Supporting Information. hollow nanofibers: enhanced photocatalytic activity based on. highly efficient charge separation and transfer

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1 Supporting Information Assembling n-bi 2 MoO 6 nanosheets on electrospun p-cual 2 O 4 hollow nanofibers: enhanced photocatalytic activity based on highly efficient charge separation and transfer Jian Zhang, Changlu Shao *, Xinghua Li *, Jiayu Xin, Ran Tao, Yichun Liu a a Center for Advanced Optoelectronic Functional Materials Research, Key Laboratory of UV-Emitting Materials and Technology (Northeast Normal University), Ministry of Education, 5268 Renmin Street, Changchun , People s Republic of China Corresponding Authors * clshao@nenu.edu.cn; Tel * lixh781@nenu.edu.cn; Tel (Summary of Content: 13 pages, 8 figures, and 2 tables) S1 / S13

2 S1. Supplemental materials and methods S1.1 Chemicals Copper nitrate trihydrate (Cu(NO 3 ) 2 3H 2 O), aluminum nitrate nonahydrate (Al(NO 3 ) 3 9H 2 O), bismuth nitrate pentahydrate (Bi(NO 3 ) 3 5H 2 O), sodium molybdate (Na 2 MoO 4 ), N, N-dimethylformamide (DMF) were purchased from Sinopharm Chemical Reagent Co. Ltd; Polyvinylpyrrolidone (PVP) (M.W.1,300,000) were obtained from Alfa Aesar. All reagents are analytical purity without further purification. S1.2 Characterization Scanning electron microscope (SEM) (FEI Quanta FEG 250) and transmission electron microscope (TEM) (JEOL JEM-2100F) were used to characterize the morphologies of the samples. X-ray diffraction (XRD) patterns were introduced by a D/max 2500 XRD spectrometer (Rigaku, Japan) with Cu Kα radiation (λ=1.5418å) with a scanning rate of 5 /min to detect the phase of the samples. X-ray photoelectron spectrometer (XPS) (ESCALAB 250Xi) equipped with an Al Kα ( ev) radiation source were used to characterize the samples and the binding energies were calibrated by C 1s at ev. UV-Vis diffuse reflection spectra (DRS) were collected on Cary 500 UV-Vis-NIR Spectrophotometer in the range of 300 ~ 800 nm using BaSO 4 as reference. Charge recombination was detected via photoluminescence (PL) technique by Jobin Yvon HR800 micro-raman spectrometer at emission light at 325 nm from a He-Cd laser. S1.3 Photocatalytic measurements Photocatalytic performance of the samples were evaluated by degrading target pollutants (RhB, MO, Cr(VI) and 4-Nitrophenol (4-NP)) under visible light irradiation of 150 W xenon lamp with an optical filter (λ 420 nm). 50 mg samples were dispersed into 50 ml pollutant solutions with an initial concentration of 10 mg/l. The suspensions were sheltered in the dark with magnetic stirring for 30 min before S2 / S13

3 illumination to achieve adsorption-desorption equilibrium. Then the light was turned on for photocatalytic reactions, during which 2 ml solution was taken every certain time for analysis by UH4150 UV-Vis-NIR Spectrophotometer. The relative intensity of absorption peaks (λ=554 nm for RhB, λ=463 nm for MO, λ=540 nm for Cr(VI) (diphenylcarbazide as chromogenic agent) and λ=400 nm for 4-NP) was compared to value the degradation ratio. S1.3 Photoelectrochemical measurements Photoelectrochemical measurements were carried out via standard three-electrode system on an electrochemical workstation (CH Instrument 660D, Shanghai). 5mg CuAl 2 O 4, Bi 2 MoO 6, their mechanical mixture and CB2 were uniformly coated onto FTO glass with an effective area of 1 cm x 1 cm serving as working electrodes. Ag/AgCl (saturated KCl) electrode and Pt wire were introduced as reference electrode and counter electrode. 0.5 M Na 2 SO 4 aqueous solution was used as electrolyte after being purged by N 2 to remove O 2. A 150 W xenon lamp with an optical filter (λ 420 nm) and 80 mwcm -2 of light intensity was employed as visible light source. The transient photocurrent of the samples with the light on and off were measured at the fixed potential of 0.5 V vs Ag/AgCl. Electrochemical impedance spectra (EIS) were measured at a sinusoidal ac perturbation of 5 mv with the frequency of 100 mhz ~ 2 MHz. S3 / S13

4 S2. Supplemental Date Table. S1 Experimental information about the dosages of precursors and the samples morphologies. Samples Precursors (mg) Bi(NO 3 ) 3 Na 2 MoO 4 CuAl 2 O 4 HNFs Morphology Bi 2 MoO nanoflower CB nanoparticle CB nanosheet CB nanosheet S4 / S13

5 Table. S2 Parameters fitted by the equivalent circuit of the samples Samples Rs(Ω) Rct(Ω) C(F) CuAl 2 O Bi 2 MoO CB S5 / S13

6 Fig. S1 SEM images of CuAl2O4 HNFs (A), pure Bi2MoO6 nanoflowers (C). TEM images of CuAl2O4 HNFs (B), CB1 (D), CB2 (E) and CB3 (F). Bi2MoO6 NSs transform into nanoflowers by self-assembling. The thickness of Bi2MoO6 NSs is almost the same as the nanosheets located on the CuAl2O4 hollow nanofibers (HNFs). S6 / S13

7 Fig. S2 UV-Vis diffuse reflectance spectra of different samples (A). The plot of (αhv) 2 vs photon energy hv of CuAl 2 O 4 HNFs and Bi 2 MoO 6 NSs (B). XPS valence band spectra of CuAl 2 O 4 (C) and Bi 2 MoO 6 (D). The inset is the enlarged spectra. S7 / S13

8 Fig. S3 EIS Nyquist plots of CuAl 2 O 4, Bi 2 MoO 6 and CB2 in 0.5 M Na 2 SO 4 solution (A) (inset is the equivalent circuit). PL spectra of CuAl 2 O 4, Bi 2 MoO 6 and CB2. S8 / S13

9 Fig. S4 Photodegradation of MO (A), Cr(VI) (D) and 4-NP (G) under visible light irradiation. With the presence of CB2, MO (B), Cr(VI) (E) and 4-NP are almost completely decomposed in 150 min, 149 min and 300 min, respectively, which exhibit the superior photocatalytic activity over CuAl 2 O 4, Bi 2 MoO 6 and their mechanical mixture. Pseudo-first-order kinetic analysis of degradation of MO (B), Cr(VI) (E) and 4-NP (H). After assembling Bi 2 MoO 6 NSs on CuAl 2 O 4 HNFs to build the hierarchical p-n heterostructures, the photocatalytic performance dramatically increases for decomposing all the target model pollutants. Recycling runs on photodegradation of MO (C), Cr(VI) (F) and 4-NP (I) with CB2. The hierarchical p-n heterostructures show good recycling stability with less decrease in the activity. S9 / S13

10 Fig. S5 Nitrogen absorption-desorption isotherms of CuAl 2 O 4 HNFs, Bi 2 MoO 6 NSs and CB2. As an important factor for photocatalytic performance, specific surface area of the samples was measured by Nitrogen absorption-desorption isotherms. From Fig. S5, all curves exhibit type IV isotherms with type H3 hysteresis loops at the range of 0.8 ~ 1 of relative pressure P/P 0, which reveals the presence of mesoporous (2 ~ 50 nm) in the samples. Brunauer-Emmett-Teller (BET) surface area of CuAl 2 O 4 HNFs and Bi 2 MoO 6 NSs are 48.6 m 2 /g and 52.7 m 2 /g, respectively. While after assembling Bi 2 MoO 6 NSs on CuAl 2 O 4 HNFs (CB2), the surface area increases to 67.2 m 2 /g, probably because the dispersity of Bi 2 MoO 6 NSs is better compared to self-assembling. There is not much difference in specific surface area of the samples, which maybe not the main factor to affect the photocatalytic activity. S10 / S13

11 Fig. S6 Photodegradation of RhB with different trapping reagents under visible light irradiation. S11 / S13

12 Fig. S7 Possible mechanism of photodegradation with p-cual 2 O 4 / n-bi 2 MoO 6 hierarchical heterostructures under visible light. S12 / S13

13 Scheme. S1 Model of possible degradative process of RhB with CuAl 2 O Bi 2 MoO 6 heterojunction. S13 / S13