Single-Atom Niobium-Triggered N-Type Conductivity Activation in Hexagonal Boron Nitride for Selective No2 Gas Recognition

Abstract

Hexagonal boron nitride (h-BN), a representative two-dimensional materials (2DMs), has garnered significant attention as a next-generation sensing material for gas sensors owing to its ultrahigh specific surface area and exceptional optoelectronic properties. While several studies have reported p-type h-BN as functional components in p-n gas-sensing heterojunctions, n-type h-BN-based gas sensors remain scarcely explored. This limitation stems from the tendency of conventional donor impurities (C, Si, O) to form deep-level defects within the mid-gap region of h-BN, which severely impedes effective n-type doping. In this study, we propose a single-atom niobium (Nb) anchoring strategy to activate shallow energy levels in 2D h-BN. The incorporation of Nb atoms facilitates electron donation to adjacent N atoms, establishing impurity-coupled orbital splitting that induces n-type characteristics in h-BN. The comprehensive analysis of h-BN-Nb configuration included systematic investigations of band structure, density of states (DOS), charge density difference (CDD), surface work function (SWF), adsorption energy (Eads), and gas sensing sensitivity. Notably, the modified h-BN-Nb configuration demonstrated a remarkable 20.08-fold enhancement in NO2 adsorption capacity compared to pristine h-BN, accompanied by excellent specificity in gas molecule recognition. This study establishes a novel theoretical framework and methodological paradigm for engineering single-atom-coupled 2D gas-sensing architectures.

Keywords: two-dimensional materials, h-BN, n-type, single-atom-coupled, impurity-coupled orbital, gas molecule recognition