Microwave assisted synthesis of ZnO-PbS heterojuction for degradation of organic pollutants under visible light

Ganapathy Mano,Alagan Viswanathan,Mahalingam Ashok,Subramanian Harinee,Sampath Sridhar

doi:10.1038/s41598-020-59066-4

Abstract

ZnO, PbS and ZnO-PbS heterojunction were prepared by microwave irradiation to improve the organic pollutants degradation under visible light irradiation. Hexagonal (wurtzite) and cubic crystal structure of ZnO and PbS respectively were confirmed by PXRD. Nano-plate, nano-sponge and nano-sponge imprinted over nano-sheet like morphology of ZnO, PbS and ZnO-PbS respectively were revealed through FESEM analysis. HR-TEM analysis provides the formation of heterojunction. XPS analysis shows the presence of the ZnO-PbS heterojunction. UV-Visible spectroscopy confirms the enhanced visible light response of ZnO-PbS heterojunction than the bare ZnO. The PL and EIS results indicate ZnO-PbS heterojunction exhibited lowest recombination of excitons and electron transfer resistance. Synergistic effect of ZnO-PbS heterojunction leads to efficient degradation against organic pollutants than bare ZnO and PbS. Aniline and formaldehyde were successfully degraded around 95% and 79% respectively, under solar light irradiation. As-prepared photocatalysts obeys pseudo first order reaction kinetics. HPLC analysis also confirms the successful mineralization of organic pollutants into water and CO2.

Highlights

ZnO, PbS and ZnO-PbS heterojunction were prepared by microwave irradiation to improve the organic pollutants degradation under visible light irradiation
PbS are exhibits hexagonal and cubic structures matched in Joint Committee on Powder Diffraction Standards (JCPDS) card numbers 75–1526 (a = 3.22 and c = 5.28) and 03-0614 (a = 5.96) respectively
The photocatalytic degradations were recorded around 95% and 79% for the aniline and formaldehyde respectively under solar spectrum when compared with previous report

Summary

Introduction

ZnO, PbS and ZnO-PbS heterojunction were prepared by microwave irradiation to improve the organic pollutants degradation under visible light irradiation. The photocatalytic efficiency is affected by several factors such as electron hole effective mass, diffusion length, exciton lifetime, defects, band bending, surface band structure, thermal stability and photocorrosion[20] To overcome these drawbacks, ZnO band structure was altered by several metals, non-metals and semiconductor coupling to extend its photo-response behavior into visible light region. Semiconductor coupling is an efficient method to reduce the photo corrosion and rate of recombination of excitions This leads to enhance the light harvesting ability up to the visible region without affecting its intrinsic character[6]. PbS sensitized nanomaterial’s are increased the visible light response and photo-conversion efficiencies It has unique photo physical properties such as multi exciton generation (MEG), high absorption coefficients, size dependent optical properties and optoelectronic properties[23,24]. Novel techniques required to overcome this problem to prepare the semiconductor coupled ZnO-PbS photocatalyst in large-scale production without any sacrification in efficiency

Methods

Results

Conclusion