Gadolinium doped-zirconium oxide-graphitic carbon nitride heterostructures for photocatalytic degradation of eosin yellow dye in water

In this paper, we present the impact of gadolinium (Gd) on the structure, optical absorption, and photocatalytic activities of zirconium oxide-graphitic carbon nitride (ZrO₂-g-C₃N₄) nanocomposites for the decomposition of eosin yellow (EY) dye in synthetic wastewater. Chemical co-precipitation was used to synthesize the photocatalysts, which was then followed by calcination. The structural examination of the synthesized samples showed that the bare ZrO₂ possesses the monoclinic phase of zirconium oxide. However, a complete monoclinic to cubic phase transformation occurred in the nanocomposites at a relatively higher dopant concentration. Additionally, optical absorbance measurement exhibited a reduction in bandgap from 3.82 to 3.17 eV which was attributed to the creation of defect states within the forbidden gap of the metal oxides, brought about by the introduction of both the Gd and the g-C₃N₄. The degradation outcome indicated that incorporating Gd into the ZrO₂-g-C₃N₄ system substantially improved its degradation activities. The tremendous degradation efficiency was confirmed to rise remarkably from 30 % to 97 %, with a corresponding rate constant (k) of $5.7\times {10}^{-4}{\min }^{-1}$ and $17.1\times {10}^{-2}{\min }^{-1}$. The photodegradation results of this study showed that the optimum dopant percentage concentration was found to be 0.8 % Gd, beyond which a decline in the photocatalytic efficiency was realized. The enhanced photodegradation performances of the Gd-ZrO₂-g-C₃N₄ heterostructures were attributed to numerous factors such as enhanced light absorption, efficient charge separation, and enhanced surface area.