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Wide bandgap semiconductor-based photocatalysts are usually limited by their low solar energy conversion efficiency due to their limited absorption solar wavelength, their rapid surface recombination of the photogenerated electron–hole pairs, and their low charge-carrier mobility. Here, we report a novel stepwise solution synthesis for achieving a new photocatalytic core–shell consisting of a titanate nanowire/reduced graphene oxide shell (or titanate/rGO) 1D-nanocomposite. The new core–shell nanocomposite maximized the specific surface area, largely reduced the charge transfer resistance and reaction energy barrier, and significantly improved the absorption of visible light. The core–shell nanocomposites' large on/off current ratio and rapid photo-responses boosted the photocurrent by 30.0%, the photocatalysis rate by 50.0%, and the specific surface area by 16.4% when compared with the results for the pure titanate nanowire core. Our numerical simulations support the effective charge separation on the new core–shell nanostructure, which can help further advance the novel photocatalysis. [ABSTRACT FROM AUTHOR]

• MoS 2 NTs in different shell thicknesses were constructed on FTO substrates. • MoS 2 NTs overcame the aggregation and enabled multiple refraction of light. • MS05 array owned the largest kinetic constant of 5.516 × 10 − 3 mi n − 1 c m − 2 . • The dye absorption, excitation and recombination dominated catalytic activity. Light trapping based on nanostructure has emerged as an effective method to improve light absorption of the photocatalytic devices. Herein, molybdenum disulfide nanotube arrays with different wall thicknesses were successfully synthesized by changing reactant concentration from 50 % to 150 %. The nanotubes overcame aggregation of the nanosheets, offered multiple scattering centers and enabled multiple refraction of light, leading to excellent light harvest in the visible range and molecule absorption efficiency as high as 21.0 %. The photodegradation efficiency of methylene blue as catalyzed by the nanotubes was modulated by the wall thickness, in which the highest degradation efficiency of 69.6 % and the largest kinetic constant of 5.516 × 10 − 3 mi n − 1 · c m − 2 were achieved for the thinnest wall. The analysis revealed that the photocatalytic activity of the nanotube arrays was dominated by the dye absorption, environment, light excitation and charge recombination, which would provide structural design for their applications in optoelectronics and photocatalysis. [ABSTRACT FROM AUTHOR]

The hollow NT with a built-in electric field at the heterogeneous semiconductor shell expanded curvature effect and generated light diffraction in the inner wall that enhanced light absorption and improved charge transfer and photocatalytic activity. [Display omitted] • MoS 2 and its heterogeneous NT arrays were synthesized on FTO substrates in a vertical alignment. • The hollow NT with the heterogeneous semiconductor shell expanded curvature effect and generated light diffraction in the inner wall that enhanced light absorption and improved charge transfer and photocatalytic activity. • The MoS 2 /ZnO/Ag 2 S array owned the best catalytic performance with efficiencies of 68.9 % and 78.1 % in 30 min under visible and UV light, respectively. • A built-in electric field at the interface pointing from MoS 2 to ZnO induced a type-II band alignment that promoted photocatalytic performance. Nanotubes are unique structures capable of producing light diffraction on their inner wall, amplifying curvature effect, and enhancing light excitation. These characteristics are of paramount importance in the fields of the optoelectronic and photocatalytic materials. In this study, MoS 2 and its heterogeneous nanotube arrays were synthesized on FTO substrates in a vertical alignment. The hollow structure of these nanotube arrays was found to significantly enhance light absorption efficiency. The core–shell MoS 2 /ZnO resulted in strong electric interaction at the interface, leading to a reduced bandgap in MoS 2. Being catalysts for the degradation of dye molecules, all the nanotube arrays achieved larger photocatalytic efficiency than that of the nanowire arrays with identical components. The ternary MoS 2 /ZnO/Ag 2 S array owned the best catalytic performance for the degradation of methylene blue, with efficiencies of 68.9 % and 78.1 % in 30 min under visible and UV light, respectively. Both experimental and theoretical analyses revealed the presence of a built-in electric field at the interface, directing from MoS 2 to ZnO. This induced a type-II band alignment that promoted photocatalytic performance. This study highlights the exceptional optoelectronic conversion properties and photocatalytic activity of nanotube heterojunctions, holding significant implications for the design of semiconductor devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Core-shell Si/TiO 2 nanowires were synthesized vertically on silicon substrate. • The heterostructure owned a wide spectral absorption with large photocurrent. • The catalytic efficiency of the sample was 86.82% in 1 h with good stability. • The excited charges were effectively separated by the internal electric field. Semiconductor photocatalysts can eliminate organic pollutants completely, but the poor utilization of solar energy and rapid recombination of photogenerated electron-hole pairs have become a vital obstacle for their widespread application. Herein Si/TiO 2 nanowire arrays with core–shell structures were fabricated by metal-assisted chemical etching and atomic-layered deposition. The physical properties and photocatalytic performance of the specimens were tested and compared with pristine Si nanowire arrays. The specimens showed perfect light absorption. The photoluminescence was generally depressed by the shell layer, and the photocurrent and photocatalytic efficiency of Si/TiO 2 were improved by 297 and 2 times respectively in contrast to Si. The magnitude of the photocurrent and photocatalytic activity could be modulated by the etching period, in which an ideal etching time of 2 h produced the highest photocatalytic performance. The high efficient photocatalysis of the heterostructure was well illustrated by the Z-scheme band alignment and large specific surface area. [ABSTRACT FROM AUTHOR]

ZnO/Si nanotrees were coated by Ag 2 S and In 2 S 3 nanoparticles. The built-in electric field of the heterojunctions induced electron-hole pair recombination in the conduction band of ZnO and valence bands of other semiconductors at the interfaces, which reduced charge recombination in the interior of the component semiconductors and improved redox ability. • Heterogeneous nanowire arrays were grown resulting in efficient dye photodegradation. • Introduction of quantum dots yielded a quarter resistance and 31-fold photocurrent. • The samples got efficiency of 62% and 55% in visible and UV light with recyclability. • Z-scheme heterojunctions played a critical role in the high photocatalytic activity. Hierarchical heterogeneous ZnO/Si nanowire arrays grown from metal-induced wet etching process on p-type silicon wafer were obtained and have been strategically sensitized by narrow bandgap semiconductors of In 2 S 3 nanosheets and Ag 2 S quantum dots via successive ionic layer adsorption and reaction technique. The photodegradation of methylene blue as catalyzed by the arrays was conducted under visible light and ultraviolet light. By introducing the coating layers, the specimens were found to achieve absorptivity higher than 94% and yield a quarter of the resistance and 31-fold of the photo-current as compared to the primary nanowire arrays. The photodegradation efficiency was improved from 48.9% to 62.0%, and 43.0% to 55.0%, respectively in visible light and ultraviolet light with an enhanced recyclability. Band structure analysis indicated that the coating brought different Z-scheme heterojunctions for efficient photocatalytic performance, while the function could only work in a given spectral range. These results would be helpful to better realize the photocatalytic mechanisms and meanwhile, could be extended to design heterogeneous semiconductor nanomaterials for their potential applications. [ABSTRACT FROM AUTHOR]