In this paper, we have engineered the interface electronic structure in Cu2O/ZnO nanorod arrays, via adjusting the carrier concentration of Cu2O, and applied them to photocatalysis. The photoinduced charge transfer kinetics at the interface between Cu2O and ZnO were systematically investigated. The Cu2O (pH 11.0)/ZnO nanorod arrays have the largest magnitude of interfacial electric field, and photoinduced charge carriers can be separated rapidly and efficiently, which generates the highest photocatalytic efficiency for the reduction of methylviologen. Heterojunction construction is an exciting direction to pursue for highly active photocatalysts, and also offers opportunities to investigate the relationship between the electronic structure and the photocatalytic performance.

Hybrid Pt–Co:ZnO nanostructure photocatalysts were prepared via a facile two-step synthetic strategy. SPS and TPV investigations demonstrate the existence of the synergetic effect between Pt and Co dopants. Such synergetic effect could make use of visible photons as well as facilitates the separation of photogenerated charges to prevent recombination, effectively prolongating the charges lifetime to participate photocatalytic reaction. The synergetic effect exist in Pt–Co:ZnO inducing as high as 7.7-fold in photovoltaic response and 10-fold in the photo–activity for hybrids compared to Co:ZnO.Keywords: hybrid nanostucture; photocatalytic activity; photovoltaic properties; Pt−Co:ZnO; synergetic effect;

•We report a simple one-step hydrothermal synthesis on Ag2S nanoparticles.•The photoelectric properties of the Ag2S nanoparticles were studied.•A mechanism for the nucleation and growth of Ag2S NPs was proposed.•The concentration of surfactants impacts the grain diameter and the photoelectric properties.In this paper, Ag2S nanoparticles (NPs) are prepared by a simple one-step hydrothermal synthesis. Various particle diameters of Ag2S NPs are obtained under different concentrations of surfactants. A mechanism for the nucleation and growth of Ag2S NPs under the influence of surfactants is proposed. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV–vis absorption spectroscopy are used to characterize the obtained product. In order to investigate the photoelectric properties of the Ag2S NPs, surface photovoltage (SPV) technique was studied. The Ag2S NPs perform intense photoelectric response in the range of NIR and visible region, which could be applied in photoelectric detector.Ag2S nanoparticles (NPs) are prepared by a simple one-step hydrothermal synthesis. Various particle diameters of Ag2S NPs are obtained under different concentrations of surfactants. A mechanism for the nucleation and growth of Ag2S NPs under the influence of surfactants is proposed. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV–vis absorption spectroscopy are used to characterize the obtained product. In order to investigate the photoelectric properties of the Ag2S NPs, surface photovoltage (SPV) technique was studied. The Ag2S NPs perform intense photoelectric response in the range of NIR and visible region, which could be applied in photoelectric detector.

The improvement of photoinduced charge separation is the key for light-harvesting systems in both photovoltaic and photoelectrochemical solar cells. In this study, the charge separation efficiency has been modulated through varying the magnitude of interfacial electric field in p–n Cu2O homojunction films prepared by simple electrodeposition method. The photoelectrochemical and surface photovoltage measurements were used to investigate the behaviors of photoinducded charge carriers in different p–n Cu2O homojunction films. The results confirmed that the p–n Cu2O homojunction film which exhibited the highest charge separation efficiency resulted in the highest activity in photocatalytic reduction of methyl viologen. These implied that it is possible to achieve high charge separation efficiency via constructing a large magnitude of interfacial electric field within a semiconductor using a simple electrodeposition method.

A visible-light-active ZnO photocatalyst system in the presence of manganese ions (Mn/ZnO) was prepared via a simple and rapid approach. XRD, XPS, Raman scattering and UV-Vis DRS confirmed the manganese exists in multivalent forms (Mn3+/Mn2+) in the ZnO lattice, furthermore, ZnO light absorption is extended to the visible region. The photocatalytic activities of the catalysts were evaluated by measuring the photodegrading efficiency of 2,4-dichlorophenol (DCP) under visible light irradiation. With an optimal molar ratio of 5% in Mn/ZnO the highest rate photodegradation was achieved under the experimental conditions. We have characterized the separation and transfer behavior of the photogenerated charges in the visible region by means of surface photovoltage (SPV), surface photocurrent (SPC) and transient photovoltage (TPV) techniques. Based on the comprehensive investigation of the photovoltaic properties of Mn/ZnO photocatalyst, we illustrate the behavior of photogenerated charges have distinct effects on the photocatalytic activity. It is demonstrated that the incorporation of multivalent Mn in ZnO promoted the separation of photogenerated charges, inhibited the recombination of photogenerated carriers, and thus prolonged the charges lifetime to participate in the photocatalytic reaction, resulting in highly efficient photocatalytic activity, which is attributed to the formation of a strong electronic interaction between the multivalent Mn and ZnO.

By using the surface photovoltage (SPV) technique based on a lock-in amplifier, surface states located 3.1 eV below the conduction band of TiO2 have been detected in TiO2 nanotube arrays prepared by anodization of titanium foil in fluoride-based ethylene glycol solution. The photo-induced charge transportation behavior of TiO2 nanotube arrays was also studied by qualitatively analyzing their SPV phase spectra measured under different external bias. When a negative bias was applied, carriers excited from surface states have the same transportation properties as those excited from the valence band; in contrast, when a positive bias was applied, these two kinds of photo-excited carriers exhibit different transportation behavior.

The behavior of photogenerated charges in the Fe3O4@Fe2O3 core/shell nanoparticles with high photocatalytic activity have been investigated by surface photovoltage (SPV) spectroscopy and transient photovoltage (TPV) measurements. The single-phase Fe3O4 and Fe2O3 particles as references have been investigated simultaneously. The results demonstrate that the junction formation in the Fe3O4@Fe2O3 nanoparticles significantly affects the separation, transport, and recombination of photogenerated charges and even changes the transport direction and recombination velocity. And the mechanisms here have been discussed in detail. These results are helpful in understanding the photoelectric process of nanoscaled materials with the heterojunction structures and further utilizing the photoelectric materials and devices.

ZnO/Cu2O heterostructure films were prepared by a two-step electrodeposition method in aqueous solution on fluorine-doped tin oxide (FTO) substrates. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and UV-vis transmission measurements were utilized to characterize the films. Surface photovoltage (SPV) technique was used to investigate the process of photoinduced charge transfer. The results show that there is an electric field located at the interface between ZnO and Cu2O film and the photoinduced electrons in Cu2O film inject into ZnO under the effect of interfacial electric field with visible light irradiation. While under ultraviolet light illumination, the photoinduced electrons in Cu2O film accumulate at the surface of Cu2O film instead of injecting into ZnO under the action of surface built-in electric field of Cu2O film. The work function measurements confirm that the direction of interfacial electric field is from ZnO to Cu2O. These results are help to future design of high performance heterostructure photovoltaic devices.

Fe2O3/TiO2 heterogeneous photocatalysts with different mass ratios of Fe2O3vs. TiO2 were synthesized by impregnation of Fe3+ on the surface of TiO2 microrods and calcination at 300 °C. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), photoluminescence spectra and X-ray diffraction (XRD) have been used to characterize the samples. The photocatalytic activities of Fe2O3/TiO2 heterocomposites, pure Fe2O3 and pure TiO2 were evaluated by the photodegrading efficiency of Orange II under visible light (λ > 420 nm). The experiments demonstrated that Orange II in aqueous solution was more efficiently photodegraded using Fe2O3/TiO2 heterogeneous photocatalysts than either pure Fe2O3 or TiO2 under visible light irradiation. With an optimal mass ratio of 7:3 in Fe2O3/TiO2 the highest rate of Orange II photodegradation was achieved under the experimental conditions. We have also compared the photoelectric properties of Fe2O3/TiO2 heterogeneous photocatalysts with that of pure Fe2O3 by surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Based on the photovoltage responses, we discussed the influence of the hetero-interface between Fe2O3 and TiO2 on transfer characteristics of photogenerated charge carriers. We demonstrated that the formation of heterojunctions between Fe2O3 and TiO2 for Fe2O3/TiO2 composites was pivotal for improving the separation and thus restraining the recombination of photogenerated electrons and holes, which accounts for the enhancement of photocatalytic activity.

ZnO/Cu2O heterostructure films were prepared by a two-step electrodeposition method in aqueous solution on fluorine-doped tin oxide (FTO) substrates. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and UV-vis transmission measurements were utilized to characterize the films. Surface photovoltage (SPV) technique was used to investigate the process of photoinduced charge transfer. The results show that there is an electric field located at the interface between ZnO and Cu2O film and the photoinduced electrons in Cu2O film inject into ZnO under the effect of interfacial electric field with visible light irradiation. While under ultraviolet light illumination, the photoinduced electrons in Cu2O film accumulate at the surface of Cu2O film instead of injecting into ZnO under the action of surface built-in electric field of Cu2O film. The work function measurements confirm that the direction of interfacial electric field is from ZnO to Cu2O. These results are help to future design of high performance heterostructure photovoltaic devices.

Fe2O3/TiO2 heterogeneous photocatalysts with different mass ratios of Fe2O3vs. TiO2 were synthesized by impregnation of Fe3+ on the surface of TiO2 microrods and calcination at 300 °C. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), photoluminescence spectra and X-ray diffraction (XRD) have been used to characterize the samples. The photocatalytic activities of Fe2O3/TiO2 heterocomposites, pure Fe2O3 and pure TiO2 were evaluated by the photodegrading efficiency of Orange II under visible light (λ > 420 nm). The experiments demonstrated that Orange II in aqueous solution was more efficiently photodegraded using Fe2O3/TiO2 heterogeneous photocatalysts than either pure Fe2O3 or TiO2 under visible light irradiation. With an optimal mass ratio of 7:3 in Fe2O3/TiO2 the highest rate of Orange II photodegradation was achieved under the experimental conditions. We have also compared the photoelectric properties of Fe2O3/TiO2 heterogeneous photocatalysts with that of pure Fe2O3 by surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Based on the photovoltage responses, we discussed the influence of the hetero-interface between Fe2O3 and TiO2 on transfer characteristics of photogenerated charge carriers. We demonstrated that the formation of heterojunctions between Fe2O3 and TiO2 for Fe2O3/TiO2 composites was pivotal for improving the separation and thus restraining the recombination of photogenerated electrons and holes, which accounts for the enhancement of photocatalytic activity.