Relation between the Photocatalytic and Photoelectrocatalytic

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The Relation Between the Photocatalytic and Photoelectrocatalytic Performance for the Particulate Semiconductor-Based Photoconversion Systems with Surface Phase Junction Structure Xiang Wang, Shaoqing Jin, Hongyu An, Xiuli Wang, Zhaochi Feng, and Can Li J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b06347 • Publication Date (Web): 15 Sep 2015 Downloaded from http://pubs.acs.org on September 18, 2015

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The Journal of Physical Chemistry

The Relation between the Photocatalytic and Photoelectrocatalytic Performance for the Particulate Semiconductor-based Photoconversion Systems with Surface Phase Junction Structure

Xiang Wang †,§, Shaoqing Jin †,‡,§, Hongyu An †,‡, Xiuli Wang †, Zhaochi Feng † and Can Li †,*

† State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡ University of the Chinese Academy of Sciences, Beijing 100049, China § X. Wang and S. Jin contributed equally to this study * To whom correspondence should be addressed Tel: 86-411-84379070; Fax: 86-411-84694447 Email: [email protected] (C. Li) Homepage: http://www.canli.dicp.ac.cn

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ACS Paragon Plus Environment


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Abstract Although surface phase junction can efficiently boost photocatalytic (PC) reactions, its role in photoelectrocatalytic (PEC) reactions has not been well understood yet. In this study, we investigated the effect of surface phase junction on the PEC performance of photoelectrodes fabricated with Ga2O3 and TiO2 particles. The surface phase junctions beneficial for PC reactions show a negative effect on PEC performance, which is mainly due to the significant influence of charge transportation between semiconductor particles by surface phase junction. Photo-generated charge separation is promoted by surface phase junction for both PC and PEC reactions, but the much more severe interfacial recombination occurs in PEC reaction when charge carriers migrate across semiconductor particles to reach a conducting substrate. The opposite effects of surface phase junction on PC and PEC performance reported here indicates that the fabrication of heterojunction or phase junction in the right structure and sequence is vital to PEC systems based on junction, which will be helpful for the development of highly efficient photoconversion systems.

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Introduction Due to the serious energy and environment crisis, photocatalytic (PC) and photoelectrocatalytic (PEC) H2 production via water splitting on semiconductor-based catalyst have been attracting considerable attention nowadays.1-4 However, the solar-to-hydrogen efficiency is still very low owing to the low separation efficiency of photo-generated carriers. Numerous ways have been developed for the promotion of photo-generated charge separation, such as doping other elements,5,6 constructing heterojunctions7-11 and loading cocatalysts12-15 etc. Among these strategies, the fabrication of heterojunction has been widely employed in photocatalysis based on semiconductor powder and photoelectrocatalysis based on semiconductor thin film. Such an idea of “Junction” has been further developed in particulate semiconductor-based photocatalysis by this group. With the surface phase structure of semiconductors characterized by UV Raman spectroscopy, we found that photo-generated charge separation and PC reactions can be efficiently promoted by surface phase junction formed by two different phases of one semiconductor,16-18 though the driving force is smaller than that for heterojunction. Generally, semiconductor particle utilized in photocatalysis could be used to fabricate a film electrode for photoelectrocatalysis, however, there are at least three differences between PC and PEC systems:4,19,20 (1). Particulate semiconductor is fabricated into a film on a conducting substrate for PEC system, while it is suspended in reaction liquid for PC system; (2) Only half reaction (oxidation or reduction reaction) takes place on the electrode fabricated with particulate semiconductor in 3



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PEC

system,

while

both

oxidation

and

reduction

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reactions

occur

on

semiconductor-based photocatalyst particles in PC system; (3). The charge transportation between semiconductor particles is a key process for PEC system, while there is no this interface in PC system. Given these differences between PC and PEC systems based on particulate semiconductors and the promotion effect of surface phase junction on the PC performance of photocatalysts, it is necessary to understand how surface phase junction affects PEC performance. Herein, we investigated the effect of surface phase junction on the PEC performance of photoelectrodes assembled with particulate Ga2O3 and TiO2 samples. We found that the surface phase junctions beneficial for PC reactions show a negative effect on PEC performance. Based on the results and analysis, we pointed out the relation

between

the

PC

and

PEC

performance

for

the

particulate

semiconductor-based photoconversion systems with surface phase junction structure. Experimental Ga2O3 samples with different α/β phase compositions were prepared by finely tuning the phase transformation of α-Ga2O3 and are denoted as Ga2O3-T (T is temperature, K).17,21 UV Raman characterization indicates that Ga2O3-673 and Ga2O3-1073 samples are in pure α phase and pure β phase, respectively (Figure S1). Ga2O3-863 and Ga2O3-883 samples possess α/β phase junction on the surface (Figure S1, S2), while Ga2O3-903 sample has an α@β core@shell structure (Figure S1). The film electrodes based on Ga2O3 particles were fabricated by electrophoretic deposition in an acetone solution (70 mL) containing Ga2O3 powder (70 mg) and iodine (30 mg). 4


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A FTO (fluorine-doped tin oxide) substrate (1.1 × 2 cm2) was immersed in a cell parallel to the Pt electrode, and a 40 V bias provided by a potentiostat (ITECH IT6834) was applied to deposit Ga2O3 particles onto the FTO substrate. The electrodes were dried in air at room temperature and then calcined at 623 K in air for 30 min. The area of Ga2O3 coating was fixed to be ca. 5 mm × 5 mm for all the electrodes. The TiO2 samples with different surface phase compositions of anatase and rutile were obtained by calcination of precursor Ti(OH)4 at different temperatures (Figure S3),16,22 and the film electrodes were also fabricated by electrophoretic deposition. PEC measurements were performed using an electrochemical analyzer (CHI 760D). SCE (saturated calomel electrode) and Pt slice were used as a reference electrode and a counter electrode, respectively. The Hamamatsu L9588-02A light was used as the light source. Linear sweep voltammetry of the electrode was performed with and without UV irradiation within each scan using a shutter. Results & Discussion Figure 1 shows the SEM images of the electrodes fabricated with Ga2O3 particles. We can clearly observe that the thicknesses of all the deposited Ga2O3 films are around 3 µm and the particle size of all the Ga2O3 samples is nearly identical. Moreover, all the particles are uniformly deposited onto the substrates, forming a flat film. These situations indicate that the comparison of PEC performance of these electrodes is reliable.

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Figure 1. SEM images of the electrodes fabricated with Ga2O3-673 (a and b), Ga2O3-863 (c and d) and Ga2O3-1073 particles (e and f).

Figure 2 shows photocurrent-potential curves of the electrodes fabricated with Ga2O3 samples with different phase structures. All the electrodes exhibit increasing photocurrent densities during the scanning from -1.2 to 1.2 V vs. SCE. The photocurrent density of Ga2O3-1073 electrode (in pure β phase, Figure 2e) is almost three times as high as that of Ga2O3-673 electrode (in pure α phase, Figure 2a). Since the difference in UV-Vis diffuse reflectance spectra (Figure S4a) between the Ga2O3 6


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samples is small, the difference in photocurrent between Ga2O3-673 and Ga2O3-1073 electrodes can be mainly attributed to the intrinsic phase property of Ga2O3 samples. Notably, the Ga2O3-863 electrode fabricated with Ga2O3 sample with a small amount of β phase exposed on the surface shows the lowest photocurrent density among all the electrodes (Figure 2b). With the amount of β phase exposed on the surface increasing, the photocurrent density increases somewhat for the Ga2O3-883 electrode (Figure 2c). When the surface region of α-Ga2O3 is fully covered by β-Ga2O3, the photocurrent density of Ga2O3-903 electrode (Figure 2d) reaches to the level of Ga2O3-1073 electrode. Therefore, the different PEC performance of Ga2O3 electrodes is mainly resulted from the different surface phase structures of Ga2O3 samples.

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Figure 2. Photocurrent-potential curves of the electrodes fabricated with Ga2O3 samples with different phase structures. The inserted at the left side of each curve is the corresponding cartoon image of Ga2O3 sample. The blue particle represents Ga2O3-673 sample in pure α phase; the red particle represents Ga2O3-1073 sample in pure β phase. Ga2O3-863 and Ga2O3-883 samples possess a small and large amount of β phase on the surface respectively, with α and β phase co-exposed. Ga2O3-903 sample has an α@β core@shell structure.

In our previous study, we found that the Ga2O3-863 and Ga2O3-883 samples with both α and β phases exposed on the surface show much higher PC activity in overall water splitting than pure α-Ga2O3 and β-Ga2O3 due to the surface α/β phase junction; the Ga2O3-903 sample with only β phase exposed on the surface shows almost the same PC activity as the Ga2O3-1073 sample (Figure S5a).17 These results indicate that the surface α/β phase junction of Ga2O3 boosting PC reaction negatively affects the PEC performance of particulate Ga2O3-based photoelectrodes. In order to verify the opposite effects of surface phase junction on PC and PEC performance, we also investigated the surface anatase/rutile phase junction of TiO2 material. The difference in UV-Vis diffuse reflectance spectra (Figure S4b) between the TiO2 samples is small and the TiO2 sample with surface anatase/rutile phase junction shows much higher activity in PC H2 evolution than individual anatase and rutile TiO2 samples (Figure S5b).16 However, as shown in Figure 3, the electrode fabricated with particulate TiO2 sample with surface anatase/rutile phase junction exhibits the lowest photocurrent density among all the electrodes. The phenomenon is very similar to that for the photoconversion systems based on Ga2O3 particles, which means that the negative effect on PEC performance is general for surface phase junctions beneficial for PC reactions in photoconversion systems based on particulate 8


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semiconductors.

Figure 3. Photocurrent-potential curves of electrodes fabricated with TiO2 samples with different phase structures. The inserted at the left side of each curve is the corresponding cartoon image of TiO2 sample. The small blue particle represents anatase TiO2 sample, the large red particle represents rutile TiO2 sample.

To understand the effect of surface phase junction on PEC performance, we also investigated the effect of cocatalyst on the PEC performance of electrodes since the separation of photo-generated carriers in semiconductors is usually facilitated by loading cocatalyst.13,23 Photo-deposited Ni cocatalyst has been demonstrated to be efficient in transferring photo-generated electrons in semiconductors and boosting PC reactions.24,25 However, as shown in Figure 4, the photocurrent densities of α-Ga2O3 and β-Ga2O3 electrodes decrease significantly after a very small amount of Ni 9



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cocatalyst in situ photo-deposited. This means that the “Schottky junction” between semiconductor and cocatalyst also shows a negative effect on PEC performance. Thus we can conclude from all above results that the surface phase junctions and semiconductor/cocatalyst “junction” beneficial for charge separation play a negative role in PEC process for photoconversion systems based on particulate semiconductors. The opposite effects of junctions on PC and PEC performance should be closely related with the charge separation and transfer processes in photocatalysis and photoelectrocatalysis.

Figure 4. Photocurrent-potential curves of electrodes fabricated with α-Ga2O3 (a) and β-Ga2O3 (b) before and after a very small amount of Ni cocatalyst in situ photo-deposited.

Figure 5 shows the PC and PEC processes for the photoconversion systems 10


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based on particulate Ga2O3 samples. Usually, the PC efficiency (ηPC) can be described as the product of the efficiency of light absorption (ηAbs), the efficiency of charge separation and transfer to the surface (ηCS), and the efficiency of chemical reactions (ηCR):26 ηPC

=

ηAbs x ηCS x ηCR (Figure 5a, 5b, 5c). Due to the separation of

photo-generated charges promoted by surface α/β phase junction (Figure 5c), ηCS increases evidently in the case of Ga2O3 with α/β phase junction on the surface. Therefore, a remarkable enhancement of PC activity in overall water splitting is observed for the Ga2O3 based photocatalysts with surface α/β phase junction.17

Figure 5. PC process for the photoconversion systems based on particulate Ga2O3 samples with pure phase (a) and surface α/β phase junction (b); (c) A scheme of band position for the surface α/β phase junction of Ga2O3 material; PEC process for the photoconversion systems based on particulate Ga2O3 samples with pure phase (d) and surface α/β phase junction (e).

However, for particulate semiconductor-based PEC systems, due to only oxidation reaction occurring on the electrode film, there is one more critical step for PEC process than PC process, the charge transportation between semiconductor 11



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particles.27 The efficiency of charge transportation between semiconductor particles (ηCT) is a very key factor influencing the performance of PEC system. And the efficiency of PEC process (ηPEC) can be expressed as the equation:27 ηPEC = ηAbs x ηCS x ηCT x ηCR (Figure 5c, 5d, 5e). As shown in Figure 5d and 5e, the promotion of photo-generated charge separation and transfer to the surface by surface α/β phase junction of Ga2O3 in PEC reactions is the same as that in PC reactions: more photo-generated electrons and holes transfer from α to β phase and β to α phase, respectively. Since only the photo-generated electrons reached the FTO substrate would contribute to the photocurrent, the photo-generated electrons have to migrate across the interface between Ga2O3 particles to reach the FTO substrate for the contribution of PEC performance. In the case of Ga2O3 particles with surface α/β phase junction, since the bottom of conduction band for β-Ga2O3 is lower than that for α-Ga2O3,17 the back transfer of photo-generated electrons from the isolated β-Ga2O3 domains to α-Ga2O3 is unfavorable. It means that it is difficult for these photo-generated electrons to reach the FTO substrate. On the contrary, as shown in Figure 5e, the interfacial recombination becomes very prominent, a very large amount of separated electrons and holes severely recombine with each other at the interface between different phases of particles, which results in a significant decrease in photocurrent. However, from another point of view, the lowest photocurrent for PEC system based on particulate Ga2O3 sample with surface α/β phase junction further demonstrates the remarkable promotion effect of surface phase junction on charge separation. 12


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Based on the above analysis, we can conclude that the opposite effects of surface phase junction on PC and PEC performance is attributed to the difference in process between PC and PEC systems based on particulate semiconductors. PEC process has one more critical step than PC process, the charge transportation between semiconductor particles. Although photo-generated charge separation is promoted by surface phase junction, the interfacial recombination becomes much more severe due to the existence of surface phase junction. This is the reason why surface phase junction shows a positive effect in PC reactions, and a negative effect on PEC performance. As for the construction of highly efficient PEC systems based on surface phase junction structure, due to the characteristics of PEC process, the efficient promotion of charge separation by surface phase junction is a necessary condition but not sufficient. To minimize the interfacial recombination of photo-generated carriers, the two phases constructed for surface phase junction should align in different space regions of electrode (such as the sandwich structure, one phase is at the middle of electrode between the conducting substrate and the other phase). Meanwhile, the alignment of the two phases must be appropriate to make the photo-generated carriers arrive at the right sides.28 For photoanode, the photo-generated electrons transfer to the conducting substrate and the photo-generated holes transfer to the surface of electrode for oxidation reaction due to surface phase junction, and vice verse. We can expect that surface phase junction will show the same positive effect on PC and PEC performance as long as these requirements are satisfied. 13



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Conclusions In summary, we have studied the effect of surface phase junction on PEC performance with photoelectrodes fabricated with Ga2O3 and TiO2 particles as examples. The surface phase junctions boosting PC reactions show a negative effect in PEC reactions. This is due to the severe interfacial charge recombination between semiconductor particles caused by surface phase junction, which further demonstrates the promotion effect of surface phase junction on charge separation from another point of view. We pointed out the relation between the PC and PEC performance for the particulate semiconductor-based photoconversion systems with surface phase junction structure. Surface phase junction will show parallel effects on PC and PEC performance once the two phases constructed for junction locate in different space regions of photoelectrodes and the alignment of the two phases is appropriate for the transferring of photo-generated carriers to the right sides. These understandings would be helpful for the development of highly efficient photoconversion systems with surface phase junction structure. Acknowledgments This work was financially supported by the National Basic Research Program of China (No. 2014CB239403) and the National Natural Science Foundation of China (No. 21090340, 21373209, 21203185). Supporting Information UV Raman spectra, HRTEM image, UV-Vis diffuse reflectance spectra and photocatalytic activity of Ga2O3 samples can be seen in the Supporting Information. 14


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This information is available free of charge via the Internet at http://pubs.acs.org Reference (1) Grätzel, M. Photoelectrochemical Cells. Nature 2001, 414, 338-344. (2) Chen, X. B.; Shen, S. H.; Guo, L. J.; Mao, S. S. Semiconductor-based Photocatalytic Hydrogen Generation. Chem. Rev. 2010, 110, 6503-6570. (3) Osterloh, F. E. Inorganic Nanostructures for Photoelectrochemical and Photocatalytic Water Splitting. Chem. Soc. Rev. 2013, 42, 2294-2320. (4) Hisatomi, T.; Kubota, J.; Domen, K. Recent Advances in Semiconductors for Photocatalytic and Photoelectrochemical Water Splitting. Chem. Soc. Rev. 2014, 43, 7520-7535. (5) Takata, T.; Domen, K. Defect Engineering of Photocatalysts by Doping of Aliovalent Metal Cations for Efficient Water Splitting. J. Phys. Chem. C 2009, 113, 19386-19388. (6) Shen, S. H.; Jiang, J. G.; Guo, P. H.; Kronawitter, C. X.; Mao, S. S.; Guo, L. J. Effect of Cr Doping on the Photoelectrochemical Performance of Hematite Nanorod Photoanodes. Nano Energy 2012, 1, 732-741. (7) Kim, H. G.; Borse, P. H.; Choi, W. Y.; Lee, J. S. Photocatalytic Nanodiodes for Visible-light Photocatalysis. Angew. Chem. Int. Ed. 2005, 44, 4585-4589. (8) Ma, B. J.; Yang, J. H.; Han, H. X.; Wang, J. T.; Zhang, X. H.; Li, C. Enhancement of Photocatalytic Water Oxidation Activity on IrOx-ZnO/Zn2-xGeO4-x-3yN2y Catalyst with the Solid Solution Phase Junction. J. Phys. Chem. C 2010, 114, 12818-12822. (9) Su, J. Z.; Guo, L. J.; Bao, N. Z.; Grimes, C. A. Nanostructured WO3/BiVO4 Heterojunction Films for Efficient Photoelectrochemical Water Splitting. Nano Lett. 2011, 11, 1928-1933. (10) Abdi, F. F.; Han, L. H.; Smets, A. H. M.; Zeman, M.; Dam, B.; Krol, R. v. d. Efficient Solar Water Splitting by Enhanced Charge Separation in a Bismuth Vanadate-silicon Tandem Photoelectrode. Nature Commun. 2013, 4, 2195-(1-7). (11) Ahmed, M. G.; Kandiel, T. A.; Ahmed, A. Y.; Kretschmer I.; Rashwan, F.; Bahnemann. Enhanced Photoelectrochemical Water Oxidation on Nanostructured Hematite Photoanodes via p-CaFe2O4/n-Fe2O3 Heterojunction Formation. J. Phys. Chem. C 2015, 119, 5864-5871. (12) Yan, H. J.; Yang, J. H.; Ma, G. J.; Wu, G. P.; Zong, X.; Lei, Z. B.; Shi, J. Y.; Li, C. Visible-Light-Driven Hydrogen Production with Extremely High Quantum Efficiency on Pt-PdS/CdS Photocatalyst. J. Catal. 2009, 266, 165-168. (13) Yang, J. H.; Wang, D. E.; Han, H. X.; Li, C. Roles of Cocatalysts in Photocatalysis and Photoelectrocatalysis. Acc. Chem. Res. 2013, 46, 1900–1909. (14) Abdi, F. F.; Firet N.; Krol, R. v. d. Efficient BiVO4 Thin Film Photoanodes Modified with Cobalt Phosphate Catalyst and W-doping. Chemcatchem 2013, 5, 490-496. (15) Yabuta, M.; Takayama, T.; Shirai, K.; Watanabe, K.; Kudo, A.; Sugimoto, T.; Matsumoto, Y. Effects of Cocatalyst on Carrier Dynamics of a Titanate Photocatalyst with Layered Perovskite Structure. J. Phys. Chem. C 2014, 118, 10972-10979. (16) Zhang, J.; Xu, Q.; Feng, Z. C.; Li, M. J.; Li, C. Importance of the Relationship between Surface Phases and Photocatalytic Activity of TiO2. Angew. Chem. Int. Ed. 2008, 47, 1766-1769. (17) Wang, X.; Xu, Q.; Li, M. R.; Shen, S.; Wang, X. L.; Wang, Y. C.; Feng, Z. C.; Shi, J. Y.; Han, H. X.; Li, C. Photocatalytic Overall Water Splitting Promoted by an α-β Phase Junction on Ga2O3. Angew. Chem. Int. Ed. 2012, 51, 13089-13092. 15



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(18) Shen, S.; Wang, X. L.; Chen, T.; Feng, Z. C.; Li, C. Transfer of Photoinduced Electrons in Anatase-rutile TiO2 Determined by Time-resolved Mid-infrared Spectroscopy. J. Phys. Chem. C 2014, 118, 12661-12668. (19) Xiao, F. X.; Miao, J. W.; Tao, H. B.; Hung, S. F.; Wang, H. Y.; Yang, H. B.; Chen, J. Z.; Chen, R.; Liu, B. One-dimensional Hybrid Nanostructures for Heterogeneous Photocatalysis and Photoelectrocatalysis. Small 2015, 11, 2115-2131. (20) Minegishi, T.; Nishimura, N.; Kubota, J.; Domen, K. Photoelectrochemical Properties of LaTiO2N Electrodes Prepared by Particle Transfer for Sunlight-driven Water Splitting. Chem. Sci. 2013, 4, 1120-1124. (21) Wang, X.; Xu, Q.; Fan, F. T.; Li, M. R.; Feng, Z. C.; Li, C. Study of the Phase Transformation of Single Particles of Ga2O3 by UV Raman Spectroscopy and High Resolution TEM. Chem. Asian J. 2013, 8, 2189-2195. (22) Zhang, J.; Li, M. J.; Feng, Z. C.; Chen, J.; Li, C. UV Raman Spectroscopic Study on TiO2. I. Phase Transformation at the Surface and in the Bulk. J. Phys. Chem. B 2006, 110, 927-935. (23) Zong, X.; Yan, H. J.; Wu, G. P.; Ma, G. J.; Wen, F. Y.; Wang, L.; Li, C. Enhancement of Photocatalytic H2 Evolution on CdS by Loading MoS2 as Cocatalyst under Visible Light Irradiation. J. Am. Chem. Soc. 2008, 130, 7176-7177. (24) Kudo, A.; Sayama, K.; Tanaka, A.; Asakura, K.; Domen, K.; Maruya, K.; Onishi, T. Nickel-loaded K4Nb6O17 Photocatalyst in the Decomposition of H2O into H2 and O2: Structure and Reaction Mechanism. J. Catal. 1989, 120, 337-352. (25) Sakata, Y.; Matsuda, Y.; Yanagida, T.; Hirata, K.; Imamura, H.; Teramura, K. Effect of Metal Ion Addition in a Ni Supported Ga2O3 Photocatalyst on the Photocatalytic Overall Splitting of H2O. Catal. Lett. 2008, 125, 22-26. (26) Kudo, A.; Miseki, Y. Heterogeneous Photocatalyst Materials for Water Splitting. Chem. Soc. Rev. 2009, 38, 253-278. (27) Cho, S. H.; Jang, J. W.; Lee, K. H.; Lee, J. S. Research Update: Strategies for Efficient Photoelectrochemical Water Splitting Using Metal Oxide Photoanodes. APL Mat. 2014, 2, 010703-(1-14). (28) Liu, J.; Yu, X. L.; Liu, Q. Y.; Liu, R. J.; Shang, X. K.; Zhang, S. S.; Li, W. H.; Zheng, W. Q.; Zhang, G. J.; Cao, H. B.; Gu, Z. J. Surface-phase Junctions of Branched TiO2 Nanorod Arrays for Efficient Photoelectrochemical Water Splitting. Appl. Catal. B-Environ. 2014, 158-159, 296-300.

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


160x94mm (300 x 300 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

150x85mm (300 x 300 DPI)


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


119x119mm (300 x 300 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

150x83mm (300 x 300 DPI)


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


99x150mm (300 x 300 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

99x175mm (300 x 300 DPI)


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Relation between the Photocatalytic and Photoelectrocatalytic

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