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Highlights: [•] The p-Cu2O/n-Cu2O homojunction film was prepared by electrodeposition. [•] We report the carrier kinetics of p-Cu2O/n-Cu2O homojunction film. [•] The interfacial electric field impacts the transfer direction of carrier. [•] The p-Cu2O/n-Cu2O homojunction film is used for sensing acetaldehyde. [ABSTRACT FROM AUTHOR]

Abstract: TiO2(B) was prepared by a facile green solvothermal method and further characterized by the powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), raman spectroscopy and nitrogen sorption analysis, and it has been found that the as-synthesized sample possesses a unique crystallites/nanopores structure and has a very large surface area (484m2 g−1). Surprisingly, it exhibits the very high photocatalytic activity and good stability for the decomposition of methyl orange (MO) compared to that of P25. [ABSTRACT FROM AUTHOR]

The loading of PDS improves the separation of photogenerated carriers, suppresses the bulk and surface recombination (including surface recombination of the back electron(BER)), and enhances the water oxidation kinetics, synthetically improves the PEC water oxidation performance [Display omitted] The kinetic competition between water oxidation/electron extraction processes and recombination behaviors is a key consideration in the development of efficient photoanodes for solar-driven water splitting. Investigating the photogenerated charge behaviors could guide the construction of high-efficiency photoanodes. In this study, the charge carrier kinetics involved in photoelectrochemical water oxidation of PDS/Ti-Fe 2 O 3 were analyzed using surface photovoltage (SPV), transient photovoltage (TPV), short-pulse transient photocurrent (TPC) and photoelectrochemical impedance spectra (PEIS). The TPC results indicate the interfacial electric field introduced by the PDS loading increases the electron extraction and suppresses the bulk recombination, enhancing the spatial separation of photogenerated charges, which is consistent with the SPV and TPV results. Besides, the surface recombination of the back electron (BER) is also attenuated, which enhances the long-lived holes at the surface of PDS/Ti-Fe 2 O 3 photoanode. Similarly, as obtained by PEIS fitting, the loading of PDS accelerates holes transfer at the photoanode/electrolyte interface, and increases the utilization of long-lived holes. In other word, the recombination behaviors of photogenerated charges are restrained both in the bulk and surface of the photoanode after the deposition of PDS, leading to enhanced PEC performance. These findings highlight the importance of understanding charge carrier dynamics in the design of high-efficient photoanodes. [ABSTRACT FROM AUTHOR]

An effective scheme and technical means for understanding the mechanism of interfacial charge transfer. [Display omitted] • The Z-scheme Ti-ZFO/In 2 O 3 photoelectrode was successfully constructed. • Ti-ZFO/In 2 O 3 reaches 2.2 mA/cm2 at 1.23 V vs. RHE, which is 7 times that of pure Ti-ZFO. • The Z-scheme Ti-ZFO/In 2 O 3 could promote the separation and transfer of charges effectively. • This work provides an effective method and technical means to understanding the Z-scheme mechanism. Ti-ZnFe 2 O 4 photoanode has attracted extensive attention in photoelectrochemical (PEC) water oxidation due to its narrow band gap and good photostability. However, its low efficiency limits its development. Herein, we designed and constructed direct Z-scheme Ti-ZnFe 2 O 4 /In 2 O 3 (Ti-ZFO/In 2 O 3) photoanode. Under the interface electric field, photogenerated holes with stronger oxidation capacity on In 2 O 3 are retained to participate in the water oxidation reaction, and the photocurrent density of Ti-ZFO/In 2 O 3 is much higher than that of pure Ti-ZFO, reaching 2.2 mA/cm2 at 1.23 V vs. RHE. Kelvin Probe, steady-state photovoltage spectroscopy (SPV), transient photovoltage spectroscopy (TPV) and in-situ double beam strategy were used to demonstrate the Z-scheme charge transfer mechanism of Ti-ZFO/In 2 O 3 photoanode. Our work provides an effective scheme and technical means for further understanding the mechanism of interfacial charge transfer. [ABSTRACT FROM AUTHOR]

An amorphous tantalum oxyhydroxide TaO x (OH) y homojunction is constructed by anchoring TaO x (OH) y (2x + y = 5) nanoparticles (NPs, size: 4–10 nm) in situ on the surface of TaO x (OH) y sphere (SP). The formation of amorphous homojunction (TaO x (OH) y NPs/SP) is demonstrated by detailed characterizations of transmission electron microscopy, thermogravimetric analysis/mass spectrometer, Fourier transfer infrared spectra and X-ray photoelectron spectroscopy. In the absence of cocatalyst, the constructed amorphous homojunction exhibits a photocatalytic H 2 evolution rate of 311.1 μmol/g/h, about 5, 40 and 1000 times higher than that of 66.8 μmol/g/h for bare TaO x (OH) y SP, 7.6 μmol/g/h for commercial Ta 2 O 5 , and 0.3 μmol/g/h for the most widely used photocatalyst P25 (mixed-phase titania). The splendid performance is attributed to the special amorphous homojunction that produces a type-II band alignment and robust separation of photo-excited charge carriers, as uncovered by ultraviolet photoelectron, photoluminescence spectroscopy, and surface/transient photovoltage data. Our findings for amorphous homojunction may provide a new strategy of developing effective noncrystalline photocatalysts. [ABSTRACT FROM AUTHOR]

The appropriate band energy of H 2 TCPP matched with Ti-Fe 2 O 3 and CoPi assists more photogenerated holes to migrate to CoPi for PEC water oxidation reaction. [Display omitted] Coupling porphyrins with semiconductors is demonstrated as one of effective means to facilitate the separation of photogenerated charge in dye-sensitized solar cells as well as photocatalytic hydrogen production. However, there are limited reports about exploring the effect of porphyrin on the behavior of photogenerated charges and photoelectrochemical (PEC) water oxidation performance. Herein, we have built a hybrid photoanode containing Ti doped α-Fe 2 O 3 (Ti-Fe 2 O 3), 5,10,15,20-tetrakis (4-carboxyl phenyl) porphyrin (H 2 TCPP) and cobalt phosphate (CoPi) cocatalyst. Because of the appropriate band alignment of Ti-Fe 2 O 3 , H 2 TCPP and CoPi, the photogenerated holes are transferred directionally from Ti-Fe 2 O 3 to CoPi across H 2 TCPP, which boosts the separation efficiency of CoPi/H 2 TCPP/Ti-Fe 2 O 3 in turn. Meanwhile, CoPi/H 2 TCPP/Ti-Fe 2 O 3 possesses higher injection efficiency as well. Under the double guarantee of high separation efficiency and injection efficiency, CoPi/H 2 TCPP/Ti-Fe 2 O 3 yields an impressive photocurrent density of 1.84 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), which is much higher than that of CoPi/Ti-Fe 2 O 3. This structure design describes an appealing maneuver to facilitate the directed migration of photogenerated charges and then enhance the PEC water oxidation performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Z-scheme NH 2 -MIL-125(Ti)/Ti-Fe 2 O 3 photoanode is designed and constructed. • NH 2 -MIL-125(Ti)/Ti-Fe 2 O 3 shows excellent PEC performance and stability. • The Z-scheme pathway is identified by surface photovoltage, ESR and fs-TAS. • Efficient separation of interface and surface carriers is simultaneously realized. The construction of Z-scheme charge transfer pathways simulating natural photosynthesis is considered a promising method for improving reaction driving forces. Here, we modified the surface of titanium doped Fe 2 O 3 (Ti-Fe 2 O 3) nanorods with NH 2 -MIL-125(Ti) (Ti-MOFs) and a promising organic-inorganic hybrid Z-scheme NH 2 -MIL-125(Ti)/Ti-Fe 2 O 3 was successfully prepared. At 1.23 V vs. RHE, the photocurrent density of the composite photoanode reaches 2.67 mA/cm2, which is 5 times higher than that of Ti-Fe 2 O 3. The results of surface photovoltage, ESR and fs-TAS indicate that this improvement is mainly due to the effective Z-scheme charge transfer mechanism providing a strong driving force for charge separation and transport, greatly suppressing carrier recombination and allowing carriers with strong oxidation ability to participate in water oxidation. Meanwhile, NH 2 -MIL-125(Ti) can enhance light absorption and reduce the surface defect state of Ti-Fe 2 O 3. This study not only provides a feasible approach for the photoanode water splitting of traditional inorganic semiconductor/MOF based heterostructures, but also provides rich and effective means for revealing Z-scheme charge transfer mechanism in depth. [ABSTRACT FROM AUTHOR]

[Display omitted] Covalent triazine-based frameworks (CTFs) have been emerged as a promising organic material for photocatalytic water splitting. However, all of the CTFs only are in the form of AA stacking model to participate in water splitting. Herein, two CTF-1 isomers with different stacking models (eclipsed AA, staggered AB) were obtained by modulating the reaction temperature. Interestingly, experimental and theoretical calculations showed that the crystalline AB stacking CTF-1 possessed a much higher activity for photochemical hydrogen evolution (362 μmol g−1 h−1) than AA stacking CTF-1 (70 µmol h−1 g−1) for the first time. The outstanding photochemical performance could be attributed to its distinct structural feature that allows more N atoms with higher electron-withdrawing property to be involved in the water reduction reaction. Notably, as a cathode material for PEC water reduction, AB stacking CTF-1 also demonstrated an excellent saturated photocurrent density up to 77 µA cm−2 at 0 V vs. RHE, which was superior to the AA stacking CTF-1 (47 µA cm−2). Furthermore, the correlation between stacking models and photocatalytic H 2 evolution of CTF-1 were investigated. This study thus paves the path for designing optimal photocatalyst and extending the novel applications of CTF-based materials. [ABSTRACT FROM AUTHOR]

The FeOCl-based photo-Fenton heterojunction catalyst holds great promise for effective water pollution treatment. A novel heterojunction FeOCl/MOF-In 2 S 3 (F/M-I) was fabricated by coating hollow MOF-In 2 S 3 nanoflowers onto the surface of FeOCl. Under the optimal conditions, the maximum photo-Fenton degradation rate constants of FeOCl/MOF-In 2 S 3 for oxytetracycline (OTC) within 20 min is 0.88192 L mg−1·min−1, which are 3.2 and 2.5 times that of pure FeOCl (0.27357 L mg−1·min−1) and MOF-In 2 S 3 (0.35222 L mg−1·min−1). Density functional theory (DFT) results confirm that the electron-rich nature of MOF-In 2 S 3 accelerates the cycle between Fe (III)/Fe (II)of FeOCl, promoting H 2 O 2 adsorption by FeOCl/MOF-In 2 S 3 and generating more hydroxyl radicals (·OH) for pollutant degradation. Based on the results of DFT, combined with the results of the reactive oxidation species scavenger (ROSs), electron paramagnetic resonance (EPR) and Mott-Schottky curves, the separation and transfer behavior of photoexcited charges in FeOCl/MOF-In 2 S 3 heterojunction and the possible photocatalytic degradation mechanism were investigated. Finally, a Z-scheme heterostructure is proposed to elucidate the catalytic mechanism. This study provides a new perspective on designing and synthesizing semiconductor materials for water treatment by photo-Fenton catalysis. [Display omitted] • The FeOCl/MOF-In 2 S 3 Z-scheme heterojunction was synthesized for the first time. • FeOCl/MOF-In 2 S 3 shows excellent photo-Fenton properties. • The DFT results confirm that MOF-In 2 S 3 accelerates the Fe(Ⅲ)/Fe(Ⅱ) cycle of FeOCl. • FeOCl/MOF-In 2 S 3 catalyst have high BET surface area and charge transfer efficiency. [ABSTRACT FROM AUTHOR]

By the aid of transient photovoltage, photo-generated carrier transfer mechanism of SnS 2 /g-C 3 N 4 composite has been suggested by interfacial electric field direction. Constructing heterojunction is an effective way to improve the photo-generated carrier separation efficiency and photocatalytic activity. Here, we construct SnS 2 /g-C 3 N 4 heterojunctions by in-situ growth of SnS 2 on the g-C 3 N 4. By adjusting annealing temperatures, the SnS 2 /g-C 3 N 4 -180 and SnS 2 /g-C 3 N 4 -120 samples could meet Z-scheme carrier transfer mechanism and conventional type-II charge transfer mechanism, respectively. By the aid of surface photovoltage spectra, the photo-generated carrier transfer direction and the driving force of the charge transfer are suggested. This difference in these two charge transfer mechanisms is supposed to be mainly related to the discrepancy in work functions of the SnS 2 treated at different temperatures. This work provides an effective method to understand the Z-scheme carrier transfer mechanism, which could help us to design Z-scheme photocatalysts for higher hydrogen evolution activity. [ABSTRACT FROM AUTHOR]

In this work, the ternary hybrid photocatalyst composed of ZnO nanorods with BiOI and Pt NPs (denoted as Pt@BiOI/ZnO) was fabricated by a simple three-step method. The as-prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectrometry (DRS) and X-ray photoelectron spectroscopy (XPS), which proved the strong interaction has occurred among the Pt, BiOI and ZnO. The phenol degradation test showed that the Pt@BiOI/ZnO ternary hybrid composite exhibited the maximum photodegradation efficiency of phenol (99.9%) under UV irradiation within 30 min compared to Pt/BiOI, BiOI/ZnO binary composites as well as Pt/ZnO. Additionally, the transient photovoltage (TPV), steady-state PL spectra and time-resolved PL spectra were used to investigate the possible mechanism for photocatalytic performance. Our results elaborated that the enhanced photocatalytic activity was mainly attributed to the synergetic effect of Pt/ZnO and BiOI/ZnO interfaces. Conversely, the interfacial interaction of Pt/BiOI is little contribution, indicating that the effective interfaces design is very important for the degradation of phenol in the preparation process of ternary hybrid photocatalyst. These findings will contribute to developing high efficiency photocatalysts for application in environmental remediation. [ABSTRACT FROM AUTHOR]

The photoexcited electrons transfer dynamics at the TiO 2 film/fluorine doped tin oxide (FTO) interface of anatase TiO 2 nanowire arrays (NWAs) and QD-sensitized TiO 2 NWAs films have been studied by using surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Various SPV and TPV responses were obtained when the laser beam was incident from the front side illumination and back side illumination. Based on the work function values of anatase TiO 2 NWAs and FTO, the results indicate that diffusion is the major way for the separation and transfer of the photoexcited charge in the both anatase TiO 2 NWAs and QD-sensitized TiO 2 NWAs films under front side illumination. And the photoexcited charge were separated by drift under the built-in electric field at the TiO 2 film/FTO interface for anatase TiO 2 NWAs and QD-sensitized TiO 2 NWAs films under back side illumination. In addition, under back side illumination the built-in electric field and band structure of CdS/CdSe QDs and anatase TiO 2 NWAs lead to the separation and transfer of the photoexcited charge for CdS/CdSe QDs sensitized TiO 2 NWAs/FTO film. As the intensity of illumination increases, the effect of built-in electric field on the separation and transfer of the photoexcited charge in the QD-sensitized TiO 2 NWAs film decreases. [ABSTRACT FROM AUTHOR]

In this paper, a series of BiOI/ZnO photocatalysts containing various BiOI contents were prepared by a facile two-step synthetic method. The structure and crystal phase, morphology, surface element analysis, optical property of as-prepared samples are measured by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectrometry (DRS). BiOI/ZnO photocatalytic activities of the prepared photocatalysts were evaluated by photocatalytic degradation of phenol under simulated light irradiation. The phenol degradation rate reached 99.9% within 2 h under simulated solar light irradiation. The probable photocatalytic mechanism of composites photocatalysts is discussed by active species trapping experiments, the surface photovoltage (SPV), the transient photovoltage (TPV) and photoluminescence (PL) measurements. The results manifest that the superior photocatalytic activity of BiOI/ZnO composites is derived from the strong internal electric field between BiOI and ZnO, which is beneficial for the effective separation and transfer of photogenerated charges in ZnO. Moreover, the loading of BiOI on the surface of ZnO inhibited the recombination of photogenerated charge carriers in ZnO, resulting in excellent photocatalytic activity. On the contrary, the effect of an extension of the light absorption range induced by the introduction of BiOI on the phenol degradation activity is not significant. [ABSTRACT FROM AUTHOR]

To better understand the behavior of photogenerated charges in the composite photocatalyst interface is beneficial to the designing of effective photocatalyst for photocatalytic reaction. In our work, the separation and transfer process of photogenerated charges in NiO/TiO 2 nanotube arrays (NiO/TiO 2 NTAs) has been studied by surface photovoltage (SPV) spectroscopy and transient photovoltage (TPV) measurement. Through the experimental results analysis, we find that an interfacial electric field is formed at NiO/TiO 2 NTAs interface, which is attributed to the work function difference between NiO and TiO 2 NTAs. The photogenerated holes in TiO 2 can transfer to the NiO layer along the interface electric field under the ultraviolet irradiation. A large amount of photogenerated holes can be separated effectively and then prolonged the holes lifetime to participate in the photocatalytic oxidation reaction. The above results show that the favorable hole-collecting process of NiO in the surface of TiO 2 NTAs is the main factor being responsible for the increase the photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Abstract: A water–dichloromethane interface-assisted hydrothermal method was employed to grow rutile TiO2 nanowires (NWs) on electrospun anatase TiO2 nanofibers (NFs), using highly reactive TiCl4 as precursor. The water–dichloromethane interface inhibited the formation of rutile NWs in water phase, but promoted the selective radial growth of densely packed rutile NWs on anatase NFs to form a branched heterojunction. The density and length of rutile NWs could be readily controlled by varying reaction parameters. A formation mechanism for the branched heterojunction was proposed which involved (1) the entrapment of rutile precursor nanoparticles at water–dichloromethane interface, (2) the growth of rutile NWs on anatase NFs via Ostwald ripening through the scavengering of interface-entrapped rutile nanoparticles. The heterojunction formed at anatase NF and rutile NW enhanced the charge separation of both under ultraviolet excitation, as evidenced by photoluminescence and surface photovoltage spectra. The branched TiO2 heterostructures showed higher photocatalytic activity in degradation of rodamine B dye solution than anatase NFs, and the mixture of anatase NFs, and P25 powders, which was discussed in terms of the synergistic effect of enhanced charge separation by anatase–rutile heterojunction, high activity of rutile NWs, and increased specific area of branched heterostructures. [Copyright &y& Elsevier]

Abstract: Carbon-doped anatase TiO2 was prepared by a facile hydrothermal process without adding additional carbon source. The as-prepared sample shows highly efficient photocatalytic activity, which only requires 4min and is about 11 times higher than that of Degussa P25 TiO2 in degradation of methyl orange (MO) dye under UV light irradiation. Moreover, a highly visible-light activity is also observed. UV–vis diffuse reflectance spectra and X-ray photoelectron spectroscopy confirm that the carbon atoms are incorporated into the interstitial positions of TiO2 lattice and form a strong interaction with titanium atoms and extend photoresponding range to 700nm. Surface photovoltage spectra (SPS) and transient photovoltage (TPV) suggest that the presence of interstitial carbons induce several localized occupied states in the gap, enhance the separation extent and restrain the recombination of the photo-induced electron and hole carriers in TiO2. [Copyright &y& Elsevier]

Abstract: Water-soluble anatase TiO2 nanocrystals (NCs) were synthesized by a simple sol–gel method. The reaction time is greatly reduced even under mild conditions. High-resolution transition electron microscopy (HRTEM), X-ray diffraction (XRD) and UV–vis were used to characterize the synthesized NCs and proved that the NCs are anatase phase and about 2 nm with near spherical shape. Surface photovoltage spectroscopy (SPS) experiments show that the synthesized anatase NCs have good photovoltaic properties compared with that of poly(vinyl pyrrolidone) (PVP) coated NCs synthesized by the similar method. [Copyright &y& Elsevier]