Influence of simultaneous cationic and anionic doping, and composite partnering on the photocatalytic dye detoxification ability of green synthesized ZnO: W:F/g-C₃N₄ nanocomposite

Tungsten (cationic) + fluorine (anionic) co-doped ZnO was coupled with 2D carbonaceous material gC₃N₄ (GCN) to form a nanocomposite via a green route using Morinda citrifolia leaf extract. This eco-friendly nanocomposite was employed as a photocatalyst to decompose toxic synthetic azo dyes rhodamine B (cationic dye) and methyl red (anionic dye). The photocatalytic ability and related material characteristics of the nanocomposite were compared with those of the undoped and doped (W, F and W + F) ZnO and reported. The nanocomposite exhibits superior photocatalytic efficiency of 98 and 94% for Rh-B and MR, respectively. The efficiency increases substantially by 15% for the cationic dye (Rh-B) when the dopants (W + F) and the composite partner are added with ZnO. Similarly, in the case of anionic dye (MR) also, the increase in efficiency is remarkable (25%). The detoxification test by seed germination experiment using two types of seeds viz. black gram and paddy confirms the near complete detoxification of the test dye molecules. The reasons for this observed augmentation in photocatalytic efficiency of the composite system and the mechanism lying behind this enhancement are addressed in this article. The structural, optical, electrical and surface morphological properties of the prepared samples were studied and their influence on the photocatalytic ability of the materials are analyzed. The results showed that ZnO: W:F/GCN nanocomposite can be used as a desirable candidate for the decomposition of anionic and cationic dyes.