Hydrothermal synthesis of ZnO quantum dot/KNb₃O₈ nanosheet photocatalysts for reducing carbon dioxide to methanol

• Xiao Shao,
• Weiyue Xin and
• Xiaohong Yin

Beilstein J. Nanotechnol. 2017, 8, 2264–2270, doi:10.3762/bjnano.8.226

• . The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and UV–vis absorption spectroscopy (UV–vis). The photocatalytic activity of the

• , similar to what occurs in natural photosynthesis. Until now, the organics produced by such artificial photosynthesis include methane [2], formaldehyde [3], methanol [4], methyl formate [5], among others. Alkaline niobates, which are great potential photocatalysts, have been developed in virtue of their

• knowledge, there have been few reports about the photocatalytic reduction of CO2 using KNb3O8 nanosheets. In this paper, we describe the synthesis of composite photocatalysts comprised of ZnO quantum dots and KNb3O8 nanosheets, produced by hydrothermal synthesis. The as-prepared photocatalysts were tested

Evaluating the toxicity of TiO₂-based nanoparticles to Chinese hamster ovary cells and Escherichia coli: a complementary experimental and computational approach

• Alicja Mikolajczyk,
• Natalia Sizochenko,
• Ewa Mulkiewicz,
• Anna Malankowska,
• Michal Nischk,
• Przemyslaw Jurczak,
• Seishiro Hirano,
• Grzegorz Nowaczyk,
• Adriana Zaleska-Medynska,
• Jerzy Leszczynski,
• Agnieszka Gajewicz and
• Tomasz Puzyn

Beilstein J. Nanotechnol. 2017, 8, 2171–2180, doi:10.3762/bjnano.8.216

• alters the rate of chemical reactions, when exposed to light (photocatalyst) [1]. TiO2-based NPs have already found wide applications as efficient photocatalysts for sterilization, sanitation, air and water purification systems, hydrogen production by water splitting, and dye-sensitized solar cells [1

Two-dimensional carbon-based nanocomposites for photocatalytic energy generation and environmental remediation applications

• Suneel Kumar,
• Ashish Kumar,
• Ashish Bahuguna,
• Vipul Sharma and
• Venkata Krishnan

Beilstein J. Nanotechnol. 2017, 8, 1571–1600, doi:10.3762/bjnano.8.159

• carbon nitride-based nanocomposites as photocatalysts for energy and environmental applications is discussed in detail. This review concludes by highlighting the advantages and challenges involved in the use of two-dimensional carbon-based nanocomposites for photocatalysis. Finally, the future

• separation rate of photogenerated charge carriers to enhance the quantum yield. Notably, such heterojunction formation with semiconductors also enhances the light absorption efficiency of photocatalysts from UV to visible region of the solar energy spectrum. Furthermore, it is noteworthy to mention here that

• the preparation of g-C3N4 based nanocomposites, which includes molecular self-assembly [93], microwave assisted heating [38], molten salt synthesis [94] and ionic liquid strategy [95]. 2D carbon-based nanocomposites as photocatalysts 2D graphene-based photocatalysts for energy generation

ZnO nanoparticles sensitized by CuInZn_xS_2+x quantum dots as highly efficient solar light driven photocatalysts

• Florian Donat,
• Serge Corbel,
• Halima Alem,
• Steve Pontvianne,
• Lavinia Balan,
• Ghouti Medjahdi and
• Raphaël Schneider

Beilstein J. Nanotechnol. 2017, 8, 1080–1093, doi:10.3762/bjnano.8.110

• air [1][2][3][4][5] and can also be used to produce energy vectors such as hydrogen from water [6][7][8]. Due to their strong catalytic activity, reasonable photo- and chemical stability, and weak toxicity, TiO2 and ZnO semiconductors are the most commonly used photocatalysts. However, their large

• bandgap (≈3.2–3.3 eV) restricts light activation to the UV range (which accounts for only ≈4% of the solar spectrum) for the generation of the charge carriers responsible for the surface redox reactions. To improve the efficient use of solar light, visible-light-responsive photocatalysts should be

• coupled to those of the QDs [10][11][12]. Heterostructured photocatalysts such as ZnO/CdS or TiO2/CdS or TiO2/PbS exhibit extended light absorption and improved photoreactivity due to the promoted separation of photo-induced charge carriers [13][14][15][16][17][18][19]. However, QDs such as CdS or PbS

Assembly of metallic nanoparticle arrays on glass via nanoimprinting and thin-film dewetting

• Sun-Kyu Lee,
• Sori Hwang,
• Yoon-Kee Kim and
• Yong-Jun Oh

Beilstein J. Nanotechnol. 2017, 8, 1049–1055, doi:10.3762/bjnano.8.106

• surface [1][2]. Because it is a relatively simple process [3], this technique opens up numerous applications, such as high-density magnetic recording media [2][4], photovoltaic devices [5][6][7][8][9][10], photocatalysts [11] and catalysts for the fabrication of carbon nanotubes and nanowires. However

High photocatalytic activity of Fe₂O₃/TiO₂ nanocomposites prepared by photodeposition for degradation of 2,4-dichlorophenoxyacetic acid

• Shu Chin Lee,
• Hendrik O. Lintang and
• Leny Yuliati

Beilstein J. Nanotechnol. 2017, 8, 915–926, doi:10.3762/bjnano.8.93

• have been widely suggested for environmental remediation under mild conditions. In the presence of only a photocatalyst and a light source of appropriate energy, the process can mineralize organic pollutants to harmless products such as carbon dioxide and water. Among the semiconductor photocatalysts

• of the best modifiers, the use of a co-catalyst has been recognized to improve the photocatalytic performance of semiconductor photocatalysts as it promotes charge separation and suppresses photocorrosion of the semiconductor photocatalyst [3][4]. One of the potential co-catalyst modifiers is iron

• (III) oxide (Fe2O3), which is nontoxic, stable, cost effective and found abundantly in the earth. It has been reported that Fe2O3 can be used to increase the photocatalytic activity or selectivity of semiconductor photocatalysts for degradation of organic pollutants [5][6][7][8][9][10][11][12][13][14

Synthesis of graphene–transition metal oxide hybrid nanoparticles and their application in various fields

• Arpita Jana,
• Elke Scheer and
• Sebastian Polarz

Beilstein J. Nanotechnol. 2017, 8, 688–714, doi:10.3762/bjnano.8.74

• ), sensors, photocatalysts, removal of organic pollutants, etc. Recent studies have shown that a single graphene sheet (GS) has extraordinary electronic transport properties. One possible route to connecting those properties for application in electronics would be to prepare graphene-wrapped TMO NPs. In this

• synthesis, properties and applications of graphene–metal oxide composite NPs are discussed in detail [21]. The review by Yin et al. focusses on graphene–NP-based hybrid sensors [22], while Xiang et al. review the state of the art in graphene–semiconductor photocatalysts [23]. In this review, we

• then the TiO2 NPs were wrapped by graphene. These hybrids have high potential for photocatalytic application [72]. Zhang et al. have reported graphene-encapsulated TiO2 nanospheres as efficient photocatalysts for the decomposition of rhodamine B with an efficiency up to 91% in 90 min, which is much

Investigation of the photocatalytic efficiency of tantalum alkoxy carboxylate-derived Ta₂O₅ nanoparticles in rhodamine B removal

• Subia Ambreen,
• Mohammad Danish,
• Narendra D. Pandey and
• Ashutosh Pandey

Beilstein J. Nanotechnol. 2017, 8, 604–613, doi:10.3762/bjnano.8.65

• and CeO2, serve as potential photocatalysts [1][2][3][4]. The properties of the metal oxide nanoparticles (surface area, band gap, porosity) determine its photocatalytic activity for the degradation of organic pollutants from water. Because of properties such as high refractive index and large band

Photocatalysis applications of some hybrid polymeric composites incorporating TiO₂ nanoparticles and their combinations with SiO₂/Fe₂O₃

• Andreea Laura Chibac,
• Tinca Buruiana,
• Violeta Melinte and
• Emil C. Buruiana

Beilstein J. Nanotechnol. 2017, 8, 272–286, doi:10.3762/bjnano.8.30

• pursued to reuse and reduce the expense caused by complex centrifugation or filtration steps of the nanostructured photocatalysts, for example, the preparation of TiO2 NPs with magnetic properties [27][28][29][30] or the immobilization of titania on/in diverse matrices such as glass, zeolite, ceramic

• maximization of the photocatalytic efficiency. An interesting route to reach this goal is the use of iron(III) added to titanium dioxide photocatalysts, which improves the photocatalytic activity under visible light reducing the recombination rates of the photo-excited carriers [38]. Also, the immobilization

• of TiO2 photocatalysts in a polymer matrix allowing a re-use seems to be beneficial in contrast to the colloidal photocatalytic systems. In fact, the fabrication of such composites from conjugated organic polymers (polypyrrole, polyaniline) and TiO2 NPs [39][40][41] or other polymer matrices as

Organoclay hybrid materials as precursors of porous ZnO/silica-clay heterostructures for photocatalytic applications

• Marwa Akkari,
• Pilar Aranda,
• Abdessalem Ben Haj Amara and
• Eduardo Ruiz-Hitzky

Beilstein J. Nanotechnol. 2016, 7, 1971–1982, doi:10.3762/bjnano.7.188

• of the prepared heterostructures were characterized by diverse physico-chemical techniques (such as XRD, FTIR, TEM, FE-SEM). The efficiency of these new porous ZnO/SiO2-clay heterostructures as potential photocatalysts in the degradation of organic dyes and the removal of pharmaceutical drugs in

• immobilized and photoactive. To confirm this, the resulting ZnO/silica-clay heterostructured porous solids have been tested in photocatalytic experiments using water solutions of methylene blue (MB) dye or ibupofren drug, as models of organic pollutants, to prove their efficiency as photocatalysts for

• heterostructures acting as photocatalysts. Apparently, ZnO/SiO2-clay materials act as efficient photocatalysts as MB is completely degraded after 180 min of irradiation in presence of ZnO/SiO2-SEP or ZnO/SiO2-CLO heterostructures, and after only 120 min in presence of the ZnO/SiO2-TSM clay heterostructure. It

Role of RGO support and irradiation source on the photocatalytic activity of CdS–ZnO semiconductor nanostructures

• Suneel Kumar,
• Rahul Sharma,
• Vipul Sharma,
• Gurunarayanan Harith,
• Vaidyanathan Sivakumar and
• Venkata Krishnan

Beilstein J. Nanotechnol. 2016, 7, 1684–1697, doi:10.3762/bjnano.7.161

• the photocatalysts. In this work, we have investigated the role of reduced graphene oxide (RGO) support and the irradiation source on mixed metal chalcogenide semiconductor (CdS–ZnO) nanostructures. The photocatalyst material was synthesized using a facile hydrothermal method and thoroughly

• photocatalytic decomposition of organic pollutants [4][5][6][7][8]. These semiconductor photocatalysts not only degrade the contaminants, but also cause their complete mineralization into CO2, H2O and mineral acids [9][10]. Thus, it is advantageous over physico-chemical methods such as flocculation–coagulation

• radiation [17]. Due to this high band gap value, ZnO can only absorb ultraviolet (UV) light and this limits its practical applications [18]. Thus, in order to design more efficient photocatalysts, which are active in visible light, many research groups have devoted their studies towards dye sensitization

High performance Ce-doped ZnO nanorods for sunlight-driven photocatalysis

• Bilel Chouchene,
• Tahar Ben Chaabane,
• Lavinia Balan,
• Emilien Girot,
• Kevin Mozet,
• Ghouti Medjahdi and
• Raphaël Schneider

Beilstein J. Nanotechnol. 2016, 7, 1338–1349, doi:10.3762/bjnano.7.125

• been developed and their ability to degrade cyanide anions [28] or organic dyes [29][30][31][32][33] like methylene blue or methyl-orange has been demonstrated. The preparation of Ce–Cu, Ce–Pd or Ce–Ag co-doped photocatalysts to enhance the solar or the visible light catalytic response was also

• solvothermal method. Ce-doping not only increases the surface area of photocatalysts but also induces a red-shift in the absorption and improves solar and visible light capacities. At the optimal Ce doping percentage of 5 mol %, Orange II degradation is complete in 80 min. under solar light irradiation and the

• good stability and can reused at least seven times, thus indicating that these materials have great potential as photocatalysts in practical applications. Experimental Materials Zn(OAc)2·2H2O (>98%, Sigma), anhydrous Ce2(SO4)3 (97%, Sigma), Orange II sodium salt (>85%, Sigma), sodium hydroxide (>97

Selective photocatalytic reduction of CO₂ to methanol in CuO-loaded NaTaO₃ nanocubes in isopropanol

• Tianyu Xiang,
• Feng Xin,
• Jingshuai Chen,
• Yuwen Wang,
• Xiaohong Yin and
• Xiao Shao

Beilstein J. Nanotechnol. 2016, 7, 776–783, doi:10.3762/bjnano.7.69

• Engineering, Tianjin University of Technology, Tianjin 300384, China 10.3762/bjnano.7.69 Abstract A series of NaTaO3 photocatalysts were prepared with Ta2O5 and NaOH via a hydrothermal method. CuO was loaded onto the surface of NaTaO3 as a cocatalyst by successive impregnation and calcination. The obtained

• photocatalysts were characterized by XRD, SEM, UV–vis, EDS and XPS and used to photocatalytically reduce CO2 in isopropanol. This worked to both absorb CO2 and as a sacrificial reagent to harvest CO2 and donate electrons. Methanol and acetone were generated as the reduction product of CO2 and the oxidation

• SiC), producing CH3OH, HCOOH, HCHO and trace amounts of CH4. In the 1990s, Ta oxide photocatalysts began to draw attention in the field of water splitting. A series of Ta catalysts, such as LiTaO3 [9], NaTaO3 [10], KTaO3 [11], AgTaO3 [12], CaTa2O6 [13], SrTa2O6 [13], KBa2Ta3O10 [14], were proved to

Impact of ultrasonic dispersion on the photocatalytic activity of titania aggregates

• Hoai Nga Le,
• Frank Babick,
• Klaus Kühn,
• Minh Tan Nguyen,
• Michael Stintz and
• Gianaurelio Cuniberti

Beilstein J. Nanotechnol. 2015, 6, 2423–2430, doi:10.3762/bjnano.6.250

• promising photocatalyst because of its commercial availability, chemical and biological inertness, and because it has no known adverse health effects on humans [5][6]. Due to its large active surface area, the suspended TiO2 powder is favored [6]. Most slurry photocatalysts have been implemented in

• illuminated batch reactors [6][7][8] and follow Langmuir–Hinshelwood kinetics [9][10]. This research has focused on the materials aspects such as the structural properties (e.g., surface area, particle size, crystal composition, porosity) [8][11] of pristine or modified photocatalysts [2][5][12]. However

• of fine, primary particles (as a result of the larger surface area) has been investigated [4][16][17][18], the behavior and properties of the aggregates is not well understood. This paper shows an engineering approach to study the aggregation in photocatalysts. The first part presents the

Green and energy-efficient methods for the production of metallic nanoparticles

• Mitra Naghdi,
• Mehrdad Taheran,
• Satinder K. Brar,
• M. Verma,
• R. Y. Surampalli and
• J. R. Valero

Beilstein J. Nanotechnol. 2015, 6, 2354–2376, doi:10.3762/bjnano.6.243

• can result in less energy and raw material consumption, and also less waste generation [118]. For example, polyoxometalates (POMs) can act as a photocatalysts in the synthesis of metallic NPs so that the reactions can take place at room temperature within several minutes [134]. Degradability: Chemical

Paramagnetism of cobalt-doped ZnO nanoparticles obtained by microwave solvothermal synthesis

• Jacek Wojnarowicz,
• Sylwia Kusnieruk,
• Tadeusz Chudoba,
• Stanislaw Gierlotka,
• Witold Lojkowski,
• Wojciech Knoff,
• Malgorzata I. Lukasiewicz,
• Bartlomiej S. Witkowski,
• Anna Wolska,
• Marcin T. Klepka,
• Tomasz Story and
• Marek Godlewski

Beilstein J. Nanotechnol. 2015, 6, 1957–1969, doi:10.3762/bjnano.6.200

• attractive material with a wide range of applications such as: transparent transistors based on semiconducting transparent oxides [4], ultraviolet (UV) light blockers [5], photocatalysts [6] or antibacterial uses [7]. The energy band gap of ZnO is ≈3.3 eV at room temperature, corresponding to a wavelength of

High photocatalytic activity of V-doped SrTiO₃ porous nanofibers produced from a combined electrospinning and thermal diffusion process

• Panpan Jing,
• Wei Lan,
• Qing Su and
• Erqing Xie

Beilstein J. Nanotechnol. 2015, 6, 1281–1286, doi:10.3762/bjnano.6.132

• , chemical fertilizers and phenol [4]. Fortunately, a new and eco-friendly photocatalysis technique has drawn much attention. Photocatalysts are capable of accelerating the oxidation and mineralization of such organic substances with a fast removal rate [5][6] by producing strongly reactive and nonselective

• metal ions [8][9][10][11], such as Ti4+, Zr4+, Ta5+, Nb5+ and V5+, as well as the development of new photocatalysts. Strontium titanate (SrTiO3), an important multifunctional semiconductor, has been applied in photocatalysis technology for water splitting and organic contaminant degradation [12][13

• excellent photocatalytic properties of Fe-doped SrTiO3, Nd-doped SrTiO3 and Ni/La co-doped SrTiO3 [18][19][20]. These new photocatalysts enable a good response to light or overcome light corrosion caused by the excessive accumulation of photogenerated carriers due to poor conductivity. However, there are

Effects of swift heavy ion irradiation on structural, optical and photocatalytic properties of ZnO–CuO nanocomposites prepared by carbothermal evaporation method

• Sini Kuriakose,
• D. K. Avasthi and
• Satyabrata Mohapatra

Beilstein J. Nanotechnol. 2015, 6, 928–937, doi:10.3762/bjnano.6.96

• ], biosensors [22] and photocatalysts [23][24][25]. Nanocomposites consisting of nanostructures of ZnO and other metal-oxide semiconductors are being widely studied due to their improved physicochemical properties as compared to the individual counterparts. CuO, a p-type narrow band gap semiconductor, is

• optimize the photocatalytic activity of ZnO–CuO nanocomposites. Figure 6 and Figure 7 show the UV–visible absorption spectra of 3.7 μM MB and MO dyes with the pristine and ion-irradiated nanocomposite samples as photocatalysts upon irradiation with sun light for different periods of time. The

• irradiation can be used to controllably engineer the shape of ZnO nanostructures (nanorods and nanosheets) and enhance the photocatalytic activity of ZnO–CuO nanocomposites, improving their applicability as reusable photocatalysts. Conclusion ZnO–CuO nanocomposite thin films were prepared by carbothermal

Tm-doped TiO₂ and Tm₂Ti₂O₇ pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase

• Desiré M. De los Santos,
• Javier Navas,
• Teresa Aguilar,
• Antonio Sánchez-Coronilla,
• Concha Fernández-Lorenzo,
• Rodrigo Alcántara,
• Jose Carlos Piñero,
• Ginesa Blanco and
• Joaquín Martín-Calleja

Beilstein J. Nanotechnol. 2015, 6, 605–616, doi:10.3762/bjnano.6.62

• studies in the literature in which pyrochlore-type compounds with high photocatalytic activity are used as a photocatalysts, such as Bi2Ti2O7 [9][10], Pb2Nb2O7 [11]; other pyrochlore compounds that have been evaluated are rare earths, such as Gd2BiSbO7 [12] or Ln2Ti2O7 (Ln = Nd, Gd, Er) [13]. In this

Palladium nanoparticles anchored to anatase TiO₂ for enhanced surface plasmon resonance-stimulated, visible-light-driven photocatalytic activity

• Kah Hon Leong,
• Hong Ye Chu,
• Shaliza Ibrahim and
• Pichiah Saravanan

Beilstein J. Nanotechnol. 2015, 6, 428–437, doi:10.3762/bjnano.6.43

• Lumpur, Malaysia 10.3762/bjnano.6.43 Abstract Freely assembled palladium nanoparticles (Pd NPs) on titania (TiO2) nano photocatalysts were successfully synthesized through a photodeposition method using natural sunlight. This synthesized heterogeneous photocatalyst (Pd/TiO2) was characterized through

• with controlled Pd NPs size ranging between 17 and 29 nm onto the surface of TiO2. Thus, it gives the characteristic for Pd NPs to absorb light in the visible region obtained through localized surface plasmon resonance (LSPRs). Apparently, the photocatalytic activity of the prepared photocatalysts was

• reusability trend proved the photostability of the prepared photocatalysts. Hence, the study provides a new insight about the modification of TiO2 with noble metals in order to enhance the absorption in the visible-light region for superior photocatalytic performance. Keywords: endocrine disrupting compound

Inorganic Janus particles for biomedical applications

• Isabel Schick,
• Steffen Lorenz,
• Dominik Gehrig,
• Stefan Tenzer,
• Wiebke Storck,
• Karl Fischer,
• Dennis Strand,
• Frédéric Laquai and
• Wolfgang Tremel

Beilstein J. Nanotechnol. 2014, 5, 2346–2362, doi:10.3762/bjnano.5.244

• conjugation to Ag nanoparticles when combined to form Ag@Fe3O4 dumbbell-like hetero-nanoparticles [47]. Moreover, plasmonic photocatalysts combine two prominent features: a Schottky junction enhancing charge separation and surface plasmon resonance, which is responsible for strong absorption of visible light

• nanoparticles is shifted to more negative potentials, thus, enabling the engineering of the Fermi level of photocatalysts dependent on the size of the conjugated metal domain [49]. Recently, Au@TiO2 Janus particles were proven useful for visible-light hydrogen generation due to the strong coupling of plasmons

Microstructural and plasmonic modifications in Ag–TiO₂ and Au–TiO₂ nanocomposites through ion beam irradiation

• Venkata Sai Kiran Chakravadhanula,
• Yogendra Kumar Mishra,
• Venkata Girish Kotnur,
• Devesh Kumar Avasthi,
• Thomas Strunskus,
• Vladimir Zaporotchenko,
• Dietmar Fink,
• Lorenz Kienle and
• Franz Faupel

Beilstein J. Nanotechnol. 2014, 5, 1419–1431, doi:10.3762/bjnano.5.154

• , antibacterial coatings, photocatalysts, and implants [13][14][15][16][17][18]. The different properties of metal–TiO2 nanocomposites mainly depend on the metal volume filling fraction and the stoichiometry of the matrix. Generally, once the nanocomposites are prepared their properties are fixed. It is therefore

Characterization and photocatalytic study of tantalum oxide nanoparticles prepared by the hydrolysis of tantalum oxo-ethoxide Ta₈(μ₃-O)₂(μ-O)₈(μ-OEt)₆(OEt)₁₄

• Subia Ambreen,
• N D Pandey,
• Peter Mayer and
• Ashutosh Pandey

Beilstein J. Nanotechnol. 2014, 5, 1082–1090, doi:10.3762/bjnano.5.121

• , 0.8 mg/mL and 1.1 mg/mL) of Ta2O5 nanoparticles as photocatalysts were taken in 50 mL of distilled water and sonicated for 5 min. Then 12.5 ppm of rhodamine B was added to it. To attain an adsorption–desorption equilibrium between the dye molecules and the catalyst surface, the solution was stirred

Photocatalysis

• Rong Xu

Beilstein J. Nanotechnol. 2014, 5, 1071–1072, doi:10.3762/bjnano.5.119

• its early stage, and many technological challenges must be solved before it can be applied to large-scale. It has been widely recognized that it is necessary to develop advanced materials and new molecules assembled preferably from earth abundant elements as efficient photocatalysts to accomplish the

• , two review articles present an excellent overview of the significance of nanostructures in visible light photocatalysis in a timely manner. Many materials aspects of photocatalysts influence the photocatalytic performance, such as the electronic, structural, and morphological features of the

• dots integrated with TiO2 nanotube arrays, and carbon nitride, have been explored to construct photocatalysts with enhanced performances. On the other hand, molecular catalysts have an advantage in design flexibility and structural tunability. A contribution based on the investigation of molecular

Functionalized nanostructures for enhanced photocatalytic performance under solar light

• Liejin Guo,
• Dengwei Jing,
• Maochang Liu,
• Yubin Chen,
• Shaohua Shen,
• Jinwen Shi and
• Kai Zhang

Beilstein J. Nanotechnol. 2014, 5, 994–1004, doi:10.3762/bjnano.5.113

• : visible-light activity, chemical stability, appropriate band-edge characteristics, and potential for low-cost fabrication. Our aim is to present a short review of our recent attempts that center on the above requirements. We begin with a brief introduction of photocatalysts coupling two or more

• the semiconductors [8]. The band gap of semiconductor photocatalysts must be larger than the potential of water electrolysis to meet the energetic requirement for overall water splitting (1.23 eV, corresponding to an absorption threshold of 1000 nm). In particular, the bottom level of the conduction

• band (CB) must be more negative than the reduction potential of water, while the top level of the valance band (VB) should be more positive than the oxidation potential of water. In order to utilize the abundant visible light from the sun, the band gap of photocatalysts has to be less than 3.0 eV