Photocatalysis of Cementitious Materials: Clean Buildings and Clean Air

Abstract

While the primary function of concrete is structural, its pervasiveness in our society lends it to other functions and creates the need for it to maintain its integrity and aesthetic quality. Therefore, concrete with added functionality–for example, self-cleaning characteristics and the ability to remove pollutants–is desirable. Heterogeneous photocatalysis (e.g., gas–solid or liquid–solid catalytic processes caused by light irradiation) by semiconductor particles or coatings has now reached a high level of development and is a promising technology for the reduction of global environmental pollutants. Among the various semiconductor materials, TiO2 in the form of anatase has attracted wide interest, due to its strong oxidizing power under near-UV radiation, its chemical stability when exposed to acidic and basic compounds, its chemical inertness in the absence of UV light, and the absence of toxicity. TiO2 has proved very effective in the reduction of pollutants such as NOx, aromatics, ammonia, and aldehydes. Surprisingly, the use of TiO2 in combination with cementitious materials has shown a favorable synergistic effect in the reduction of pollutants. These new materials have already found relevant applications in self-cleaning building walls and in the reduction of urban pollutants.

Photocatalytic roads: from lab tests to real scale applications

“…An overview is given in [9]. A distinction can be made by the type of air flow; in the flow-through method according to ISO 22197-1 [12], the air, with a concentration of 1 ppmV of NO, passes over the sample which is illuminated by a UV-lamp with light intensity equal to 10 W/m 2 in the range between 300 and 400 nm, as illustrated in Fig.…”

“…Another, similar application consists of using a double layered concrete with addition of TiO 2 (in the mass and/or as dispersion on the surface) to the top layer, which will be discussed later on. The use of TiO 2 in combination with cement leads to a transformation of the NO x into NO 3 -, which is adsorbed at the surface due to the alkalinity of the concrete [9]. Thus, a synergetic effect is created in the presence of the cement matrix, which helps to effectively trap the reactant gases (NO and NO 2 ) together with the nitrate salt formed.…”

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

“…Semiconductor photocatalysis has been presented and trialed as a practical solution to the NOx pollution issue since the 1980s [8][9][10] . TiO 2 has been the most widely applied photocatalyst in construction materials, e.g.…”

New Photocatalyst LiNbO3 for Corrosion Reducing and Environment Friendly Sustainable Concrete Construction

“…Indeed, it promotes faster decomposition of pollutants and prevents them from accumulating on the surfaces [20], [21]. We proposed that the use of LiNbO 3 in construction purpose could make an effective contribution to improve air quality by reducing pollutants [2] and reducing corrosion problem of reinforcement.…”