Towards a higher photostability of ZnO photo-electrocatalysts in the degradation of organics by using MMO substrates

Lorena A Goulart; Géssica O S Santos; Katlin I B Eguiluz; Giancarlo R Salazar-Banda; Marcos R V Lanza; Cristina Saez; Manuel A Rodrigo

doi:10.1016/j.chemosphere.2020.129451

Towards a higher photostability of ZnO photo-electrocatalysts in the degradation of organics by using MMO substrates

Chemosphere. 2021 May:271:129451. doi: 10.1016/j.chemosphere.2020.129451. Epub 2020 Dec 30.

Authors

Lorena A Goulart¹, Géssica O S Santos², Katlin I B Eguiluz³, Giancarlo R Salazar-Banda³, Marcos R V Lanza⁴, Cristina Saez⁵, Manuel A Rodrigo⁶

Affiliations

¹ Institute of Chemistry - São Carlos, University of São Paulo, P.O. Box 780, CEP-13560-970, São Carlos, SP, Brazil; Department of Chemical Engineering, Universidad de Castilla-La Mancha, Campus Universitario S/n, 13071, Ciudad Real, Spain.
² Processes Engineering Post-graduation - PEP, Universidade Tiradentes, 49037-580, Aracaju, SE, Brazil; Department of Chemical Engineering, Universidad de Castilla-La Mancha, Campus Universitario S/n, 13071, Ciudad Real, Spain.
³ Processes Engineering Post-graduation - PEP, Universidade Tiradentes, 49037-580, Aracaju, SE, Brazil; Electrochemistry and Nanotechnology Laboratory, Research and Technology Institute (ITP), Aracaju, SE, Brazil.
⁴ Institute of Chemistry - São Carlos, University of São Paulo, P.O. Box 780, CEP-13560-970, São Carlos, SP, Brazil. Electronic address: marcoslanza@iqsc.usp.br.
⁵ Department of Chemical Engineering, Universidad de Castilla-La Mancha, Campus Universitario S/n, 13071, Ciudad Real, Spain.
⁶ Department of Chemical Engineering, Universidad de Castilla-La Mancha, Campus Universitario S/n, 13071, Ciudad Real, Spain. Electronic address: manuel.rodrigo@uclm.es.

PMID: 33450425
DOI: 10.1016/j.chemosphere.2020.129451

Abstract

In this work, it is proposed a novel strategy to increase the photostability of the ZnO photoelectrocatalyst under prolonged light irradiation, without the addition or deposition of metals and/or semiconductor oxides during their synthesis. This strategy is based on the use of a mixed metal oxide (MMO-Ru_0.3Ti_0.7O₂) coating as the substrate for the electrodeposition of ZnO. To assess it, the electrodeposition of ZnO films on Ti and Ti/MMO substrates and the photoelectrocatalytic activity of these materials for the degradation of the herbicide clopyralid were studied. The results showed that the substrate directly influenced the photo-stability of the ZnO film. Under the incidence of UV light and polarization, the novel Ti/MMO/ZnO electrode showed greater photocurrent stability as compared to Ti/ZnO, which is a very important outcome because the behavior of these electrodes was similar when compared in terms of the degradation of clopyralid. Single electrolysis was not able to degrade efficiently clopyralid at the different potentials studied. However, the irradiation of UV light on the polarized surface of the Ti/ZnO and Ti/MMO/ZnO electrodes increased markedly the degradation rate of clopyralid. A synergistic effect was observed between light and electrode polarization, since the rate of degradation of clopyralid was twice as high in photoelectrocatalysis (PhEC) than in photocatalysis (PhC) and different intermediates were formed. From these results, mechanisms of degradation of clopyralid for the PhC and PhEC systems with the Ti/ZnO and Ti/MMO/ZnO electrodes were presented. Therefore, the Ti/MMO/ZnO electrode could be a cheap and simple alternative to be applied in the efficient photodegradation of organic pollutants, presenting the great advantage of having a facile synthesis and high capacity to work at relatively low potentials.

Keywords: Clopyralid; Electrodeposition; Photoanode; Photoelectrocatalysis; Ti/MMO/ZnO; Ti/ZnO.

MeSH terms

Electrodes
Electrolysis
Oxidation-Reduction
Oxides
Zinc Oxide*

Substances

Oxides
Zinc Oxide