Bandgap Modulation via Al Photodeposition on C-Doped g-C3N4 for Enhanced Photocatalytic Hydrogen Production

Abstract

g-C₃N₄ has drawn more and more attention because of its visible-light activity, facile synthesis from easily available and low-cost precursor materials, chemical stability, and layered structure. However, the photocatalytic activity of a pure g-C₃N₄ photocatalyst is hindered by its narrow absorption range, small surface area, and fast electron–hole recombination rate. To cope with this issue, aluminum-deposited C-doped g-C₃N₄ (Al_n/C_7.5-MA) was synthesized by the polycondensation of melamine and sucrose, followed by in situ photodeposition of Al. The XPS and EDX analyses confirmed the successful deposition of Al nanoparticles over the C_7.5-MA surface. The synthesized photocatalyst was employed to generate hydrogen (H₂) via photocatalytic water splitting. Al₁₀/C_7.5-MA showed the most significant photocatalytic efficiency, achieving an H₂ evolution rate of 14167 μmol g^–1 h^–1, which is 1.6 and 11.5 times greater than that of C-doped g-C₃N₄ and pristine g-C₃N₄, respectively. The comprehensive analysis demonstrated that C-doping followed by deposition of Al considerably narrowed its bandgap, expanded the light absorption range, boosted photoresponse, and improved photogenerated charge carrier separation due to the surface plasmon resonance (SPR) effect of Al. The findings emphasize the synergistic effect of C-doping and Al deposition in improving the photocatalytic ability of g-C₃N₄, presenting a viable approach for sustainable H₂ production under visible-light irradiation.