Zn1-xCuxAl2O4 solid solution synthesized by a facile modified sol-gel method for photocatalytic hydrogen generation

Abstract

This work reports the photocatalytic hydrogen generation through the use of Zn1-xCuxAl2O4 solid solution materials synthesized by a modified sol-gel technique. The materials were studied using X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscope (SEM), UV–vis spectroscopy, cyclic voltammetry, chronoamperometry, and EIS. According to analysis by X-ray diffraction, the photocatalysts synthesized present the spinel structure type, furthermore, morphological analysis shows the irregular shape nanoparticles. Bandgap energy was estimated from the UV–Vis data using the Tauc plot, finding values between 1.88 and 4.53 eV. Using the bandgap energy values, the position of the valence and conduction bands was determined in two ways, Mulliken electronegativity and cyclic voltammetry. Through the generation of H2 by division of water, the activities of the photocatalysts were tested under UV-light irradiation without the use of a sacrificial agent, where the highest activity was obtained by Zn0.1Cu0.9 (295.56μmolg−1h−1) and the lowest by Zn0.9Cu0.1 (26.03μmolg−1h−1), thus increasing up to 11 times the hydrogen production by increasing the Cu content to 0.9 at %. Likewise, the highest performance was attributed to an appropriate coupling of the electronic band of the semiconductors and the presence of CuO segregations in the sample. In addition, due to the high current density that was relational to the decreasing recombination of the photogenerated carriers.