Two-dimensional (2D) materials exhibit exceptional properties, such as a large specific surface area, high electron mobility, and unique optical characteristics, making them promising candidates for various applications, including gas sensing, batteries, and solar cells [[1], [2], [3], [4], [5], [6], [7], [8]]. In this work, we focus on investigating the electrochemical properties of a 2D material for its potential use in gas sensors and detectors. However, the low binding strength between gas molecules and 2D materials limits their usefulness in this application [9]. Various strategies have been proposed to enhance gas-material interactions, including doping, surface decoration with heteroatoms, application of strain, and introduction of electric fields [[10], [11], [12], [13], [14]]. For instance, graphene [15] and its derivatives have been extensively studied and shown high sensitivity for gas adsorption. Other 2D materials, such as silicene, phosphorene, and germanene, and Borophene [[15], [16], [17], [18], [19]] have demonstrated potential in gas sensing due to their tunable electronic properties. Among the family of synthetic 2D materials [[20], [21], [22], [23], [24], [25]], borophene, a lightweight metalloid with remarkable electronic properties, stands out as a promising candidate, despite challenges such as inherent instability when not supported, susceptibility to surface oxidation. In a recent development, Nishino et al. achieved the creation of a monolayer of hydrogen boride (HB) under room temperature conditions [26]. HB exhibits excellent properties, including stability, tunable electronic structure, and a large surface area, making it a compelling candidate for gas sensing applications. However, the interaction of HB with gases such as CO, CO2, and NO remains underexplored, particularly when modified with metallic decorations.

Despite these promising attributes, the interaction of HB with critical environmental pollutants, particularly CO2, remains underexplored. Given the increasing need for efficient gas sensors to mitigate the environmental impact of CO2 emissions, a deeper understanding of its adsorption behavior is crucial. Functionalizing HB with metallic decorations, such as lithium (Li) and iron (Fe), presents a compelling strategy to enhance its CO2 adsorption capacity and sensitivity by leveraging strong metal-gas interactions [[27], [28], [29], [30]].

In this study, we employ first-principles density functional theory (DFT) to investigate the adsorption of CO2 on pristine HB monolayer decorated with Li and Fe atoms. Fe was chosen as a dopant due to its partially filled d-orbitals, which promote strong and selective interactions with CO2 [31], Li was selected due to its low atomic mass and high electropositivity, which effectively modulate the surface charge distribution [32].

Additionally, we analyze the interactions of CO and NO to provide a comparative perspective on gas adsorption behavior. Key parameters such as adsorption energies, charge transfer, work function, and electronic properties are examined to evaluate the potential of HB as an efficient gas sensor. Our findings highlight the role of metallic decoration in improving CO2 adsorption while also offering insights into the interactions of CO and NO, paving the way for HB-based sensors in environmental monitoring and pollution control.