Enhancing sensitivity of C₃N monolayer to CH₄ molecule through doping 3d transition metal: A first-principles study

Methane (CH₄) is a highly flammable and explosive gas, underscoring the urgent need for the development of reliable sensors to ensure safety. Traditional methane sensors, relying on metal oxide semiconductors, face significant limitations due to poor conductivity at lower temperatures. In contrast, monolayer C₃N—a newly developed hexagonal nanomaterial composed of carbon and nitrogen—emerges as a promising alternative, exhibiting superior chemical reactivity and structural stability compared to graphene. Here, we employ first-principles methods to systematically investigate the electronic properties and surface adsorption characteristics of monolayer C₃N doped with various 3d transition metals, with a specific focus on its sensitivity to CH₄ adsorption and the underlying interaction mechanisms. Through the optimization of the C₃N structure during the methane adsorption process and an analysis of the effects of different metal dopants, we uncover universal trends that enhance surface gas adsorption sensitivity. Moreover, we evaluate the gas-sensing capabilities of doped C₃N for other gases, including H₂S, CO₂, H₂O, and N₂, providing a comprehensive assessment of its potential for next-generation gas sensors. These findings offer valuable insights into how doping can modulate the surface gas adsorption properties of C₃N, paving the way for the design of efficient sensors employing doping strategies.