Nitrogen and phosphorus Co-doped ZnO-CdO nanocomposite with boosted photocatalytic degradation of crystal violet

Nitrogen (N) and phosphorus (P) co-doped ZnO-CdO nanocomposites were synthesized from bioprecursors such as rice (O. Sativa L.), chickpea (Cicer arietinum L.), soybean (G. max (L.) Merr) and sesame (Sesamum indicum L.) through self-doping into the ZnO-CdO composite. The as synthesized composites were characterized using PXRD, XPS, TGA, SEM, Cs-corrected (S) TEM, EDS, FT-IR, AAS and UV-vis spectrophotometer. Effect of biogenic doping on the band structures of the binary heterojunction was also studied using Density Functional Theory (DFT). The theoretical results showed that NP co-doping in ZnO-CdO nanocomposite improves the absorption edge to longer wavelengths in line with the experimental finding obtained from UV-vis measurement. Biogenic NP co-doped ZnO-CdO nanocomposites showed greater photocatalytic activity compared to the undoped congeners under visible light irradiations. Comparatively, photocatalytic activity of biogenic NP co-doped ZnO-CdO samples showed the order: soybean-ZC > chickpea-ZC > rice-ZC > sesame-ZC at optimal conditions under visible light irradiation. The binary ZnO-CdO nanocomposite also showed better photocatalytic activity compared to the host crystal ZnO under the same experimental conditions. Highest photocatalytic degradation efficiency of biogenic NP co-doped ZnO-CdO could be attributed to the lower rate of recombination of the photogenerated electrons and holes as well as its lower band gap energy and good reusability.