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

Thomas Caswell, Mbongiseni W. Dlamini, Peter J. Miedziak, Samuel Pattisson, Philip R. Davies, Stuart H. Taylor, Graham J. Hutchings

Research output: Contribution to journalArticlepeer-review

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%).

Original languageEnglish
Pages (from-to)2082-2091
Number of pages10
JournalCatalysis Science and Technology
Volume10
Issue number7
Early online date3 Mar 2020
DOIs
Publication statusPublished - 7 Apr 2020

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