Nanostructured systems to combat NOx air pollution through Vis-light activated nanoarchitectonics: how, where and why…?

Abstract

Nitrogen oxides (NOx) gases generated from various anthropogenic sources have a very detrimental impact on both human health and the environment. Among the possible routes for their efficient removal from the atmosphere (DeNOx), a mandatory issue in compliance with the ever more stringent regulations, photocatalytic processes offer sustainable and eco-friendly toolkits for NOx elimination at parts per billion (ppb) levels. To date, a great deal of work has been performed on UV-activated photocatalysts based on TiO2, but real-world applications require the use of Vis-light-active materials enabling to effectively harness solar energy, a renewable and largely available and natural resource. In this general framework, the present contribution provides an original summary of recent advances in the preparation, characterization and functional validation of Vis-active DeNOx photocatalysts free from TiO2, an overview which, to our knowledge, is not available in the literature to our knowledge. In particular, the attention is concentrated on a tailored nanostructure control in the target materials, with particular focus on nano- and heterocomposites enabling an improved charge carrier separation and, hence, enhanced performances. The main issues in preparation and characterization, with particular regard to the catalyst stability and selectivity towards NOx conversion into harmless nitrates, are discussed in relation to selected materials categories, with an eye on multi-faceted design strategies and on the outlook of Vis-light active, TiO2-free DeNOx photocatalysts. The presently proposed overview is expected to inspire frontier advancements in the mastering of Vis-light active photocatalysts for air purification, an issue of key importance to promote an effective sustainable development.

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