The impact of crystal defects towards oxide semiconductor photoanode for photoelectrochemical water splitting

Abstract

Photoelectrochemical (PEC) water oxidation for sustainable clean energy and fuel production is a potential solution to the demands of organic pollutant removal and growing energy consumption. Development of high performance photoanodes, which is a key component in the system, is one of the central topics in the area. The crystal defect is an old concept but fruiting new understanding with promotive impact to the development of high performance photoanodes. In this review, we elucidated the typical defects involved in the photoanode with the position where they play the roles in the structure and how the properties of photoanode are influenced. In addition, we summarized the feasible protocols to maximize the pros but reduce the cons brought by having defects to the photoanode performance based on recent most prominent research advancements in the field. Finally, we briefly sketched the future perspective with the challenges of this topic when in the scenario of possible developments into practical applications.

Keywords

photoanode / defect engineering / oxide semiconductor / water splitting / charge transfer

References

[1] Z. Wang, Y. Inoue, T. Hisatomi, R. Ishikawa, Q. Wang, T. Takata, S. S. Chen, N. Shibata, Y. Ikuhara, and K. Domen, Overall water splitting by Ta₃N₅ nanorod single crystals grown on the edges of KTaO₃ particles, Nat. Catal. 1(10), 756 (2018)

[2] J. Ran, J. Zhang, J. Yu, M. Jaroniec, and S. Z. Qiao, Earth-abundant cocatalysts for semiconductorbased photocatalytic water splitting, Chem. Soc. Rev. 43(22), 7787 (2014)

[3] T. Hisatomi, J. Kubota, and K. Domen, Recent advances in semiconductors for photocatalytic and photoelectrochemical water splitting, Chem. Soc. Rev. 43(22), 7520 (2014)

[4] M. G. Walter, E. L. Warren, J. R. McKone, S. W. Boettcher, Q. Mi, E. A. Santori, and N. S. Lewis, Solar water splitting cells, Chem. Rev. 110(11), 6446 (2010)

[5] Y. Kuang, Q. Jia, G. Ma, T. Hisatomi, T. Minegishi, H. Nishiyama, M. Nakabayashi, N. Shibata, T. Yamada, A. Kudo, and K. Domen, Ultrastable low-bias water splitting photoanodes via photocorrosion inhibition and in situ catalyst regeneration, Nat. Energy 2(1), 16191 (2017)

[6] N. S. Lewis, Research opportunities to advance solar energy utilization, Science 351(6271), aad1920 (2016)

[7] S. Chen and L. W. Wang, Thermodynamic oxidation and reduction potentials of photocatalytic semiconductors in aqueous solution, Chem. Mater. 24(18), 3659 (2012)

[8] J. Y. Kim, G. Magesh, D. H. Youn, J. W. Jang, J. Kubota, K. Domen, and J. S. Lee, Single-crystalline, wormlike hematite photoanodes for efficient solar water splitting, Sci. Rep. 3(1), 2681 (2013)

[9] J. Seo, M. Nakabayashi, T. Hisatomi, N. Shibata, T. Minegishi, M. Katayama, and K. Domen, The effects of annealing barium niobium oxynitride in argon on photoelectrochemical water oxidation activity, J. Mater. Chem. A Mater. Energy Sustain. 7(2), 493 (2019)

[10] T. W. Kim and K. S. Choi, Nanoporous BiVO₄ photoanodes with dual-layer oxygen evolution catalysts for solar water splitting, Science 343(6174), 990 (2014)

[11] Y. Kuang, Q. Jia, H. Nishiyama, T. Yamada, A. Kudo, and K. Domen, A front-illuminated nanostructured transparent BiVO₄ photoanode for>2% efficient water splitting, Adv. Energy Mater. 6(2), 1501645 (2016)

[12] J. Yang, J. K. Cooper, F. M. Toma, K. A. Walczak, M. Favaro, J. W. Beeman, L. H. Hess, C. Wang, C. Zhu, S. Gul, J. Yano, C. Kisielowski, A. Schwartzberg, and I. D. Sharp, A multifunctional biphasic water splitting catalyst tailored for integration with high-performance semiconductor photoanodes, Nat. Mater. 16(3), 335 (2017)

[13] X. Li, S. Liu, K. Fan, Z. Liu, B. Song, and J. Yu, MOF-based transparent passivation layer modified ZnO nanorod arrays for enhanced photo-electrochemical water splitting, Adv. Energy Mater. 8(18), 1800101 (2018)

[14] K. Sivula and R. van de Krol, Semiconducting materials for photoelectrochemical energy conversion, Nat. Rev. Mater. 1(2), 15010 (2016)

[15] J. Nowotny, M. A. Alim, T. Bak, M. A. Idris, M. Ionescu, K. Prince, M. Z. Sahdan, K. Sopian, M. A. Mat Teridi, and W. Sigmund, Defect chemistry and defect engineering of TiO₂-based semiconductors for solar energy conversion, Chem. Soc. Rev. 44(23), 8424 (2015)

[16] S. Sato, R. Nakane, T. Hada, and M. Tanaka, Spin injection into silicon in three-terminal vertical and fourterminal lateral devices with Fe/Mg/MgO/Si tunnel junctions having an ultrathin Mg insertion layer, Phys. Rev. B 96(23), 235204 (2017)

[17] N. S. J. Frougier, D. Deng, M. Jerry, A. Aziz, L. Liu, G. Lavallee, T. S. Mayer, S. Gupta, and S. Datta, Phase-transition-FET exhibiting steep switching slope of 8 mV/decade and 36% enhanced ON current, IEEE Symposium on VLSI Technology2158 (2016)

[18] W. Zhang, D. Yan, X. Tong, and M. Liu, Ultrathin lutetium oxide film as an epitaxial hole-blocking layer for crystalline bismuth vanadate water splitting photoanodes, Adv. Funct. Mater. 28(10), 1705512 (2018)

[19] F. L. Souza, K. P. Lopes, E. Longo, and E. R. Leite, The influence of the film thickness of nanostructured alpha-Fe₂O₃ on water photooxidation, Phys. Chem. Chem. Phys. 11(8), 1215 (2009)

[20] O. Zandi, B. M. Klahr, and T. W. Hamann, Highly photoactive Ti-doped α-Fe₂O₃ thin film electrodes: Resurrection of the dead layer, Energy Environ. Sci. 6(2), 634 (2013)

[21] F. Le Formal, S. R. Pendlebury, M. Cornuz, S. D. Tilley, M. Grätzel, and J. R. Durrant, Back electron–hole recombination in hematite photoanodes for water splitting, J. Am. Chem. Soc. 136(6), 2564 (2014)

[22] W. Zhang, D. Yan, K. Appavoo, J. Cen, Q. Wu, A. Orlov, M. Y. Sfeir, and M. Liu, Unravelling photocarrier dynamics beyond the space charge region for photoelectrochemical water splitting, Chem. Mater. 29(9), 4036 (2017)

[23] M. Huang, C. Li, L. Zhang, Q. Chen, Z. Zhen, Z. Li, and H. Zhu, Twin structure in BiVO₄ photoanodes boosting water oxidation performance through enhanced charge separation and transport, Adv. Energy Mater. 8(32), 1802198 (2018)

[24] Y. Liang, T. Tsubota, L. P. A. Mooij, and R. van de Krol, Highly improved quantum efficiencies for thin film BiVO₄ photoanodes, J. Phys. Chem. C 115(35), 17594 (2011)

[25] S. Byun, B. Kim, S. Jeon, and B. Shin, Effects of a SnO₂ hole blocking layer in a BiVO₄-based photoanode on photoelectrocatalytic water oxidation, J. Mater. Chem. A Mater. Energy Sustain. 5(15), 6905 (2017)

[26] Y. Asakura, T. Higashi, H. Nishiyama, H. Kobayashi, M. Nakabayashi, N. Shibata, T. Minegishi, T. Hisatomi, M. Katayama, T. Yamada, and K. Domen, Activation of a particulate Ta₃N₅ water-oxidation photoanode with a GaN hole-blocking layer, Sustainable Energy Fuels 2(1), 73 (2018)

[27] E. Alarcón-Lladó, L. Chen, M. Hettick, N. Mashouf, Y. Lin, A. Javey, and J. W. Ager, BiVO4 thin film photoanodes grown by chemical vapor deposition, Phys. Chem. Chem. Phys. 2014(4), 1651 (2014)

[28] A. Annamalai, P. S. Shinde, A. Subramanian, J. Y. Kim, J. H. Kim, S. H. Choi, J. S. Lee, and J. S. Jang, Bifunctional TiO₂ underlayer for α-Fe₂O₃ nanorod based photoelectrochemical cells: Enhanced interface and Ti⁴⁺ doping, J. Mater. Chem. A Mater. Energy Sustain. 3(9), 5007 (2015)

[29] T. Hisatomi, H. Dotan, M. Stefik, K. Sivula, A. Rothschild, M. Gratzel, and N. Mathews, Enhancement in the performance of ultrathin hematite photoanode for water splitting by an oxide underlayer, Adv. Mater. 24(20), 2699 (2012)

[30] Y. Pihosh, I. Turkevych, K. Mawatari, T. Asai, T. Hisatomi, J. Uemura, M. Tosa, K. Shimamura, J. Kubota, K. Domen, and T. Kitamori, Nanostructured WO₃/BiVO₄ photoanodes for efficient photoelectrochemical water splitting, Small 10(18), 3692 (2014)

[31] X. Shi, I. Y. Choi, K. Zhang, J. Kwon, D. Y. Kim, J. K. Lee, S. H. Oh, J. K. Kim, and J. H. Park, Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures, Nat. Commun. 5(1), 4775 (2014)

[32] A. Hayakawa, O. Yoshikawa, T. Fujieda, K. Uehara, and S. Yoshikawa, High performance polythiophene/fullerene bulk-heterojunction solar cell with a TiO_xhole blocking layer, Appl. Phys. Lett. 90(16), 163517 (2007)

[33] W. Ke, G. Fang, J. Wan, H. Tao, Q. Liu, L. Xiong, P. Qin, J. Wang, H. Lei, G. Yang, M. Qin, X. Zhao, and Y. Yan, Efficient hole-blocking layer-free planar halide perovskite thin-film solar cells, Nat. Commun. 6(1), 6700 (2015)

[34] P. Chakthranont, T. R. Hellstern, J. M. McEnaney, and T. F. Jaramillo, Design and fabrication of a precious metal-free tandem core-shell p+n Si/W-doped BiVO₄ photoanode for unassisted water splitting, Adv. Energy Mater. 7(22), 1701515 (2017)

[35] T. Hisatomi, J. Brillet, M. Cornuz, F. Le Formal, N. Tétreault, K. Sivula, and M. Grätzel, A Ga₂O₃ underlayer as an isomorphic template for ultrathin hematite films toward efficient photoelectrochemical water splitting, Faraday Discuss. 155, 223 (2012)

[36] P. M. Rao, L. Cai, C. Liu, I. S. Cho, C. H. Lee, J. M. Weisse, P. Yang, and X. Zheng, Simultaneously efficient light absorption and charge separation in WO₃/BiVO₄ core/shell nanowire photoanode for photoelectrochemical water oxidation, Nano Lett. 14(2), 1099 (2014)

[37] B. Lamm, L. Zhou, P. Rao, and M. Stefik, Atomic layer deposition of space-efficient SnO₂ underlayers for BiVO₄ host-guest architectures for photoassisted water splitting, ChemSusChem 12, 1 (2018)

[38] H. Fujishima and K. Honda, Electrochemical photolysis of water at a semiconductor electrode, Nature 238(5358), 37 (1972)

[39] T. Ohno, T. Mitsui, and M. Matsumura, Photocatalytic activity of S-doped TiO₂ photocatalyst under visible light, Chem. Lett. 32(4), 364 (2003)

[40] N. Liu, V. Haublein, X. Zhou, U. Venkatesan, M. Hartmann, M. Mackovic, T. Nakajima, E. Spiecker, A. Osvet, L. Frey, and P. Schmuki, “Black” TiO₂ nanotubes formed by high-energy proton implantation show noblemetal- co-catalyst free photocatalytic H₂-evolution, Nano Lett. 15(10), 6815 (2015)

[41] X. Chen, L. Liu, P. Y. Yu, and S. S. Mao, Increasing solar absorption for photocatalysis with black hydrogenated titanium dioxide nanocrystals, Science 331(6018), 746 (2011)

[42] J. Cai, M. Wu, Y. Wang, H. Zhang, M. Meng, Y. Tian, X. Li, J. Zhang, L. Zheng, and J. Gong, Synergetic enhancement of light harvesting and charge separation over surface-disorder-engineered TiO₂ photonic crystals, Chem 2(6), 877 (2017)

[43] Y. Yang, L. C. Yin, Y. Gong, P. Niu, J. Q. Wang, L. Gu, X. Chen, G. Liu, L. Wang, and H. M. Cheng, An unusual strong visible-light absorption band in red anatase TiO₂ photocatalyst induced by atomic hydrogen-occupied oxygen vacancies, Adv. Mater. 30(6), 1704479 (2018)

[44] R. Asahi, T. Morikawa, and K. A. Ohwaki, Visible-light photocatalysis in nitrogen-doped titanium oxides, Science 293(5528), 269 (2001)

[45] S. Sakthivel, M. Janczarek, and H. Kisch, Visible light activity and photoelectrochemical properties of nitrogendoped TiO₂, J. Phys. Chem. B 108(50), 19384 (2004)

[46] X. Wang, R. Long, D. Liu, D. Yang, C. Wang, and Y. Xiong, Enhanced full-spectrum water splitting by confining plasmonic Au nanoparticles in N-doped TiO₂ bowl nanoarrays, Nano Energy 24, 87 (2016)

[47] T. M. R. Asahi, T. Ohwaki, and K. Aoki, Visible-light photocatalysis in nitrogen-doped titanium oxides, Science 293(5528), 269 (2001)

[48] G. Wang, X. Xiao, W. Li, Z. Lin, Z. Zhao, C. Chen, C. Wang, Y. Li, X. Huang, L. Miao, C. Jiang, Y. Huang, and X. Duan, Significantly enhanced visible light photoelectrochemical activity in TiO₂ nanowire arrays by nitrogen implantation, Nano Lett. 15(7), 4692 (2015)

[49] T. Lin, C. Yang, Z. Wang, H. Yin, X. Lü, F. Huang, J. Lin, X. Xie, and M. Jiang, Effective nonmetal incorporation in black titania with enhanced solar energy utilization, Energy Environ. Sci. 7(3), 967 (2014)

[50] S. Hejazi, N. T. Nguyen, A. Mazare, and P. Schmuki, Aminated TiO₂ nanotubes as a photoelectrochemical water splitting photoanode, Catal. Today 281, 189 (2017)

[51] S. A. Ansari and M. H. Cho, Highly visible light responsive, narrow band gap TiO₂ nanoparticles modified by elemental red phosphorus for photocatalysis and photoelectrochemical applications, Sci. Rep. 6(1), 25405 (2016)

[52] S. Komatsuda, Y. Asakura, J. J. M. Vequizo, A. Yamakata, and S. Yin, Enhanced photocatalytic NO decomposition of visible-light responsive F-TiO₂/(N; C)-TiO₂ by charge transfer between F-TiO₂ and (N; C)-TiO₂ through their doping levels, Appl. Catal. B 238, 358 (2018)

[53] X. Kang, X. Z. Song, Y. Han, J. Cao, and Z. Tan, Defect-engineered TiO₂ hollow spiny nanocubes for phenol degradation under visible light irradiation, Sci. Rep. 8(1), 5904 (2018)

[54] J. Premkumar, Development of super-hydrophilicity on nitrogen-doped TiO2thin film surface by photoelectrochemical method under visible light, Chem. Mater. 16(21), 3980 (2004)

[55] S. A. Ansari, M. M. Khan, M. O. Ansari, and M. H.Cho, Nitrogen-doped titanium dioxide (N-doped TiO₂) for visible light photocatalysis, New J. Chem. 40(4), 3000 (2016)

[56] X. Pan, M. Q. Yang, X. Fu, N. Zhang, and Y. J. Xu, Defective TiO₂ with oxygen vacancies: Synthesis, properties and photocatalytic applications, Nanoscale 5(9), 3601 (2013)

[57] H. Choi, D. Shin, B. C. Yeo, T. Song, S. S. Han, N. Park, and S. Kim, Simultaneously controllable doping sites and the activity of a W–N codoped TiO₂ photocatalyst, ACS Catal. 6(5), 2745 (2016)

[58] Q. Sun, D. Cortie, S. Zhang, T. J. Frankcombe, G. She, J. Gao, L. R. Sheppard, W. Hu, H. Chen, S. Zhuo, D. Chen, R. L. Withers, G. McIntyre, D. Yu, W. Shi, and Y. Liu, The formation of defect-pairs for highly efficient visiblelight catalysts, Adv. Mater. 29(11), 1605123 (2017)

[59] H. Cui, W. Zhao, C. Yang, H. Yin, T. Lin, Y. Shan, Y. Xie, H. Gu, and F. Huang, Black TiO₂ nanotube arrays for high-efficiency photoelectrochemical water-splitting, J. Mater. Chem. A Mater. Energy Sustain. 2(23), 8612 (2014)

[60] J. Liang, N. Wang, Q. Zhang, B. Liu, X. Kong, C. Wei, D. Zhang, B. Yan, Y. Zhao, and X. Zhang, Exploring the mechanism of a pure and amorphous black-blue TiO₂:H thin film as a photoanode in water splitting, Nano Energy 42, 151 (2017)

[61] M. Krzywiecki, L. Grzadziel, A. Sarfraz, D. Iqbal, A. Szwajca, and A. Erbe, Zinc oxide as a defect-dominated material in thin films for photovoltaic applications – Experimental determination of defect levels, quantification of composition, and construction of band diagram, Phys. Chem. Chem. Phys. 17(15), 10004 (2015)

[62] R. A. Wahyuono, F. Hermann-Westendorf, A. Dellith, C. Schmidt, J. Dellith, J. Plentz, M. Schulz, M. Presselt, M. Seyring, M. Rettenmeyer, and B. Dietzek, Effect of annealing on the sub-bandgap, defects and trapping states of ZnO nanostructures, Chem. Phys.483–484, 112 (2017)

[63] Y. Zhang, H. Zhao, X. Zhao, J. Lin, N. Li, Z. Huo, Z. Yan, M. Zhang, and S. Hu, Narrow-bandgap Nb₂O₅ nanowires with enclosed pores as high-performance photocatalyst, Sci. China Mater. 62(2), 203 (2019)

[64] W. L. M. Lamers, M. Favaro, D. E. Starr, D. Friedrich, S. Lardhi, L. Cavallo, M. Harb, R. van de Krol, L. H. Wong, and F. F. Abdi, Enhanced carrier transport and bandgap reduction in sulfur modified BiVO₄ photoanodes, Chem. Mater. 30, 8630 (2018)

[65] V. Pasumarthi, T. Liu, M. Dupuis, and C. Li, Charge carrier transport dynamics in W/Mo-doped BiVO₄: First principles-based mesoscale characterization, J. Mater. Chem. A Mater. Energy Sustain. 7(7), 3054 (2019)

[66] T. Li, J. He, B. Pena, and C. P. Berlinguette, Curing BiVO₄ photoanodes with ultraviolet light enhances photoelectrocatalysis, Angew. Chem. Int. Ed. 55(5), 1769 (2016)

[67] R. Niishiro, Y. Takano, Q. Jia, M. Yamaguchi, A. Iwase, Y. Kuang, T. Minegishi, T. Yamada, K. Domen, and A. Kudo, A CoO_x-modified SnNb₂O₆ photoelectrode for highly efficient oxygen evolution from water, Chem. Commun. (Camb.) 53(3), 629 (2017)

[68] Y. Hosogi, Y. Shimodaira, H. Kato, H. Kobayashi, and A. Kudo, Role of Sn²⁺ in the band structure of SnM₂O₆ and Sn₂M₂O₇ (M= Nb and Ta) and their photocatalytic properties, Chem. Mater. 20(4), 1299 (2008)

[69] Y. Shimodaira, H. Kato, H. Kobayashi, and A. Kudo, Investigations of electronic structures and photocatalytic activities under visible light irradiation of lead molybdate replaced with chromium (VI), Bull. Chem. Soc. Jpn. 80(5), 885 (2007)

[70] D. Noureldine and K. Takanabe, State-of-the-art Sn²⁺-based ternary oxides as photocatalysts for water splitting: Electronic structures and optoelectronic properties, Catal. Sci. Technol. 6(21), 7656 (2016)

[71] H. Seo, Y. Ping, and G. Galli, Role of point defects in enhancing the conductivity of BiVO₄, Chem. Mater. 30(21), 7793 (2018)

[72] F. F. Abdi, T. J. Savenije, M. M. May, B. Dam, and R. van de Krol, The origin of slow carrier transport in BiVO₄ thin film photoanodes: A time-resolved microwave conductivity study, J. Phys. Chem. Lett. 4(16), 2752 (2013)

[73] Z. Zhu, P. Sarker, C. Zhao, L. Zhou, R. L. Grimm, M. N. Huda, and P. M. Rao, Photoelectrochemical properties and behavior of alpha-SnWO₄ photoanodes synthesized by hydrothermal conversion of WO₃ films, ACS Appl. Mater. Interfaces 9(2), 1459 (2017)

[74] A. Ziani, M. Harb, D. Noureldine, and K. Takanabe, UVVis optoelectronic properties of a-SnWO₄: A comparative experimental and density functional theory based study, APL Mater. 3(9), 096101 (2015)

[75] D. Bohra and W. A. Smith, Improved charge separation via Fe-doping of copper tungstate photoanodes, Phys. Chem. Chem. Phys. 17(15), 9857 (2015)

[76] Y. Gao and T. W. Hamann, Quantitative hole collection for photoelectrochemical water oxidation with CuWO₄, Chem. Commun. 53(7), 1285 (2017)

[77] S. Byun, G. Jung, Y. Shi, M. Lanza, and B. Shin, Aging of a vanadium precursor solution: Influencing material properties and photoelectrochemical water oxidation performance of solution-processed BiVO₄ photoanodes, Adv. Funct. Mater.1806662 (2019)

[78] M. Ziwritsch, S. Müller, H. Hempel, T. Unold, F. F. Abdi, R. van de Krol, D. Friedrich, and R. Eichberger, Direct time-resolved observation of carrier trapping and polaron conductivity in BiVO₄, ACS Energy Lett. 1(5), 888 (2016)

[79] B. J. Trześniewski, I. A. Digdaya, T. Nagaki, S. Ravishankar, I. Herraiz-Cardona, D. A. Vermaas, A. Longo, S. Gimenez, and W. A. Smith, Near-complete suppression of surface losses and total internal quantum efficiency in BiVO₄ photoanodes, Energy Environ. Sci. 10(6), 1517 (2017)

[80] J. K.Cooper, S. B. Scott, Y. Ling, J. Yang, S. Hao, Y. Li, F. M. Toma, M. Stutzmann, K. V. Lakshmi, and I. D. Sharp, Role of hydrogen in defining the n-type character of BiVO₄ photoanodes, Chem. Mater. 28(16), 5761 (2016)

[81] F. F. Abdi, N. Firet, and R. van de Krol, Efficient BiVO4 thin film photoanodes modified with cobalt phosphate catalyst and W-doping, ChemCatChem 5(2), 490 (2013)

[82] Y. Bu, J. Tian, Z. Chen, Q. Zhang, W. Li, F. Tian, and J. P. Ao, Optimization of the photo-electrochemical performance of Mo-Doped BiVO₄ photoanode by controlling the metal-oxygen bond state on (020) facet, Adv. Mater. Interfaces 4(10), 1601235 (2017)

[83] S. K. Cho, H. S. Park, H. C. Lee, K. M. Nam, and A. J. Bard, Metal doping of BiVO₄ by composite electrodeposition with improved photoelectrochemical water oxidation, J. Phys. Chem. C 117(44), 23048 (2013)

[84] J. H. Xin Zhao, X. Yao, S. Chen, and Z. Chen, Clarifying the roles of oxygen vacancy in W-doped BiVO₄ for solar water splitting, ACS Appl. Energy Mater. 1(7), 3410 (2018)

[85] V. Nair, C. L. Perkins, Q. Lin, and M. Law, Textured nanoporous Mo:BiVO₄ photoanodes with high charge transport and charge transfer quantum efficiencies for oxygen evolution, Energy Environ. Sci. 9(4), 1412 (2016)

[86] G. V. Govindaraju, J. M. Morbec, G. A. Galli, and K. S. Choi, Experimental and computational investigation of lanthanide ion doping on BiVO₄ photoanodes for solar water splitting, J. Phys. Chem. C 122(34), 19416 (2018)

[87] K. P. Parmar, H. J. Kang, A. Bist, P. Dua, J. S. Jang, and J. S. Lee, Photocatalytic and photoelectrochemical water oxidation over metal-doped monoclinic BiVO₄ photoanodes, ChemSusChem 5(10), 1926 (2012)

[88] K. Ding, B. Chen, Z. Fang, Y. Zhang, and Z. Chen, Why the photocatalytic activity of Mo-doped BiVO₄ is enhanced: a comprehensive density functional study, Phys. Chem. Chem. Phys. 16(26), 13465 (2014)

[89] H. W. Jeong, T. H. Jeon, J. S. Jang, W. Choi, and H. Park, Strategic modification of BiVO₄ for improving photoelectrochemical water oxidation performance, J. Phys. Chem. C 117(18), 9104 (2013)

[90] J. A. Seabold, K. Zhu, and N. R. Neale, Efficient solar photoelectrolysis by nanoporous Mo:BiVO₄ through controlled electron transport, Phys. Chem. Chem. Phys. 16(3), 1121 (2014)

[91] H. S. Park, K. E. Kweon, H. Ye, E. Paek, G. S. Hwang, and A. J. Bard, Factors in the metal doping of BiVO₄ for improved photoelectrocatalytic activity as studied by scanning electrochemical microscopy and first-principles density-functional calculation, J. Phys. Chem. C 115(36), 17870 (2011)

[92] I. Cesar, K. Sivula, A. Kay, R. Zboril, and M. Grätzel, Influence of feature size, film thickness, and silicon doping on the performance of nanostructured hematite photoanodes for solar water splitting, J. Phys. Chem. C 113(2), 772 (2009)

[93] F. F. Abdi, L. Han, A. H. Smets, M. Zeman, B. Dam, and R. van de Krol, Efficient solar water splitting by enhanced charge separation in a bismuth vanadate-silicon tandem photoelectrode, Nat. Commun. 4(1), 2195 (2013)

[94] A. J. Rettie, H. C. Lee, L. G. Marshall, J. F. Lin, C. Capan, J. Lindemuth, J. S. McCloy, J. Zhou, A. J. Bard, and C. B. Mullins, Combined charge carrier transport and photoelectrochemical characterization of BiVO₄ single crystals: Intrinsic behavior of a complex metal oxide, J. Am. Chem. Soc. 135(30), 11389 (2013)

[95] W. Zhang, F. Wu, J. Li, D. Yan, J. Tao, Y. Ping, and M. Liu, Unconventional relation between charge transport and photocurrent via boosting small polaron hopping for photoelectrochemical water splitting, ACS Energy Lett. 3(9), 2232 (2018)

[96] L. Zhang, X. Ye, M. Boloor, A. Poletayev, N. A. Melosh, and W. C. Chueh, Significantly enhanced photocurrent for water oxidation in monolithic Mo:BiVO₄/SnO₂/Si by thermally increasing the minority carrier diffusion length, Energy Environ. Sci. 9(6), 2044 (2016)

[97] J. W. Jang, D. Friedrich, S. Müller, M. Lamers, H. Hempel, S. Lardhi, Z. Cao, M. Harb, L. Cavallo, R. Heller, R. Eichberger, R. van de Krol, and F. F. Abdi, Enhancing charge carrier lifetime in metal oxide photoelectrodes through mild hydrogen treatment, Adv. Energy Mater. 7(22), 1701536 (2017)

[98] D. K. Lee, D. Lee, M. A. Lumley, and K. S. Choi, Progress on ternary oxide-based photoanodes for use in photoelectrochemical cells for solar water splitting, Chem. Soc. Rev. 48(7), 2126 (2019)

[99] G. Wang, H. Wang, Y. Ling, Y. Tang, X. Yang, R. C. Fitzmorris, C. Wang, J. Z. Zhang, and Y. Li, Hydrogentreated TiO₂ nanowire arrays for photoelectrochemical water splitting, Nano Lett. 11(7), 3026 (2011)

[100] N. Guijarro, P. Bornoz, M. Prévot, X. Yu, X. Zhu, M. Johnson, X. Jeanbourquin, F. Le Formal, and K. Sivula, Evaluating spinel ferrites MFe₂O₄ (M= Cu, Mg, Zn) as photoanodes for solar water oxidation: Prospects and limitations, Sustainable Energy Fuels 2(1), 103 (2018)

[101] Y. Tang, N. Rong, F. Liu, M. Chu, H. Dong, Y. Zhang, and P. Xiao, Enhancement of the photoelectrochemical performance of CuWO₄ films for water splitting by hydrogen treatment, Appl. Surf. Sci. 361, 133 (2016)

[102] Y. Ling, G. Wang, J. Reddy, C. Wang, J. Z. Zhang, and Y. Li, The influence of oxygen content on the thermal activation of hematite nanowires, Angew. Chem. Int. Ed. 51(17), 4074 (2012)

[103] A. Milbrat, W. J. C. Vijselaar, Y. Guo, B. Mei, J. Huskens, and G. Mul, Integration of molybdenum-doped, hydrogen-annealed BiVO₄ with silicon microwires for photoelectrochemical applications, ACS Sustain. Chem. & Eng. 7(5), 5034 (2019)

[104] Y. Zhang, X. Zhang, D. Wang, F. Wan, and Y. Liu, Protecting hydrogenation-generated oxygen vacancies in BiVO₄ photoanode for enhanced water oxidation with conformal ultrathin amorphous TiO₂ layer, Appl. Surf. Sci. 403, 389 (2017)

[105] G. Wang, Y. Ling, H. Wang, X. Yang, C. Wang, J. Z. Zhang, and Y. Li, Hydrogen-treated WO₃ nanoflakes show enhanced photostability, Energy Environ. Sci. 5(3), 6180 (2012)

[106] W. Li, P. Da, Y. Zhang, Y. Wang, X. Lin, X. Gong, and G. Zheng, WO3 nanoflakes for enhanced photoelectrochemical conversion, ACS Nano 8(11), 11770 (2014)

[107] D. Ma, J. Xie, J. Li, S. Liu, F. Wang, H. Zhang, W. Wang, A. Wang, and H. Sun, Synthesis and hydrogen reduction of nano-sized copper tungstate powders produced by a hydrothermal method, Int. J. Refract. Met. Hard Mater. 46, 152 (2014)

[108] D. Hu, P. Diao, D. Xu, M. Xia, Y. Gu, Q. Wu, C. Li, and S. Yang, Copper(II) tungstate nanoflake array films: Sacrificial template synthesis, hydrogen treatment, and their application as photoanodes in solar water splitting, Nanoscale 8(11), 5892 (2016)

[109] J. H. Kim, Y. J. Jang, J. H. Kim, J. W. Jang, S. H. Choi, and J. S. Lee, Defective ZnFe₂O₄ nanorods with oxygen vacancy for photoelectrochemical water splitting, Nanoscale 7(45), 19144 (2015)

[110] S. Wang, P. Chen, J. H. Yun, Y. Hu, and L. Wang, An electrochemically treated BiVO₄ photoanode for efficient photoelectrochemical water splitting, Angew. Chem. Int. Ed. 56(29), 8500 (2017)

[111] S. K. Pilli, T. E. Furtak, L. D. Brown, T. G. Deutsch, J. A. Turner, and A. M. Herring, Cobalt-phosphate (Co-Pi) catalyst modified Mo-doped BiVO₄ photoelectrodes for solar water oxidation, Energy Environ. Sci. 4(12), 5028 (2011)

[112] Q. Shi, S. Murcia-López, P. Tang, C. Flox, J. R. Morante, Z. Bian, H. Wang, and T. Andreu, Role of tungsten doping on the surface states in BiVO₄ photoanodes for water oxidation: Tuning the electron trapping process, ACS Catal. 8(4), 3331 (2018)

[113] W. Luo, Z. Yang, Z. Li, J. Zhang, J. Liu, Z. Zhao, Z. Wang, S. Yan, T. Yu, and Z. Zou, Solar hydrogen generation from seawater with a modified BiVO₄ photoanode, Energy Environ. Sci. 4(10), 4046 (2011)

[114] L. Gao, Y. Li, J. Ren, S. Wang, R. Wang, G. Fu, and Y. Hu, Passivation of defect states in anatase TiO₂ hollow spheres with Mg doping: Realizing efficient photocatalytic overall water splitting, Appl. Catal. B 202, 127 (2017)

[115] C. Chen, Y. Wei, G. Yuan, Q. Liu, R. Lu, X. Huang, Y. Cao, and P. Zhu, Synergistic effect of Si doping and heat treatments enhances the photoelectrochemical water oxidation performance of TiO₂ nanorod arrays, Adv. Funct. Mater. 27(31), 1701575 (2017)

[116] A. G. Hufnagel, H. Hajiyani, S. Zhang, T. Li, O. Kasian, B. Gault, B. Breitbach, T. Bein, D. Fattakhova-Rohlfing, C. Scheu, and R. Pentcheva, Why tin-doping enhances the efficiency of hematite photoanodes for water splittingthe full picture, Adv. Funct. Mater. 28(52), 1804472 (2018)

[117] Y. Guo, N. Zhang, X. Wang, Q. Qian, S. Zhang, Z. Li, and Z. Zou, A facile spray pyrolysis method to prepare Ti-doped ZnFe₂O₄ for boosting photoelectrochemical water splitting, J. Mater. Chem. A Mater. Energy Sustain. 5(16), 7571 (2017)

[118] J. H. Kim, J. H. Kim, J. W. Jang, J. Y. Kim, S. H. Choi, G. Magesh, J. Lee, and J. S. Lee, Awakening solar water-splitting activity of ZnFe₂O₄ nanorods by hybrid microwave annealing, Adv. Energy Mater. 5(6), 1401933 (2015)

[119] C. D. Morton, I. J. Slipper, M. J. K. Thomas, and B. D. Alexander, Synthesis and characterisation of Fe–V–O thin film photoanodes, J. Photochem. Photobiol. Chem. 216(2–3), 209 (2010)

[120] G. Peng, J. Albero, H. Garcia, and M. Shalom, A watersplitting carbon nitride photoelectrochemical cell with efficient charge separation and remarkably low onset potential, Angew. Chem. Int. Ed. 57(48), 15807 (2018)

[121] X. Shi, K. Zhang, K. Shin, J. H. Moon, T. W. Lee, and J. H. Park, Constructing inverse opal structured hematite photoanodes via electrochemical process and their application to photoelectrochemical water splitting, Phys. Chem. Chem. Phys. 15(28), 11717 (2013)

[122] L. Pei, B. Lv, S. Wang, Z. Yu, S. Yan, R. Abe, and Z. Zou, Oriented growth of Sc-doped Ta₃N₅ nanorod photoanode achieving low-onset-potential for photoelectrochemical water oxidation, ACS Appl. Energy Mater. 1(8), 4150 (2018)

[123] J. Seo, H. Nishiyama, T. Yamada, and K. Domen, Visiblelight- responsive photoanodes for highly active, stable water oxidation, Angew. Chem. Int. Ed. 57(28), 8396 (2018)

[124] M. Zhong, T. Hisatomi, Y. Kuang, J. Zhao, M. Liu, A. Iwase, Q. Jia, H. Nishiyama, T. Minegishi, M. Nakabayashi, N. Shibata, R. Niishiro, C. Katayama, H. Shibano, M. Katayama, A. Kudo, T. Yamada, and K. Domen, Surface modification of CoO_xloaded BiVO₄ photoanodes with ultrathin p-type NiO layers for improved solar water oxidation, J. Am. Chem. Soc. 137(15), 5053 (2015)

[125] Z. Zhu, H. Tian, M. Zhang, B. Liang, and W. Li, Preparation of a-SnWO₄ hierarchical spheres by Bi³⁺-doping and their enhanced photocatalytic activity under visible light, Ceram. Int. 42(13), 14743 (2016)

[126] S. Yao, M. Zhang, J. Di, Z. Wang, Y. Long, and W. Li, Preparation of a-SnWO₄/SnO₂ heterostructure with enhanced visible-light-driven photocatalytic activity, Appl. Surf. Sci. 357, 1528 (2015)

[127] I. S. Cho, C. H. Kwak, D. W. Kim, S. Lee, and K. S. Hong, Photophysical, photoelectrochemical, and photocatalytic properties of novel SnWO₄ oxide semiconductors with narrow band gaps, J. Phys. Chem. C 113(24), 10647 (2009)

[128] Y. Wang, H. Sun, S. Tan, H. Feng, Z. Cheng, J. Zhao, A. Zhao, B. Wang, Y. Luo, J. Yang, and J. G. Hou, Role of point defects on the reactivity of reconstructed anatase titanium dioxide (001) surface, Nat. Commun. 4(1), 2214 (2013)

[129] G. Liu, H. G. Yang, X. Wang, L. Cheng, H. Lu, L. Wang, G. Q. M. Lu, and H. M. Cheng, Enhanced photoactivity of oxygen-deficient anatase TiO₂ sheets with dominant {001} facets, J. Phys. Chem. C 113(52), 21784 (2009)

[130] G. Liu, J. Pan, L. Yin, J. T. S. Irvine, F. Li, J. Tan, P. Wormald, and H. M. Cheng, Heteroatom-modulated switching of photocatalytic hydrogen and oxygen evolution preferences of anatase TiO₂ microspheres, Adv. Funct. Mater. 22(15), 3233 (2012)

[131] J. Hu, X. Zhao, W. Chen, and Z. Chen, Enhanced charge transport and increased active sites on-Fe₂O₃ (110) nanorod surface containing oxygen vacancies for improved solar water oxidation performance, ACS Omega 3(11), 14973 (2018)

[132] C. Fàbrega, D. Monllor-Satoca, S. Ampudia, A. Parra, T. Andreu, and J. R. Morante, Tuning the Fermi level and the kinetics of surface states of TiO₂ nanorods by means of ammonia treatments, J. Phys. Chem. C 117(40), 20517 (2013)

[133] A. L. Linsebigler, G. Lu, and J. T. Yates, Photocatalysis on TiO₂ surfaces: Principles, mechanisms, and selected results, Chem. Rev. 95(3), 735 (1995)

[134] A. Yamakata, T. Ishibashi, and H. Onishi, Kinetics of the photocatalytic water-splitting reaction on TiO₂ and Pt/TiO₂ studied by time-resolved infrared absorption spectroscopy, J. Mol. Catal. Chem. 199(1–2), 85 (2003)

[135] T. Zhang, Y. Liu, J. Liang, and D. Wang, Enhancement of photoelectrochemical and photocathodic protection properties of TiO₂ nanotube arrays by simple surface UV treatment, Appl. Surf. Sci. 394, 440 (2017)

[136] T. Zhang, S. Cui, B. Yu, Z. Liu, and D. Wang, Surface engineering for an enhanced photoelectrochemical response of TiO₂ nanotube arrays by simple surface air plasma treatment, Chem. Commun. 51(95), 16940 (2015)

[137] T. L. Villarreal, R. Go’mez, M. Neumann-Spallart, N. Alonso-Vante, and P. Salvador, Semiconductor photooxidation of pollutants dissolved in water: A kinetic model for distinguishing between direct and indirect interfacial hole transfer (I): Photoelectrochemical experiments with polycrystalline anatase electrodes under current doubling and absence of recombination, J. Phys. Chem. B 108(39), 15172 (2004)

[138] A. Kafizas, Y. Ma, E. Pastor, S. R. Pendlebury, C. Mesa, L. Francàs, F. Le Formal, N. Noor, M. Ling, C. Sotelo-Vazquez, C. J. Carmalt, I. P. Parkin, and J. R. Durrant, Water oxidation kinetics of accumulated holes on the surface of a TiO₂ photoanode: A rate law analysis, ACS Catal. 7(7), 4896 (2017)

[139] S. H. Szczepankiewicz, A. J. Colussi, and M. R. Hoffmann, Infrared spectra of photoinduced species on hydroxylated titania surfaces, J. Phys. Chem. B 104(42), 9842 (2000)

[140] M. A. Grela, M. E. J. Coronel, and A. J. Colussi, Quantitative spin-trapping studies of weakly illuminated titanium dioxide sols: Implications for the mechanism of photocatalysis, J. Phys. Chem. 100(42), 16940 (1996)

[141] X. Cheng, Q. Cheng, X. Deng, P. Wang, and H. Liu, A facile and novel strategy to synthesize reduced TiO2 nanotubes photoelectrode for photoelectrocatalytic degradation of diclofenac, Chemosphere 144, 888 (2016)

[142] J. Cheng, J. VandeVondele, and M. Sprik, Identifying trapped electronic holes at the aqueous TiO₂ interface, J. Phys. Chem. C 118(10), 5437 (2014)

[143] Y. Ji, B. Wang, and Y. Luo, GGA+Ustudy on the mechanism of photodecomposition of water adsorbed on rutile TiO₂ (110) surface: Free vs. trapped hole, J. Phys. Chem. C 118(2), 1027 (2014)

[144] T. Hisatomi, F. Le Formal, M. Cornuz, J. Brillet, N. Tétreault, K. Sivula, and M. Grätzel, Cathodic shift in onset potential of solar oxygen evolution on hematite by 13-group oxide overlayers, Energy Environ. Sci. 4(7), 2512 (2011)

[145] Z. Hu, Z. Shen, and J. C. Yu, Covalent fixation of surface oxygen atoms on hematite photoanode for enhanced water oxidation, Chem. Mater. 28(2), 564 (2016)

[146] C. Li, Z. Luo, T. Wang, and J. Gong, Surface, bulk, and interface: Rational design of hematite architecture toward efficient photo-electrochemical water splitting, Adv. Mater. 30(30), 1707502 (2018)

[147] Y. He, J. E. Thorne, C. H. Wu, P. Ma, C. Du, Q. Dong, J. Guo, and D. Wang, What limits the performance of Ta3N5 for solar water splitting? Chem 1(4), 640 (2016)

[148] Y. He, P. Ma, S. Zhu, M. Liu, Q. Dong, J. Espano, X. Yao, and D. Wang, Photo-induced performance enhancement of tantalum nitride for solar water oxidation, Joule 1(4), 831 (2017)

[149] E. Nurlaela, Y. Sasaki, M. Nakabayashi, N. Shibata, T. Yamada, and K. Domen, Towards zero bias photoelectrochemical water splitting: onset potential improvement on a Mg:GaN modified-Ta₃N₅ photoanode, J. Mater. Chem. A Mater. Energy Sustain. 6(31), 15265 (2018)

[150] Y. Kuang, T. Yamada, and K. Domen, Surface and interface engineering for photoelectrochemical water oxidation, Joule 1(2), 290 (2017)

[151] P. Y. Tang, H. B. Xie, C. Ros, L. J. Han, M. Biset-Peiró, Y. M. He, W. Kramer, A. P. Rodríguez, E. Saucedo, J. R. Galán-Mascarós, T. Andreu, J. R. Morante, and J. Arbiol, Enhanced photoelectrochemical water splitting of hematite multilayer nanowire photoanodes by tuning the surface state via bottom-up interfacial engineering, Energy Environ. Sci. 10(10), 2124 (2017)

[152] R. d. Krol and M. Grätzel, Photoelectrochemical Hydrogen Production, Springer, New York, 2011, p 321

[153] K. J. McDonald and K. S. Choi, Synthesis and photoelectrochemical properties of Fe₂O₃/ZnFe₂O₄ composite photoanodes for use in solar water oxidation, Chem. Mater. 23(21), 4863 (2011)

[154] B. Klahr, S. Gimenez, F. Fabregat-Santiago, J. Bisquert, and T. W. Hamann, Electrochemical and photoelectrochemical investigation of water oxidation with hematite electrodes, Energy Environ. Sci. 5(6), 7626 (2012)

[155] X. Yang, C. Du, R. Liu, J. Xie, and D. Wang, Balancing photovoltage generation and charge-transfer enhancement for catalyst-decorated photoelectrochemical water splitting: A case study of the hematite/MnO_x combination, J. Catal. 304, 86 (2013)

[156] G. Liu, S. Ye, P. Yan, F. Xiong, P. Fu, Z. Wang, Z. Chen, J. Shi, and C. Li, Enabling an integrated tantalum nitride photoanode to approach the theoretical photocurrent limit for solar water splitting, Energy Environ. Sci. 9(4), 1327 (2016)

[157] F. F. Abdi and R. van de Krol, Nature and light dependence of bulk recombination in Co-Pi-catalyzed BiVO₄ photoanodes, J. Phys. Chem. C 116(17), 9398 (2012)

[158] B. Klahr, S. Gimenez, F. Fabregat-Santiago, J. Bisquert, and T. W. Hamann, Photoelectrochemical and impedance spectroscopic investigation of water oxidation with “Co-Pi”-coated hematite electrodes, J. Am. Chem. Soc. 134(40), 16693 (2012)

[159] D. K. Zhong, M. Cornuz, K. Sivula, M. Grätzel, and D. R. Gamelin, Photo-assisted electrodeposition of cobalt– phosphate (Co-Pi) catalyst on hematite photoanodes for solar water oxidation, Energy Environ. Sci. 4(5), 1759 (2011)

[160] S. D. Tilley, M. Cornuz, K. Sivula, and M. Grätzel, Lightinduced water splitting with hematite: Improved nanostructure and iridium oxide catalysis, Angew. Chem. Int. Ed. 49(36), 6405 (2010)

[161] W. Y. Sohn, J. E. Thorne, Y. Zhang, S. Kuwahara, Q. Shen, D. Wang, and K. Katayama, Charge carrier kinetics in hematite with NiFeO_x coating in aqueous solutions: Dependence on bias voltage, J. Photochem. Photobiol. Chem. 353, 344 (2018)

[162] X. Yang, R. Liu, C. Du, P. Dai, Z. Zheng, and D. Wang, Improving hematite-based photoelectrochemical water splitting with ultrathin TiO₂ by atomic layer deposition, ACS Appl. Mater. Interfaces 6(15), 12005 (2014)

[163] R. Liu, Z. Zheng, J. Spurgeon, and X. Yang, Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers, Energy Environ. Sci. 7(8), 2504 (2014)

[164] M. Zhong, T. Hisatomi, Y. Sasaki, S. Suzuki, K. Teshima, M. Nakabayashi, N. Shibata, H. Nishiyama, M. Katayama, T. Yamada, and K. Domen, Highly active GaN-stabilized Ta₃N₅ thin-film photoanode for solar water oxidation, Angew. Chem. Int. Ed. 56(17), 4739 (2017)

[165] S. Hu, M. R. Shaner, J. A. Beardslee, M. Lichterman, B. S. Brunschwig, and N. S. Lewis, Amorphous TiO₂ coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidation, Science 344(6187), 1005 (2014)

[166] D. Eisenberg, H. S. Ahn, and A. J. Bard, Enhanced photoelectrochemical water oxidation on bismuth vanadate by electrodeposition of amorphous titanium dioxide, J. Am. Chem. Soc. 136(40), 14011 (2014)

[167] A. G. Scheuermann, J. P. Lawrence, K. W. Kemp, T. Ito, A. Walsh, C. E. Chidsey, P. K. Hurley, and P. C. McIntyre, Design principles for maximizing photovoltage in metal-oxide-protected water-splitting photoanodes, Nat. Mater. 15(1), 99 (2016)

[168] S. Hu, M. H. Richter, M. F. Lichterman, J. Beardslee, T. Mayer, B. S. Brunschwig, and N. S. Lewis, Electrical, photoelectrochemical, and photoelectron spectroscopic investigation of the interfacial transport and energetics of amorphous TiO₂/Si heterojunctions, J. Phys. Chem. C 120(6), 3117 (2016)

[169] T. Yao, R. Chen, J. Li, J. Han, W. Qin, H. Wang, J. Shi, F. Fan, and C. Li, Manipulating the interfacial energetics of n-type silicon photoanode for efficient water oxidation, J. Am. Chem. Soc. 138(41), 13664 (2016)

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