Effect of the sulfur termination on the properties of Hf 2 CO 2 MXene.

A computational study was carried out to investigate the effect of surface termination on Janus Hf 2 COS MXene by substituting partly the O-terminated layer with S atoms. Our predictions confirm that this chemical strategy allows one to tailor the band gap of MXenes. Indeed, the semiconducting character of Hf 2 CO 2 MXene decreases by the exchange of O by S atoms. From a structural point of view, dynamical, mechanical, and thermal analysis confirm the thermodynamic stability of the Janus Hf 2 COS MXene, which shows metallic character. Furthermore, topological chemical analysis indicates an ionic nature of Hf 2 CO 2 MXene that tends to be reduced by increasing the concentration of S atoms, promoting a covalent character. Shortly, the present study illustrates how the properties of MXenes can be tailored by functionalizing them with different chemical terminations.