Enhanced photocatalytic efficiency by layer-by- layer self-assembly of graphene and titanium dioxide on shrink thermopla
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TECHNICAL PAPER
Enhanced photocatalytic efficiency by layer-by- layer self-assembly of graphene and titanium dioxide on shrink thermoplastic film Peng Zhou1 • Tianhong Cui1 Received: 20 April 2020 / Accepted: 28 April 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this work, reduced graphene oxide/titanium dioxide (rGO/TiO2) composite material was immobilized on shrink thermoplastic film using layer-by-layer (LBL) self-assembly to remove pollutants in water, and the results were compared with immobilized TiO2 on glass and shrink thermoplastic film. The structural and morphological properties of the immobilized photocatalysts were investigated using atomic force microscope and scanning electron microscope. The photocatalytic efficiency was measured by photodegradation of methylene blue under solar light illumination. The immobilized rGO/TiO2 on shrink thermoplastic film showed doubled photocatalytic efficiency than TiO2 on glass substrate, and no decrease of photocatalytic efficiency was shown after 5 h of operation. The use of shrink thermoplastic film and the introduction of graphene material contribute to an increase in catalytic efficiency of 63% and 28%, respectively. These results lead us to believe that the LBL self-assembled rGO/TiO2 composite on shrink thermoplastic film could be used in photocatalytic degradation of other water pollutants.
1 Introduction Water shortage is becoming a global challenge. Access to clean water is a problem not only in developing countries, but also in developed countries including the United States because of economic growth, demographic shift and climate change. There are approximately four billion people facing water scarcity, and water pollution makes their situation even more severe. In fact, the United Nations lists addressing water scarcity and water pollution as one of the goal challenges for sustainable development by 2030 (Desa 2016). Photocatalytic technology based on titanium dioxide (TiO2) has gained wide attention in the past decades as a low-cost, environmentally friendly and sustainable water treatment technology. This technology uses semiconductor catalysts such as TiO2 to mineralize refractory organic compounds, water pathogens and disinfection by-products (Pera-Titus et al. 2004). When TiO2 is illuminated under photon energy greater than or equal to the bandgap energy of TiO2, the distinct lone electron in the outer orbital is & Tianhong Cui [email protected] 1
Department of Mechanical Engineering, University of Minnesota, Minneapolis, USA
photoexcited to the empty conduction band, leaving a hole in the valence band. A series of redox reactions occur at the photo active surface and can remove the organics in water (Fujishima et al. 2008). However, low efficiency, catalyst agglomeration during operation, and the complex postseparation process are the primary barriers that prevent practical applications of this technology. Graphene, a flat monolayer of sp2-bonded carbon atoms, is bel
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