Fabricating a g-C3N4/CuOx heterostructure with tunable valence transition for enhanced photocatalytic activity

Abstract

Heterostructured g-C₃N₄/CuO_x nanocomposites were successfully prepared with varying the content of g-C₃N₄ via a mixed solvent-thermal method. Organic ammonia ethanolamine was used as the reductant to adjust the valence of CuO_x. Meanwhile, the bulk g-C₃N₄ was efficiently exfoliated into ultrathin nanoplates during the synthesis process. It is found that the different contents of g-C₃N₄ can effectively accelerate the valence transition of Cu in the nanocrystals. That is, the successive appearance of CuO and Cu₂O with the enhancement of g-C₃N₄ content. These heterostructured composites were characterized for structural, morphological, elemental distribution, optical properties, specific surface area and photo-generated carrier separation efficiency by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum. The photocatalytic performance investigations indicate that the CN5–CuO_x is stable enough and shows a remarkable photocatalytic efficiency for degrading methyl orange (MO) under simulated sunlight irradiation, compared with the pure CuO_x nanocrystals. The enhanced photocatalytic performance can be attributed to the enlarged surface area, beneficial heterojunction among Cu₂O@g-C₃N₄ and efficient carrier separation efficiency. The abundant Cu substrate in the CuO_x nanocrystals functions as a rapid electron/hole pair transfer avenue and inhibits their recombination. Thus the photocatalytic efficiency is tremendously enhanced.