The physical properties of Li-doped g-C3N4 monolayer sheet investigated by the first-principles

• Systematically research on Li-doped g-C3N4 monolayer sheets by first-principles calculation.
• Optimal dopant concentration for optical absorption is 7.12%.
• Thermodynamics stability of the doped substrate g-C3N4 decreased with Li dopant concentration increasing.
• The values of work function Φ decreased monotonously with the increasing of Li dopant concentration.

The geometric, electronic, optical properties, thermodynamic stability, and work function of Li-doped g-C3N4 monolayer were investigated by the first-principles calculation. It was found that the Li atoms were preferentially substituted the open-hollow sites of g-C3N4. Interestingly, the “odd” number of Li doped g-C3N4 showed metallic properties, while the “even” number of Li atoms widened the band gap of g-C3N4. The HOMO and LUMO distributions reveal that the active sites located at edge N and C atoms for both pristine and the Li-doped g-C3N4. In addition, thermodynamic analysis showed that the doped Li atoms reduced the thermodynamic stability of g-C3N4 monolayer sheets.

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