Heterogeneous photocatalysis on construction materials: effect of catalyst properties on the efficiency for degrading NOx and self cleaning

Abstract

This paper analyzes the effect of some properties of different catalysts on the photocatalytic activity. The efficiency has been determined for two different processes: NOx abatement and self-cleaning for Rhodamine B and tobacco extract being, the TiO 2 based photocatalyst, supported as coatings on white mortar. Eight different catalysts were tested, seven commercial ones and one home-made catalyst with improved visible light absorption properties. Additionally, some of them were submitted to exposition to water and/or calcinations to alter their physical properties. A kinetic approach was used to evaluate the photocatalytic activity, being the first reaction constant (for NO) and just empirical constants (for self-cleaning) the parameters used for the comparison of the different materials. As a result, the efficiency, even for ranking, is dependent on the type of contaminant used in the experiment. In general, NO oxidation and tobacco followed similar trends while no clear relations were found for Rhodamine B. RESUMEN: Fotocatálisis heterogénea en materiales de construcción: efecto de las propiedades de los catalizadores en la eficiencia de degradación de NOx y autolimpieza.En este trabajo se analiza el efecto de las propiedades de distintos catalizadores en la actividad fotocatalítica de degradación de NOx y autolimpieza, para Rodamina B y extracto de tabaco. Se han ensayado ocho fotocatalizadores, basados en TiO 2 y soportados sobre mortero blanco; siete de ellos comerciales y uno sintetizado en el laboratorio con absorción mejorada en el visible. Adicionalmente, las propiedades físicas de algunos de ellos se alteraron mediante tratamientos con agua y/o por calcinación. La actividad fotocatalítica se ha evaluado mediante aproximación cinética, siendo la constante de reacción de primer orden (para NO) y constantes empíricas de ajuste (para autolimpieza) los parámetros de comparación entre materiales. Como resultado, la eficiencia depende del contaminante utilizado en el experimento de evaluación. En general, en este estudio, oxidación de NO y de extracto de tabaco presentan tendencias similares mientras para Rodamina B no se encontró correlación clara ninguna.

Quantification of hydroxyl radicals on cementitious materials by fluorescence spectrophotometry as a method to assess the photocatalytic activity

“…Larger specific surface areas are generally considered as positive factors concerning the rate of photocatalytic degradation. However, it should also be taken into account that a large specific surface area is usually associated with weak crystallization and large amounts of crystalline defects, which favors the recombination of photo-generated electrons and h + , leading to poor photocatalytic activity [19,39].…”

Effects of Nano-TiO2on the Toughness and Durability of Cement-Based Material

“…Such type of concrete has been used on some pavement [7]. The photocatalysis mechanism of nano-TiO 2 has been systematically studied [8][9][10] and provided a solid theoretical foundation for its application in building materials. On account of strong binding property of cementbased materials, nano-TiO 2 can be conveniently applied in these materials without any further processing.…”

Synthesis and Characterization of Nanocomposite of Functionalized Graphene Oxide with Multi Core-Shell Fe3O4-ZnO-TiO2 Nanoparticles

“…Graphene and graphene oxide have been synthesized in various ways, such as mechanical exfoliation [9], chemical vapor deposition, epitaxial growth, and chemical derivation techniques [9][10][11]. It has been shown in the literature that when graphene combines with other semiconductor oxides, improve the overall behavior of the system [12][13][14][15]. Magnetic nanoparticles (MNPs), such as Fe3O4, have the ability to overcome numerous challenges and also have strong potential to develop new classes of advanced nanomaterials [16][17][18][19].…”