Gangqiang Zhu,Mirabbos Hojamberdiev,Shaolin Zhang,Syed Taj Ud Din,Woochul Yang
In order to further improve its photocatalytic activity , the BiOI microspheres were activated by a synchronous coupling of Bi metal and graphene under solvothermal conditions. The effects of the synthesis temperature (160–200 °C) on crystallinity, morphology, and photocatalytic activity were studied in particular. As expected, the ternary Bi-BiOI/graphene photocatalyst synthesized at 180 °C exhibited higher photocatalytic activity for NO oxidation removal under visible light irradiation than individual BiOI, and binary Bi-BiOI and BiOI/graphene composites. The photocatalytic efficiency for the NO removal of the ternary Bi-BiOI/graphene photocatalyst synthesized at 180 °C reached 51.8% within 30 min of visible light irradiation. The enhanced photocatalytic activity of the ternary Bi-BiOI/graphene photocatalyst is attributed to (I) the efficient transfer of photo-generated electrons from BiOI and Bi to graphene, leading to the effective separation of the photo-generated electron-hole pairs and (II) the surface plasmon resonance effect of Bi nanoparticles in the composite photocatalyst. Furthermore, the results of the scavenger experiments and DMPO-ESR spin-trapping measurements reveal that O 2 − radical species play the most critical role and holes serve as a secondary active species in the oxidative removal process of NO by 180BOI/GR composite under visible light irradiation.
Rong Hao,Xin Xiao,Xiaoxi Zuo,Junmin Nan,Weide Zhang
A novel microsphere-like BiOI hierarchical material was successfully synthesized by a one-step solution method at room temperature using polyvinylpyrrolidone (PVP) as structure directing reagent, its morphology, structure, surface area, photoabsorption were characterized, and the removal of tetracycline hydrochloride (TC) was evaluated under dark adsorption and visible light irradiation. It was shown that the BiOI microspheres formed in the precursor solution with PVP exhibit a mesoporous surface layer, 28.1 m 2 g −1 surface area, 1.91 eV band gap energy ( E g value), and twofold removal ability to tetracycline hydrochloride (TC), i.e. adsorptive separation and visible light photocatalytic degradation . The adsorption process of TC on BiOI microspheres can be described by pseudo-second-order kinetics model and both Freundlich and Langmuir equations well described the adsorption isotherm but the former is better. More importantly, the BiOI microspheres exhibit an excellent photocatalytic degradation and mineralization capability to TC under visible light irradiation, which comes from its electronic band structure, high surface area and high surface-to-volume ratio. In addition, the BiOI microspheres are stable during the reaction and can be used repeatedly, showing promising prospect for the treatment of TCs in future industrial application.
Hollow/flower-like BiOI microspheres have been prepared through a facile precipitation route in a water–ethanol mixed solution with the assistance of PVP and citric acid (CA) at low temperature (70 °C). The obtained products were characterized by a range of methods such as XRD, FESEM, TEM, UV-vis, DRS, PL and nitrogen sorption. A three-stage growth mechanism of such hierarchical hollow/flower-like microstructures has been proposed by observing the XRD analysis and FESEM of the intermediate products at different reaction times. Interestingly, the structure of BiOI from hollow to flower-like could be obtained by only adjusting the different amounts of reagents in the reaction system. The photocatalytic activities of the hollow/flower-like microspheres were evaluated by the degradation of RhB under visible-light irradiation, compared with the nanoplate sample and P25. Although the hollow BiOI microspheres had a higher specific surface area, the flower-like BiOI microspheres exhibited much higher adsorption and photocatalytic activities than the former. This controllable morphology method and particular properties of BiOI hierarchical microstructures could be used to synthesize bismuth-based semiconductors or other structure-controllable materials and to explore remarkable potential applications of their photocatalytic degradation ability.
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