The electrodeposition, in particular the electro-base generation method, is an alternative to conventional washcoating to coat open-cell metallic foams, especially small pore size ones. In this work, the method was applied for the in-situ synthesis of cerium-based coatings, CeO 2 and Pd-CeO 2 , on 100 pores per inch (ppi) FeCrAl foams. The range of parameters suitable for the electrodeposition of CeO 2 films of different thickness and morphology was firstly investigated, i.e. Ce(NO 3 ) 3 concentration, potential applied, and deposition time. Then the most challenging one step Pd-CeO 2 electrodeposition was studied; the Pd content and distribution were optimized considering also the electrochemistry and chemistry of Pd 2+ species, i.e. by selection of a suitable Pd 2+ complex precursor (Pd(NH 3 ) 4 (NO 3 ) 2 or PdCl 2 in HCl). Coated foams were calcined at 550 °C to obtain the structured catalysts. The CO oxidation was used as a model reaction to test the activity of Pd-CeO 2 catalysts. The electrodeposition of cubic fluorite CeO 2 coatings on the surface of the foam ranging from few to 18 μm and made by compact and/or platelet particles was easily achieved and with a high reproducibility. The Pd-CeO 2 samples prepared from the ammine-containing electrolyte, though generated a well-adhered coating, resulted in a lower Pd content than the nominal value of the electrolyte. A high electrolyte concentration containing PdCl 2 combined with a short time allowed to deposit a rather thick Pd-containing CeO 2 coating avoiding the massive Pd° deposition. CO oxidation tests, especially at high flow rates, confirmed the key role of the coating and Pd distribution on the activity of the structured catalysts. A comparison of the conversion in mass transfer regime and estimates with literature correlations was presented, showing that, despite the very complex geometry of the support, a remarkably high quantity of the available surface is effectively exploited, paving the way for compact catalytic converters.
Ho P.H., Ambrosetti M., Groppi G., Tronconi E., Fornasari G., Vaccari A., et al. (2019). Electrodeposition of CeO 2 and Pd-CeO 2 on small pore size metallic foams: Selection of deposition parameters. CATALYSIS TODAY, 334, 37-47 [10.1016/j.cattod.2019.02.005].
Electrodeposition of CeO 2 and Pd-CeO 2 on small pore size metallic foams: Selection of deposition parameters
Fornasari G.;Vaccari A.;Benito P.
2019
Abstract
The electrodeposition, in particular the electro-base generation method, is an alternative to conventional washcoating to coat open-cell metallic foams, especially small pore size ones. In this work, the method was applied for the in-situ synthesis of cerium-based coatings, CeO 2 and Pd-CeO 2 , on 100 pores per inch (ppi) FeCrAl foams. The range of parameters suitable for the electrodeposition of CeO 2 films of different thickness and morphology was firstly investigated, i.e. Ce(NO 3 ) 3 concentration, potential applied, and deposition time. Then the most challenging one step Pd-CeO 2 electrodeposition was studied; the Pd content and distribution were optimized considering also the electrochemistry and chemistry of Pd 2+ species, i.e. by selection of a suitable Pd 2+ complex precursor (Pd(NH 3 ) 4 (NO 3 ) 2 or PdCl 2 in HCl). Coated foams were calcined at 550 °C to obtain the structured catalysts. The CO oxidation was used as a model reaction to test the activity of Pd-CeO 2 catalysts. The electrodeposition of cubic fluorite CeO 2 coatings on the surface of the foam ranging from few to 18 μm and made by compact and/or platelet particles was easily achieved and with a high reproducibility. The Pd-CeO 2 samples prepared from the ammine-containing electrolyte, though generated a well-adhered coating, resulted in a lower Pd content than the nominal value of the electrolyte. A high electrolyte concentration containing PdCl 2 combined with a short time allowed to deposit a rather thick Pd-containing CeO 2 coating avoiding the massive Pd° deposition. CO oxidation tests, especially at high flow rates, confirmed the key role of the coating and Pd distribution on the activity of the structured catalysts. A comparison of the conversion in mass transfer regime and estimates with literature correlations was presented, showing that, despite the very complex geometry of the support, a remarkably high quantity of the available surface is effectively exploited, paving the way for compact catalytic converters.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
