Conducting Polymer–TiO2 Hybrid Materials: Application in the Removal of Nitrates from Water

Materials able to produce the reduction of nitrate from water without the need of a metal catalyst and with avoiding the use of gaseous hydrogen have been developed by combining the synergistic properties of titania and two conducting polymers. Polymerization of aniline and pyrrol on titanium dioxide in the presence of two different oxidants/dopants (iron trichloride or potassium persulfate) has been evaluated. The resulting hybrid materials have good thermal stability imparted by the titania counterpart, and a considerable conductivity provided by the conducting polymers. The capability of the hybrid materials of reducing aqueous nitrate has been assessed and compared to the catalytic hydrogenation of nitrate using a platinum catalyst supported on these hybrid synthesized materials. The mechanism of nitrate abatement implies adsorption of nitrate on the polymer by ion exchange with the dopant anion, followed by the reduction of nitrate. The electron transfer from titania to the conducting polymer in the hybrid material favors the reductive ability of the polymer, in such a way that nitrate is selectively reduced with a very low production of undesirable side products. The obtained results show that the activity and selectivity of the catalytic reduction of nitrate with dihydrogen in the presence of a platinum catalyst supported on the hybrid materials are considerably lower than those of the metal-free nanocomposites.Financial support from Generalitat Valenciana, Spain (PROMETEOII/2014/004) and Ministry of Economy and Competitivity (MAT2016-80285-P) is gratefully acknowledged. E.S. acknowledges the Spanish MINECO and AEI/FEDER (ref CTQ2015-74494-JIN) and the University of Alicante (ref UATALENTO16-03)

Effect of cold Ar plasma treatment on the catalytic performance of Pt/CeO2 in water-gas shift reaction (WGS)

The effect of Ar plasma treatment on the catalytic performance of Pt/CeO2 has been studied. The catalyst was activated using different procedures separately or in combination: calcination, reduction under pure H2 and cold Ar plasma treatment. The resulting materials were characterized by X-ray photoelectron spectroscopy, X-ray adsorption near edge structure and temperature-programmed reduction with H2. The resulting materials were tested in the water-gas shift reaction (WGS). It has been found that the combination of calcination, plasma and hydrogen treatments leads to a very active catalyst for WGS. Furthermore, the catalyst structure–performance relationship has been assessed. The plasma treatment generated electron-enriched Pt particles which show a very strong interaction with the ceria support. This favoured CO chemisorption and increased the reducibility of the support, which takes part in the WGS the reaction by favouring water splitting.Financial support from Generalitat Valenciana (project PROMETEOII/2014/004) and MINECO (Project MAT2013-45008-P) is gratefully acknowledged. EVRF also thanks MINECO for his Ramon y Cajal fellow RYC-2012-11427 and the following project MAT2016-81732-ERC