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Bifunctional Fabric with Photothermal Effect and Photocatalysis for Highly Efficient Clean Water Generation Dandan Hao, Yudi Yang, Bi Xu, and Zaisheng Cai ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b02094 • Publication Date (Web): 14 Jun 2018 Downloaded from http://pubs.acs.org on June 14, 2018

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ACS Sustainable Chemistry & Engineering

Bifunctional Fabric with Photothermal Effect and Photocatalysis for Highly Efficient Clean Water Generation Dandan Haoa, Yudi Yanga, Bi Xua,b,*, and Zaisheng Caia

a

College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, 2999

North Renmin Road, Songjiang District, Shanghai, P. R. China 201620 b

Key Laboratory of Textile Science & Technology, Ministry of Education, Donghua University,

2999 North Renmin Road, Songjiang District, Shanghai, P. R. China 201620

Corresponding author: Bi Xu E-mail: [email protected] Tel: +86 21 67792617; Fax: +86 21 67792608.

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Abstract Fresh water scarcity has become a global challenge owing to the limited fresh water resource and the increasing water pollution. Solar-driven water evaporation with the interfacial heat localization is a promising technology to mitigate the fresh water scarcity. Here, we propose a bifunctional cotton fabric with both photothermal and photocatalytic properties by in situ polymerization of pyrrole (Py) on the cotton and subsequent deposition of titanium dioxide (TiO2) nanoparticles. The morphology of the polypyrrole (PPy) can be adjusted, and fibrous PPy with a high hydrophilicity and a higher surface area was obtained on the cotton fibers in the presence of polydopamine (PDA). The TiO2-PDA/PPy/cotton showed a solar evaporation rate of 1.55 kg m-2 h-1 under 1 sun illumination, which is higher than most previously reported evaporation system. Besides the efficient solar vapor generation, the TiO2-PDA/PPy/cotton also presented an excellent photocatalysis with a ~96 % degradation of methyl orange (MO) under simulated solar irradiation over 3 h. The PDA/PPy structure can enhance the photocatalytic activity of TiO2 by promoting the separation of photo-generated electron-hole pairs and decreasing charge recombination. This bifunctional fabric will provide a new approach for addressing the issue of fresh water scarcity.

Keywords: titanium dioxide, polypyrrole, solar vapor generation, interfacial heat localization, photocatalysis

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Introduction Fresh water shortage is one of the grand challenges in relation to human survival and social development in our time.1 It is estimated that only a tiny fraction (~1 %) of global water resource is suitable for direct use.2 Currently, about 40 % of the world population live in the extremely arid or semi-arid areas and this number is predicted to increase to nearly two thirds by 2025.3 Solar-driven evaporation is an ancient but useful technology to generate clean water in a very simple way. Traditionally, sunlight passes through the water and falls onto the black bottom surface to trigger the enhanced water evaporation.4 This process belongs to the bulk heating of water, which causes a low solar thermal conversion efficiency and a low water evaporation rate due to the unavoidable energy loss. Since the water evaporation is an interfacial phenomenon, the concept of localized heating at the liquid-vapor interface comes up and has been applied for solar vapor generation recently.5, 6 Heat localization is achieved by floating a solar absorber at the air-water interface, improving light-to-heat conversion efficiency by avoiding uniformly heating the entire water. In this system, several necessary features to enable efficient solar vapor generation have been proved: (1) a broadband sunlight absorption of the interfacial surface to enhance solar thermal conversion, (2) a thermal insulator to confine heat transfer and support the solar absorber, (3) the hydrophilicity of the material to ensure efficient transport of water from the bulk to material surface. Recently, different photothermal materials, including metal-based nanoparticles (e.g., gold,7 silver,8 and aluminum9), carbon-based materials (e.g., carbon nanotubes,10 carbon black,11 graphite,12 graphene13), metallic oxide (e.g., black TiO2,14 ferroferric oxide15) and polymers (e.g., PPy,16 PDA17) have been reported due to their high absorptivity of solar light. These solar-to-thermal

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materials usually exist in the form of thin film on the supporting substrates (e.g., wood,17 paper,18 polystyrene (PS) foam,19 aerogel,20 stainless steel mesh,16 ceramic fiber wool21 etc.) to form bilayer structures. These double-layer materials can enhance solar evaporation rate through a high solar absorption and the low heat loss. However, some of these designed structures involve either expensive materials or complex fabrication process and a large amount of energy consumption, which would hinder their potentials for practical applications. Nowadays, a great deal of dyeing effluent is created every day and discharged directly into the nature. This leads to the severe water pollution, further exacerbating the fresh water scarcity. Various studies have been done to purify hazardous dyeing wastewater. One effective approach to get clean water is to degrade dyeing byproducts by a photocatalytic process. TiO2 has been widely used as a photocatalyst because it is versatile, stable, low toxic, and environmentally friendly.22-24 However, the large band gap (anatase, ~3.2 eV) and easy recombination of photogenerated electron-hole pairs limit the practical applications of TiO2.25, 26 Different strategies such as doping with metals or non-metals,27, 28 co-doping29 and sensitization with organic dyes30 or conductive polymers31 have been developed to improve the photocatalytic activity of TiO2. Among these methods, modification of TiO2 with conductive polymers is thought to be effective because these polymers can help promote the separation of photo-generated electron-hole pairs and decrease charge recombination.32 As one of the most promising conductive polymers, PPy shows several advantages in improving the fresh water security. On the one hand, PPy exhibits a broadband solar absorption spanning the ultraviolet, visible and even near-infrared (NIR) regions and shows an excellent photothermal transduction, making it be a promising solar absorber. On the other hand, PPy can act as one of the most promising visible-light photosensitizers for TiO2 because of its high

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absorption coefficient in the visible part of sunlight, high charge carrier mobility and non-toxicity. Meanwhile, Zhao et al. reported the morphology of PPy can be effectively adjusted with bioinspired catechol derivative such as dopamine (DA).33, 34 Various morphologies of DA-PPy nanostructures, including nanosphere, nanofiber, nanorod, and nanoflake can be achieved by simply varying the DA/Py reacting mole ratio.35 The morphology shift from globular to fibrous structure increases the surface area of PPy, which will be beneficial to enhance the solar water evaporation rate and photocatalytic performance.36 In this work, we present a bifunctional cotton fabric which can be utilized not only for solar vapor generation but also for photocatalytic degradation of dyes. Firstly, the fibrous PPy with good hydrophilicity was synthesized on cotton surface in the presence of DA. Secondly, the asprepared TiO2 was coated onto the PDA/PPy/cotton by a simple dip-dry-cure process to obtain a cotton fabric with photocatalysis under visible light. Furthermore, hydrophobic PS foam with an extremely low thermal conductivity (~0.038 W m-1 K-1) was utilized to support TiO2PDA/PPy/cotton fabric, which can significantly reduce heat transfer from the fabric to the bulk water. This bifunctional cotton fabric offers a new approach to solve fresh water shortage.

Experimental Section Chemicals and Materials Titanium tetraisopropoxide (98 %), acetic acid (99.8 %), hydrochloric acid (HCl), anhydrous ethanol, sodium hydroxide, ferric trichloride (FeCl3), pyrrole, dopamine hydrochloride and methyl orange were obtained from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). Pure cotton fabrics (twill weave, 228 g m-2) were provided by Zhongheng Dayao Textile Technology Co., Ltd. (Jiangsu, China). The cotton fabric was cleaned in sodium hydroxide 5



solution (15 g L-1) for 1 h to remove any possible impurities. Deionized water was used in all experiments. Synthesis of TiO2 sol Titanium tetraisopropoxide (5 mL) was added dropwise to the acidic water solution (100 mL) containing 10 mL acetic acid under vigorous stirring at 60 oC for 4 h. Keep stirring the mixture at 60 oC for 24 h before the mixture was put into an oven and aged at 60 oC for 1 week to obtain the TiO2 sol.37 Preparation of PPy/cotton and PDA/PPy/cotton PPy coated fabric was prepared based on the method reported by Zhao.35 Py monomer (0.18 mL) was dissolved in 30 mL of HCl (1 M) and cooled down to about 0 oC. FeCl3/HCl solution (1 g/10 mL) was dropwise added into the Py solution containing the cleaned cotton under mild stirring for 3 h. The reaction was maintained for 9 h under magnetic stirring keeping reaction temperature at 0 oC. The fabric was taken out and then soaked into ethanol for 10 min, followed by washing thoroughly with deionized water. Finally, the cotton fabric was dried at 60 oC in a vacuum oven and named PPy/cotton. The preparation of PDA/PPy/cotton is similar to the PPy/cotton except for an extra addition of dopamine hydrochloride to Py solution (Py:DA molar ratio = 1:0.032). Preparation of TiO2 coated fabrics The cotton fabric, PPy/cotton and PDA/PPy/cotton were firstly immersed into the TiO2 sol for 5 min respectively and then dried at 80 oC for 5 min. The above process was repeated twice, and finally the samples were cured at 120 oC for 3 min. The prepared samples were named TiO2cotton, TiO2-PPy/cotton and TiO2-PDA/PPy/cotton, respectively.

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Characterization X-ray diffraction (XRD, D/max-2550 PC, Rigaku, Japan) was performed to analyze the crystal phase of TiO2 powders. The morphology of TiO2 was characterized by a transmission electron microscopy (TEM, JEM-2100F, Japan) and a field emission scanning electron microscope (FESEM, S-4800, HITACHI, Japan) with an energy dispersive X-ray spectroscopy (EDXS). The total reflectance (R) and transmittance (T) of the fabric samples were measured using the ultraviolet-visible-near-infrared spectrometer (UV-Vis-NIR, UV 3600, Shimadzu Scientific Instruments, Japan) with an integrating sphere. The absorptance (A) was calculated according to the Eq. (1): = 1−−

(1)

Fourier-transform infrared (FTIR, Frontier Optica Perkin Elmer, the United States) spectra were obtained from 4000 cm-1 to 500 cm-1 at room temperature. The contact angles of different samples were measured by a goniometer (OCA40, Dataphysics, Germany) using 5 µL water at ambient temperature. The Brunauer-Emmett-Teller specific surface area of different samples was measured by a nitrogen adsorption apparatus (BET, V-Sorb 2800P, Gold APP Instrument Corporation, China). The UV-vis absorption spectra of methyl orange were recorded using the ultraviolet-visible spectrometer (UV-vis, U3310, Hitachi, Japan). Evaporation under simulated solar irradiation The solar evaporation tests were performed during April to May at Songjiang Campus, Donghua University, Shanghai, China. The surrounding temperature was around 25 oC and the relative humidity was about 50 %. The solar-driven interfacial water evaporation experiments were carried out to evaluate the light-to-heat conversion performance of different cotton fabrics

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(Figure 1). In the experiment, 10 mL MO was put into a beaker and a piece of foam with a diameter of 2.4 cm and a thickness of 0.5 cm was floated on the MO solution. A sun-shape fabric was placed on top of the foam and its four strips (0.5 cm × 2 cm) were immersed into the underlying MO solution to transport the water to the top surface by capillary force for interfacial evaporation. The simulated solar light was provided by a xenon lamp (PLS-SXE 300/300UV, Perfect Light, China, the wavelength spectrum can be found in Figure S1 in Supporting Information) and the light intensity can be tuned by using an irradiatometer (FZ-A, Photoelectric Instrument Factory of Beijing Normal University, China). The surface temperature and thermal pictures were taken by an infrared camera (FLIR ONE, FLIR, the United States). The mass changes during the evaporation were obtained by an analytical balance (ME 204E, Mettler Toledo, the United States) connected to a computer for real-time monitoring. The evaporation rates in this work were obtained by the measured evaporation rates under the solar illumination minus the evaporation rate under dark condition. The solar vapor generation efficiency was calculated without considering the reflection and surface radiation loss. The solar vapor generation efficiency was calculated by Eq. (2).

= ⁄ = ×

（2）

where v is the water evaporation rate (kg m-2 h-1), HLV is the total enthalpy (kJ kg-1) that cause water change from its liquid to vapor phase (latent heat, the sensible heat is neglected here for the calculation of solar vapor generation efficiency since it just results in higher temperature vapor rather than generates more vapor). Ei is the total light power on the material surface provided by the light source (). m is the water mass during illumination process, S is the projected irradiation area of the sample and t is illumination time.

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Figure 1. Schematic illustration of the solar-driven evaporation experiment setup. Photocatalytic experiments The MO solution (10 mg L-1) was utilized to evaluate the photocatalytic performances of different cotton samples. The experiment setup is same as the above evaporation experiment . The absorbance spectrum of the samples was measured every 45 min by using a UV-vis spectrometer. The degradation of MO was characterized by C/C0, C is the concentration of MO at the illumination time of t and C0 is the initial concentration. The method to measure C and C0 was shown in the Supporting Information. Results and Discussion Characterization of TiO2

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Figure 2. Characterization of TiO2 nanoparticles: (a) XRD. (b) low-resolution TEM, (c) highresolution TEM. The inset in (c) is the selected area electron diffraction (SAED) pattern for the observed TiO2 nanoparticles. TiO2 is one of the most promising photocatalysts. To investigate the crystal phases of the TiO2 nanoparticles by XRD, the TiO2 solid powders were extracted from the TiO2 sol. The sharp and strong characteristic anatase peaks (25.2o, 37.8o, 48.0o and 53.9o) of solid TiO2 particles were observed in the XRD pattern (Figure 2a). According to JCPDS Card No: 21-1272, the above peaks attribute to the crystal plane diffraction bands of (101), (004), (200) and (105). A weak peak at 62.7o matches with (002) plane diffraction band of rutile TiO2 based on JCPDS Card No: 21-1276. These results demonstrated that the prepared TiO2 was mainly anatase phase with a small amount of rutile crystallites. It was reported the electrons of mixed-phase TiO2 can transfer from anatase to a lower energy rutile electron trapping site, reducing recombination rate of electron-hole and enhancing the catalytic performance.38 In addition, TEM images showed that the TiO2 nanoparticles existed in the form of clusters (Figure 2b). It is mainly because the small sized TiO2 nanoparticles were apt to aggregate due to the huge surface energy. Meanwhile, no 10


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dispersant was added during the synthesis of TiO2, which may be another reason to cause the aggregation. Figure 2c shows the lattice fringe spacing of small nanocrystallites is 0.36 nm (marked by lines and arrows), which is assigned to (101) planes of anatase TiO2. Characterization of the bifunctional fabric

Figure 3. SEM images of (a) pristine cotton, (b) PPy/cotton, (c) PDA/PPy/cotton, (d) TiO2cotton, (e) TiO2-PPy/cotton, (f, g) TiO2-PDA/PPy/cotton, (h) FTIR and (i) XRD pattern of different cotton fabrics. The as-prepared TiO2 sol was coated onto different cotton fabrics (cotton, PPy/cotton, PDA/PPy/cotton) through a dip-dry-cure process to obtain a bifunctional fabric. The pristine cotton fiber showed a flat surface with fibrillous texture (Figure 3a). A layer of PPy with granular particles was covered on the surface of cotton (Figure 3b). Meanwhile, fibrous PPy was

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obtained and coated onto cotton fibers when Py was polymerized in the presence of DA (Figure 3c). Dopamine, with the chemical structure of catecholamine, is the main composition of melanin. After incorporating DA into the system, catechol chemically reacted with Py ring. This hindered the agglomeration and entanglement of PPy polymer chain, leading to fibrous morphology.33 After coating with TiO2 sol, a uniform TiO2 layer was formed on the pristine cotton, PPy/cotton and PDA/PPy/cotton, respectively (Figure 3d-g). In comparison with the granular PPy, fibrous PDA/PPy showed a higher surface area. This is beneficial for the enhancement of solar vapor generation, which will be discussed later.36, 39 To further verify the formation of TiO2-PDA/PPy/cotton, the chemical composition of different cotton fabrics was characterized by FTIR (Figure 3h) and XRD (Figure 3i). In the FTIR spectrum of TiO2-PPy/cotton, the peaks at 1156 cm-1 and 1276 cm-1 were attributed to the C-N stretching vibration. The peaks at 1529 cm-1 and 1018 cm-1 were assigned to the five-membered ring stretching and the C-H in-plane bending vibration, respectively.40 These peaks are symbols of the formation of PPy on the cotton fibers. In addition, the peak at 1415 cm-1 was attributed to the six-membered ring stretching vibration, suggesting the formation of PDA.34 Moreover, compared with the FTIR spectrum of cotton, characteristic peaks of cellulose at ~3300 cm-1 (OH group) and ~2900 cm-1 (the asymmetrically stretching vibration of C-H in the pyranoid ring) were subdued or even disappeared in the FTIR spectra of TiO2-PPy/cotton and TiO2PDA/PPy/cotton, which further indicated the cotton was almost covered by PPy or PDA/PPy.41 XRD spectra shown in Figure 3i demonstrated that there was a weak peak at around 25o for TiO2-cotton and TiO2-PPy/cotton. Meanwhile, this peak for TiO2-PDA/PPy/cotton was too weak to be observed. On the one hand, the cotton fabric showed a strong diffraction peak. On the other hand, the weak diffraction peak was attributed to the low dosage of TiO2 on the substrate. The

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specific surface area of PDA/PPy/cotton increased from 2.71 m2 g-1 to 9.54 m2 g-1 after the deposition of TiO2 (Table S1). This small increase of specific surface area (6.83 m2 g-1) indicated the relatively low loading mass of TiO2 on the cotton fabrics. Moreover, the EDXS mapping (Figure S2) indicated that the element of Ti was uniformly distributed on the surface of different fabrics (cotton, PPy/cotton and PDA/PPy/cotton), demonstrating the TiO2 had been successfully deposited on these substrates.

Figure 4. Reflectance (a) and transmittance (b) spectra of different treated cotton. (c) Photograph and infrared images (d) of the system for illustrating wettability of TiO2-PDA/PPy/cotton. To characterize the solar absorption performance, the optical transmittance and reflectance spectra of different cotton samples were measured by an ultraviolet-visible-near infrared spectrophotometer. In comparison with the pristine cotton fabric, TiO2-cotton showed a strong

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light absorption in ultraviolet region (Figure 4a-b). Both TiO2-PPy/cotton and TiO2PDA/PPy/cotton showed almost the same low transmission (~1 %) and reflection (~4 %) over a wavelength range of 200 nm to 1100 nm, leading to a high solar absorption of ~95 % in this range. Wettability of photothermal materials plays an essential role in sufficient water supply during the interfacial water vapor generation. A TiO2-PDA/PPy/cotton was placed on a PS foam (Figure 4c) and the infrared thermal images were captured to characterize the wetting process of TiO2-PDA/PPy/cotton once in touch with water. In the initial state, the surface temperature of TiO2-PDA/PPy/cotton was obviously higher than that of the surrounding environment. Then the surface temperature gradually decreased as the wetting proceeded, and the fabric was completely wetted after ~30 s. The prompt wetting ability of the TiO2-PDA/PPy/cotton is conducive to enhance solar vapor generation. Furthermore, all the cotton fabrics presented a strong water absorbency (Figure S3). There is rarely difference in wetting for the treated fabrics and the pristine one. Evaporation under simulated solar irradiation

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Figure 5. (a) IR images showing the surface temperatures of different samples before and after solar illumination for 10 min. (b) Mass change of water as a function of solar irradiation time. (c) Solar vapor generation efficiency and evaporation rate of different samples (1: water, 2: cotton, 3: TiO2-cotton, 4: TiO2-PPy/cotton, 5: TiO2-PDA/PPy/cotton) under 1 sun illumination. The photothermal activity and solar vapor generation performance of different cotton fabrics were investigated in our experiment. An infrared camera with a measurement error of ~0.4 oC was utilized to carefully record surface temperature changes of different samples (water, pristine cotton, TiO2-cotton, TiO2-PPy/cotton and TiO2-PDA/PPy/cotton). Typical infrared thermal pictures of the surfaces were displayed in Figure 5a. Before xenon light illumination, all samples exhibited a surface temperature around 22.4 oC ~ 23.6 oC. After the simulated solar illumination with a power density of 1 kW m-2 for 10 min, the surface temperature of TiO2-PPy/cotton and TiO2-PDA/PPy/cotton rapidly increased to 45.1 oC and 47.7 oC due to the high solar absorption

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and effective light-to-thermal conversion performance. For the samples without PPy or PDA/PPy, the surface temperature had a relatively smaller increase (about 10 oC ~17 oC). The solar vapor generation performance of different samples was evaluated by monitoring the mass loss of water in beakers with time under 1 sun illumination. The cumulative weight loss of water in different samples increased linearly as a function of irradiation time. The evaporation rate was calculated according to the curves of mass changes. The evaporation rate of TiO2PDA/PPy/cotton was found to be 1.55 kg m-2 h-1, which is 4.1 times higher than that (0.38 kg·m2

·h-1) of pristine cotton. This evaporation rate is higher than most of the previously reported

results and maintained after 10 cycling tests (Figure S4a in the Supporting Information). Meanwhile, the TiO2-PPy/cotton showed an evaporation rate of 1.28 kg·m-2·h-1. The solar vapor generation enhancement can be explained by the relationship between the temperature and evaporation rate using the Dalton evaporation Eq. (3).42 = ( − )

(3)

where E, Ps, P, and C are the evaporation rate, saturation vapor pressure, realistic vapor pressure, and correlation constant, respectively. And the enhancement of evaporation rate was calculated using Eq. 4. = ! ⁄" = (! − )⁄(" − )

(4)

Here, the realistic vapor pressure (P) of water is 2810 Pa at 23 oC, and the saturation vapor pressure of water at 33 oC and 48 oC are 5033 Pa and 11171 Pa, respectively.43 By the calculation, the evaporation rate of TiO2-PDA/PPy/cotton is about 3.76 times higher than that of water under 1 sun illumination.

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Furthermore, the solar vapor generation efficiency of water, pure cotton, TiO2-cotton and TiO2-PPy/cotton was calculated to be 21 %, 24 %, 26 % and 80 %, respectively (Figure 5c). Due to the high light absorption in the ultraviolet region, the TiO2-cotton owned a slightly higher solar vapor generation efficiency than water and cotton. Compared with the water, cotton exhibited a relatively higher solar vapor generation efficiency since the water was pumped to the cotton surface and localized interfacial heating was realized. According to the Eq. 2 which was widely utilized to evaluate the solar thermal conversion performance, the calculated solar vapor generation efficiency of TiO2-PDA/PPy/cotton reached 98 %, which is higher than most of the previously reported evaporation system (Table S2). This efficiency seems a contravention of the principle of conservation-of-energy since the total heat loss including radiation, conduction and convection is about 28.54% (Detailed calculation of heat loss is shown in the Supporting Information). We name this efficiency (98%) apparent efficiency in this study. We also think the calculation of solar vapor or energy conversion efficiency deserves more attention and discussion. In our opinion, the increased surface area of the absorber is the main drive for the high apparent efficiency. According to Eq. 2, the efficiency and evaporation rate are inversely proportional to the surface area of the absorber. On the one hand, the cotton fabric showed an instinctive rough structure due to the multiple interlocked fibers and the interlacing of yarns (Figure S5b). On the other hand, the PDA/PPy displayed a much higher surface area due to its fibrous structure (Figure S5c). Therefore, the actual surface area of our absorber is much larger than the projected surface area (Figure 5a) which was employed in the calculation of the water evaporation rate, resulting in a high apparent efficiency. Recently, Zhu44 and Gan45 respectively reported an ideal solar vapor generator with a 100% solar energy conversion efficiency by increasing the actual surface area within a given projection area. Their elaborately designed vapor generators showed

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high vapor generation rates which surpassed the theoretical upper limit of solar evaporation rate. Moreover, Xu and Liu et al. recently reported a solar evaporation system with an efficiency over 100% when the optical power is higher than 2.0 sun.17 They suspected the interfacial water layer on the absorber was superheated. Under this circumstance, vapor bubbles might spontaneously produce, grow and burst. A large amount of water transpired into air without experiencing the phase transition from liquid to vapor. This significantly saved energy. Furthermore, Yu, Qu and Yang et al. presented a floating solar vapor generator with a record high rate of 3.2 kg m-2 h-1 (1 sun) and the corresponding energy conversion efficiency is 94%.46 They proved the vaporization enthalpy of water confined in their absorber is smaller than that of bulk water through the evaporation measurements and differential scanning calorimetry experiments. The water molecules are more likely to escape the polymer network as small clusters rather than individual molecules. As such, the water is evaporated to a state with a lower enthalpy change than conventional latent heat. Therefore, the actual vaporization enthalpy of water is possible to be lower than the conventional latent heat which is employed in the calculation of the water evaporation rate and conversion efficiency. This may be the other reason for the high apparent efficiency. Photocatalytic property

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-2 Figure 6. (a) Photodegradation of MO with different samples under simulated solar (1 kW m )

for 180 min; (b) UV-vis adsorption spectra showing photodegradation of MO with TiO2PDA/PPy/cotton under 1 kW m-2 illumination; (c) The optical images of different samples after 180 min illumination; (d) Pictures showing the color change of the MO solution containing TiO2PDA/PPy/cotton. The photocatalytic performance of different samples (cotton, TiO2-cotton, TiO2-PPy/cotton and TiO2-PDA/PPy/cotton) under a simulated solar illumination was studied through

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photodegradation experiments using MO as the contaminant model. Figure 6a showed a plot of normalized concentration of MO with irradiation time. The aqueous solution with pristine cotton showed the plateaued line, which indicated the pure cotton had no photocatalytic property and MO was stable at this condition. The photocatalytic activity of TiO2-cotton, TiO2-PPy/cotton and TiO2-PPy/PDA/cotton

increased

gradually

(TiO2-cotton

Bifunctional Fabric with Photothermal Effect and ... - ACS Publications

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