Synthesis and Characterization of 1D FeVO4@ZnO (n-n type) Heterojunctions for Enhanced Photoelectrochemical (PEC) Water Splitting

Abstract

One dimensional metal oxides are attractive nanomaterials for photoelectrochemical water splitting application due to the fast charge diffusion in one directional pathway. In this work I have studied the morphological effect of precursor growth solution concentration on one dimensional ZnO. Different morphologies including nanowires, nanorods, nanotubes and nanoflakes was obtained in just one step hydrothermal process at different concentrations of 25 mM, 50 mM, 100 mM and 200 mM respectively. Heterojunction of FeVO4@ZnO were prepared by 3x, 6x and 9x times spin coating of FeVO4. These Morphological structures were confirmed by XRD, SEM-EDX and Raman Spectroscopy. Thickness and surface roughness were calculated by AFM and optical profilometry. UVVis Spectroscopy indicated the red shift in band gap of the ZnO which was further reduced by heterojunction formation due to the enhanced absorption in visible region. The photoelectrochemical and electrochemical study was done in three electrode system by using Na2SO3 (pH=7.5) electrolyte. Electrode prepared at 100 mM concentration have nanotubes of ZnO showed maximum current density of 1.18 mA/cm2 at 1.23 V vs RHE with donor density of 4.59x1013 and electron life time of 356.9 μs under illumination. The formation of heterojunction of FeVO4@ZnO nanotubes further enhanced the current density up to 2.67 mA/cm2 at 1.23 V vs RHE in 6x coated FeVO4 with increased donor density of 8.52x1013 cm-3 and reduced lifetime of electron up to 86.4 μs under illumination. Chronoamperometry up to 600 s of illumination at 1.23 V vs RHE showed that all the electrodes are stability. Mott-Schottky analysis under dark showed the flat band potential of 0.47 V for 6x coated FeVO4@ZnO nanotubes.