  The adsorption behavior of toxic gas molecules (NO, CO, NO2, and NH3) on
graphene-like BC3 are investigated using first-principle density functional
theory (DFT). The most stable adsorption configurations, adsorption
energies,binding distances,charge transfers,electronic band structures,and the
conductance modulations are calculated to deeply understand the impacts of the
molecules above on the electronic and transport properties of the BC3
monolayer. The graphene-like BC3 monolayer is a semiconductor with a band gap
of 0.733 eV. The semi-metal graphene has a low sensitivity to the
abovementioned molecules. However, it is discovered that all the above gas
molecules are chemically adsorbed on the BC3 sheet with the adsorption energies
less than -1 eV. The NO2 gas molecule is totally dissociated into NO and O
species through the adsorption process, while the other gas molecules retain
their molecular forms. The amounts of charge transfer upon adsorption of CO and
NH3 gas molecules on BC3 are found to be small. Hence, the band gap changes in
BC3 as a result of interactions with CO and NH3 are only 4.63% and 16.7%,
indicating that the BC3-based sensor has a low and moderate sensitivity to CO
and NH3, respectively. Contrariwise, upon adsorption of NO or NO2 on BC3, a
significant charge is transferred from the molecules to the BC3 sheet, causing
a semiconductor-metal transition. It is found that the BC3-based sensor has
high potential for NO detection due to the significant conductance changes,
moderate adsorption energy, and short recovery time. More excitingly, the BC3
is a likely catalyst for dissociation of the NO2 gas molecule. Our findings
divulge promising potential of the graphene-like BC3 as a highly sensitive
molecular sensor for NO and NH3 detection and a catalyst for NO2 dissociation
