A Cocatalytic Electron‐Transfer Cascade Site‐Selectively Placed on TiO2 Nanotubes Yields Enhanced Photocatalytic H2 Evolution

Separation and transfer of photogenerated charge carriers are key elements in designing photocatalysts. TiO₂ in numerous geometries has been for many years the most studied photocatalyst. To overcome kinetic limitations and achieve swift charge transfer, TiO₂ has been widely investigated with cocatalysts that are commonly randomly placed nanoparticles on a TiO₂ surface. The poor control over cocatalyst placement in powder technology approaches can drastically hamper the photocatalytic efficiencies. Here in contrast it is shown that the site‐selective placement of suitable charge‐separation and charge‐transfer cocatalysts on a defined TiO₂ nanotube morphology can provide an enhancement of the photocatalytic reactivity. A TiO₂–WO₃–Au electron‐transfer cascade photocatalyst is designed with nanoscale precision for H₂ production on TiO₂ nanotube arrays. Key aspects in the construction are the placement of the WO₃/Au element at the nanotube top by site‐selective deposition and self‐ordered thermal dewetting of Au. In the ideal configuration, WO₃ acts as a buffer layer for TiO₂ conduction band electrons, allowing for their efficient transfer to the Au nanoparticles and then to a suitable environment for H₂ generation, while TiO₂ holes due to intrinsic upward band bending in the nanotube walls and short diffusion length undergo a facilitated transfer to the electrolyte where oxidation of hole‐scavenger molecules takes place. These photocatalytic structures can achieve H₂ generation rates significantly higher than any individual cocatalyst–TiO₂ combination, including a classic noble metal–TiO₂ configuration.     

WO3/TiO2 nanocomposites: Salt–ultrasonic assisted hydrothermal synthesis and enhanced photocatalytic activity

A series of WO₃/TiO₂ composite photocatalysts were fabricated via a facile salt–ultrasonic assisted hydrothermal process. The obtained samples were characterized by X-ray diffraction, scanning eletron microscopy, energy dispersive X-ray spectroscopy and UV–vis diffused reflectance spectroscopy. It was confirmed that anatase TiO₂ and monoclinic WO₃ coexisted in the composites. The photocatalytic activity of as-prepared WO₃/TiO₂ composites for degradation of Rhodamin B (RhB) under visible light irradiation was investigated. The results showed that WO₃/TiO₂ composites have a higher photocatalytic activity than those of pure TiO₂ and pure WO₃. First-principle calculations based on density functional theory were performed to explore the electronic structure and illustrate the photocatalytic mechanism of WO₃/TiO₂. The calculated energy gap was 2.53 eV, which was close to the experimental observation (2.58 eV). Due to the combination of WO₃/TiO₂, the photoinduced electrons and holes transfer between the WO₃ and TiO₂ in opposite directions, thus providing sufficient charge separation, which contributed to the photocatalytic activity enhancement.     

Tracking Heterogeneous Interface Charge Reverse Separation in SrTiO3/NiO/NiS Nanofibers with In Situ Irradiation XPS

Photocatalytic conversion of H₂O and CO₂ into solar fuels is considered to be a green and renewable technology while photocatalytic performance is hampered by the severe recombination of photogenerated electron–hole pairs. Drawing inspiration from the concepts of the electrons transfer layer (ETL) and the holes transfer layer (HTL) in perovskite solar cells, a multicomponent photocatalyst SrTiO₃/NiO/NiS that incorporates p–n heterojunction and Schottky junction is constructed for converting solar energy into easily storable solar fuels. The NiS and NiO play the roles analogy to the ETL and the HTL which accomplishes the reverse migration of electrons and holes, accordingly, SrTiO₃/NiO/NiS exhibits a noticeable enhancement in photocatalytic performance. However, the lack of direct observation of charge transfer pathways in complex multicomponent photocatalysts makes it challenging to thoroughly investigate their catalytic mechanisms. Herein, the in situ irradiation X-ray photoelectron spectroscopy (ISI–XPS) is employed to track photogenerated charges migration pathways between microscopic heterogeneous interfaces, thereby providing a comprehensive elucidation of the catalytic mechanism and heterojunction formation process by integrating the photoelectrochemical tests. This study not only serves as compelling evidence for the capability of ISI–XPS in directly and accurately tracking charge transfer pathways but also as an intriguing highlight within the catalyst design strategy.     

Improved Photocatalytic Performance of Heterojunction by Controlling the Contact Facet: High Electron Transfer Capacity between TiO2 and the {110} Facet of BiVO4 Caused by Suitable Energy Band Alignment

Charge separation at the interface of heterojunctions is affected by the energy band alignments of the materials that compose the heterojunctions. Controlling the contact crystal facets can lead to different energy band alignments owing to the varied electronic structures of the different crystal facets. Therefore, BiVO₄‐TiO₂ heterojunctions are designed with different BiVO₄ crystal facets at the interface ({110} facet or {010} facet), named BiVO₄‐110‐TiO₂ and BiVO₄‐010‐TiO₂, respectively, to achieve high photocatalytic performance. Higher photocurrent density and lower photoluminescence intensity are observed with the BiVO₄‐110‐TiO₂ heterojunction than those of the BiVO₄‐010‐TiO₂ heterojunction, which confirms that the former possesses higher charge carrier separation capacity than the latter. The photocatalytic degradation results of both Rhodamine B and 4‐nonylphenol demonstrate that better photocatalytic performance is achieved on the BiVO₄‐110‐TiO₂ heterojunction than the BiVO₄‐010‐TiO₂ heterojunction under visible light (≥422 nm) irradiation. The higher electron transfer capacity and better photocatalytic performance of the BiVO₄‐110‐TiO₂ heterojunction are attributed to the more fluent electron transfer from the {110} facet of BiVO₄ to TiO₂ caused by the smaller interfacial energy barrier. This is further confirmed by the selective deposition of Pt on the TiO₂ surface as well as the longer lifetime of Bi⁵⁺ in the BiVO₄‐110‐TiO₂ heterojunction.     

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

A novel hierarchical structured photoanode based on metal–organic frameworks (MOFs)‐derived porous Co₃O₄‐modified TiO₂ nanorod array grown on Si (MOFs‐derived Co₃O₄/TiO₂/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co₃O₄/TiO₂/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO₂ and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO₂, the photogenerated electrons from TiO₂ will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO₂ at the TiO₂/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO₂ and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co₃O₄ obviously improves the optical‐response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs‐derived Co₃O₄/TiO₂/FTO photoanode, the synergistic function in the MOFs‐derived Co₃O₄/TiO₂/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm^?2 in alkaline electrolyte. This work provides promising methods for constructing high‐performance PEC water splitting photoanode based on MOFs‐derived materials.     

A Band‐Edge Potential Gradient Heterostructure to Enhance Electron Extraction Efficiency of the Electron Transport Layer in High‐Performance Perovskite Solar Cells

As the key component in efficient perovskite solar cells, the electron transport layer (ETL) can selectively collect photogenerated charge carriers produced in perovskite absorbers and prevent the recombination of carriers at interfaces, thus ensuring a high power conversion efficiency. Compared with the conventional single‐ or dual‐layered ETLs, a gradient heterojunction (GHJ) strategy is more attractive to facilitate charge separation because the potential gradient created at an appropriately structured heterojunction can act as a driving force to regulate the electron transport toward a desired direction. Here, a SnO₂/TiO₂ GHJ interlayer configuration inside the ETL is reported to simultaneously achieve effective extraction and efficient transport of photoelectrons. With such an interlayer configuration, the GHJs formed at the perovskite/ETL interface act collectively to extract photogenerated electrons from the perovskite layer, while GHJs formed at the boundaries of the interconnected SnO₂ and TiO₂ networks throughout the entire ETL layer can extract electron from the slow electron mobility TiO₂ network to the high electron mobility SnO₂ network. Devices based on GHJ ETL exhibit a champion power conversion efficiency of 18.08%, which is significantly higher than that obtained from the compact TiO₂ ETL constructed under the comparable conditions.     

Hybridized Nanowires and Cubes: A Novel Architecture of a Heterojunctioned TiO2/SrTiO3 Thin Film for Efficient Water Splitting

A unique morphology of SrTiO₃ nanocubes precipitated on TiO₂ nanowires is successfully synthesized in the form of a thin‐film heterojunctioned TiO₂/SrTiO₃ photocatalyst using facile hydrothermal techniques. The formation mechanisms of the synthesized photocatalysts are meticulously studied and described. Growth of SrTiO₃ single crystal nanocubes (≈50 nm in width) on anatase polycrystalline nanowires follows an in situ dissolution‐precipitation pathway. This is consonant with the classic LaMer model. By analyzing the results of field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X‐ray diffraction (XRD), energy dispersive X‐ray (EDX) spectroscopy, X‐ray photoelectron spectroscopy (XPS), and UV‐vis spectrophotometry, a comprehensive structural and morphological characterization of the photocatalysts is established. FESEM images reveal that the anatase film comprises mainly of nanowires bristles while the tausonite film is primarily made up of nanocube aggregations. In comparison to the respective pristine semiconductor photocatalysts, the heterostructured photocatalyst demonstrates the highest efficiency in photocatalytic splitting of water to produce H₂, 4.9 times that of TiO₂ and 2.1 times that of SrTiO₃. The enhanced photocatalytic efficiency is largely attributed to the efficient separation of photogenerated charges at heterojunctions of the two dissimilar semiconductors, as well as a negative redox potential shift in the Fermi level.     

2D WC/WO3 Heterogeneous Hybrid for Photocatalytic Decomposition of Organic Compounds with Vis–NIR Light

Developing catalysts to improve charge‐carrier transfer and separation is critical for efficient photocatalytic applications driven by low‐energy photons. van der Waals stacking of 2D materials has opened up opportunities to engineer heteromaterials for strong interlayer excitonic transition. However, fabrication of 2D heteromaterials with clean and seamless interfaces remains challenging. Here, a 2D tungsten carbide/tungsten trioxide (WC/WO₃) heterogeneous hybrid in situ synthesized by a chemical engineering method has been reported. The hybrid comprises of layer‐by‐layer stacked WC and WO₃ monolayers. The WC and specific interfacial interfaces between the WC and WO₃ layers exhibit synergetic effects, promoting interfacial charge transfer and separation. Binderless WC performing platinum‐like behavior works as a potential substitute for noble metals and accelerates multielectron oxygen reduction, consequently speeding up the photocatalytic decomposition of organic compounds over the WO₃ catalyst. The specific interfacial interaction between WC and WO₃ layers potentially improves interfacial charge transfer from conduction band of WO₃ to WC. In the absence of noble metals, the WC/WO₃ hybrid as a catalyst exhibits distinct decomposition of organic compounds with vis–NIR light (λ = 400–800 nm). This finding provides a cost‐effective approach to capture low‐energy photons in environmental remediation applications.     

An In Situ Simultaneous Reduction‐Hydrolysis Technique for Fabrication of TiO2‐Graphene 2D Sandwich‐Like Hybrid Nanosheets: Graphene‐Promoted Selectivity of Photocatalytic‐Driven Hydrogenation and Coupling of CO2 into Methane and Ethane

A novel, in situ simultaneous reduction‐hydrolysis technique (SRH) is developed for fabrication of TiO₂‐‐graphene hybrid nanosheets in a binary ethylenediamine (En)/H₂O solvent. The SRH technique is based on the mechanism of the simultaneous reduction of graphene oxide (GO) into graphene by En and the formation of TiO₂ nanoparticles through hydrolysis of titanium (IV) (ammonium lactato) dihydroxybis, subsequently in situ loading onto graphene through chemical bonds (Ti–O–C bond) to form 2D sandwich‐like nanostructure. The dispersion of TiO₂ hinders the collapse and restacking of exfoliated sheets of graphene during reduction process. In contrast with prevenient G‐TiO₂ nanocomposites, abundant Ti³⁺ is detected on the surface of TiO₂ of the present hybrid, caused by reducing agent En. The Ti³⁺ sites on the surface can serve as sites for trapping photogenerated electrons to prevent recombination of electron–hole pairs. The high photocatalytic activity of G‐TiO₂ hybrid is confirmed by photocatalytic conversion of CO₂ to valuable hydrocarbons (CH₄ and C₂H₆) in the presence of water vapor. The synergistic effect of the surface‐Ti³⁺ sites and graphene favors the generation of C₂H₆, and the yield of the C₂H₆ increases with the content of incorporated graphene. The work may open a new doorway for new significant application of graphene for selectively catalytic C–C coupling reaction     

Structure,morphology and photocatalytic activity of Cu2O/Pt/TiO2 three-layered nanocomposite films

Novel Cu₂O/Pt/TiO₂ three-layered nanocomposite films were prepared by deposition on glass substrates using the magnetron sputtering method. Their structure, surface morphology as well as optical and photocatalytic properties were examined by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, UV–visible spectroscopy, and photoluminescence spectroscopy. As a comparison, Cu₂O/TiO₂ double-layer films were also investigated. The results show that Cu₂O/TiO₂ double-layer films have relatively smooth surfaces with agglomerated Cu₂O particle, whereas the surface layer of the Cu₂O/Pt/TiO₂ three-layered nanocomposite films was composed of fine nano-sized columnar Cu₂O and they had a rough surface morphology due to the insertion of the Pt layer. The photocatalytic activity of the three-layered films is significantly higher than that of the Cu₂O/TiO₂ double-layered composite films. Such enhancement is closely related to the presence of the Pt layer and the rough surface, which was composed of fine nano-sized Cu₂O columns; this increases the utilization of visible light as well as promotes the transfer of interfacial charge and the separation of photogenerated electron–holes.     

Tuning the Electronic Bandgap of Graphdiyne by H-Substitution to Promote Interfacial Charge Carrier Separation for Enhanced Photocatalytic Hydrogen Production

Graphdiyne (GDY), which features a highly π-conjugated structure, direct bandgap, and high charge carrier mobility, presents the major requirements for photocatalysis. Up to now, all photocatalytic studies are performed without paying too much attention on the GDY bandgap (1.1 eV at the G₀W₀ many-body theory level). Such a narrow bandgap is not suitable for the band alignment between GDY and other semiconductors, making it difficult to achieve efficient photogenerated charge carrier separation. Herein, for the first time, it is demonstrated that tuning the electronic bandgap of GDY via H-substitution (H-GDY) promotes interfacial charge separation and improves photocatalytic H₂ evolution. The H-GDY exhibits an increased bandgap energy ( ≈ 2.5 eV) and exploitable conduction band minimum and valence band maximum edges. As a representative semiconductor, TiO₂ is hybridized with both H-GDY and GDY to fabricate a heterojunction. Compared to the GDY/TiO₂, the H-GDY/TiO₂ heterojunction leads to a remarkable enhancement of the photocatalytic H₂ generation by 1.35 times under UV–visible illumination (6200 µ mol h⁻¹ g⁻¹) and four times under visible light (670 µ mol h⁻¹ g⁻¹). Such enhancement is attributed to the suitable band alignment between H-GDY and TiO₂, which efficiently promotes the photogenerated electron and hole separation, as supported by density functional theory calculations.     

Heterojunction Architecture of N‐Doped WO3 Nanobundles with Ce2S3 Nanodots Hybridized on a Carbon Textile Enables a Highly Efficient Flexible Photocatalyst

The availability of robust, versatile, and efficient photocatalysts is the main bottleneck in practical applications of photocatalytic degradation of organic pollutants. Herein, N‐WO₃/Ce₂S₃ nanotube bundles (NBs) are synthesized and successfully immobilized on a carbon textile, resulting in a flexible and conducting photocatalyst. Due to the large interfacial area between N‐WO₃ and Ce₂S₃, the interwoven 3D carbon architecture and, more importantly, the establishment of a heterojunction between N‐WO₃ and Ce₂S₃, the resultant photocatalyst exhibits excellent light absorption capacity and superior ability to separate photoinduced electron–hole pairs for the photocatalytic degradation of organic compounds in air and water media. Theoretical calculations confirm that the strong electronic interaction between N‐WO₃ and Ce₂S₃ can be beneficial to the enhancement of the charge carrier transfer dynamics of the as‐prepared photocatalyst. This work provides a new protocol for constructing efficient flexible photocatalysts for application in environmental remediation.     

An Effective Approach for High‐Efficiency Photoelectrochemical Solar Cells by Using Bifunctional DNA Molecules Modified Photoanode

This paper firstly reports the effect of deoxyribonucleic acid (DNA) molecules extracted from chickpea and wheat plants on the injection/recombination of photogenerated electrons and sensitizing ability of dye‐sensitized solar cells (DSSCs). These high‐yield DNA molecules are applied as both linker bridging unit as well as thin tunneling barrier (TTB) at titanium dioxide (TiO₂ )/dye interface, to build up high‐efficient DSSCs. With its favorable energy levels, effective linker bridging role, and double helix structure, bifunctional DNA modifier shows an efficient electron injection, suppressed charge recombination, longer electron lifetime, and higher light harvesting efficiency, which leads to higher photovoltaic performance. In particular, a photoconversion efficiency (PCE) of 9.23% is achieved by the binary chickpea and wheat DNA‐modified TiO₂ (CW@TiO₂) photoanode. Furthermore, time‐resolved fluorescence spectroscopy measurements confirm a better electron transfer kinetics for DNA‐modified TiO₂ photoanodes, implying a higher electron transfer rate (k_ET). This work highlights a great contribution for the photoanodes that are linked with DNA molecule, which act as both bridging unit and TTB to control the charge recombination and injection dynamics, and hence, boost the photovoltaic performance in the DSSCs.     

Self‐Assembling TiO2 Nanorods on Large Graphene Oxide Sheets at a Two‐Phase Interface and Their Anti‐Recombination in Photocatalytic Applications

TiO₂ nanorods are self‐assembled on the graphene oxide (GO) sheets at the water/toluene interface. The self‐assembled GO–TiO₂ nanorod composites (GO–TiO₂ NRCs) can be dispersed in water. The effective anchoring of TiO₂ nanorods on the whole GO sheets is confirmed by transmission electron microscopy (TEM), X‐ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), and thermogravimetric analysis (TGA). The significant increase of photocatalytic activity is confirmed by the degradation of methylene blue (MB) under UV light irridiation. The large enhancement of photocatalytic activity is caused by the effective charge anti‐recombination and the effective absorption of MB on GO. The effective charge transfer from TiO₂ to GO sheets is confirmed by the significant photoluminescence quenching of TiO₂ nanorods, which can effectively prevent the charge recombination during photocatalytic process. The effective absorption of MB on GO is confirmed by the UV‐vis spectra. The degradation rate of MB in the second cycle is faster than that in the first cycle because of the reduction of GO under UV light irradiation.     

2D/2D Heterojunction of Ultrathin MXene/Bi2WO6 Nanosheets for Improved Photocatalytic CO2 Reduction

Exploring cheap and efficient cocatalysts for enhancing the performance of photocatalysts is a challenge in the energy conversion field. Herein, 2D ultrathin Ti₃C₂ nanosheets, a kind of MXenes, are prepared by etching Ti₃AlC₂ with subsequent ultrasonic exfoliation. A novel 2D/2D heterojunction of ultrathin Ti₃C₂/Bi₂WO₆ nanosheets is then successfully prepared by in situ growth of Bi₂WO₆ ultrathin nanosheets on the surface of these Ti₃C₂ ultrathin nanosheets. The resultant Ti₃C₂/Bi₂WO₆ hybrids exhibit a short charge transport distance and a large interface contact area, assuring excellent bulk‐to‐surface and interfacial charge transfer abilities. Meanwhile, the improved specific surface area and pore structure endow Ti₃C₂/Bi₂WO₆ hybrids with an enhanced CO₂ adsorption capability. As a result, the 2D/2D heterojunction of ultrathin Ti₃C₂/Bi₂WO₆ nanosheets shows significant improvement on the performance of photocatalytic CO₂ reduction under simulated solar irradiation. The total yield of CH₄ and CH₃OH obtained on the optimized Ti₃C₂/Bi₂WO₆ hybrid is 4.6 times that obtained on pristine Bi₂WO₆ ultrathin nanosheets. This work provides a new protocol for constructing 2D/2D photocatalytic systems and demonstrates Ti₃C₂ as a promising and cheap cocatalyst.     

Piezoelectric‐Effect‐Enhanced Full‐Spectrum Photoelectrocatalysis in p–n Heterojunction

Photoelectrochemical (PEC) water splitting offers a promising strategy for converting solar energy to chemical fuels. Herein, a piezoelectric‐effect–enhanced full‐spectrum photoelectrocatalysis with multilayered coaxial titanium dioxide/barium titanate/silver oxide (TiO₂/BTO/Ag₂O) nanorod array as the photoanode is reported. The vertically grown nanorods ensure good electron conductivity, which enables fast transport of the photogenerated electrons. Significantly, the insertion of a piezoelectric BaTiO₃ (BTO) nanolayer at the p‐type Ag₂O and n‐type TiO₂ interface created a polar charge‐stabilized electrical field. It maintains a sustainable driving force that attract the holes of TiO₂ and the electrons of Ag₂O, resulting in greatly increased separation and inhibited recombination of the photogenerated carriers. Furthermore, Ag₂O as a narrow bandgap semiconductor has a high ultraviolet–visible–near infrared (UV–vis–NIR) photoelectrocatalytic activity. The TiO₂/BTO/Ag₂O, after poling, successfully achieves a prominent photocurrent density, as high as 1.8 mA cm^?2 at 0.8 V versus Ag/Cl, which is about 2.6 times the TiO₂ nanorod photoanode. It is the first time that piezoelectric BaTiO₃ is used for tuning the interface of p‐type and n‐type photoelectrocatalyst. With the enhanced light harvesting, efficient photogenerated electron–hole pairs' separation, and rapid charge transfer at the photoanode, an excellent photoelectrocatalytic activity is realized.     

In Situ Growth of [hk1]‐Oriented Sb2S3 for Solution‐Processed Planar Heterojunction Solar Cell with 6.4% Efficiency

Binary compound antimony sulfide (Sb₂S₃) with its nontoxic and earth‐abundant constituents, is a promising light‐harvesting material for stable and high efficiency thin film photovoltaics. The intrinsic quasi‐1D (Q1D) crystal structure of Sb₂S₃ is known to transfer photogenerated carriers rapidly along the [hk1] orientation. However, producing Sb₂S₃ devices with precise control of [hk1] orientation is challenging and unfavorable crystal orientations of Sb₂S₃ result in severe interface and bulk recombination losses. Herein, in situ vertical growth of Sb₂S₃ on top of ultrathin TiO₂/CdS as the electron transport layer (ETL) by a solution method is demonstrated. The planar heterojunction solar cell using [hk1]‐oriented Sb₂S₃ achieves a power conversion efficiency of 6.4%, performing at almost 20% higher than devices based on a [hk0]‐oriented absorber. This work opens up new prospects for pursuing high‐performance Sb₂S₃ thin film solar cells by tailoring the crystal orientation.     

Oxygen Vacant Semiconductor Photocatalysts

Semiconductor photocatalysis acts as a sustainable green technology to convert solar energy for environmental purification and production of renewable energy. However, the current photocatalysts suffer from inefficient photoabsorption, rapid recombination of photogenerated electrons and holes, and inadequate surface reactive sites. Introduction of oxygen vacancies (OVs) in photocatalysts has been demonstrated to be an efficacious strategy to solve these issues and improve photocatalytic efficiency. This review systematically summarizes the recent progress in the oxygen vacant semiconductor photocatalysts. Firstly, the formation and characterizations of OVs in semiconductor photocatalysts are briefly introduced. Then, highlighted are the roles of OVs in the photocatalytic reactions of three types of typical oxygen-containing semiconductors, including metal oxides (TiO₂, ZnO, WO₃, W₁₈O₄₉, MoO₃, BiO_2-x, SnO₂, etc), hydroxides (In(OH)₃, Ln(OH)₃ (Ln=La, Pr, and Nd), Layered double hydroxides) and oxysalts (bismuth-based oxysalts and others) photocatalysts. Moreover, the advanced photocatalytic applications of oxygen vacant semiconductor photocatalysts, such as pollutant removal, H₂ production, CO₂ reduction, N₂ fixation and organic synthesis are systematically summarized. Finally, an overview on the current challenges and a prospective on the future of oxygen vacant materials is proposed.     

An Interface Engineered Multicolor Photodetector Based on n‐Si(111)/TiO2 Nanorod Array Heterojunction

A multicolor photodetector based on the heterojunction of n‐Si(111)/TiO₂ nanorod arrays responding to both ultraviolet (UV) and visible light is developed by utilizing interface engineering. The photodetector is fabricated via a consecutive process including chemical etching, magnetron sputtering, hydrothermal growth, and assembling. Under a small reverse bias (from 0 to ≈?2 V), only the photogenerated electrons in TiO₂ are possible to tunnel through the low barrier of ΔE_C, and the device only responses to UV light; as the reverse bias increases, the photogenerated holes in Si also begin to tunnel through the high barrier of ΔE_V. As a result, the device is demonstrated to have the capacity to detect both UV and visible lights, which is useful in the fields of rapid detection and multicolor imaging. It has been also observed that the crystal orientation of Si affects the characteristics of bias‐controlled spectral response of the n‐Si/TiO₂ heterojunctions.     

One-pot synthesis of TiO2–WO3 composite nanocrystallites with improved photocatalytic properties under natural sunlight irradiation

TiO₂–WO₃ composite crystallites were prepared by a one-pot synthesis via hydrothermal reaction using Ti(SO₄)₂ and Na₂WO₄·2H₂O as source materials. The samples were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectrometer (EDS) methods. Results reveal that the WO₃ particles are uniformly dispersed on the surface of TiO₂ particles without any detectable change in crystal structure and morphology of the TiO₂–WO₃ composite nanocrystallites. Corresponding photocatalytic properties of the pure TiO₂ and TiO₂–WO₃ crystallites are found to increase first and then decrease with increasing W/Ti molar ratios. The sample with a W/Ti molar ratio of 1:99 shows the highest photodegradation rate (95.8%) for Rhodamine B under natural sunlight irradiation.