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11 pages, 3209 KiB

Open AccessArticle

Electrochromic and Electrochemical Properties of Co₃O₄ Nanosheets Prepared by Hydrothermal Method

by Xinrui Yue, Gang Wang, Jing Wang, Licai Fan, Jian Hao, Shen Wang, Mingli Yang and Yang Liu

Coatings 2022, 12(11), 1682; https://doi.org/10.3390/coatings12111682 - 5 Nov 2022

Cited by 7 | Viewed by 1658

Abstract

In this paper, Co₃O₄ nanosheets were prepared by the hydrothermal method. The structure of the material was analyzed by morphological characterization and physical phase analysis, which confirmed the preparation of the product, Co₃O₄, showing a nanosheet [...] Read more.

In this paper, Co₃O₄ nanosheets were prepared by the hydrothermal method. The structure of the material was analyzed by morphological characterization and physical phase analysis, which confirmed the preparation of the product, Co₃O₄, showing a nanosheet structure. By studying the electrochromic properties of the prepared products, the results show that the transmittance modulation range of the Co₃O₄ nanosheet is 75% at 780 nm. The coloring response time and bleaching response time is about 3.8 s and 3.4 s, respectively. Electrochemical tests show that the Co₃O₄ nanosheets have good capacitive properties. Their specific capacitance reaches 1850 F/g when the current density is 1 A/g. When the current density is 5 A/g, the specific capacitance can still maintain 99.6% after 5000 cycles. In addition, Co₃O₄//CNTs devices can provide a maximum energy density of 79.52 Wh/kg (1 A/g) and a maximum power density of 11,000 W/kg (15 A/g), showing good energy storage capacity. The above data results indicate that the prepared Co₃O₄ nanosheets can be used as good candidates for supercapacitors. This paper provides a new idea and method for preparing Co₃O₄ materials. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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13 pages, 2978 KiB

Open AccessArticle

Synthesis of the Porous ZnO Nanosheets and TiO₂/ZnO/FTO Composite Films by a Low-Temperature Hydrothermal Method and Their Applications in Photocatalysis and Electrochromism

by Xusong Liu, Gang Wang, Hui Zhi, Jing Dong, Jian Hao, Xiang Zhang, Jing Wang, Danting Li and Baosheng Liu

Coatings 2022, 12(5), 695; https://doi.org/10.3390/coatings12050695 - 19 May 2022

Cited by 16 | Viewed by 3430

Abstract

In this paper, porous zinc oxide (ZnO) nanosheets were successfully prepared by a simple low-temperature hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) tests showed that the synthesized product was ZnO with porous sheet structure. [...] Read more.

In this paper, porous zinc oxide (ZnO) nanosheets were successfully prepared by a simple low-temperature hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) tests showed that the synthesized product was ZnO with porous sheet structure. The diameter of porous nanosheets was about 100 nm and the thickness was about 8 nm. As a photocatalyst, the degradation efficiencies of porous ZnO nanosheets for methyl orange (MO), methylene blue (MB) and Rhodamine B (RhB) were 97.5%, 99% and 96.8%, respectively. In addition, the degradation efficiency of ZnO for mixed dyes (Mo, MB and RhB) was satisfactory, reaching 97.7%. The photocatalytic stability of MB was further tested and remained at 99% after 20 cycles. In the experiment, ZnO/FTO (fluorine-doped tin oxide) composites were prepared by using ZnO as the conductive layer. Titanium dioxide (TiO₂) was deposited on the surface of ZnO/FTO by electrodeposition, so as to obtain a TiO₂/ZnO/FTO composite. By studying the electrochromic properties of this composite, it was found that the TiO₂/ZnO/FTO composite shows a large light modulation range (55% at 1000 nm) and excellent cycle stability (96.6% at 200 cycles). The main reason for the excellent electrochromic properties may be the synergistic effect between the porous structure and the polymetallic oxides. This study is helpful to improve the photocatalytic efficiency and cycling stability of metal oxides, improve the transmittance of thin films and provide a new strategy for the preparation of ZnO composite materials with excellent photocatalytic and electrochromic properties. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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11 pages, 3743 KiB

Open AccessArticle

Electrochromic and Capacitive Properties of WO₃ Nanowires Prepared by One-Step Water Bath Method

by Xusong Liu, Gang Wang, Jun Wang, Xue Gong, Jiang Chang, Xiangyang Jin, Xiang Zhang, Jing Wang, Jian Hao and Baosheng Liu

Coatings 2022, 12(5), 595; https://doi.org/10.3390/coatings12050595 - 27 Apr 2022

Cited by 5 | Viewed by 2005

Abstract

In this paper, WO₃ nanowires were successfully synthesized via a one-step water bath method at an appropriate temperature. The XRD (Energy Dispersive Spectrometer), SEM (Scanning electron microscope), TEM (Transmission Electron Microscope) and other characterization methods proved that the synthesized product was WO [...] Read more.

In this paper, WO₃ nanowires were successfully synthesized via a one-step water bath method at an appropriate temperature. The XRD (Energy Dispersive Spectrometer), SEM (Scanning electron microscope), TEM (Transmission Electron Microscope) and other characterization methods proved that the synthesized product was WO₃, and the product of water bath reaction for 9 h showed the nanowires’ structure. The nanowires were evenly distributed, and the length ranged from 2 μm to 4 μm. The results showed that the nanowires had excellent light transmittance (66%), a very short response time (1.2 s, 2 s) and excellent color rendering efficiency (115.2 cm² C⁻¹) at 650 nm. The electrochemical performance test showed that the specific capacity of the WO₃ nanowires was up to 565 F/g at 1 A/g. Change the different current densities and cycle 100 times, then return to the initial current density, accounting for 99% of the initial specific capacity of 565 F/g. We used this method for the first time to prepare tungsten oxide nanowires and investigated the bifunctional properties of the material, namely the electrochromic and capacitive properties. All of these data indicate that WO₃ nanorods have excellent electrochromic and electrochromic properties and have potential market prospects in the fields of electrochromic glass, variable glasses, advertising, and supercapacitors. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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10 pages, 2600 KiB

Open AccessArticle

Enhanced Electrochromic Performance of All-Solid-State Electrochromic Device Based on W-Doped NiO Films

by Xin Zhao, Xiang Zhang, Zhiwei Yin, Wenjie Li, Changpeng Yang, Wenhai Sun, Hulin Zhang and Yao Li

Coatings 2022, 12(2), 118; https://doi.org/10.3390/coatings12020118 - 21 Jan 2022

Cited by 10 | Viewed by 3153

Abstract

Electrochromic materials have attracted much attention due to their promising applications in smart windows and thermal control. However, NiO is a weak point for a complementary ECD and needs to be improved due to its low optical modulation and charge density. In this [...] Read more.

Electrochromic materials have attracted much attention due to their promising applications in smart windows and thermal control. However, NiO is a weak point for a complementary ECD and needs to be improved due to its low optical modulation and charge density. In this work, the W-doped NiO films are designed and prepared by RF magnetron co-sputtering to improve the performance of the NiO. The results shows that the optical modulation of the W-NiO (52.7%) is significantly improved compared with pure NiO (33.8%), which can be assigned to the increase in lattice boundaries due to the W doping. The response time of W-NiO is 8.8 s for coloring and 7.2 s for bleaching, which is similar to that of NiO film. The all-solid-state electrochromic devices (ECDs) that employed W-NiO as a complementary layer are prepared and exhibit a high-transmittance modulation of 48.5% in wavelengths of 450–850 nm and an emittance modulation of 0.28 in 2.5–25 μm, showing great application potential in the field of smart windows and spacecraft thermal control devices. The strategy of preparing NiO doped by W indicates an innovative direction to obtain ECDs with high performance. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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9 pages, 17037 KiB

Open AccessArticle

Investigation on Solar Absorption and Thermal Emittance of Al Films Deposited by Magnetron Sputtering

by Jinxin Gu, Xin Zhao, Feifei Ren, Hang Wei, Shuhui Liang, Chenchen Geng, Huan Guan, Xiang Zhang, Shuliang Dou and Yao Li

Coatings 2022, 12(1), 17; https://doi.org/10.3390/coatings12010017 - 23 Dec 2021

Cited by 2 | Viewed by 2286

Abstract

A metal layer with high reflectance is widely used as the bottom mirror of smart radiation devices. Reduced solar absorption and enhanced emittance tunability are required for smart radiation devices applied in aerospace. Thus, reducing the absorption in the metal is also necessary. [...] Read more.

A metal layer with high reflectance is widely used as the bottom mirror of smart radiation devices. Reduced solar absorption and enhanced emittance tunability are required for smart radiation devices applied in aerospace. Thus, reducing the absorption in the metal is also necessary. Here, Al films have been prepared by direct current magnetron sputtering on the fused silica substrate. The structure, morphology, and optical properties of the films have been analyzed at various deposition temperatures and deposition times. The spectrum absorption tends to increase with the increase of surface roughness due to the agglomeration and size increase of Al particles, which has been further demonstrated by the simulated results. The optimized Al film exhibits small solar absorption of 0.14 and low emittance of 0.02, which benefits the application for smart radiation devices and solar reflectors. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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10 pages, 2904 KiB

Open AccessArticle

Electrochromic Performance and Capacitor Performance of α-MoO₃ Nanorods Fabricated by a One-Step Procedure

by Ying Duan, Chen Wang, Jian Hao, Yang Jiao, Yanchao Xu and Jing Wang

Coatings 2021, 11(7), 783; https://doi.org/10.3390/coatings11070783 - 30 Jun 2021

Cited by 11 | Viewed by 2201

Abstract

In this paper, we propose for the first time the synthesis of α-MoO₃ nanorods in a one-step procedure at mild temperatures. By changing the growth parameters, the microstructure and controllable morphology of the resulting products can be customized. The average diameter of [...] Read more.

In this paper, we propose for the first time the synthesis of α-MoO₃ nanorods in a one-step procedure at mild temperatures. By changing the growth parameters, the microstructure and controllable morphology of the resulting products can be customized. The average diameter of the as-prepared nanorods is about 200 nm. The electrochromic and capacitance properties of the synthesized products were studied. The results show that the electrochromic properties of α-MoO₃ nanorods at 550 nm have 67% high transmission contrast, good cycle stability and fast response time. The MoO₃ nanorods also exhibit a stable supercapacitor performance with 98.5% capacitance retention after 10,000 cycles. Although current density varies sequentially, the nanostructure always exhibits a stable capacitor to maintain 100%. These results indicate the as-prepared MoO₃ nanorods may be good candidates for applications in electrochromic devices and supercapacitors. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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12 pages, 4494 KiB

Open AccessArticle

Thermochromic Behavior of VO₂/Polymer Nanocomposites for Energy Saving Coatings

by Michalis Xygkis, Emmanouil Gagaoudakis, Leila Zouridi, Olga Markaki, Elias Aperathitis, Kyriaki Chrissopoulou, George Kiriakidis and Vassilios Binas

Coatings 2019, 9(3), 163; https://doi.org/10.3390/coatings9030163 - 1 Mar 2019

Cited by 22 | Viewed by 5306

Abstract

Vanadium dioxide (VO₂) is a well-known thermochromic material that can potentially be used as a smart coating on glazing systems in order to regulate the internal temperature of buildings. Most growth techniques for VO₂ demand high temperatures (>250 °C), making [...] Read more.

Vanadium dioxide (VO₂) is a well-known thermochromic material that can potentially be used as a smart coating on glazing systems in order to regulate the internal temperature of buildings. Most growth techniques for VO₂ demand high temperatures (>250 °C), making it impossible to comply with flexible (polymeric) substrates. To overcome this problem, hydrothermally synthesized VO₂ particles may be dispersed in an appropriate matrix, leading to a thermochromic coating that can be applied on a substrate at a low temperature (<100 °C). In this work, we reported on the thermochromic properties of a VO₂/Poly-Vinyl-Pyrrolidone (PVP) nanocomposite. More specifically, a fixed amount of VO₂ particles was dispersed in different PVP quantities forming hybrids of various VO₂/PVP molar ratios which were deposited as films on fused silica glass substrates by utilizing the drop-casting method. The crystallite size was calculated and found to be 35 nm, almost independent of the PVP concentration. As far as the thermochromic characteristics are concerned, the molar ratio of the VO₂/PVP nanocomposite producing VO₂ films with the optimum thermochromic properties was 0.8. These films exhibited integral solar transmittance modulation (overall wavelengths) ΔTr_sol = 0.35%–1.7%, infrared (IR) switching at 2000 nm ΔTr_IR = 10%, visible transmittance at 550 nm Tr_Vis = 38%, critical transition temperature T_C = 66.8 °C, and width of transmittance hysteresis loop ΔT_C = 6.8 °C. Moreover, the critical transition temperature was observed to slightly shift depending on the VO₂/PVP molar ratio. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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11 pages, 3396 KiB

Open AccessArticle

Synthesis of Solution-Stable PEDOT-Coated Sulfonated Polystyrene Copolymer PEDOT:P(SS-co-St) Particles for All-Organic NIR-Shielding Films

by Soeun Im, Chanil Park, Wonseok Cho, Jooyoung Kim, Minseok Jeong and Jung Hyun Kim

Coatings 2019, 9(3), 151; https://doi.org/10.3390/coatings9030151 - 26 Feb 2019

Cited by 5 | Viewed by 5678

Abstract

We prepared poly(3,4-ethylenedioxythiophene) (PEDOT)-coated sulfonated polystyrene copolymer particles as efficient heat-shielding agents, which showed strong near-infrared (NIR) absorption, with high solid contents and good solution stability. The poly(styrene sulfonate-co-styrene) (P(SS-co-St)) copolymers were successfully synthesized via radical solution polymerization, and PEDOT-coated P(SS-co-St) (PEDOT:P(SS-co-St)) was [...] Read more.

We prepared poly(3,4-ethylenedioxythiophene) (PEDOT)-coated sulfonated polystyrene copolymer particles as efficient heat-shielding agents, which showed strong near-infrared (NIR) absorption, with high solid contents and good solution stability. The poly(styrene sulfonate-co-styrene) (P(SS-co-St)) copolymers were successfully synthesized via radical solution polymerization, and PEDOT-coated P(SS-co-St) (PEDOT:P(SS-co-St)) was synthesized via Fe⁺-catalyzed oxidative polymerization. PEDOT:P(SS-co-St) was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopies. The particle size and morphology of PEDOT:P(SS-co-St) were examined using transmission electron microscopy, dynamic light scattering, and zeta potential measurements. The maximum NIR-shielding efficiency of the film was 92.0% with 40% transmittance. The high solution stability of PEDOT:P(SS-co-St) make it an ideal candidate for heat-insulating materials that find application in semi-transparent heat-insulator-coated windows. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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Review

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23 pages, 6362 KiB

Open AccessFeature PaperEditor’s ChoiceReview

TiO₂ Nanotubes Architectures for Solar Energy Conversion

by Yin Xu and Giovanni Zangari

Coatings 2021, 11(8), 931; https://doi.org/10.3390/coatings11080931 - 4 Aug 2021

Cited by 14 | Viewed by 2995

Abstract

Electromagnetic light from the Sun is the largest source, and the cleanest energy available to us; extensive efforts have been dedicated to developing science and engineering solutions in order to avoid the use of fossil fuels. Solar energy transforms photons into electricity via [...] Read more.

Electromagnetic light from the Sun is the largest source, and the cleanest energy available to us; extensive efforts have been dedicated to developing science and engineering solutions in order to avoid the use of fossil fuels. Solar energy transforms photons into electricity via the photovoltaic effect, generating about 20 GW of energy in the USA in 2020, sufficient to power about 17 million households. However, sunlight is erratic, and technologies to store electric energy storage are unwieldy and relatively expensive. A better solution to store energy and to deliver this energy on demand is storage in chemical bonds: synthesizing fuels such as H₂, methane, ethanol, and other chemical species. In this review paper we focus on titania (TiO₂) nanotubes grown through electrochemical anodization and various modifications made to them to enhance conversion efficiency; these semiconductors will be used to implement the synthesis of H₂ through water splitting. This document reviews selected research efforts on TiO₂ that are ongoing in our group in the context of the current efforts worldwide. In addition, this manuscript is enriched by discussing the latest novelties in this field. Full article

(This article belongs to the Special Issue Smart Coatings for Energy Saving Applications)

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