] Water molecules can dissociatively adsorb on the{0 0 1} facets, but only physically adsorb on the {1 0 1} facets.[30]

The hydrogen production activity of TiO2 can be enhanced bythe exposed {0 0 1} facets, as reported by other research-ers.[32–36] When Vogel et al.[50, 51] studied the sensitization of TiO2

by the sulfides (e.g. , PbS), they found that the optimized rela-tive energetic levels at the interface between TiO2 and the sul-fides facilitated the charge separation.

In Figure 7, the stabilities of the samples after cycling 20times are shown. Compared with the initial cycles, 95.3 % and73.1 % of hydrogen production amounts were maintained after

5 cycles for S3 and S4, respectively. Furthermore, the leachingexperiments demonstrated that after 5 cycles, an amount ofCuO nanoparticles clearly leached from TiO2 nanorods, as re-vealed by inductively coupled plasma, but no CuO nanoparti-cles leached from TiO2 nanosheets under the same conditions.The results further confirm the interaction of CuO with TiO2

nanosheets is stronger than that of CuO with TiO2 nanorods.The effect of the surface structure of TiO2 on the photoelectro-chemical and hydrogen production performances of the cou-pled photocatalysts have also been reported by the others re-searchers.[52, 53]

In Figure 8, the schematic structure model of Pt@CuO/TiO2 isshown. Under UV light irradiation, electrons are excited fromVB to CB of TiO2. The excited electrons in CB of TiO2 may trans-fer to the CB of CuO through the CuO/TiO2 interface, while thephotogenerated holes remain in the VB of TiO2. As a result,electrons and holes can be separated effectively. Hereby, wecan assume that p–n heterojunctions can form at the CuO/TiO2

interface, because the CB level of CuO is more positive thanthat of TiO2. At the same time, the electrons in the VB of CuOcan also be excited to reach the CB. The excess electron accu-mulation in CB of CuO leads to a negative overpotential, lowerthan the redox potential of H+/H2. Bandara et al.[9] reportedthat both TiO2 and CuO could be simultaneously excited underUV-light irradiation and the excess electrons would accumulatein the CBs of CuO. A negative shift of the Fermi level of CuOwould result in the required negative potential required forwater splitting as a result of the accumulated excess electrons.Owing to the higher surface energy of the {0 0 1} facets than ofthe {1 0 1} facets, the interaction of CuO with TiO2 nanosheetsis stronger than with nanorods. As a result, a more stable p–nheterojunction can form at the interface between CuO andTiO2 nanosheets, which facilitates the separation of carriers.Furthermore, the stable p–n heterojunction can also increasethe stability of the CuO/TiO2, which effectively prevents theleaching of CuO from TiO2 nanosheets. After deposition of Pton the CuO/TiO2, the Schottky barriers for Pt@CuO andPt@TiO2 are also beneficial to reduce the recombination ofelectrons and holes. Summarily, the TiO2 nanosheet-basedPt@CuO/TiO2 has the enhanced activity and structure stability,which can be of great interest for practical applications. Jianget al.[54] elucidated that the good photoelectrochemical celland direct heterogeneous reaction efficiencies are related tointimately connected particles that facilitate easy charge trans-fer ; and that the {0 1 0} facets of anatase TiO2 can enhanceelectron–hole separation and create specific surface states thatfacilitate interactions across the semiconductor/electrolyte in-terfaces. Yu et al. also reported that Pt/TiO2 nanosheets withexposed (0 0 1) facets can enhance the performance of photo-catalytic water splitting[24] Furthermore, the single-crystallinestructure of TiO2 nanosheets with a low density of defects canalso reduce the recombination rate of photogenerated elec-tron–hole pairs on grain boundaries and crystalline defects,thus improving the photocatalytic efficiency[32, 33] Therefore, wehold that the TiO2 with different facets exposed have a signifi-

Figure 7. H2 production amounts of the Pt/S3 and Pt/S4 samples after 2 hUV light irradiation over 20 cycles (0.1 g catalyst).

Figure 8. Schematic model of Pt@CuO/TiO2.

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cant influence on the interfacial structure stability of CuO/TiO2

p–n heterojunctions, electron transfer, as well as cycle stability.The immobilized photocatalysts in the current study havea clear advantage of easy reactivation and reuse in numerouspractical applications.

Conclusions

Stable CuO/TiO2 (p–n) heterojunctions and Schottky barriers ofboth Pt@CuO and Pt@TiO2 can form in Pt@CuO/TiO2 compo-sites prepared from TiO2 nanosheet or nanorod precursors.Owing to a higher surface energy of the {0 0 1} facets, the TiO2

nanosheet-based Pt@CuO/TiO2 photocatalyst has a higher hy-drogen production activity and a higher recyclability than thenanorod-based one.

Acknowledgements

This work is financially supported by National Science Founda-tion of China (21377060, 21103049), Six Talent Climax Foundationof Jiangsu (20100292), Jiangsu Science Foundation of China(BK2012862), Jiangsu Province of Academic Scientific Research In-dustrialization Projects (JHB2012-10, JH10-17), The Project of For-eign Culture and Education expert (N0502001003), Jiangsu prov-ince of Key Environmental protection projects (2012028), Teach-ing Reform Project to Enhance the Practice Innovation of NUIST-2013 (N1885013014), Support Program for Undergraduate Disser-tation of NUIST-2013 (N1085002008), A Project Funded by the Pri-ority Academic Program Development of Jiangsu Higher Educa-tion Institutions (PAPD), and Jiangsu Province Innovation Plat-form for Superiority Subject of Environmental Science and Engi-neering, “333” Outstanding Youth Scientist Foundation of Jiangsu(2011–2015), the Project Sponsored by SRF for ROCS, SEM(2013S002).

Keywords: conducting materials · copper · nanostructures ·photochemistry · titanium

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Received: October 13, 2013Published online on February 14, 2014

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