Adsorption of alkali metals on graphitic carbon nitride: A first-principles study

The electronic and optical properties of the adsorption of alkali metals (Li, Na, K, Rb, Cs) on graphitic carbon nitride (g-C 3 N[Formula: see text] were calculated and studied based on the first principles of density functional theory. The results investigate that alkali metals adsorbed g-C 3 N 4 has metallic properties, while intrinsic g-C 3 N 4 was semiconducting. Importantly, the charge density differential investigated the charge transfer discovered between the alkali metal and the g-C 3 N 4 monolayer. Meanwhile, the charges (electrons) transfer from the alkali metals to the g-C 3 N 4 system leading to the increase of most carriers in the g-C 3 N 4 system, reducing the resistance of sensors, which is conducive to sensor detection applications. The work function of g-C 3 N 4 decreased from 4.82 eV to 4.09 eV. Especially, the work function of Cs-adsorbed g-C 3 N 4 is the lowest at 4.09 eV, and the reduction rate is 15.15 %, indicating it easier to emit electrons from an external electric field. Moreover, the absorption spectrum of the alkali metal adsorbed on g-C 3 N 4 in the visible light range shows absorption peaks at 380 nm, 412 nm, 420 nm and 476 nm, which cover the visible light area. Thus, the alkali metals adsorbed g-C 3 N 4 system can be used for visible light catalytic. Adsorption of alkali metals can expand the application of g-C 3 N 4 in optoelectronic devices.