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Nanocomposites based on TiO2 nanotube arrays (TiO2-NTA) have received increasing attention for photoconversion and photocatalytic reactions. Here, TiO2-NTA were prepared by an anodic oxidation process. ZnO and ZnCr2O4 nanoparticles were further anchored on the surface of the pre-synthesized TiO2-NTA to form a ternary ZnO/ZnCr2O4@TiO2-NTA (Zn-Cr-O@TiO2-NTA) nanocomposite by an electrochemical reduction-oxidation strategy. Compared to bare TiO2-NTA, the Zn-Cr-O@TiO2-NTA nanocomposite shows remarkably higher photovoltaic conversion efficiency (nine times greater) under visible light irradiation, and photocatalytic H2 evolution activity (2.8 times greater) under simulated sunlight irradiation, respectively. The construction of ternary nanocomposite is beneficial to enhancing the absorption of simulated sunlight irradiation. Moreover, the Type-II semiconductor heterojunction facilitates separation of electron-hole pairs and interfacial charge transport. As a result, improvement of photoconversion efficiency has been obtained. This work may have fundamental importance to designing complex and efficient photoelectrodes for energy-harvesting applications, including photovoltaic solar cells and water splitting. [ABSTRACT FROM AUTHOR]

In this contribution, the ternary ZnO/Zn6Al2O9/Al2O3 nanocomposite was obtained by in situ incorporation of Al3+ during the synthesis of ZIF-8, aiming to improve the adsorption and photocatalytic performance of ZIF-8-derived ZnO under simulated sunlight irradiation. XRD, SEM, TEM, HRTEM, XPS, UV-vis DRS, BET and PL techniques were employed for the analysis of the crystalline structure, composition, morphology, light absorption and charge separation of the samples. The photocatalytic activity of the samples was evaluated by the degradation of methyl orange (MO) under simulated sunlight irradiation. Compared to ZIF-8-derived ZnO, the formation of the ZnO/Zn6Al2O9/Al2O3 nanocomposite can provide a high BET specific surface area, reduce the band gap, inhibit the recombination of the electron–hole pairs, and hence greatly improve the photocatalytic activity. The maximum photocatalytic degradation rate of 97.5% for a high initial MO concentration of 150 mg L−1 was obtained over the ZnO/Zn6Al2O9/Al2O3 nanocomposite with a 1 : 1 molar ratio of Al/Zn under simulated sunlight irradiation for 60 min, which is 3.18 times higher than that of ZIF-8-derived ZnO. [ABSTRACT FROM AUTHOR]

Abstract: Spinel-type CuYyFe2−y O4–CuCo2O4 nanocomposites have been successfully synthesized via a facile citric acid (CA)-assisted sol–gel method. And the as-synthesized nanocomposites have been characterized by techniques of X-ray diffraction (XRD), nitrogen adsorption BET method, and transmission electron microscopy (TEM). The samples are composed of primary ultrafine nanoparticles with nearly spherical morphology and mean particle size of about 80nm. Moreover, the photocatalytic H2 evolution activity of the as-obtained samples has been evaluated from aqueous oxalic acid solution under visible light irradiation. The influence of photocatalyst type, calcination temperature, Y3+ doping content, and the durability of the as-obtained photocatalyst have been investigated in detail. The best photocatalytic H2 evolution activity was obtained over the as-synthesized CuY0.08Fe1.92O4–CuCo2O4 nanocomposite. [Copyright &y& Elsevier]

Abstract: Copper ferrite (CuFe2O4) nanoparticles have been successfully synthesized via a citric acid-assisted sol–gel method. For comparison, CuFe2O4 materials were also fabricated by solid-state reaction and co-precipitation method. Techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis diffuse reflectance spectrum (UV–vis DRS) have been employed to characterize the as-synthesized CuFe2O4 products. The CuFe2O4 sample prepared by sol–gel approach is composed of almost uniform nanoparticles with a grain size of about 80nm and crystallized in a tetragonal crystal phase structure. Moreover, the photocatalytic activity of the as-obtained CuFe2O4 has been evaluated based on the H2 evolution from aqueous oxalic acid solution under visible light irradiation. The effects of preparation routes, photocatalyst mass concentration, initial sacrificial reagent concentration and the durability of the as-obtained CuFe2O4 have been investigated in detail. The best result of the photocatalytic H2 evolution activity (1.72mmolh−1 gcat −1) was obtained over the sol–gel synthesized CuFe2O4 nanoparticles when the photocatalyst concentration is 1.0gl−1 and the oxalic acid concentration is 0.05M. [Copyright &y& Elsevier]

Abstract: CuCr2O4/TiO2 heterojunction has been successfully synthesized via a facile citric acid (CA)-assisted sol–gel method. Techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectrum (UV–vis DRS) have been employed to characterize the as-synthesized nanocomposites. Furthermore, photocatalytic activities of the as-obtained nanocomposites have been evaluated based on the H2 evolution from oxalic acid solution under simulated sunlight irradiation. Factors such as CuCr2O4 to TiO2 molar ratio in the composites, calcination temperature, photocatalyst mass concentration, and initial oxalic acid concentration affecting the photocatalytic hydrogen producing have been studied in detail. The results showed that the nanocomposite of CuCr2O4/TiO2 is more efficient than their single part of CuCr2O4 or TiO2 in producing hydrogen. The optimized composition of the nanocomposites has been found to be CuCr2O4·0.7TiO2. And the optimized calcination temperature and photocatalyst mass concentration are 500°C and 0.8gl−1, respectively. The influence of initial oxalic acid concentration is consistent with the Langmuir model. [Copyright &y& Elsevier]