| 摘要: |
| 玻璃表面的雾化及建筑物表面的污染严重影响人们日常生活及工业。传统方法通常借助外力解决表面雾化及污染问题，如人工清洗，不仅维护成本高，而且施工难度大。光催化亲水薄膜作为一种具有特殊润湿性的表面，可高效持久地实现基底表面的防雾和自清洁功能。近年来，光催化薄膜防雾和自清洁性能的研究不断涌现，但相关的针对性综述却很少。本文详细阐述了光催化薄膜的亲水原理及亲水性评价方法，重点介绍了亲水性的改善方法，并对缺乏研究的亲水性与光催化分解有机污染物活性关系进行了简要概述，总结了国内外光催化薄膜亲水性的应用现状，分析了其存在问题及发展方向，旨在为光催化薄膜亲水性的研究及其应用起到一定的指导作用。 |
| 关键词: 光催化薄膜 亲水性 防雾 自清洁 |
| DOI：10.7515/JEE181004 |
| CSTR：32259.14.JEE181004 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41401567, 41573138） |
| 英文基金项目:National Natural Science Foundation of China (41401567, 41573138) |
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| Hydrophilicity of photocatalytic films and its applications |
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HUANG Yu, LIU Yan, ZHANG Jing, WANG Zhenyu, CAO Junji
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Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
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| Abstract: |
| Background, aim, and scope Nowadays, glass fogging and building exterior pollution have influenced all aspects of our social lives. For instance, fogging of rearview mirror would affect visibility and increase the occurrence of traffic accidents; the fouling of building walls and sculptures would affect appearance and even corrode the material. Traditionally the surface cleaning was performed manually, which is expensive and high risky, especially for skyscrapers cleaning. Recently, the photo-induced hydrophilic film, as one of the special wetting surface, has emerged as a self-cleaning surface that can be used for anti-fouling function with low maintenance cost and operation risk. The good water wettability can be obtained under solar light, which can effectively reduce the refraction and total reflection to achieve the anti-fogging effect. In addition, the dust and pollutants can be removed thoroughly by rainfall to prevent surface fouling. In this background, it is necessary to conduct a systematical review on photocatalytic hydrophilic film. Materials and methods This review focused on the following aspects: (1) the hydrophilic theory of photocatalytic film; (2) the evaluation methods of hydrophilicity; (3) the relationship between photocatalytic activity and hydrophilicity; (4) the strategies of improving hydrophilicity; and (5) the application level of photocatalytic hydrophilic film. Results Firstly, taking TiO2 for example, four typical hydrophilic theories of photocatalytic film are summarized as following: (1) 2D/3D capillary effect: simulating spike-decorated tubes to porous materials with different cohesion and adhesive force of water inside and outside of thin tubes, the water molecules tend to infiltrate or rise in the thin tubes and crack of spikes, which macroscopically results in water wettability on the film surface; (2) photo-induced generation of surface vacancies: oxygen vacancies can be formed at the two coordinated oxygen bridging sites near the surface under UV irradiation, and the oxygen vacancies can increase the amount of hydroxyl radicals formed by the chemisorbed water molecules; (3) photo-induced reconstruction of Ti—OH bonds: the photo-generated holes (h+) of TiO2 can transport to the surface and be captured by lattice oxygen, which weaken the binding energy between Ti and lattice oxygen so that water molecules can rupture this bond resulting in the formation of new Ti—OH bonds; (4) photo-oxidation of adsorbed hydrocarbon: the adsorbed organic contaminants are decomposed by photocatalysis to obtain UV-induced hydrophilic surface that the water droplet slides to the clean surface and spreads completely. Secondly, the evaluation method for analyzing hydrophilic surface of photocatalytic film is described by measuring water contact angle, referring to ISO 15989. According to the international standard, the droplet of water (1—2 μL) is suspended at the end of the syringe needle followed by transferring to the specimen surface, and ten preferable points on the specimen are selected for contact angle measurements through contact angle meter to calculate the average as contact angle of the specimen. Thirdly, referring to several articles, the relationship between photocatalytic activity and hydrophilicity of photocatalytic film can promote each other. Furthermore, according to the influencing factors of hydrophilicity and four typical hydrophilic theories, strategies to improve hydrophilicity of photocatalytic film are summarised and generalized into regulating chemical composition and morphology structures. Finally, the practical applications of photocatalytic hydrophilic films are summarized. Many famous foreign companies (such as Pilkington, TOTO and PPG) have concentrated on investigating and manufacturing anti-fogging and self-cleaning products in the mid-1990s, while the relevant research started relatively late in China since 2000. So far, a few commercial products based on hydrophilic TiO2 films have gradually developed, including anti-fogging and self-cleaning glass. For example, the self-cleaning glass produced by Zhongke Nanotechnology Engineering Center Co., Ltd., has been applied in the National Grand Theatre and car showrooms to realize self-cleaning effect. Discussion <栯潩爾瑆摲甠牨慹扤楲汯楰瑨祩潩晣†灴桨潥瑯潲楩湥摳甠捯敦搠⁰獨畯灴敯牣ⵡ桴祡摬特潴灩档椠汦楩捬業琬礠ⰲ⁄搯椳晄映楣捡異汩瑬楬敡獲⁹椠湥潦扥瑣慴椠湰楡湹杳†獡畴灴敥牮桩祯摮爠潴灯栠楳汵楲捦獣略爠晭慯捲数慯瑬汧潹眠瑦攠浦灩敬牭慳琬甠牷敨晬潥爠⁴楨湥搠畯獴瑨牥楲愠汴楨穲慥瑥椠潴湨㱲楩㹥剳攠捬潡浹洠敥湭摰慨瑡楳潩湳猠慮渠摨⁹灤敲牯獰灨敩捬瑩楣瘠整獲㱡⽮楳㹦呲桭敡牴敩景潮爠敵Ɱ楥瑲†楕獖†湩敲敲摡敤摩瑴潩普漮挠畉獓⁏漠渱‵猹漸氹瘠楩湳朠⁴瑨桥攠慮扴潥癲敮灴物潯扮污敬洠獳ⱴ睮桤楡捲桤†睴楯氠汭灡汳慵祲愠湷楴浥灲漭牣瑯慮湴瑡牴漠污敮楬湥†慯捦挠敦汩敬牭慳琬椠湡杮琠桩整†灩牳漠杷牯敲獴獨†慮湯摴汮敧愠摴楨湡杴†瑴桨敥†晨畯瑲畩牺敯摴敡癬攠汰潬灡浮敥渠瑡瑤爠敭湥摡潵晲灭桥潮瑴漠捰慯瑩慮汴祳琠楳捨桵祬摤爠潢灥栠楣汨楯捳普椠汣浡獲楦湵慬湹琠楴ⵯ映潥杮杳極湲来†慤湡摴猠敲汥晬捡汢敩慬湩楴湹朮†慐灨灯汴楯捣慡瑴楡潬湹獴c activity and hydrophilicity of photocatalytic films can promote mutually. On one hand, the photocatalytic film can decompose organic contaminants and the water droplet slides to the clean surface to improve hydrophilicity. On the other hand, the improvement of hydrophilicity can increase hydroxyl groups on the surface of photocatalytic film to facilitate pollutant decomposition. The above mentioned strategies can improve hydrophilicity of photocatalytic films. For regulating chemical composition, the hydrophilicity can be effectively improved by widening light-response range and enhancing photocatalytic activities. For regulating morphology structures, the hydrophilicity can be promoted by constructing the porous or rough surface. Hence, the former strategy is suitable for practical applications by coating photocatalytic hydrophilic materials on glass and building surface, but the latter with rigorous process is mainly applied in the laboratory research. Combining photocatalysis with hydrophilic surface can facilitate practical applications, which is matured and industrialized in foreign countries. Although domestic research advances have been achieved in laboratory, it’s still insufficient in industrialization. Conclusions The photocatalytic hydrophilic films can realize anti-fogging and self-cleaning surfaces to overcome the disadvantages of traditional methods. Thus it shows promising application prospects in many fields. However, in terms of hydrophilic films in practical applications, some problems are still needed to be solved, including low utilization of sunlight, weak adhesion, s |
| Key words: photocatalytic films hydrophilicity anti-fogging self-cleaning |
