Ultraviolet enhanced inorganic graphenylene-like ZnMgX2 (X=O, S) for sensitive and reversible detection of toxic formaldehyde at room temperature: A first-principles study

This study investigates the interaction between formaldehyde (HCHO) and newly predicted graphenylene-like ZnMgX2 (X=O, S) monolayers based on first-principles calculations. It was found that the adsorption performance of HCHO molecule on pure ZnMgX2 monolayers was favorable and exothermic in nature, exhibiting no need for the presence of a metal support. Their experimental feasibility was proven through various analyses, including the evaluation of cohesive energy, phonon dispersion and ab initio molecular dynamics (AIMD) sim-ulations. The results of the topological analysis indicate that the examined monolayers are stabilized by the mixed ionic-covalent bond. By systematically analyzing the adsorption energy, charge transfer, band gap, work function and presence of competing gases (H2O, N2, O2 and H2), their detection sensitivity and response times were determined. Under the presence of ultraviolet (UV) irradiation, the ZnMgO2 system demonstrates suitability as an electronic sensor for HCHO detection at room temperature, while ZnMgS2 with its large adsorption energy has the potential to be used for scavenging HCHO. Further investigation into the adsorption of H2O and O2 yields supporting evidence for high selectivity and improved recovery time of HCHO and potential formation of hydroxyl (center dot OH) and superoxide (O2 center dot  ) radicals, thereby establishing favorable conditions for eventual catalytic degradation of HCHO. This study will serve as a theoretical foundation for the development of HCHO gas sensors intended for both small-scale and industrial applications.