Shuying Zhu

Photocatalytic reduction of CO2 with H2O to CH4 over ultrathin SnNb2O6 2D nanosheets under visible light irradiation

Monolayer SnNb2O6 two-dimensional (2D) nanosheets with high crystallinity are prepared by an one-pot and eco-friendly hydrothermal method without any organic additives. For the first time, these SnNb2O6 nanosheets are applied to the photocatalytic reduction of CO2 with H2O to CH4 in the absence of co-catalysts and sacrificial agents under visible light irradiation. The structural features, morphology, photoabsorption performance, and photoelectric response have been investigated in detail. Results show the as-prepared SnNb2O6 samples with typical 2D nanosheets in the thickness of about 1 nm. Owing to the unique features of the nanosheets, the surface area, photoelectrical properties and the surface basicity of SnNb2O6 are greatly improved compared with the counterpart prepared by traditional solid state reaction. Furthermore, the adsorption capacity of CO2 on SnNb2O6 nanosheets is much higher than that of layered SnNb2O6. Thus, the photocatalytic activity of SnNb2O6 nanosheets for the reduction of CO2 is about 45 and 4 times higher than those of the references (layered SnNb2O6 and common N-doped TiO2), respectively. To understand the interactions between the CO2 molecule and the surface of the photocatalyst, and the reactive species in the reduction process, the intermediates have also been detected by in situ FTIR with and without visible light irradiation. Finally, a possible mechanism for the photocatalytic reduction of CO2 with H2O to CH4 on SnNb2O6 nanosheets is proposed. We believe this work will provide new opportunities for expanding the family of visible-light driven photocatalysts for the reduction of CO2.

ZrO2-incorporated Bi6O6(OH)3(NO3)3.1.5H2O with superior photocatalytic activity for degradation of malachite green

Bi6O6(OH)3(NO3)3·1.5H2O and ZrO2-modified Bi6O6(OH)3(NO3)3·1.5H2O as novel photocatalysts were successfully synthesized via a facile hydrothermal method and utilized in aqueous solution for the photocatalytic degradation of malachite green. The prepared samples were characterized by X-ray diffraction, BET surface area analysis and UV-vis reflectance spectrum. Comparing with the samples synthesized via bare Bi6O6(OH)3(NO3)3·1.5H2O, the ZrO2-modified sample exhibits higher catalytic activity and more durable stability in the photodegradation of malachite green. The electronic band structure was determined by the combination of optical absorption spectra and Mott–Schottky plots. Base on the research of structural characterization, band gap structure and electrochemical tests, the possible reasons for enhance photocatalytic performance by ZrO2-incorporation were proposed. It has been considered that the large specific surface area, more positive position of valance band and higher migration rate of photogenerated carriers have strong influence on the improvement of photocatalytic activity. Moreover, the ZrO2-modification delays photo corrosion behavior resulting in higher stability under irradiation.

Constructing a MoS₂ QDs/CdS Core/Shell Flowerlike Nanosphere Hierarchical Heterostructure for the Enhanced Stability and Photocatalytic Activity.

MoS2 quantum dots (QDs)/CdS core/shell nanospheres with a hierarchical heterostructure have been prepared by a simple microwave hydrothermal method. The as-prepared samples are characterized by XRD, TEM, SEM, UV-VIS diffuse reflectance spectra (DRS) and N2-sorption in detail. The photocatalytic activities of the samples are evaluated by water splitting into hydrogen. Results show that the as-prepared MoS2 QDs/CdS core/shell nanospheres with a diameter of about 300 nm are composed of the shell of CdS nanorods and the core of MoS2 QDs. For the photocatalytic reaction, the samples exhibit a high stability of the photocatalytic activity and a much higher hydrogen evolution rate than the pure CdS, the composite prepared by a physical mixture, and the Pt-loaded CdS sample. In addition, the stability of CdS has also been greatly enhanced. The effect of the reaction time on the formations of nanospheres, the photoelectric properties and the photocatalytic activities of the samples has been investigated. Finally, a possible photocatalytic reaction process has also been proposed.

Photochemical treatment of As(III) with α-Fe2O3 synthesized from Jarosite Waste

Endeavoring to mitigate and remedy Arsenic (As) in groundwater, we developed a one-step process for As(III) oxidation and subsequent adsorption by using α-Fe2O3 under UV irradiation. The α-Fe2O3 with high surface area was successfully prepared through a mild hydrothermal reaction using Jarosite waste as precursor. During the treatment of As(III) in aqueous solution, the as-obtained α-Fe2O3 can release ferric ions stimulated by UV irradiation. This led to the effective oxidation of As(III) to As(V) which is further adsorbed on α-Fe2O3, realizing the removal of As from water. This simple and efficient route may be potential for the remediation of polluted water containing As ions.

HZSM-5 zeolites containing impurity iron species for the photocatalytic reduction of CO2 with H2O

We report the application of the commercial HZSM-5 zeolite as an efficient and stable photocatalyst for the photoreduction of CO2 with H2O at room temperature. CO and H2 were the main reduction products besides a trace amount of hydrocarbons. The activity of CO evolution was dependent on the source of various zeolites. The highest CO evolution rate over the HZSM-5 samples was 3.32 μmol g−1 h−1 under UV-light irradiation. The control experiments combined with the characterization results of XRD, UV-vis DRS and ESR revealed that the photocatalytic activity was not related to Si/Al ratios or Al–O units but was associated with the content of Fe impurities in the zeolite samples. A reaction mechanism of CO2 photoreduction on Fe species in zeolites was proposed. [Fe3+–O2−] species as a photoactive centre can be excited by UV light to form a charge-transfer excited state, [Fe2+–O−]*, which was responsible for the CO2 reduction reaction. This work demonstrates zeolite molecular sieves as an efficient photocatalyst for CO2 conversion and helps us to understand the photocatalytic nature of zeolites.