Facile synthesis of ZnMoO₄/AlPO₄-5 nanorod composites as visible-light-driven photocatalysts and high-performance energy storage materials

Abstract

The present article describes the facile one-step hydrothermal synthesis of single-crystalline ZnMoO₄/AlPO₄-5 nanorod composites. The physicochemical properties of the synthesized materials, such as structure, morphology, and bandgap, were determined using techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), N₂ adsorption-desorption isotherms, X-ray photoelectron (XPS), ultraviolet-visible (UV-vis), and photoluminescence (PL). The XRD pattern of synthesized ZnMoO₄/AlPO₄-5 verifies the synthesis of nanocomposites. Diffuse UV-vis spectra reveal that ZnMoO₄/AlPO₄-5 nanorod composites exhibit an indirect semiconductor with an optical bandgap between 3.15 and 3.7 eV depending on Mo : Zn ratio. In comparison to pure AlPO₄-5, ZnMoO₄/AlPO₄-5 nanocrystal composites showed significantly higher photocatalytic activity for the degradation of <i>para</i>-nitrophenol (PNP, 0.04 g l^-1), with 14, 99, 70, and 54% for AlPO₄-5, Mo : Zn (2)/AlPO₄-5, Mo : Zn (4)/AlPO₄-5, and Mo : Zn (6)/AlPO₄-5, respectively. This result might be attributed to the composite's efficient charge transfer and optimized electron-hole pair recombination. The supercapacitive ability of ZnMoO₄/AlPO₄-5 nanorod composites was also investigated in this work. For the prepared electrodes using AlPO₄-5, Mo : Zn (2)/AlPO₄-5, Mo : Zn (4)/AlPO₄-5, and Mo : Zn (6)/AlPO₄-5, the capacitance values were 400, 725, 450, and 481.25 F g^-1, respectively, at a current density of 0.5 A g^-1. This study shows that ZnMoO₄/AlPO₄-5 nanorod composites are a potential visible-light-responsive photocatalyst. The electrochemical results further demonstrate the high capacitance of ZnMoO₄/AlPO₄-5 nanorod composites toward energy-storage applications.