Iron-based catalysts for NO_x reduction: Reaction mechanism and anti-poisoning strategies

Iron-based metal oxide catalysts are widely used for selective catalytic reduction (SCR) of NO_x with NH₃ due to their excellent catalytic performance at medium and high temperatures, high nitrogen selectivity, robust resistance to sulfur dioxide poisoning, environmental sustainability and cost effectiveness. However, several challenges including sub-optimal low-temperature catalytic activity, narrow operating temperature range, poor resistance to alkali/alkaline earth metal poisoning, as well as insufficient thermal stability and H₂O/SO₂ resistance always hinder the further application of iron-based metal oxide catalysts, which is in urgent need of further improvement in practical applications. This review provides a comprehensive overview of the development, applications and challenges associated with different types of iron-based metal oxide catalysts and suggests corresponding modification strategies to address the as-mentioned issues. Iron oxide catalysts can promote low-temperature catalytic performance by adjusting crystal structures and exposing specific crystal faces; however, their thermal stability and resistance to SO₂/H₂O and alkali metals still have substantial room for improvement. Iron-based composite metal oxide catalysts can effectively increase the resistance to SO₂/H₂O by coupling multiple metals and modulating adjacent electronic sites. Iron-based acidic salt catalysts greatly enhance the resistance to alkali metal poisoning by enriching the surface acid sites and providing sacrificial sites. Supported iron-based metal oxide catalysts can significantly improve both catalytic performance and resistance by modulating reaction pathways and constructing core-shell structures. This review clarifies the important direction of further research on iron-based metal oxide catalysts, and provides scientific basis and design ideas for the development and application of high-efficiency low-temperature NO_x reduction catalysts.