SEMINAIRE LMGP - 04.04.2023 - Adrien BAILLARD

“Investigation of ZnO nanowire arrays for photocatalysis”


Adrien BAILLARD
PhD student,
Grenoble INP, LMGP, équipe Nanomat

Abstract

  In one century, fresh water world demand has been multiplied by a factor of six¹ and and hence new accessible and eco-efficient water treatment processes are needed. Advanced oxidation processes including heterogeneous photocatalysis are of high interest to address this challenge. Zinc oxide (ZnO) is a widely studied semiconducting material because it is non-toxic, bio-compatible, and offers a wide band gap energy (3.37 eV) that is favourable for electron-hole pair generation under UV light². ZnO nanowires (NWs) grown by chemical bath deposition (CBD), as an inexpensive, low-temperature and green chemistry compatible method, have emerged as highly promising.

Because, ZnO crystallizes into the highly anisotropic wurzite phase³, this induce the possible formation of polar, semi-polar, and non-polar planes when grown as NWs which can affect the photocatalytic behaviour. The influence of each ZnO surface plane on the photocatalytic activity and processes will be discussed by assessing the organic dye degradation occurring on ZnO single crystals and ZnO NWs.

After investigating the shape effect on the photocatalytic activity, the extrinsic doping is an usual strategy to improve the photocatalytic activity through the generation of new energy levels in the bandgap aiming at limiting the electron-hole pair recombination⁴. In a CBD process, a relevant approach consists in adding extra salts (i.e. dopant) in the bath and driving attractive electrostatic forces thanks to pH to incorporate dopants into ZnO NWs^5–7. This approach has been applied so far to the incorporation of Al, Ga or Cu but its relevance for the development of co-doping to further control the physical properties of ZnO NWs will be discussed.

However, the effect of extrinsic doping on the photocatalytic activity and processes of ZnO NWs is still highly debated and largely unknown. In this work, we investigate the extrinsic doping of ZnO NWs with several elements such as Al, Ga, Cu, Sb and Cl using CBD to assess their effects on the photocatalytic activity and processes. The aim of this work is to understand how doping affects the photocatalytic reaction kinetics and processes during the organic dye degradation under UV light. In this work, we also assay the influence of the nature of dopants on the degradation pathways.

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