High selectivity of H₂O₂ activation to ·O₂^– for efficient NO oxidation over Co single-atom catalyst

NO oxidation with H₂O₂ as the oxidant is a promising green denitration technology. However, the current metal oxide catalysts still have many disadvantages for this reaction, such as insufficient catalytic activity for H₂O₂ activation, poor selectivity, and low stability. In this study, we employ atomically dispersed Co anchored on SBA-15 with Co-O₄ structure for NO oxidation, which achieves a 90% removal efficiency of NO under low molar ratio of H₂O₂ to NO (1.56), ultra-low temperature (80 °C), and ultra-high space velocity (720,000 h^–1), representing the top-level performance among previously reported catalysts. More interestingly, our work reveals that by taking advantage of the uniform Co-O₄ structure, H₂O₂ is mainly directionally converted into ·O₂^– at the Co-O₄ site, and ·O₂^– plays a key role for achieving the deep-oxidation of NO to produce NO₃^–, which is contrast to the previously reports that ¹O₂ is the main free radical for NO oxidation. This study highlights the great potentials of single-atom catalysts for improving the H₂O₂ utilization performance for NO oxidation.