Construction of a push–pull system in g-C3N4 for efficient photocatalytic hydrogen evolution under visible light

Abstract

A facile “one-pot” method to improve the utilization of visible light using organic chemistry protocols is reported. The incorporation of acetylacetone (acac) into the conjugated polymer matrix g-C₃N₄ derived from urea (UCN) can tune the electronic structure effectively. As a result, the modified g-C₃N₄ showed a narrowed band gap and enhanced charge carrier migration and separation. Meanwhile, the high utilization ratio of visible light leads to efficient photocatalytic hydrogen evolution, and an apparent quantum efficiency (AQE) as high as 18.8% at 450 nm is achieved, exceeding that of most of the previously reported doped g-C₃N₄ photocatalysts. Furthermore, density functional theory (DFT) calculations certify the proposed structure of g-C₃N₄ by incorporation of acetylacetone and explain the enhanced ability to harvest photons due to the introduction of an electron push–pull system into the CN network. In addition, the incorporation of acac into g-C₃N₄ is also found to be applicable to other precursors (dicyandiamide and thiourea) through similar synthetic routes. Optical absorption under visible light is extended similarly, highlighting the universality of the current strategy. The work provides a route of organic chemistry to design and synthesize functional g-C₃N₄ with high photocatalytic performance.