TiO2 and TiO2–SiO2 coated cement: Comparison of mechanic and photocatalytic properties

Abstract

a b s t r a c tAn increasingly known application of nanomaterials in the construction industry is related to the photoactivity ability of semiconductors, where nano-anatase TiO 2 is perhaps the most well-known photocatalytic semiconductor and one which possesses a strong oxidizing capability. To analyze the photo-efficiency of four TiO 2 coatings and the effect of SiO 2 interlayer on the mechanic and photocatalytic activity in Rhodamine B (RhB) and NO x photodegradation, two photocatalytic cement series have been prepared. First, cement mortar was coated with three commercial TiO 2 suspensions (GG1, GC7 and CG13) and a home-made titania sol-gel (TEA), and secondly an insertion of a SiO 2 layer was applied on cement surface before spraying the TiO 2 layer.All studied TiO 2 -cements exhibited a significant RhB and NO x photodegradation, arising almost total RhB molar conversions, and upper 53% for NO x photo-oxidation respectively. Nevertheless, although SiO 2 layer deposited in between mortar and TiO 2 -cement did not stabilize the commercial TiO 2 coatings, a good adhesion was observed when silica was applied joint to the home-made titania gel (TEA), probably as a consequence of the interactions encountered between SiO 2 and TiO 2 gels. CG7-Si-Cem exhibited high rate at shorter irradiation times, but TEA-Cem and TEA-Si-Cem can be considered as very interesting and potential photocatalytic mortars due to useful mechanical properties, with a very good coatings adhesion that provides promising outdoor use, and good photo-efficiencies in RhB and NO x photo-oxidation.

Different Roles of Water in Photocatalytic DeNOx Mechanisms on TiO2: Basis for Engineering Nitrate Selectivity?

“…in glass and concrete products, and its photocatalytic activity, i.e. the rate of normalized NOx concentration decrease, has been exclusively used as an indicator of efficiency [11][12][13][14][15][16][17] . The nature of the exposure regimes (of the photocatalyst to light and reactants) is the primary differentiating factor for the various approaches to supporting photocatalysts and has led to a number of innovative and effective strategies for performance improvements [18][19][20] .…”

Photocatalytic hydrophobic concrete coatings to combat air pollution

“…The results (Fig. 2) showed that even references were able to whitening the MB spots, which highlights one of the difficulties when performing experiments on concrete specimens, where porosity and pore humidity/pH could cause hydrolysis in absence of light due to the basicity of concrete pore water [45,46], while in the silica sol coated could be originated by deeper adsorption of MB promoted by the hydrophilicity of acidic SiO 2 sol, joined to photochemical decoloration [47][48][49]. The quantification of spot area reduction and, specially, the calculated MB initial photodegradation rate (Table 2) pointed out the significant photocatalytic activity presented by the coated specimens that exhibited larger and faster decreases of stained area under halogen light activation.…”

Admixtures in Cement-Matrix Composites for Mechanical Reinforcement, Sustainability, and Smart Features

“…This material gathers solar radiation, which can decompose organic pollutants that come into contact with the nanoparticle [153]. It has been tested both as an admixture added to the cement blend [154] and as a coating, given that this phenomenon occurs on the surface of the cement product [155]. Jafari et al [156] have found a better performance of the hybrid nano-TiO 2 -SiO 2 coating compared to nano-TiO 2 coating.…”