Designing robust M–N–C single-atom catalysts for NOx sensing

Sensitive and selective detection of nitrogen oxides (NOx) is increasingly critical for both environmental protection and human health. However, current detecting methods are based on metal oxide sensors, which are greatly limited by issues of high energy consumption, low selectivity, and poor environmental compatibility. Herein, we systematically explore the potential of eleven experimentally available transition metal single atoms (M = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in nitrogen-doped graphene (M–N–C) for NOx detection. It is revealed that Ni–N–C exhibits exceptional selectivity and sensitivity toward NOx, as evidenced by the preferable and moderate adsorption strength and significant changes in microscopic electronic structures and macroscopic current–voltage characteristics. Furthermore, applying proper external electric fields or strains enables to accelerate the recovery of Ni–N–C. This work highlights the promising potential of Ni–N–C for real-time NOx monitoring and offers valuable insight into the application of single-atom catalysts in sensing.