One-step synthesis of Al2O3/Al-doped g-C3N4 heterostructures for efficient photocatalytic H2 evolution and CO2 reduction

Photocatalytic water splitting and CO 2 reduction offer renewable pathways for generating green fuels. Nevertheless, traditional photocatalysts are often limited by rapid electron-hole recombination. To address this difficulty, we devised a one-step thermal calcination method that concurrently doped graphitic carbon nitride (g-C 3 N 4 ) with aluminum and generates Al 2 O 3 in situ, an Al-doped g-C 3 N 4 heterojunction. Upon excitation by visible light, photo-excited electrons in Al-doped g-C 3 N 4 transfer to the surface Al 2 O 3 nano domains, which act as an electron sink due to their defective and reduced bandgap structure, and holes remain on g-C 3 N 4 . The effective charge separation is facilitated by interfacial band bending and the consequent internal electric field at the heterojunction that collectively inhibits electron-hole recombination and extends charge-carrier lifetimes for redox processes. The Al-doped g-C 3 N 4 /Al 2 O 3 catalyst attains a hydrogen evolution rate 9.4 times greater and a CO 2 reduction rate 6.5 folds greater than pristine CN when exposed to visible-light illumination. The improvement in performance highlights the capability of our single-step designed photocatalyst for solar-driven hydrogen production and CO 2 -to-fuel conversion, supporting the goal of carbon-neutral fuels and the progress of renewable green energy solutions.