Impact of Gd on the photocatalytic performance and hydrogen evaluation of the cubic phase of ZrO2

Abstract

Zirconium dioxide (ZrO₂) in the cubic phase has been identified as a suitable material for use as a photocatalyst. However, its wide bandgap (∼5 eV) prevents it from efficiently absorbing visible light, which is a necessity in solar-induced photocatalytic processes. In this paper, the result of gadolinium (Gd) doping on the cubic ZrO₂ material in terms of structural, optical, and photocatalytic properties is examined. To make Gd-doped cubic ZrO₂, the sol-gel technique was employed, and the prepared samples were characterized by XRD, scanning electron microscopy (SEM), UV–visible spectroscopy, and EIS spectroscopy. A critical evaluation of the XRD results demonstrated that the cubic phase of ZrO₂ was stabilized by Gd incorporation, and the volume lattice increased from 134 to 135 Å³. Furthermore, UV–vis spectroscopy substantiated the decrease in the bandgap (from 5.0 eV for undoped ZrO₂ to 4.4 eV for the 2.5 wt% Gd-doped sample), thereby facilitating enhanced visible light absorption. The photocatalytic nature of the materials was confirmed through the degradation efficiency of methyl Orange (MO) dye under a visible light source. The enhanced photocatalytic activity of the optimized Gd-doped cubic ZrO₂ was observed as the degradation efficiency reached 79 % within 120 min, while that of the undoped ZrO₂ was 55 %. These improved performances are due to the combined reduction of the band gap, better charge separation, and higher surface reactivity stimulated by Gd doping. This fact was reflected in the results obtained and demonstrated the prospects of using Gd-doped cubic ZrO₂ as an effective photocatalyst for cleaning the environment and using solar energy. This work offers a good understanding of rare-earth doping for engineering ZrO₂'s properties and an effective approach for synthesizing superior photocatalysts.