Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS
New composite photocatalysts have been obtained by chemical bath deposition of CdS on top of either nanostructured crystalline ZrO<sub>2</sub> or TiO<sub>2</sub> films previously deposited on conductive glass FTO. Their morphological, photoelectrochemical and photochemical pr...
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| Format: | Article |
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MDPI AG
2022-05-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/27/9/2924 |
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| author | Michele Mazzanti Martina Milani Vito Cristino Rita Boaretto Alessandra Molinari Stefano Caramori |
| author_facet | Michele Mazzanti Martina Milani Vito Cristino Rita Boaretto Alessandra Molinari Stefano Caramori |
| author_sort | Michele Mazzanti |
| collection | DOAJ |
| description | New composite photocatalysts have been obtained by chemical bath deposition of CdS on top of either nanostructured crystalline ZrO<sub>2</sub> or TiO<sub>2</sub> films previously deposited on conductive glass FTO. Their morphological, photoelectrochemical and photochemical properties have been investigated and compared. Time resolved spectroscopic, techniques show that in FTO/TiO<sub>2</sub>/CdS films the radiative recombination of charges, separated by visible illumination of CdS, is faster than in FTO/ZrO<sub>2</sub>/CdS, evidencing that carrier dynamics in the two systems is different. Photoelectrochemical investigation evidence a suppression of electron collection in ZrO<sub>2</sub>/CdS network, whereas electron injection from CdS to TiO<sub>2</sub> is very efficient since trap states of TiO<sub>2</sub> act as a reservoir for long lived electrons storage. This ability of FTO/TiO<sub>2</sub>/CdS films is used in the reductive cleavage of N=N bonds of some azo-dyes by visible light irradiation, with formation and accumulation of reduced aminic intermediates, identified by ESI-MS analysis. Needed protons are provided by sodium formate, a good hole scavenger that leaves no residue upon oxidation. FTO/TiO<sub>2</sub>/CdS has an approximately 100 meV driving force larger than FTO/ZrO<sub>2</sub>/CdS under illumination for azo-dye reduction and it is always about 10% more active than the seconds. The films showed very high stability and recyclability, ease of handling and recovering. |
| first_indexed | 2024-03-10T03:53:29Z |
| format | Article |
| id | doaj.art-3da629bf8a04430294318fc70f171f92 |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-03-10T03:53:29Z |
| publishDate | 2022-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Molecules |
| spelling | doaj.art-3da629bf8a04430294318fc70f171f922023-11-23T08:51:40ZengMDPI AGMolecules1420-30492022-05-01279292410.3390/molecules27092924Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdSMichele Mazzanti0Martina Milani1Vito Cristino2Rita Boaretto3Alessandra Molinari4Stefano Caramori5Dipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, Università di Ferrara, Via Luigi Borsari 46, 44121 Ferrara, ItalyDipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, Università di Ferrara, Via Luigi Borsari 46, 44121 Ferrara, ItalyDipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, Università di Ferrara, Via Luigi Borsari 46, 44121 Ferrara, ItalyDipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, Università di Ferrara, Via Luigi Borsari 46, 44121 Ferrara, ItalyDipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, Università di Ferrara, Via Luigi Borsari 46, 44121 Ferrara, ItalyDipartimento di Scienze Chimiche, Farmaceutiche ed Agrarie, Università di Ferrara, Via Luigi Borsari 46, 44121 Ferrara, ItalyNew composite photocatalysts have been obtained by chemical bath deposition of CdS on top of either nanostructured crystalline ZrO<sub>2</sub> or TiO<sub>2</sub> films previously deposited on conductive glass FTO. Their morphological, photoelectrochemical and photochemical properties have been investigated and compared. Time resolved spectroscopic, techniques show that in FTO/TiO<sub>2</sub>/CdS films the radiative recombination of charges, separated by visible illumination of CdS, is faster than in FTO/ZrO<sub>2</sub>/CdS, evidencing that carrier dynamics in the two systems is different. Photoelectrochemical investigation evidence a suppression of electron collection in ZrO<sub>2</sub>/CdS network, whereas electron injection from CdS to TiO<sub>2</sub> is very efficient since trap states of TiO<sub>2</sub> act as a reservoir for long lived electrons storage. This ability of FTO/TiO<sub>2</sub>/CdS films is used in the reductive cleavage of N=N bonds of some azo-dyes by visible light irradiation, with formation and accumulation of reduced aminic intermediates, identified by ESI-MS analysis. Needed protons are provided by sodium formate, a good hole scavenger that leaves no residue upon oxidation. FTO/TiO<sub>2</sub>/CdS has an approximately 100 meV driving force larger than FTO/ZrO<sub>2</sub>/CdS under illumination for azo-dye reduction and it is always about 10% more active than the seconds. The films showed very high stability and recyclability, ease of handling and recovering.https://www.mdpi.com/1420-3049/27/9/2924TiO<sub>2</sub>CdSn–n junctionsphotocatalysisphotoreductionvisible light |
| spellingShingle | Michele Mazzanti Martina Milani Vito Cristino Rita Boaretto Alessandra Molinari Stefano Caramori Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS Molecules TiO<sub>2</sub> CdS n–n junctions photocatalysis photoreduction visible light |
| title | Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS |
| title_full | Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS |
| title_fullStr | Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS |
| title_full_unstemmed | Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS |
| title_short | Visible Light Reductive Photocatalysis of Azo-Dyes with n–n Junctions Based on Chemically Deposited CdS |
| title_sort | visible light reductive photocatalysis of azo dyes with n n junctions based on chemically deposited cds |
| topic | TiO<sub>2</sub> CdS n–n junctions photocatalysis photoreduction visible light |
| url | https://www.mdpi.com/1420-3049/27/9/2924 |
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