Recent advances in Electrochemical Promotion of Catalysis

P. Vernoux (1) , M. Tsampas (1) , F. Sapountzi (1) , A. Boreave (1)

1 AIR - AIR

Ionically conducting ceramics can be utilized as active catalyst supports in a solid electrolyte cell. In this case, the electrochemical cell is then called “electrochemical catalyst” and one of the electrodes is also a catalyst. Gaseous reactant mixture (e.g. a mixture of C2H4 and O2) is fed over the catalyst-electrode. Considering an oxygen conducting ceramic, the application of a potential (ą2 V) between the catalyst and a counter electrode induces the migration of oxygen ions, O2-, which are in situ supplied or removed from the catalyst during the catalytic experiments. It has been found that, rather surprisingly, this “oxygen pumping” operation, can lead over a wide temperature range (220-550°C) to very pronounced and non-Faradaic reversible modifications in the catalytic activity (changes that are not proportional to the current), frequently accompanied by very significant changes in product selectivity. This phenomenon is known in the literature either as Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA effect) or, more commonly in recent years, as Electrochemical Promotion of Catalysis (EPOC). EPOC has been investigated by a variety of techniques which merge to the conclusion that this process is due to electrochemically controlled migration (spillover or reverse spillover) of promoting or poisoning ionic species from the ceramic support to the catalyst surface. These ionic species are accompanied by their image charge in the metal, thus forming overall neutral dipoles which “decorate” the catalyst surface. In-situ electrochemically supplied ions act as promoting or inhibiting agents for the reaction. EPOC can be considered as an electrochemically controlled metal support interaction Starting from model reactions, i.e. propane and propylene deep oxidation, and from a model electrochemical catalyst, i.e. Pt/YSZ (Yttria-Stabilized Zirconia, an O2- conductor), this lecture will give an overview of recent advances in the EPOC mechanism understanding as well as in the quest for EPOC of dispersed catalysts.

Domaines: Catalyse; Environnement et Société

P. Vernoux, M. Tsampas, F. Sapountzi, A. Boreave. Recent advances in Electrochemical Promotion of Catalysis. 6th Irsee Symposium on Selective Oxidation Catalysis,, Jul 2013, IRSEE, Germany. ⟨hal-00842346⟩