Heterostructure charge transfer dynamics on self-assembled ZnO on electronically different single-walled carbon nanotubes

Debika Devi Thongam; Harsh Chaturvedi

doi:10.1016/j.chemosphere.2023.138239

Heterostructure charge transfer dynamics on self-assembled ZnO on electronically different single-walled carbon nanotubes

Chemosphere. 2023 May:323:138239. doi: 10.1016/j.chemosphere.2023.138239. Epub 2023 Feb 24.

Authors

Debika Devi Thongam¹, Harsh Chaturvedi²

Affiliations

¹ School of Energy Science and Engineering, Indian Institute of Technology Guwahati, Assam, 781039, India. Electronic address: devi176151105@iitg.ac.in.
² School of Energy Science and Engineering, Indian Institute of Technology Guwahati, Assam, 781039, India. Electronic address: harshc@iitg.ac.in.

PMID: 36841447
DOI: 10.1016/j.chemosphere.2023.138239

Abstract

The charge transfer kinetics of the catalyst particles play a key role in advanced oxidation processes (AOP) for the complete destruction of recalcitrant and persistent contaminants in water. Here, a significant improvement in the photocatalytic performance is observed in the Single-Walled Carbon Nanotube (SWCNT)-ZnO heterostructure photocatalyst. The charge transfer dynamics and factors affecting AOP are studied using ZnO nanoparticles self-assembled onto three electronically different SWCNTs (metallic, semiconducting, and pristine) via the precipitation method, introducing a heterojunction interface. The creation of the SWCNT/ZnO heterostructure interface improves charge transfer and separation, resulting in a charge carrier lifetime of 7.37 ns. Also, surface area, pore size, and pore volumes are increased by 4.2 times compared to those of ZnO. The nanoparticles-coated face-mask fabric used as the floating photocatalyst exhibited high stability and recyclability with 99% RhB degradation efficiency under natural sunlight and 94% under UV light after the 5th cycle. The surface and crystal defects-oxygen or zinc defects/interstitials open new reaction active sites that assist in charge carrier transfer and act as pollutant absorption and interaction sites for enhanced performance. The ideal band edge positions of the valence band and conduction band favor the generation of H₂O/OH•, OH·/OH, and O₂/HO₂• reactive oxygen species. OH• radicals are found to play a vital role in this AOP by using ethanol as an OH• scavenger.

Keywords: Charge transfer; Defects; Natural sunlight; Photocatalytic advanced oxidation process; SWCNT/ZnO heterostructures; Self-assembly.