Abstract
In this paper, the Ag-doped zinc oxide nanorods embedded reduced graphene oxide (ZnO:Ag/rGO) nanocomposite was synthesized for photocatalytic degradation of methyl orange (MO) in the water. The microstructural results confirmed the successful decoration of Ag-doped ZnO nanorods on rGO matrix. The photocatalytic properties, including photocatalytic degradation, charge transfer kinetics and photocurrent generation, are systematically investigated using electrochemical impedance spectroscopy (EIS), photocurrent transient response (PCTR) and open circuit voltage decay (OCVD). The results of photocatalytic dye degradation measurements indicated that ZnO:Ag/rGO nanocomposite is more effective than pristine ZnO to degrade the MO dye, and the degradation rate reached 40.6% in 30 min. The decomposition of MO with ZnO:Ag/rGO nanostructure followed first-order reaction kinetics with a reaction rate constant (Ka) of 0.01746 min−1. The EIS, PCTR and OCVD measurements revealed that the Ag doping and incorporation of rGO could suppress the recombination probability in ZnO by the separation of photo-generated electron–hole pairs, which leads to the enhanced photocurrent generation and photocatalytic activity. The photocurrent density of ZnO:Ag/rGO, ZnO/rGO and pristine ZnO are 206, 121.4 and 88.8 nA cm−2, respectively.
Highlights
In day-to-day life, water contamination is one of the serious issues for humankind and the environment
The electrochemical impedance spectroscopy (EIS), photocurrent transient response (PCTR) and open circuit voltage decay (OCVD) measurements revealed that the Ag doping and incorporation of rGO could suppress the recombination probability in ZnO by the separation of photo-generated electron–hole pairs, which leads to the enhanced photocurrent generation and photocatalytic activity
This study reveals that the photocurrent properties of ZnO can be markedly improved by the addition of rGO and Ag doping
Summary
In day-to-day life, water contamination is one of the serious issues for humankind and the environment. Among the other metal oxides, ZnO is the first and widely used material in heterogeneous photocatalysis [7,8,9,10] It has numerous advantages in the photocatalytic process, the fast recombination of photo-excited charge carriers in ZnO hinders the photocurrent generation and photocatalytic efficiency. The defects and vacancies act as the recombination centre for photo-induced electrons, which improves the diffusion of photo-generated electrons in ZnO, facilitating the charge carrier separation and thereby reducing the recombination rate [23] In this context, Wang et al have reported that the photocatalytic activity of ZnO was enhanced due to silver doping. The electrochemical properties, including the photocatalytic activity, charge transfer kinetics, photocurrent generation, are systematically investigated from photocatalytic degradation of methyl orange (MO) dye, electrochemical impedance spectroscopy (EIS), photocurrent transient response (PCTR) and open circuit voltage decay (OCVD)
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