Creation of carbon defects and in-plane holes with the assistance of NH4Br to enhance the photocatalytic activity of g-C3N4

Abstract

Microstructure modulation is an effective strategy to improve the photocatalytic efficiency of graphitic carbon nitride (g-C₃N₄) for solar energy conversion. In the present work, abundant carbon defects and holes in g-C₃N₄ have been successfully created with a novel NH₄Br-assisted programmed heating method. The decomposition of NH₄Br provides an ammonia atmosphere for the preparation of g-C₃N₄. It also acts as an exfoliating agent, which not only dramatically decreases the average layer thickness, but also creates abundant holes on the surface of planar nanosheets. The g-C₃N₄ nanosheets prepared have a significantly enlarged surface area and more exposed catalytically active sites. More importantly, carbon vacancies were simultaneously introduced in the tri-s-triazine repeating units of g-C₃N₄, which leads to greatly suppressed recombination of charge carriers and increased concentration of photogenerated electrons and holes. As a result, this holey g-C₃N₄ (CN–Br) photocatalyst showed a much higher photocatalytic H₂ evolution activity (5-fold) and photooxidative ability (12 times) under visible light irradiation in comparison with bulk CN. The newly developed synthetic strategy is simple and convenient, and might be used in the design of other efficient photocatalysts.