Silver/Platinum Supported on TiO2 P25 Nanocatalysts for Non-photocatalytic and Photocatalytic Denitration of Water
Denitration of water was investigated by non-photocatalytic and/or photocatalytic processes (UV-A irradiation at 365 nm) using a mixture of Ag/P25 + Pt/P25 monometallic catalysts and Ag–Pt(Pt–Ag)/P25 bimetallic catalysts (2 wt% Ag; 4 wt% Pt) prepared by drop-wise wetness impregnation of TiO2 P25 support. In the bimetallic samples, the influences of the Pt precursor (H2PtCl6·6H2O; K2PtCl6) and of the impregnation order of the metallic salts were examined. The highest N2 yield (42.3%) in the non-photocatalytic process was achieved with the Ag/P25 + Pt/P25 mixture but with ca. 12.6% NO2 − yield. Photocatalytic activity was enhanced in presence of H2 in comparison to H2-free condition. Ag/P25 is the most active photocatalyst, however high NO2 − yield is obtained (32.5%). The bimetallic samples exhibit high versatility, being active both in the non-photocatalytic and the photocatalytic processes. Low NO3 − conversion and high NO2 − selectivity results were obtained from impregnation of Ag first. In contrast, impregnation of Pt precursor from K2PtCl6 first effectively promoted NO3 − reduction towards N2 yield of 36% and particularly low NO2 − yield of 2.7%, due the presence of metallic nanoparticles of different sizes and interaction with TiO2 with a peculiar strong Pt and Ag interaction. Best results obtained in non-photocatalytic and photocatalytic processes are almost similar.
KeywordsNitrate Catalytic reduction Photocatalytic reduction Ag–Pt TiO2
This work was supported by the Spanish Ministry of Economy and Competitiveness (Project CTQ2012-35789-C02-02). A.M.A. acknowledges the financial support to Universitat Rovira i Virgili, École Nationale Supérieure de Chimie de Montpellier, Eurorregión Pirineos Mediterráneo, Aplicacions Medioambientals i Industrials de la Catàlisi, Anton Dafinov and Thomas Cacciaguerra.
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