Insight into the effect of Li/P co-doping on the electronic structure and photocatalytic performance of g-C3N4 by the first principle

[Display omitted] •Synthesis of Li/P-g-C3N4 nanosheets for photocatalytic dye degradation.•Almost 2.6 times faster dye degradation rate compared to pristine-g-C3N4.•Improved visible light absorption and charge separation than the pristine-g-C3N4.•The combined effect of Li/P doping results in exceptional photocatalytic efficiency. In recent years element doping has been considered an essential method for developing low-cost and highly efficient graphitic carbon nitride (g-C3N4) photocatalysts for environmental remediation. In this work, we have synthesized Li and P co-doped g-C3N4 nanosheet (Li/P-g-C3N4) by a facile calcination process for the methylene blue (MB) dye degradation. With increased visible light (VL) absorption, improved electron-hole (e-/h+) pair separation, and larger surface area, the dye degradation rate constant (k) for Li/P-g-C3N4 is approximately 2.6 times faster than g-C3N4 under visible light. The density functional theory (DFT) calculation has also confirmed that Li and P co-doping into the g-C3N4 narrowed the bandgap, increased the photogenerated e-/h+ delocalization, and increased the charge transfer (CT) rate. Hence, the combined effect of metal and non-metal co-doping is the reason behind the outstanding photocatalytic efficiency of the Li/P-g-C3N4. The current study expands the performance window for metal/non-metal co-doped g-C3N4 while maintaining excellent quality.