Three narrow band-gap semiconductors modified Z-scheme photocatalysts, Er3+:Y3Al5O12@NiGa2O4/(NiS, CoS2 or MoS2)/Bi2Sn2O7, for enhanced solar-light photocatalytic conversions of nitrite and sulfite

Preparation of PVDF/CdS/Bi2WO6/ZnO hybrid membrane with enhanced visible-light photocatalytic activity for degrading nitrite in water

In this work, a visible light-driven ternary heterojunction photocatalyst, CdS/Bi₂WO₆/ZnO, was synthesized using hydrothermal, ultrasonic dispersion, and deposition precipitation methods. The results show that photocatalysts with flower-like heterostructures were obtained, which could efficiently separate electron-hole pairs, and the photocatalytic activity was thereby significantly enhanced. Furthermore, CdS/Bi₂WO₆/ZnO and polyvinylidene fluoride (PVDF) were used to fabricate hybrid membranes via a phase-conversion method. The samples were characterized using SEM, TEM, EDX, XRD, DRS, XPS, PL, and N₂ adsorption-desorption isotherms, and the transient photocurrent response. The photocatalytic activity of the hybrid membrane was evaluated, and 92.58% of the nitrite was converted into non-toxic substances within 4 h under simulated sunlight irradiation. This result indicated that the photocatalyst exhibited a good photocatalytic activity after immobilization. The possible mechanism was elucidated by studying the product during the photocatalytic degradation, and the effects of different pH values, electron scavengers, and hole scavengers on the photocatalytic performance were further investigated.

The design of a polyaniline-decorated three dimensional W18O49 composite for full solar spectrum light driven photocatalytic removal of aqueous nitrite with high N2 selectivity

Photocatalysis using solar energy is the most promising green technology for nitrite removal. However, effective photocatalytic performance is often challenged by the limited light absorption, utilization of expensive noble metals and undesired products (nitrate and ammonium). Here, we report for the first time that a full solar light response polyaniline-decorated three dimensional W₁₈O₄₉ composite (PANI@W₁₈O₄₉), a noble metal-free photocatalyst, possesses excellent photocatalytic activity for aqueous nitrite removal with high N₂ selectivity. The prepared sample was thoroughly identified via XRD, Raman, FTIR, SEM, TEM, UV-vis DRS and PL. The catalytic results demonstrated that over 80% N₂ selectivity (initial concentration 1.0 mM) was achieved through the PANI@W₁₈O₄₉ without sacrificial agent under 300 W Xe lamp irradiation for 60 min. Such advantages were attributed to the built-in junction between n-type W₁₈O₄₉ and p-type PANI, offering suitable redox levels of electron-hole pairs for NO₂^- reaction. The modification of PANI also benefited the light harvesting ability and activated carriers migration, the calculated rate constant of PANI@W₁₈O₄₉ is about four times as high as that of W₁₈O₄₉. The current study not only prepared a promising photocatalyst, but also provides new insights into improving the photocatalytic activity and N₂ selectivity for nitrite treatment.