A boron-doped ZrS ₂ monolayer as a promising gas sensing material for the detection of volatile organic compounds: a DFT study

Detecting volatile organic compounds (VOCs) with high sensitivity and selectivity is essential for environmental monitoring and health protection. This study employs first-principles calculations to explore the structural, electronic, and adsorption properties of pristine and boron-doped ZrS₂ (B-ZrS₂) monolayers toward key VOCs: formaldehyde (CH₂O), methanol (CH₃OH), acetaldehyde (CH₃CHO), and acetone (C₃H₆O). Boron atoms stably incorporate at hollow sites, forming strong covalent B-S bonds and significantly narrowing the band gap from 0.861 eV to 0.091 eV. Pristine ZrS₂ exhibits weak physisorption and minimal charge transfer with VOCs, limiting sensing capability. In contrast, B doping creates chemically active sites that promote chemisorption through B-O bond formation and enhanced charge transfer. Density of states analyses reveal strong electronic coupling between adsorbates and the B-ZrS₂ surface, causing notable electronic structure changes. Frontier molecular orbital theory shows that VOC adsorption increases the band gap, reducing electrical conductivity and modulating the sensor signal. Calculated sensitivities indicate that B-ZrS₂ responds effectively to all four VOCs at room temperature, especially CH₃OH, with rapid recovery facilitated by temperature-dependent desorption kinetics. Among typical atmospheric interferents like N₂, O₂, CO₂, and H₂O, the pronounced chemisorptive interaction between O₂ and the B-ZrS₂ surface could potentially disrupt the sensing of VOCs. Overall, these results demonstrate that B-ZrS₂ is a promising, sensitive, selective, and thermally adaptable resistive-type gas sensor for the detection of environmental VOCs.