Enhancing AsH3 Gas Adsorption Potentials of Graphitic Carbon Nitride by Codoping Cr/P, Mo/P, and W/P Atoms: A DFT Investigation

The adsorption mode of arsine (AsH3) molecules on the P‒doped, Cr‒, Mo‒, W‒embedded, and also Cr/P‒, Mo/P‒, and W/P‒codoped graphitic carbon nitride (g-C3N4) compounds were investigated upon density functional theory (DFT) computations. The calculated adsorption energy of AsH3 gas on the aforementioned systems were -0.508, -2.413, -2.642, -3.094, -2.432, -2.702, and -3.105 eV, respectively. These results displayed that the sensitivity of g-C3N4 system for the adsorption of AsH3 gas can be significantly improved by introducing an appropriate transition metal (TM) dopant. Therefore, the TM/P–modified g-C3N4 systems were found more suitable for adsorption and detection of AsH3 gas than the pure g-C3N4 system. Furthermore, the band structure results illustrated that with codoping of Cr/P, Mo/P, and W/P atoms on the g-C3N4 and then adsorption of AsH3 molecules, the electrical conductivity of systems remarkably reduces due to the created new impurity energy levels close to the Fermi level. The results of the relaxed structures revealed that with adsorption of AsH3 on the g-C3N4 and the modified g-C3N4 with TM/P atoms, the initial structure of g-C3N4 system automatically chances from planar to wrinkles structure. In addition, the results of charge transfer analysis showed that the electron density accumulation region is located on the orbitals of AsH3 molecules, resulting from the electron transfer from TM‒modified g-C3N4 systems to AsH3 gas. Overall, it can be inferred that the W/P–codoped g-C3N4 with the highest adsorption energy of -3.105 eV is more suitable than those of Cr/P‒ and Mo/P‒codoped g-C3N4 systems for detecting and removing of AsH3 molecules from the environment.