Rapid assessment of the photocatalytic activity in construction materials: Pros and cons of reductive inks and oxidative fluorescence probes versus standardized NOx testing

Abstract

The photocatalytic activity of a wide variety of photocatalytic construction materials with different intrinsic properties, mainly microstructure and TiO2 crystallographic phases, were obtained using alternative methods (Rz and NBT-reductive inks and TA-oxidative fluorescence probe) and the NOx removal standard ISO 22197-1:2007. The Rz-ink test was shown to be unsuitable for some of the materials due to spontaneous colour change in the dye upon contact with these (here denominated) reactive samples, in the absence of radiation. No such shortcomings were observed for either NBT-ink or TA-probe. Comparison of the three set of results showed a reasonably high correlation among the activities determined by the different methods, despite the wide variation in the characteristics of the photocatalytic materials tested, underlying reaction mechanisms and the physics and chemistry of the inter-phase contact (ink/probe/contaminant-substrate). The findings attest to the possible relationship between the rates of oxidative and reductive reactions in semiconductor photocatalysis. These alternative methods may be regarded as a new 'cheap and simple' approach to photocatalytic activity measurements.

Optimising processing conditions for the functionalisation of photocatalytic glazes by ZnO nanoparticle deposition

“…The photocatalytic activity indicator ink comprised a dye (Rz), a sacrificial electron donor (SED, glycerol), and a polymer (hydroxyethyl cellulose, HEC) to encapsulate the dye and SED after the ink dried. The effectiveness of the Rz dye as a photocatalytic activity indicator ink has been previously demonstrated for a wide range of photocatalytic samples (12,39,(52)(53)(54)(55). It can simply, rapidly, and cheaply probe the photocatalytic activity.…”

New Holistic Conceptual Framework for the Assessment of the Performance of Photocatalytic Pavement

“…The results of several laboratory studies proved that photocatalysis effectively deactivates and mineralizes most of the harmful contaminants such as NO x (Cassar, 2004;Chen and Poon, 2009a,b;Bengtsson and Castellote, 2010;Folli et al, 2010;Lucas et al, 2013;Bloh et al, 2014;Mendoza et al, 2015;Mills and Elouali, 2015;Hernández Rodríguez et al, 2016;Mothes et al, 2016;Jimenez-Relinque and Castellote, 2019b;Chen et al, 2020). Furthermore, this technology has already been tested on the pilot and real scales in several projects; the results indicate photocatalytic effectiveness (Beeldens et al, 2007;Maggos et al, 2007Maggos et al, , 2008Chen and Chu, 2011;Boonen and Beeldens, 2013;Suarez et al, 2014;Folli et al, 2015;Gallus et al, 2015;George et al, 2016;Jiménez-Relinque et al, 2019;Cordero et al, 2020).…”