Abstract:The reduction of nitrogen oxides (NOx) in industrial flue gas is crucial for achieving coordinated control of fine particulate matter (PM2.5) and ozone (O3) in China′s atmosphere. The most common NOx removal method for stationary sources is selective catalytic reduction (SCR) technology using NH3 as a reducing agent, referred to as NH3-SCR. However, the negative effects associated with NH3 introduction, such as secondary pollution caused by NH3 slip and higher carbon emissions, have gradually attracted widespread attention in recent years. This article provides a review and outlook on the research status and application prospects of selective catalytic reduction technology using carbon monoxide (CO) as a reducing agent (CO-SCR). Research has shown that developing high-performance catalysts is the key challenge for CO-SCR technology. CO-SCR catalysts can be broadly categorized into two types: transition metal oxides and supported noble metal materials. Typical catalysts, including Cu-, Co-, Mn-, and Ir-based catalysts, are reviewed in this article. The microscopic reaction process of CO-SCR involves three main steps: (1) the adsorption of reactant molecules, (2) the conversion of intermediate molecules, and (3) desorption and diffusion of product molecules. Among these steps, the preferential adsorption of NO molecules on the active site, followed by dissociation, is deemed to be the rate-determining step. The interaction between NO and the substrate strongly depends on the surface state and tends to occur at oxygen vacancies on transition metal oxides, while it occurs at unsaturated coordination cation centers on supported noble metal materials. In addition, the impact of CO/NO, oxygen (O2), sulfur dioxide (SO2), and water vapor (H2O) on CO-SCR performance has also been discussed in detail. For example, on the surface of Ir-based catalysts, Ir0 (serving as the main active site) is unlikely to remain unchanged throughout the entire reaction process. It is anticipated that Ir0 will be converted to oxidized Irδ+ after donating electrons to the anti π* orbital of the NO molecule. If new electrons are not replenished promptly, the catalytic activity will gradually decrease as oxidized Irδ+ becomes the predominant species, which is the primary reason for the poor stability of the catalyst in the presence of O2. Interestingly, SO2 stabilizes the catalyst and facilitates the generation of Ir0 sites under O2-containing conditions. Therefore, future research should prioritize the development of catalysts tailored to specific applications, and refine the CO-SCR reaction model under diverse conditions, with a focus on synergistic technologies such as the selective circulation coupling of CO-SCR in steel sintering flue gas. Furthermore, the high cost of catalysts remains a crucial obstacle hindering the widespread adoption of CO-SCR technology. Close-