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Issue 7, 2020
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Enhancement in the rate of nitrate degradation on Au- and Ag-decorated TiO2 photocatalysts

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Abstract

The solar-driven reduction of nitrate to nitrogen has been studied in the presence of a formate hole scavenger, over a series of Au- and Ag-decorated TiO2 catalysts. In this study, the catalyst preparation protocol was found to influence the nitrate transformation in the order: incipient wetness impregnation > stabilizer-free sol immobilization > sol immobilization. However, the sequence of performing specific treatment steps such as drying, calcination and sieving had a less pronounced effect. Low-conversion conditions were utilized to study the photo-degradation of nitrate over a range of monometallic and bimetallic catalysts with metal concentrations in the range M = 0–1 wt% (M: Au, Ag, Pd, AuAg). Our findings demonstrate that selectively degrading nitrate to N2 over these co-catalysts is non-trivial and is metal content dependent. For Au-doped TiO2 catalysts, the highest activity was measured over 0.2 wt% Au/TiO2 while a higher metal loading of 0.4 wt% was required for the Ag/TiO2 photocatalyst. Product selectivity was also demonstrated to be dependent on metal and metal loading: approximately 22% nitrite selectivity was determined over a 0.1 wt% Ag-doped catalysts, however this product was not detected when utilising Au-doped catalysts. Total selectivity to dinitrogen was shown to be possible on both Au and Ag doped catalysts, and again this was dependent on the concentration of the metal (Ag > 0.3 wt%; 0.2 < Au ≥ 0.4 wt%).

Graphical abstract: Enhancement in the rate of nitrate degradation on Au- and Ag-decorated TiO2 photocatalysts

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Supplementary files

Article information


Submitted
06 Dec 2019
Accepted
03 Mar 2020
First published
03 Mar 2020

Catal. Sci. Technol., 2020,10, 2082-2091
Article type
Paper

Enhancement in the rate of nitrate degradation on Au- and Ag-decorated TiO2 photocatalysts

T. Caswell, M. W. Dlamini, P. J. Miedziak, S. Pattisson, P. R. Davies, S. H. Taylor and G. J. Hutchings, Catal. Sci. Technol., 2020, 10, 2082
DOI: 10.1039/C9CY02473E

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