Homojunction and ohmic contact coexisting carbon nitride for efficient photocatalytic hydrogen evolution

Carbon nitride (CN) has attracted intensive attention as a visible light photocatalyst, but the rapid recombination of photogenerated charge carriers limits its photocatalytic activity. Herein, we develop a new strategy to construct both homojunction and ohmic junction into CN via selectively introducing metallized CN (MCN), which leads to rapid separation and transfer of photogenerated charge carriers. The polymerization of urea in the presence of KOH creates CN homojunction with amino and cyano groups. The subsequent molten salt treatment induces a new type of cyano-terminated CN that can be converted to MCN through photodoping, forming homojunction and ohmic contact coexisting CN (HOCN). The formed HOCN photocatalyst exhibits a high photocatalytic H-2 evolution rate of 18.5 mmol.g(-1).h(-1) under visible light irradiation, 45-fold higher than that of bulk CN. This strategy provides a new idea for designing ohmic contact between semiconductor and metal, and realizing efficient photocatalysis by improving charge separation and transfer.