Man Ou

Efficient visible-light photocatalytic oxidation of gaseous NO with graphitic carbon nitride (g–C3N4) activated by the alkaline hydrothermal treatment and mechanism analysis

In this paper, an enhanced visible-light photocatalytic oxidation (PCO) of NO (∼ 400 ppm) in the presence of the graphitic carbon nitride (g-C3N4) treated by the alkaline hydrothermal treatment is evaluated. Various g-C3N4 samples were treated in different concentrations of NaOH solutions and the sample treated in 0.12 mol L(-1) of NaOH solution possesses the largest BET specific surface area as well as the optimal ability of the PCO of NO. UV-vis diffuse reflection spectra (DRS) and photoluminescence (PL) spectra were also conducted, and the highly improved photocatalytic performance is ascribed to the large specific surface area and high pore volume, which provides more adsorption and active sites, the wide visible-light adsorption edge and the narrow band gap, which is favorable for visible-light activation, as well as the decreased recombination rate of photo-generated electrons and holes, which could contribute to the production of active species. Fluorescence spectra and a trapping experiment were conducted to further the mechanism analysis of the PCO of NO, illustrating that superoxide radicals (O2(-)) play the dominant role among active species in the PCO of NO.

Highly efficient simulated solar-light photocatalytic oxidation of gaseous NO with porous carbon nitride from copolymerization with thymine and mechanistic analysis

We synthesized novel and efficient porous carbon nitride (CN) photocatalysts by facial supramolecular approach using cyanuric acid (C), melamine (M) and thymine (T) as starting material. The T-modified CNs display excellent photophysical and photochemical properties: high specific surface area, strong light adsorption as well as low recombination rate of photoinduced electron–hole pairs. They exhibit tremendous enhanced photocatalytic activity on photocatalytic oxidation (PCO) of NO (∼400 ppm) under simulated solar-light irradiation, wherein the CM + 2.5 mol%-T possesses the highest photoactivity (93.3% in 40 min). The enhanced photocatalytic performance is ascribed to the synergic effect of large specific surface area and high separation and transfer efficiency of photoinduced electron–hole pairs. In the PCO of NO process, the main reaction product is NO3−, which was confirmed by Ion Chromatography. In addition, the mechanism of PCO is also intuitively analyzed by trapping experiment. The results indicate that ˙O2− plays a leading role in the PCO of NO process.

Z-scheme CaIn2S4/Ag3PO4 nanocomposite with superior photocatalytic NO removal performance: fabrication, characterization and mechanistic study

The development of the economy benefits from fossil fuels, but their consumption inevitably results in environmental pollution. For example, nitric oxide (NO) removal from coal-fired flue gas is a significant aspect of atmospheric pollution control. Based on its unique advantages to resolve atmospheric pollution, photocatalytic oxidation (PCO) is regarded as an effective technique to remove NO. Herein, we have first fabricated Z-scheme CaIn2S4/Ag3PO4 nanocomposites and studied their performance in the PCO of NO (400 ppm) with the assistance of H2O2. The results indicate that the CaIn2S4/Ag3PO4 nanocomposites exhibit superior photocatalytic performance, and the PCO efficiency of NO can reach 83.61%. The excellent photocatalytic ability belongs to the low recombination rate of the photoinduced electron–hole pairs. The production and participation of more active species is another critical factor due to the injected H2O2. FTIR and ion chromatography results reveal that NO3− is the final product. Furthermore, the fluorescence spectra combined with the electron spin resonance and the trapping experiment suggest that ˙OH and ˙O2− might play a predominant role in NO removal.

Promotional effect and mechanism study of nonmetal-doped Cr/CexTi1−xO2 for NO oxidation: tuning O2 activation and NO adsorption simultaneously

Nonmetal-doped Cr/CexTi1−xO2 catalysts were evaluated for selective catalytic oxidation (SCO) of NO, and these were synthesized by using cyanamide as a nonmetal source. The aim of this paper was to elucidate the detailed composition–structure–property relationships. The characterization results demonstrated that the optimized performance was correlated with the formation of superoxide radicals, which was derived from the nonmetal doping and confirmed by EPR studies. H2-TPR and O2-TPD experiments indicated that the addition of cyanamide was beneficial to tune O2 activation and improve NO adsorption strength simultaneously. XPS results suggested that N species were successfully incorporated into the lattice of a cerium–titanium solid solution and substituted for oxygen. Additionally, the designed FTIR and Raman measurements were applied to identify the doping sites, that is, N species were inclined to substitute the O atoms around cerium to form the Ce–N–Ti and Ce–N–Ce bonds. Finally, the catalytic mechanism was tentatively proposed based on the analysis of in situ DRIFTS results.

Low-Temperature NOX (x = 1, 2) Removal with •OH Radicals from Catalytic Ozonation over α-FeOOH

ABSTRACT FeOOH(H), FeOOH(P) and FeOOH(O) prepared by hydrothermal, precipitant-hydrolysis and oxidation-hydrolysis methods were tested as ozonation catalysts for the low-temperature NOX (x = 1, 2) removal. FeOOH(H) exhibits higher catalytic activities than FeOOH(P) and FeOOH(O), achieving 85.6% of NOX removal efficiency with a low ozone concentration. Compared to FeOOH(P) and FeOOH(O), FeOOH(H) shows much higher BET surface areas and higher density of surface -OH, both of which are critical for the •OH radical generation over the catalysts. These radicals can be successfully transferred into the duct under the coupling effect of hydroxyl radicals and O3, oxidizing and removing the NOX (x = 1, 2). Results of ion chromatography (IC) indicate that the oxidation products are all NO3− without any NO2− in the tail solutions.