Improving the photo-oxidative capability of BiOBr via crystal facet engineering

Cai

et al. 2018

Chemistry A European J

117

BiOCl I solid solutions with different band gaps were synthesized by adjusting the initial Cl to I molar ratios through a chemical precipitation method at room temperature. The structures, morphologies and optical properties of the samples were characterized by XRD, XPS, Raman, SEM, TEM and UV/Vis, respectively. The photocatalytic experiments showed that the BiOCl I sample totally decomposed a large concentration of 50 mg L aqueous Rhodamine B (RhB) solution within 12 minutes under visible light irradiation (λ>420 nm), which is 11 times higher than that of pure BiOI. Furthermore, the electron band structure and density of states of BiOCl, BiOI and BiOCl I have been investigated using the DFT (density functional theory) calculation method and electrochemical methods. It was found that there are multiple crystal defects of Bi , Bi , and oxygen vacancies in the BiOCl I samples. The results for Mott-Schottky plots and valence-band XPS spectra showed the position of conduction band (CB) for BiOCl I was up-shifted, which is favourable to the redox capacity for the photocatalysts. It could be elucidated that the synergistic effects of multiple crystal defects and unique band structure are critical to improving solar driven photocatalytic activity. This work provides a new highlight toward the construction of high property photocatalysts by tuning the crystal defect and band structure in a simple and efficient way.

Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Bi⁵⁺, Bi^(3−x)+, and Oxygen Vacancy Induced BiOCl_xI_1−x Solid Solution toward Promoting Visible‐Light Driven Photocatalytic Activity

Cai

et al. 2018

Chemistry A European J

117

“…The flat band potentials ( E fb ) of the samples can be estimated using the extrapolation of the Mott-Schottky plot at the frequency of 1000 Hz and found to be − 0.685 eV for the SnNb 2 O 6 , − 0.67 eV for the mixed phases of SnNb 2 O 6 and Sn 2 Nb 2 O 7 , and − 0.626 eV for the Sn 2 Nb 2 O 7 . It was known that the conduction band potentials of n-type semiconductors were closed to the flat potential [39, 79, 80]. Hence, the positions the conduction band of the prepared samples were − 0.685, − 0.67, and − 0.626 eV for SnNb 2 O 6 , the mixed phases of SnNb 2 O 6 and Sn 2 Nb 2 O 7 , and the Sn 2 Nb 2 O 7 , respectively (inset of Additional file 1: Figure S6).…”

Section: Resultsmentioning

confidence: 99%

Steering Charge Kinetics of Tin Niobate Photocatalysts: Key Roles of Phase Structure and Electronic Structure

et al. 2018

Tin niobate photocatalysts with the phase structures of froodite (SnNb2O6) and pyrochlore (Sn2Nb2O7) were obtained by a facile solvothermal method in order to explore the impact of phase structure and electronic structure on the charge kinetics and photocatalytic performance. By employing tin niobate as a model compound, the effects of phase structure over electronic structure, photocatalytic activity toward methyl orange solution and hydrogen evolution were systematically investigated. It is found that the variation of phase structure from SnNb2O6 to Sn2Nb2O7 accompanied with modulation of particle size and band edge potentials that has great consequences on photocatalytic performance. In combination with the electrochemical impedance spectroscopy (EIS), transient photocurrent responses, transient absorption spectroscopy (TAS), and the analysis of the charge-carrier dynamics suggested that variation of electronic structure has great impacts on the charge separation and transfer rate of tin niobate photocatalysts and the subsequent photocatalytic performance. Moreover, the results of the X-ray photoelectron spectroscopy (XPS) indicated that the existent of Sn4+ species in Sn2Nb2O7 could result in a decrease in photocatalytic activity. Photocatalytic test demonstrated that the SnNb2O6 (froodite) catalyst possesses a higher photocatalytic activity toward MO degradation and H2 evolution compared with the sample of Sn2Nb2O7 (pyrochlore). On the basis of spin resonance measurement and trapping experiment, it is expected that photogenerated holes, O2−•, and OH• active species dominate the photodegradation of methyl orange.Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2578-2) contains supplementary material, which is available to authorized users.

“…Previous explorations have shown the profound influence of facets on the photocatalysis. For example, Yuan et al demonstrated the crystal facet-correlated photocatalytic activity of α-Fe 2 O 3 for water splitting [35]; Wu et al reported that {010} faceted BiOBr nanocrystals displayed a better photo-oxidative capability than {001} faceted nanocrystals for water oxidation and formic acid degradation [36]; Qi et al found that {101} faceted TiO 2 showed superior catalytic activity to {001} and {010} faceted TiO 2 for anthracene degradation [37]; Rong et al reported that {310} faceted α-MnO 2 nanowires exhibited much better activity than {100} and {110} facets for formaldehyde oxidation [38]. It is clear that little attention is paid on the facet-dependent photocatalytic activity of ZnWO 4 , although such a phenomenon is well studied in a number of functional materials [31,32,33,34,35,36,37,38].…”

Section: Introductionmentioning

confidence: 99%

Eu2+ and Eu3+ Doubly Doped ZnWO4 Nanoplates with Superior Photocatalytic Performance for Dye Degradation

Huang

Yang

et al. 2018

Nanomaterials

Eu2+ and Eu3+ doubly doped ZnWO4 nanoplates with highly exposed {100} facets were synthesized via a facile hydrothermal route in the presence of surfactant cetyltrimethyl ammonium bromide. These ZnWO4 nanoplates were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, diffuse UV-vis reflectance spectroscopy, photoluminescence spectrophotometry, and photoluminescence lifetime spectroscopy to determine their morphological, structural, chemical, and optical characteristics. It is found that Eu-doped ZnWO4 nanoplates exhibit superior photo-oxidative capability to completely mineralize the methyl orange into CO2 and H2O, whereas undoped ZnWO4 nanoparticles can only cleave the organic molecules into fragments. The superior photocatalytic performance of Eu-doped ZnWO4 nanoplates can be attributed to the cooperative effects of crystal facet engineering and defect engineering. This is a valuable report on crystal facet engineering in combination with defect engineering for the development of highly efficient photocatalysts.