First-principles investigation of transition metal and nitrogen co-doped graphene as gas-sensing materials for poisonous and hazardous gas molecules

Carbon monoxide (CO), sulfur dioxide (SO₂), and ammonia (NH₃) are three prevalent hazardous gases that pose significant threats to human health and the environment. Therefore, there is an urgent need for highly efficient gas-sensitive materials to detect harmful gases. Perfect graphene (PG) is considered an excellent gas-sensitive material because of its substantial surface area and superior electrical characteristics, yet its chemical inertness restricts its sensitivity. This study utilized density functional theory (DFT) to induce defects onto the PG surface, thus creating defective graphene (DG). Thereafter, transition metal atoms: scandium(Sc), titanium(Ti), vanadium(V), and chromium(Cr) were co-doped with nitrogen(N) atoms into DG to produce MN_xC_4-x-DG (x = 0–4, M = Sc/Ti/V/Cr) structures, and their stability was examined. Based on the most stable configuration MN₄-DG (M = Sc, Ti, V, Cr), its adsorption behavior for the three gases was studied. The research results indicate that the formation of defects and the co-doping of transition metals and N atoms enhance the adsorption capacity of PG for three toxic and harmful gases. The material qualities were analyzed in terms of recovery time, sensitivity, and selectivity. The findings indicated that the TiN₄-DG and CrN₄-DG structures demonstrate regenerative ability, rapid response characteristics and selectivity establishing a theoretical foundation for advancing novel gas-sensitive materials.