Transition-metal single atom catalyst embedded in C₂N for toxic-gas reduction reaction and selective gas-sensing application: Atomic-scale study

Exploring advanced materials for detecting noxious gases is a key requirement for maintaining healthy air quality in the environment. The catalytic activity of four magnetic transition metal “TM” elements (e.g., Mn, Fe, Co and Ni) embedded in C₂N pores, as single-atom catalysts (SAC), has been tested towards detecting toxic oxidizing gases. As a model, we tested the sensing efficiency of these catalysts towards two toxic gases, namely NO and NO₂. For our calculations, we have used a formalism based on the combination of density functional theory (DFT) and non-equilibrium green's function (NEGF). From our findings we have drawn a strong correlation between the sensor response and the reduction in magnetization (ΔM ≅ −1.40 to −0.55 μ_B). The results of spin-polarized transport properties showed that Ni- and Fe-embedded C₂N are the most efficient in detecting NO/ NO₂ and NO₂ molecules (with ΔM/M₀ = −98%, −38% to −18%, respectively). The main reason for the magnetization reduction was the formation of chemical bonds between SAC and molecules thereby causing an enormous reduction in the number of unpaired d-electrons. Thus, Fe- and Ni-C₂N are recommended for either toxic-gas reduction reactions or platform materials in disposable gas sensors for efficient capturing of toxic gases.