Wu Zhongbiao

In situ FT-IR investigation on visible light photocatalytic NO oxidation mechanism with (BiO) 2 CO 3 and N-doped (BiO) 2 CO 3 hiararchical microspheres

With the rapid development of industry, air pollution has become a focused issue worldwide. As one of the major air pollutants, nitric oxide (NO) would lead to serious atmospheric problems such as acid rain, haze, and photochemical smog. Photocatalysis, as a green and effective technology, has become one of the most promising technologies for solving air pollution problems. As one of the typical photocatalyst, (BiO)2CO3 consists of alternating layers of [Bi2O2]2+ and CO32− groups and has good optical absorption property, emerging as an attractive photocatalyst. In this work, (BiO)2CO3 and in situ N-doped (BiO)2CO3 hierarchical microspheres were fabricated by a one-pot hydrothermal method and applied to photocatalytic NO removal. The as-prepared samples were characterized by XRD, SEM, TEM, XPS, UV-vis DRS, PL and ESR. The photocatalytic NO oxidation process was monitored by in situ DRIFTS. The results indicated that the addition of urea has significant impact on (BiO)2CO3. The changed exposed facet influenced the morphological structure, band gap has narrowed and electronic-hole recombination rate of the as-prepared N doped (BiO)2CO3 has decreased. There are a lot of reports on photocatalytic NO oxidation, and the photocatalytic reaction mechanism for NO purification has been proposed for some photocatalysts with ·O2− and ·OH radicals as the main reactive species and nitrates as the final products. However, little is known about the reaction intermediates during photocatalysis. To reveal the reaction mechanism of photocatalytic NO oxidation, in situ DRIFTS investigation was applied to probe the reaction process. The photocatalytic NO oxidation mechanism was revealed based on the in situ DRIFTS and ESR results. With N doping, the reaction process and the free radicals which participated during the photocatalystic reaction process become different from the pure (BiO)2CO3 sample. For BOC, ·O2− is main active radical, but for NBOC, the active radical changed to ·OH. A new intermediate of NO+ was discovered during photocatalysis, which increased the efficiency of the reaction. Because of the N doping, the electronic structure of (BiO)2CO3 has been broken, which leads to the formation of more oxygen vacancy. The present work could provide new perspectives for advancing the photocatalysis efficiency, offer a new insight into the photocatalytic NO oxidation process and promote large-scale environmental applications of high-performance photocatalysts.

Performance and mechanism of visible-light-inducedplasmonic photocatalytic purification of NO with Ag/AgX

Photocatalysis technology could utilize solar energy for pollutants degradation and water splitting, displaying great potential in environmetnal remidiation and clean enerfy development. Significant progresses have been made on promoting photocatalysis efficiency and extending light absorption range. Specific semiconductors and plasmonic metals can behave photocatalysts. Recently, the plasmonic photocatalysis with Ag/AgX (X=Cl, Br, I) has been received increasing research interests. The preparation and application of Ag/AgX plasmonic photocatalysts have extensively explored. However, the Ag/AgX plasmonic photocatalysts were mainly applied in water splitting and degradation of aquous pollutants. The application of Ag/AgX in air purification has been rarely reported. Also, the mechanism of photocatalytic NO purification with Ag/AgX has never been revealed.

In situ synthesis, bandstructure analysis and of visible light photocatalysis enhancementmechanism of K-doped C 3 N 4

For the past few years, air quality has surged to worldwide attention. For NO x purification, semiconductor photocatlysis as a green technology that could use sunlight to purify air pollutants, provides an attractive alternative to decrease pollution. Recently, polymeric graphitic carbon nitride (g-C 3 N 4 ) materials have drawn intensive attention because of its metal-free and high-hardness features, reliable chemical inertness, thermal stability, as well as its versatile optical, electrochemical, and efficient photocatalytic properties. But pure g-C 3 N 4 suffers from rapid recombination of photo- generated electron-hole pairs resulting in low photocatalytic activity. Thus, several coping modifying methods were employed to improve the photocatalytic performance of g-C 3 N 4 . The present work developed a facile in situ method to construct novel k-doped g-C 3 N 4 (CN-K) structure with molecular composite precursors. In this work, the samples were prepared via pyrolysis of thiourea and a certain amount of KI as the potassium source in a muffle furnace. Different mass ratio (1%, 3%, 5%, 10%) of K-doping g-C 3 N 4 samples were prepared by changing the amount of KI. The as-prepared samples were systematically characterized by XRD, SEM, TEM, XPS, BET, UV-vis DRS and PL. Material studio was used to simulated the crystalline structure of potassium doped g-C 3 N 4 . The bond structure of as-prepared samples can be theoretical calculation by DFT theoretical calculation. Both the experimental and theoretical calculation results indicated that potassium ion which were formed chemical bond with nitrogen existed in the interlayer of g-C 3 N 4 . The modified catalyst exhibited outstanding photocatalytic activity and photochemical stability towards degradation of NO at ppb-level under visible light irradiation. The superior activity can be ascribed to the significant function of potassium ion worked on morphological structure, band gap and electronic-hole recombination of as prepared samples. Firstly, evidenced by valence band XPS and DFT theoretical calculation, potassium doping has the function of modifying band-gap, making for down-shift both conduction band and valence band, however, The extent of the conduction band down shifting more than the valence band, shortening down the optical band gap more while making a significant enhancement of the solar light response range, thus the absorption capacity of as prepared samples strengthen significantly. Secondly, the separation efficiency of photon-generated carriers increased with potassium doped in the interlayer of g-C 3 N 4 verified by room temperature PL spectra. Thirdly, the in situ K-doped g-C 3 N 4 showed higher oxidation capacity of photo-induced holes for degradating NO, ascribed to a more positive valence band. Integrated three factors, purification efficiency of NO has been significantly improved. This work could provide a new perspective for modification of photocatalyst with alkali metals and mechanism understanding of NO degradation.