Coupled surface-internal structural engineering in the skeleton of graphite carbon nitride for efficient photocatalytic hydrogen production

The enhanced driving force of charge carriers is crucial for improving the efficiency of photocatalytic hydrogen evolution of graphite carbon nitride (CN). N vacancy, grafted O and bridging C are successfully constructed to fabricate novel CN based photocatalyst (COV N @CN-20), using urea as precursor, maltodextrin as carbon and oxygen source via two-stage thermal polymerization. N vacancies serve as electron trap to providing more activation sites for hydroxyl and hydrogen ions. The surface grafted O becomes the electron enrichment center, providing electrons for hydrogen evolution reaction. The bridging C replaces the bridging N in the heptazine skeleton, enhancing the delocalized π state of electrons within the inner layer. The coupling effect of N vacancy, grafted O and bridging C facilitates band gap narrowing and promotes the efficient separation and migration of surface charge in COV N @CN-20. The experiments of photocatalytic hydrogen production indicate that the hydrogen yield of COV N @CN-20 reaches 1720.32 μmol g −1 without the need for any co-catalysts, 37.50 times than that of CN. The theoretical calculations indicate that the coupled surface-internal bridging engineering optimize its inherent electronic properties through surface defects, self-build-in electric field and electron enrichment, thereby improving carrier utilization for efficient hydrogen production.