The elimination of the gaseous pollutants is an environmental issue of huge scientific and social interest. The contamination of urban areas by NOx gases is becoming a severe environmental and human health issue, since many towns worldwide frequently suffer peaks in NOx contamination, far superior to the current legislation’s approved values.
Photocatalysis is one of the technologies that could be applied in the remediation of this problem, where TiO2 and TiO2-based compounds are more extensively studied as one of the most efficient photocatalytic systems for the oxidative decomposition of NOx (deNOx). In this sense, a broad catalogue of titania based photocatalytic building materials (benchmark products) are known today. Unfortunately, in spite of their excellent performance as photocatalyst, TiO2 has just been proposed to be classified as suspected of causing cancer when inhaled. This could limit their applications and, therefore, a rapid advance in the study and development of new deNOx photocatalysts is required.
In this work we study the deNOx ability of ZnO based photocatalysts. Even though ZnO, a proved safe compound, is a preferred photocatalyst because its high photosensitivity, mechanical-thermal stability and tunable morphology, only very scarce studies have been recently reported for this application.
Two new deNOx photocatalysts are here presented:
i) ZnAl-CO3 LDHs. Because of their unique properties and easy preparation, layered double hydroxides (LDHs), also known as hidrotalcite-like materials, have been studied for many potential applications. In the recent years, these compounds have also emerged as an important photocatalyst group. By first time is here studied the application of LDHs to remove NO from air.
ii) ZnO/SiO2 composites prepared by a simple methodology using of rice husk ash (RHA) as photocatalyst support, a strategy successfully employed in the preparation of metals and metal oxides (photo)catalysts.
The physico-chemical characterization and photocatalytic activity of different ZnO based compounds are presented. Remarkably, the studied compounds exhibit high efficiency and selectivity towards the photocatalytic elimination of NO from air.