Yong-Ming Dai

Controlled hydrothermal synthesis of BiOxCly/BiOmIn composites exhibiting visible-light photocatalytic degradation of crystal violet

A series of BiOxCly/BiOmIn composites were prepared using autoclave hydrothermal methods. The composition and morphologies of the BiOxCly/BiOmIn composites were controlled by adjusting the experimental conditions: the reaction pH value, temperature, and KCl/KI molar ratio. The products were characterized using X-ray diffraction, scanning electron microscopy-electron dispersive X-ray spectroscopy, UV-vis diffuse reflectance spectroscopy, Brunauer-Emmett-Teller specific surface areas, cathodoluminescence, high-resolution transmission electron microscopy, and high-resolution X-ray photoelectron spectroscopy. The photocatalytic efficiencies of composite powder suspensions were evaluated by monitoring the crystal violet (CV) concentrations. In addition, the quenching effects of various scavengers indicated that the reactive O2(-) played a major role, and OH or h(+) played a minor role in CV degradation. The intermediates formed during the decomposition process were isolated, identified, and characterized using high performance liquid chromatography-photodiode array-electrospray ionization-mass spectrometry to elucidate the CV decomposition mechanism.

Novel synthesis of bismuth oxyiodide/graphitic carbon nitride nanocomposites with enhanced visible-light photocatalytic activity

The first systematic synthetic study of bismuth oxyiodide/graphitic carbon nitride (BiOxIy/g-C3N4) nanocomposite preparation using a controlled hydrothermal method is reported. The structure and morphology of BiOxIy/g-C3N4 photocatalysts are characterized by XRD, TEM, FT-IR, HR-XPS, FE-SEM-EDS, UV-vis-DRS and BET. The photodegradation activities are evaluated against the decolorization of crystal violet (CV) in aqueous solution under visible light illumination. In particular, the catalytic performance illustrates the best reaction rate constant, being 0.170 h−1 using Bi7O9I3/Bi5O7I/g-C3N4 composite as the photocatalyst; which is 5, 4, and 1.5 times higher than the reaction rate constant of BiOI, g-C3N4, and Bi7O9I3/Bi5O7I, as photocatalysts, respectively. From the quenching effects of different scavengers, the EPR results demonstrate that the reactive O2˙− plays the major role and h+ and ˙OH play minor roles in the CV degradation. The probable photodegradation mechanisms are proposed and discussed in this research. This work is useful for the synthesis of BiOxIy/g-C3N4 and the photocatalytic degradation of the CV for future applications in environmental pollution and control.

A series of BiOxIy/GO photocatalysts: synthesis, characterization, activity, and mechanism

A series of bismuth oxyiodide (BiOxIy)-grafted graphene oxide (GO) sheets with different GO contents were synthesized through a simple hydrothermal method. This is the first report where four composites of BiOI/GO, Bi4O5I2/GO, Bi7O9I3/GO, and Bi5O7I/GO have been characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. The assembled BiOxIy/GO composites exhibited excellent photocatalytic activities in the degradation of crystal violet (CV) under visible light irradiation. The order of rate constants was as follows: Bi7O9I3/GO > Bi4O5I2/GO > Bi4O5I2 > Bi7O9I3 > Bi5O7I/GO > BiOI/GO > BiOI > Bi5O7I > GO. The photocatalytic activity of the Bi7O9I3/GO (or Bi4O5I2/GO) composite reached a maximum rate constant of 0.351 (or 0.322) h−1, which was 1.8 (or 1.7) times higher than that of Bi7O9I3 (or Bi4O5I2), 6–7 times higher than that of BiOI/GO, and 119–130 times higher than that of BiOI. The quenching effects of different scavengers and electron paramagnetic resonance demonstrated that the superoxide radical (O2˙−) played a major role and holes (h+) and hydroxyl radicals (˙OH) played a minor role as active species in the degradation of crystal violet (CV) and salicylic acid (SA). Possible photodegradation mechanisms are proposed and discussed in this research.

A novel heterojunction photocatalyst, Bi2SiO5/g-C3N4: synthesis, characterization, photocatalytic activity, and mechanism

A new type of heterojunction photocatalyst, Bi2SiO5/g-C3N4, was prepared using a controlled hydrothermal method. The structure and morphology of the Bi2SiO5/g-C3N4 photocatalyst were characterized by XRD, HR-TEM, FE-SEM-EDS, HR-XPS, FT-IR, PL, BET, EPR, and UV-Vis-DRS. The obtained Bi2SiO5/g-C3N4 photocatalyst exhibits enhanced photocatalytic activity on the decolorization of crystal violet (CV) under visible-light irradiation. In particular, the catalytic performance illustrates the best reaction rate constant of 0.1257 h−1 using Bi2SiO5/g-C3N4 as the photocatalyst, which is 5 and 3 times higher than the reaction rate constants of Bi2SiO5 and g-C3N4 as photocatalysts, respectively. This study shows that Bi2SiO5/g-C3N4 can be used to suppress the recombination of photoinduced electron–hole pairs and contribute to the enhanced photocatalytic efficiency of semiconductors in the visible light-driven catalysis. The quenching effects of different scavengers, and EPR results demonstrate that the reactive O2˙− plays the major role and ˙OH, h+ and 1O2 play minor roles in CV degradation. The probable photodegradation mechanisms are proposed and discussed.

Catalytic activity of mesoporous Ni/CNT, Ni/SBA-15 and (Cu, Ca, Mg, Mn, Co)–Ni/SBA-15 catalysts for CO2 reforming of CH4

The CO2 reforming of CH4 to H2 over a catalyst is an effective method for renewable energy generation. In this study, SBA-15 and CNT were chosen as supports for the Ni-based catalysts prepared by the impregnation method. The FESEM images demonstrated that NiO particles were rhombic and well distributed on the SBA-15 surface. The XRD patterns showed that the chemical state of Ni changed after the reforming reaction; the main crystals on the fresh and spent Ni/SBA-15 were found to be NiO and Ni0. The catalytic performance of Ni/SBA-15 in CO2/CH4 reforming was found to be superior to that of Ni/CNT. The results of the TGA and BET analysis demonstrated that spent Ni/SBA-15 (at 600 °C) showed no catalytic decay as an insignificant amount of coke was deposited on the catalyst supports. Moreover, Ni-based bimetallic catalysts were studied for the reforming reaction, and the activity of the catalysts with respect to metals was observed to follow a particular order: Cu–Ni > Mg–Ni > Co–Ni > Ca–Ni > Mn–Ni. The Cu–Ni/SBA-15 catalyst exhibited higher catalytic activity at a reaction temperature of 650 °C as compared to the others; the H2 yield (40%) was not decreased as the reaction time increased, and the conversion of CO2 and CH4 is 77% and 75%, respectively.