Supplementary Information

Transcription

1 Supplementary Information Vertically Aligned Graphene Sheets Membrane for Highly Efficient Solar Thermal Generation of Clean Water Panpan Zhang 1, Jing Li 1, Lingxiao Lv, Yang Zhao and Liangti Qu* Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Key Laboratory of Cluster Science, Ministry of Education, School of Chemistry, Beijing Institute of Technology, Beijng , P. R. China, Figure S1. SEM images of rgo samples prepared with additives of (a, b) methanol, (c, d) acetone, (e, f) n-propyl alcohol, (g, h) pyridine, (i, j) cyclohexane, and (k, l) acetic acid. The additive amount is 100 µl for all the samples. An vertically aligned graphene sheets array was observed for the samples prepared with additive antifreezes such as methanol, acetone and n-propyl alcohol, ratther than those with pyridine, cyclohexane and acetic acid. 1

2 Figure S2. (a, b) SEM images of rgo samples prepared by directional freezing of GO suspension without ethanol. (c f) SEM images of rgo samples by undirectional freezing of GO suspension with ethanol. The orientation of the assembly of graphene sheets is uncertain. Figure S3. (a) Photograph of the monolith VA-GSM, which can be bend to ca. 120 o. (b) The stress-strain curves of VA-GSM at different set strains (50% to 90%). (c) Cyclic stress-strains curves of VA-GSM at ε = 80% for 1000 cycles. 2

3 Figure S4. (a, b) SEM images of VA-GSM in low magnifications. (c) Pore size distributions of VA-GSM. (d) Nitrogen adsorption-desorption isotherms of VA-GSM. Figure S5. SEM images of rgo samples prepared with different amount of ethanol of (a, b) 30 µl, (c, d) 60 µl, (e, f) 100 µl, (g, h) 150 µl, (i, j) 200 µl, (k, l) 300 µl, respectively. The formation of well-ordered skeletal structure is strongly dependent on the introduction of suitable amount of ethanol, and the optimized amount of ethanol is 100 µl. 3

4 Figure S6. (a) The CA of VA-GSM before and after the O 2 -plasma treatment. (b) Mass change of water with VA-GSM in different surface wetting characters under 1 sun. (c) Photographs of VA-GSM floating on water before and after O 2 -plasma treatment. The red line in (c) shows that the surface of VA-GSM is filled with water after O 2 -plasma treatment, indicating that the hydrophilic behavior promotes the infiltration of water to the surface. Figure S7. (a) Surface temperatures of VA-GSM (2 cm 2 cm) in different thicknesses without contacting to water under solar illumination of 1 sun power. VA-GSM with the thicknesses of 2, 4, 6, and 8 mm have the similar surface temperatures, higher than that of VA-GSM with the thickness of 1mm. (b) Mass change of water with VA-GSM in different thicknesses. The VA-GSM with thickness of 2 mm delivered the highest average water evaporation rate of 1.57 kg m 2. The added thickness increases the transport distance of water during solar steam generation and the optimized thickness is 2 mm. 4

5 Figure S8. (a) Photographs of rgo film with the size of 5 cm 5 cm. (b) Top side SEM image of rgo film. (c) Cross section SEM image of rgo film. (d) The enlarged SEM image is correspond to the marked area in (c), showing tightly layer-by-layer assembled structure. Table S1. Solar steam generation based on VA-GSM in this work compared with other materials without the assistance of thermally-insulating layer. Sample Mass change (kg m -2 h -1 ) Solar intensity (kw m 2 ) Energy conversion efficiency (%) VA-GSM Our work Porous N-doped graphene Au/NPT Al NP/AAM RGO/BNC:BNC aerogel Black gold membranes Ref. 5

6 Figure S9. (a-d) The photographs of the sandwich sample for solar steam generation with thermally insulating layers. (a) The polystyrene foam ( 4 mm thick) with a gap in the center, and the hydrophilic glass fiber threads the gap. (b) The hydrophilic glass fiber ( 0.1 mm thick) flatted on the polystyrene foam serves to deliver water. (c) The cross section of the sandwich sample. (d) The thermally insulating layers float the entire structure on water. (e-h) Temperatures of water under VA-GSM without thermally insulating layers after 60 min light illumination under 1 sun, and the temperature changes about 9.7 o C (from 22.1 to 31.8 o C). Figure S10. (a) The photographs of the labmade apparatus for collecting water before and after 1 h solar illumination of 4 sun. Obviously water drops are observed, and the water in the glass tube decreases significantly. (b) 2.40 g condensed water are collected, and the area of VA-GSM is 3.8 cm 2. 6

7 Table S2. Solar steam generation based on VA-GSM in this work compared with other carbon materials with the assistance of thermally-insulating layer reported in recent years. Sample Mass change (kg m -2 h -1 ) Solar intensity (kw m 2 ) Insulating layer Energy conversion efficiency (%) Exfoliated graphite Carbon foam GO film Polystyrene foam Carbon nanotube Macroporous silica Graphite _ 12 Polystyrene foam VA-GSM Polystyrene foam 86.5 Our work VA-GSM Polystyrene foam 94.2 Our work Ref. Figure S11. (a-d) Surface temperatures of VA-GSM without contacting water after 30 s solar illumination, pure water before solar illumination, pure water after 10 min solar illumination, and VA-GSM floating on the surface of water after 5 min solar illumination of 4 sun taken by an IR camera, respectively. Figure S12. Mass change of water with VA-GSM in diffrent water samples of seawater (Bohai Sea), acid solution (8 mol ml -1 ), alkali solution (8 mol ml -1 ) and heavy metal mixed solution (100 mg ml -1 ) under 1 sun. 7

8 Figure S13. (a) The ion rejection of five acid solutions after solar thermal purification, and the original concentrations of H + are 0.2, 2, 4, 6, 8 mol ml -1, respectively. (b) The ion rejection of five alkali solutions undergoing the solar thermal purification, and the original concentrations of OH - are 0.2, 2, 4, 6, 8 mol ml -1, respectively. (c) The ion rejection of Cr 3+, Pb 2+, Zn 2+, Ni 2+, Cu 2+ in the simulated wastewater after solar thermal purification. 8