Adsorptive Characteristics of an HfSe₂ Monolayer Functionalized with Metal Oxides (ZnO, TiO₂) for Sensing...

Utilizing density functional theory (DFT) computational techniques, this paper examines how dissolved gases (CO, H₂, CH₄, C₂H₂, and C₂H₄) in transformer oil adhere to HfSe₂ monolayers enhanced with metal oxides (ZnO, TiO₂). The results demonstrate that the pristine HfSe₂ monolayer exhibits weak physisorption for all five gases, characterized by small adsorption energies and long adsorption distances. Upon modification with ZnO and TiO₂, the adsorption performance improves significantly, particularly for CO, C₂H₂, and C₂H₄. These improvements are reflected in stronger adsorption energies, reduced adsorption distances, and increased charge transfer, indicating stronger interactions and, in some cases, chemisorption. Among the two modified systems, ZnO-HfSe₂ demonstrates superior gas sensing potential compared to that of TiO₂-HfSe₂. The adsorption capacity follows the order C₂H₄ > C₂H₂ > CO > CH₄ > H₂ for ZnO-HfSe₂ and C₂H₂ > C₂H₄ > CO > CH₄ > H₂ for TiO₂-HfSe₂. Analysis of the electronic properties reveals that ZnO modification enhances electrical conductivity, while TiO₂ modification reduces it. Recovery time analysis suggests that both modified materials are unsuitable for H₂ and CH₄ detection due to their extremely short recovery times. However, they are promising candidates for CO, C₂H₂, and C₂H₄ sensing, with recovery times that can be optimized by adjusting the temperature. This study offers theoretical foundations for creating advanced gas sensors that utilize metal-oxide-modified HfSe₂ to identify dissolved gases present in transformer oil.