Dopant inculcated ZnO based photoelectrodes for revitalizing photoelectrochemical water splitting

Abstract

In this present work, Sn and Al co-doped ZnO nanorods (NRs) were prepared for photoelectrochemical water splitting (PEC) application. Inspite of having a great deal of optoelectronic properties, the wide bandgap of ZnO semiconductor confines its photoelectrochemical performance supressing the charge separation efficiency. Modification of charge separation efficiency requires band engineering of the semiconductor. For bandgap modulation, introduction of dopants was found to be an effective method. X-ray diffraction (XRD) and Field emission scanning electron microscope (FESEM) study revealed that the grown NRs showed a hexagonal wurtzite structure. The UV–Vis absorption spectroscopy manifested the enhancement of absorbance in the visible region with the introduction of dopants in ZnO lattice structure, while diminishing the bandgap from 3.26 eV to 2.87 eV for Sn0.05Al0.03Zn0.92O. Under visible light illumination (20 mW/cm2) the (Sn,Al) doped samples exhibited augmented photocurrent densities. The results of linear sweep voltammetry (LSV) showed that a photocurrent density of 1.87 mA/cm2 was achieved at 1.2 V vs Ag/AgCl for Sn0.05Al0.03Zn0.92O which is approximately 10 times intensified than that of ZnO NRs (0.18 mA/cm2). It also posess highest photoconversion efficiency (PCE) among all the doped samples due to its enhanced light absorption and rapid charge transfer property. Moreover, the Mott-Schottky (M-S) and Electrochemical Impedance Spectroscopy (EIS) assesments suggests that the n-type doped semiconductor had highest charge carrier density facilitated by huge separation of electron-hole pairs. The results obtained clearly gives an indication that the synthesised photocatalysts can meticulously act as an effective photoelectrode for an enhanced photoelectrochemical performance.