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Band gap narrowing is important and advantageous for potential visible light photocatalytic applications involving metal oxide nanostructures. This paper reports a simple biogenic approach for the promotion of oxygen vacancies in pure zinc oxide (p-ZnO) nanostructures using an electrochemically active biofilm (EAB), which is different from traditional techniques for narrowing the band gap of nanomaterials. The novel protocol improved the visible photocatalytic activity of modified ZnO (m-ZnO) nanostructures through the promotion of oxygen vacancies, which resulted in band gap narrowing of the ZnO nanostructure (Eg = 3.05 eV) without dopants. X-ray diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, Raman spectroscopy, photoluminescence spectroscopy and high resolution transmission electron microscopy confirmed the oxygen vacancy and band gap narrowing of m-ZnO. m-ZnO enhanced the visible light catalytic activity for the degradation of different classes of dyes and 4-nitrophenol compared to p-ZnO, which confirmed the band gap narrowing because of oxygen defects. This study shed light on the modification of metal oxide nanostructures by EAB with a controlled band structure.

This study reports a biogenic approach to the synthesis of Au@CeO2 nanocomposite using electrochemically active biofilms (EABs) in water under normal pressure and 30 °C. This work presents the results of extensive morphological, structural, optical, visible light photoelectrochemical and photocatalytic studies of Au@CeO2 nanocomposite. The presence of a large number of interfaces between Au nanoparticles and CeO2 for charge transfer is believed to play a key role in enhancing the optical and visible light photoelectrochemical and photocatalytic performance of Au@CeO2 nanocomposite. The enhanced visible light degradation of methyl orange and methylene blue by Au@CeO2 nanocomposite was much higher than that by pure CeO2. The reusability, stability, and other results suggests that the Au@CeO2 nanocomposite could be exploited as potential candidates for visible light photocatalysis, photovoltaic, and photoelectrochemical devices.

This paper reports that the introduction of elemental red phosphorus (RP) into TiO 2 can shift the light absorption ability from the UV to the visible region, and confirmed that the optimal RP loading and milling time can effectively improve the visible light driven-photocatalytic activity of TiO 2 . The resulting RP-TiO 2 nanohybrids were characterized systematically by a range of techniques and the photocatalytic ability of the RP-TiO 2 photocatalysts was assessed further by the photodegradation of a model Rhodamine B pollutant under visible light irradiation. The results suggest that the RP-TiO 2 has superior photodegradation ability for model contaminant decomposition compared to other wellknown photocatalysts, such as TiO 2 and other reference materials. Furthermore, as a photoelectrode, electrochemical impedance spectroscopy, differential pulse voltammetry, and linear scan voltammetry were also performed in the dark and under visible light irradiation. These photoelectrochemical performances of RP-TiO 2 under visible light irradiation revealed more efficient photoexcited electron-hole separation and rapid charge transfer than under the dark condition, and thus improved photocatalytic activity. These findings show that the use of earth abundant and inexpensive red phosphorus instead of expensive plasmonic metals for inducing visible light responsive characteristics in TiO 2 is an effective strategy for the efficient energy conversion of visible light.The design of a photocatalyst for the utilization of solar energy is considered one of the most promising and clean approaches towards pollutant removal from aquatic environments. Metal oxide-mediated photocatalysis under UV light and/or visible light have been reported widely in terms of stability, efficiency and metal free photocatalysts 1-4 . Among them, TiO 2 is a more popular photocatalyst for the conversion of solar energy, hydrogen generation via water splitting reaction and dye degradation because of its stability, high catalytic activity, low cost, easy availability etc. 3,4 . On the other hand, the catalytic efficiency of TiO 2 in the wider spectrum of solar energy is still low because of its wide band gap and high recombination rate of photoinduced electrons and holes. Several attempts have been made to enhance the photocatalytic activity and extend the absorption edge of TiO 2 to the visible region via metal and non-metal doping, anchoring of noble metals, textural designing and surface defect engineering [2][3][4][5] . On the other hand, the catalytic efficiency and absorption ability of TiO 2 over the wide spectrum of solar energy is still feeble and unsatisfactory.Recently, elemental semiconductors, such as α -sulphur 6 and red phosphorus (RP), have attracted considerable attention in the field of photocatalysis because of their unique advantages, such as wide visible light absorption ability, low cost, and earth abundance, which make it suitable for a range of practical applications 6,7 . Among them, RP has been reported to be a promising candid...

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