Original exploration of transition metal single-atom catalysts for NOx reduction

The development of highly active single-atom catalysts (SACs) to gain insights into NOx reduction is an attractive route for NOx removal. Herein, for the first time, atomically dispersed transition metal-coordinated graphite carbon materials were synthesized for NOx reduction. The effects of different synthesis factors (carbon support, transition metal species, metal content, calcination atmosphere, and catalyst promoter) on the catalytic activity were investigated. The atomic dispersion of Mn sites and their coordination structure were confirmed by aberration-corrected electron microscopy atomic resolution and X-ray absorption fine structure analysis. Mn-SAC with 5% Mn loaded on graphite carbon demonstrated a stable catalytic activity while proper K doping promoted NOx conversion and N-2 selectivity. A TOF of 1.8 h(-1) with a NOx conversion of 98.0% and N-2 selectivity of 92.1% was achieved using 4% K/Mn-SAC at 275 degrees C. The catalyst framework of the Mn-C-N-O structure was partly decomposed due to the reduced C(O)O and metal-N groups. This study is beneficial for exploiting the design of single-atom catalysts and promoting their applications.