Smart surfaces for environmental remediation. Highly efficient photocatalytic nanocomposites incorporating metal oxides and graphene related materials.

After the Kyoto Protocol, the World Health Organization estimated in2016 that up to date one out of every nine deaths was related to outdoor/indoor air pollution[1]. As a consequence the World’s population expressed the need to have Healthier Cities and the design of new technologies to eliminate air pollutants[e.g. nitrogen oxides(NOx)and organics] by using natural sunlight, and their integration into smart cities became the centre of an ever increasing research[2]. Photocatalysts based on TiO2 are already on the market[3] and embedded in commercial products, such as cement[4]. However, they work only with the UV light λ<380nm [5], with a significant drop of performance in the visible[6]. In this work I enhanced and extend the TiO2 spectral activity by creating hybrid photocatalysts with organics (e.g perylenes), or graphene and related materials (GRM-PCs)(e.g. graphene, MoS2, WS2 and red phosphorous (RP)). We test the photocatalytic activity by monitoring the dye degradation(rhodamineB,(RhB))caused by GRM-PCs after a fixed irradiation time with respect to pristine TiO2. GRM-PCs based on TiO2 mixed with exfoliated graphite (TiO2-Gr) or with RP show ~90% higher photocatalytic activity, in terms of dye degradation, than pristine TiO2, after 20 min UV-Vis irradiation. Tests in the visible range (400<λ<800nm) how that RP is ideal for indoor applications, with a~800%improvement of photocatalytic activity with respect to TiO2, after 40min vis-light irradiation (5mW/cm2). The photocatalytic activity of TiO2-Gr is tested after mixing in an industrial concrete matrix, resulting in an increment of dye degradation of50%. These data underpin the potential of GRM-PCs for smart surfaces. In a city such as Milan, covering 15% of urban surfaces with TiO2-based cement photocatalysts would enable a reduction in pollution~50%. An efficient dispersion of the new cementitious coatings I have developed will allow to reach an abatement of the pollution of90% with2.5% surface covering. ...