Decorating tungsten single atoms on MnO nanorods for enhanced selective catalytic reduction of NO with NH.

Manganese dioxide (MnO) shows significant potential for selective catalytic reduction with NH (NH-SCR). However, the selectivity and water vapor tolerance of MnO are generally unsatisfactory. This study tackles these issues by decorating tungsten single atoms (W SAs) onto MnO nanorods. The resulting W/MnO catalysts exhibit markedly improved performance, especially the 1.8 wt% W/MnO catalyst, which exhibits superior reactivity (over 90% conversion and over 80% N selectivity) across an extended operational temperature range of 75-350 °C, along with improved water tolerance. Structural characterizations based on X-ray diffraction (XRD) and aberration-corrected scanning transmission electron microscopy (AC-STEM) reveal that the initial W/MnO catalyst is characterized by W SAs that are partially embedded within the MnO lattice and partially dispersed on the surface. During the reaction, the catalyst undergoes structural transformations, characterized by the further incorporation of surface-dispersed W SAs into the MnO lattice. The incorporation of W SAs enhances both the surface acidity and oxygen vacancy density of the catalyst, thereby improving its catalytic performance. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies suggest that the NH-SCR reaction proceeds via both the Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. This work provides valuable insights into the structure-performance relationships of W/MnO catalysts in NH-SCR, offering important implications for the design and fabrication of efficient SCR catalysts.