Band structure engineering and efficient injection rich-π-electrons into ultrathin g-C3N4 for boosting photocatalytic H2-production

Simultaneously regulate energy band structure and efficient injection rich-pi-electrons to achieving high photocatalytic H-2 evolution (PHE) activity are highly desirable. Herein, the C-substitution for N to the formation of C=C in ultrathin g-C3N4 was prepared by urea and pi-electron-rich 2-Aminopyrimidine copolymerization. DFT theory calculations and experimental results exhibit that introduction of C=C into ultrathin g-C3N4 not only narrows its band gap from 2.7 eV to 2.48 eV and produce a large number of -CH defects, but also effectively boosts the dissociation of photogenerated excitons and reduces hydrogen (H-2) adsorption energy. Additionally, compared to the pure g-C3N4, the introduction of C=C into ultrathin g-C3N4 also can increase visible light absorption and shift up the conduction band (CB) position for favor of proton reduction to produce H-2. As a result, the PHE activity of optimal C-substitution for N to obtained g-C3N4 (1840.38 mu mol h(-1) g(-1)) is higher than 6.06 times that of pure g-C3N4 under the visible-light irradiation. And the AQE value is evaluated to be 4.8% at 420 nm. This work provides a promising strategy for developing high-efficiency photocatalyst through band structure engineering and efficient injection rich-pi-electrons.