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

Abstract

The development of highly active single-atom catalysts (SACs) to gain insights into NO_x reduction is an attractive route for NO_x removal. Herein, for the first time, atomically dispersed transition metal-coordinated graphite carbon materials were synthesized for NO_x 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 NO_x conversion and N₂ selectivity. A TOF of 1.8 h⁻¹ with a NO_x conversion of 98.0% and N₂ selectivity of 92.1% was achieved using 4% K/Mn-SAC at 275 °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.