supporting information...† state key laboratory of high performance ceramics and superfine...

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Supporting Information

Flexible Salt-Rejecting Photothermal Paper Based on Reduced Graphene Oxide and

Hydroxyapatite Nanowires for High-Efficiency Solar Energy-Driven Vapor Generation

and Stable Desalination

Zhi-Chao Xiong,†,‡ Ying-Jie Zhu,*,†,‡ Dong-Dong Qin,†,‡ and Ri-Long Yang†,‡

† State Key Laboratory of High Performance Ceramics and Superfine Microstructure,

Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P. R. China

‡ Center of Materials Science and Optoelectronics Engineering, University of Chinese

Academy of Sciences, Beijing 100049, P. R. China

*Corresponding author (Ying-Jie Zhu).

E-mail: y.j.zhu@mail.sic.ac.cn. Tel: 0086-21-52412616. Fax: 0086-21-52413122.

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Figure S1. Digital images of the testing device for solar energy-driven vapor generation.

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Figure S2. Digital images of aqueous suspensions. (a) Ultralong hydroxyapatite nanowires

(HNs); (b) graphene oxide (GO); (c) GO/HN nanocomposite.

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Figure S3. (a–d) Digital images of the fabrication process of the GO/HN paper with a

diameter of 20 cm using a commercial paper sheet former by the vacuum-assisted filtration

method, and a free-standing GO/HN paper is obtained after drying at 95 oC for 10 min.

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Figure S4. Digital images and SEM images of the GO and rGO membranes. (a) A the

vacuum-assisted filter for preparing the GO membrane; (b) the as-prepared GO membrane on

a filter paper; (c, d) the surface and cross-section SEM micrographs of the GO membrane; (e,

f) the surface and cross-section SEM micrographs of the rGO membrane.

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Figure S5. (a, b) TEM micrographs of the as-prepared HNs; (c, d) the surface and cross-

section SEM micrographs of the HN paper containing 20 wt.% glass fibers.

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Figure S6. XRD patterns of HNs, GO/HN, and hydroxyapatite (JCPDS No. 09–0432).

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Figure S7. SEM micrographs: (a, b) glass fibers; (c, d) the surface SEM images of the

GO/HN paper containing 18 wt.% glass fibers.

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Figure S8. TEM micrograph of GO nanosheets.

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Figure S9. Mechanical properties of the HN paper, GO/HN paper, rGO/HN-I photothermal

paper, and rGO/HN-II photothermal paper. (a) Stress-strain curves; (b) ultimate tensile

strength; (c) strain at failure.

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Figure S10. FTIR spectra of ultralong hydroxyapatite nanowires (black curve) and GO/HN

paper (red curve).

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Figure S11. XPS patterns of the GO/HN paper (black curve), rGO/HN-I paper (red curve),

and rGO/HN-II paper (blue curve).

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Figure S12. FTIR spectra of GO (black curve), rGO obtained after thermal treatment of GO

at 150 oC for 2 h (rGO-I, red curve), and rGO obtained after thermal treatment of GO at 150

oC for 6 h (rGO-II, blue curve).

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Figure S13. Surface and cross-section SEM images of the rGO/HN photothermal paper. (a–c)

The rGO/HN-I photothermal paper; (d–f) the rGO/HN-II photothermal paper.

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Figure S14. (a–d) Digital images of the wetting process of the rGO/HN-I photothermal paper

in contact with a wet air-laid paper for different times, the top surface of the rGO/HN-I paper

can be wetted rapidly by water. (e–g) Digital images of the rGO/HN-II photothermal paper in

contact with a wet air-laid paper for different times, the top surface of the rGO/HN-II paper

cannot be wetted by water. (h) Digital image of the bottom surface of the rGO/HN-II paper

after being in contact with a wet air-laid paper for 5 min, water drops can adhere to the bottom

surface of the rGO/HN-II paper.

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Figure S15. Atomic force microscopy (AFM) images. (a) The GO/HN paper; (b) the

rGO/HN-I photothermal paper; (c) the rGO/HN-II photothermal paper. The corresponding

surface roughness value is measured to be 57.3, 52.0, and 58.5 nm, respectively.

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Figure S16. IR thermal images of paper samples over time under one sun illumination in air

for 600 s. (a) The HN paper; (b) the GO/HN paper; (c) the rGO/HN-I photothermal paper; (d)

the rGO/HN-II photothermal paper.

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Figure S17. IR thermal images of paper samples over time during the water evaporation

process under one sun illumination. (a) The HN paper; (b) the GO/HN paper; and (c) the

rGO/HN-II photothermal paper.

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Figure S18. Cumulative mass change of water in the presence of the rGO/HN-I photothermal

paper sheets with different rGO contents versus solar light irradiation time under one sun

illumination.

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Figure S19. (a–c) UV-vis absorption spectra and (d) corresponding digital images of aqueous

solution of congo red, rose bengale, and brilliant green, and the collected water after solar

energy-driven water purification.

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Figure S20. (a) Concentrations, (b) rejection percentages and (c) corresponding digital

images of aqueous solution containing Fe3+, Cu2+, and Ni2+ ions, and the collected water after

solar energy-driven water purification.

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Figure S21. Digital images and SEM micrographs of the rGO/HN-II photothermal paper

before (a) and after (b) continuous solar energy-driven desalination of the actual seawater

sample for 20 days (8 h light irradiation each day) under one sun illumination.

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Table S1. Calculation results of energy conversion efficiency under one sun illumination

[R1] Dortmund Data Bank Software & Separation Technology, DDBST GmbH, Oldenburg

2016.

Materials m (kg m-2 h-1) hLV (kJ kg-1) [R1] η (%)

HN paper 0.36 2340 15.6

GO/HN paper 1.29 2352 76.5

rGO/HN-I paper 1.48 2361 89.2

rGO/HN-II paper 1.25 2358 74.1

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Table S2. Comparison of solar vapor generation performance of some previously reported

photothermal materials and the rGO/HN photothermal paper under one sun illumination

Materials Evaporation rate

(kg m-2 h-1)

Energy

efficiency (%)

Reference Year

Graphene oxide membrane 1.45 80 S1 2016

Reduced graphene oxide-sodium alginate-

carbon nanotube aerogel

1.622 83 S2 2017

Carbonized mushrooms 1.475 78 S3 2017

Plasmonic Wood 1.1 67 S4 2017

3D printed porous carbon black/graphene oxide

composite

1.27 87.5 S5 2017

Graphene oxide/SBA-15 1.31 83 S6 2017

Three-dimensional gold nanoflower gel 1.356 85.6 S7 2018

Graphite-coated wood 1.15 80 S8 2018

Carbon black/ polymethylmethacrylate/

polyacrylonitrile membrane

1.3 72 S9 2018

3D graphene foam 1.3 87 S10 2018

Geopolymer-biomass mesoporous carbon

composite

1.58 84.95 S11 2018

Reduced graphene oxide-wrapped plant fiber

sponges

1.375 88.8 S12 2018

Carbonized moldy bread 0.96 71.4 S13 2018

Reduced graphene oxide-multi-walled carbon

nanotubes composite membrane

1.22 80.4 S14 2018

Hollow carbon nanotubes aerogel 1.44 86.8 S15 2019

Three dimensional MXene architecture 1.41 88.7 S16 2019

Nitrogen-doped hydrophilic graphene

nanopetals with hydrophobic graphene foam

1.27 88.6 S17 2019

Biomimetic MXene textures 1.37 90.1 S18 2019

Wood-polypyrrole composite 1.27 88.6 S19 2019

Vertically aligned Janus MXene aerogel 1.46 87 S20 2019

Reduced graphene oxide/hydroxyapatite

nanowires photothermal paper 1.48 89.2 This work

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