First-Principles Study of CO, NH₃, HCN, CNCl, and Cl₂ Gas Adsorption Behaviors of Metal and Cyclic C–Metal B- and N-Site-Doped h-BNs

Effective detection of toxic gases such as carbon monoxide (CO), ammonia (NH₃), hydrogen cyanide (HCN), cyanogen chloride (CNCl), and chlorine (Cl₂) is highly important. Herein, the potential applications of metal and cyclic carbon (C)–metal doping at the boron (B) and nitrogen (N) sites of hexagonal boron nitride (h-BN) as CO, NH₃, HCN, CNCl, and Cl₂ gas detection materials, and the performance characteristics of those systems, were investigated based on first principles. The calculated parameters for systems containing each gas along with different metal and cyclic C–metal B- and N-site-doped h-BN substrates include adsorption energy, energy band structure, charge transfer, density of states, differential charge density, and recovery time. Among the systems studied, h-BN@B-zinc (Zn)/CO, h-BN@B-Zn/HCN, h-BN@B-Zn/CNCl, h-BN@B-Zn/Cl₂, and h-BN@B-3C-tin(Sn)/Cl₂ were characterized by strong adsorption, high electrosensitivity, and strong orbital hybridization, and were unaffected by N₂ and O₂ in the air environment. In addition, the desorption performance of these systems could be improved by varying degrees by modulating the adsorption energy using an applied electric field, which further facilitated thermoelectrolytic adsorption. These results imply that metal and cyclic C–metal B- and N-site-doped h-BN can be used to realize gas-sensing devices with good gas-sensing and adsorption properties.

The doping of N-site of h-BN can significantly increase the conductivity. h-BN@B-Zn can effectively detect CO, HCN, CNCl and Cl₂, h-BN@B-3C-Sn can effectively detect Cl₂.h-BN@B-Zn and h-BN@B-3C-Sn. The substrate is not affected by air during detection. CO, HCN and CNCl can be desorbed effectively at h-BN@B-Zn at temperatures up to 334 K. Electric field can improve the desorption effect and further achieve thermoelectric desorption.