A Review of the Use of Nano-Catalysts for Air Quality Improvement with Emphasis on Vehicle Exhaust Treatment

Air pollution remains a threat to human health and environment particularly in the places where traffic and industries are denser. Nano-catalysts have emerged as a promising prospect of enhancing the quality of air due to their high surface area and controllable reactivity alongside their capability to decompose pollutants at mild operating conditions. This review examines more recent advances in the field of nano-catalyst based air purification with specific focus on vehicle exhaust treatment. Photocatalytic nano materials have great potential for removing Nitrogen Oxides (NOx), Volatile Organic Compounds (VOCs) and particulate matter with the help of adsorption and oxidation mechanisms. These materials include TiO2, graphene, perovskites, metal oxides and metal-organic frameworks. They have also tested their performance in catalytic converters, diesel particulate filters and in photocatalytic coating that have been applied to transport infrastructures. This review will discuss the various categories of pollutants, limitations of traditional methods of air purification, nano-catalytic activity and as well as the updated advancements of nano-enabled filters. It also highlights the new technologies such as plasma-assisted photocatalysis, electrospun nanofibre filters and the graphene-enhanced filtration networks which are more durable and have higher degradation efficiency. Despite these materials showing good laboratory scale performance, there are still questions on their toxicity, environmental exposure, cost and long-term stability. This review also discusses these challenges along with future research interests that are focused on safer material designs and intelligent catalytic systems for vehicle emission control. In general, nano-catalysts offer cleaner air and more efficient purification of vehicle exhausts. These might support a shift towards healthier urban environments.