Electrochemical promotion of NO reduction by propene on Pt/YSZ

Abstract

International audienceThe reduction of NO by C₃H₆ in the presence of oxygen, is of great environmental importance. Platinum-based catalysts are very active but not selective towards N₂ production and mainly convert NO into N₂O, which participates to the greenhouse effect. Moreover, their operating temperature window is quite narrow. Electrochemical promotion was used to improve platinum catalytic behaviour. Platinum was deposited on YSZ (Y₂O₃ — stabilised ZrO₂), an O²-conductor. It was found that a negative current increased the rate of NO reduction and CO₂ formation. This rate enhancement was non-Faradaic with an apparent Faradaic efficiency (Λ) close to 180 indicating the manifestation of a NEMCA effect. However, the current application had no effect on the N₂ selectivit

NOx and propene conversion on La0.85Sr0.15MnO3+d/Ce0.9Gd0.1O1.95 symmetrical cells

“…In this cell, propene conversion decreased with increasing temperature, opposite to what is expected for a platinum catalyst [29]. This result suggests that something changes in the structure of the cell that inhibited this oxidation reaction.…”

“…This effect might be explained by the behavior of NOx reduction on Pt, which is known to peak as a function of temperature. This peak occurs at a lower temperature upon polarization [29], which means that if one is looking at only three temperatures, the peak could easily be missed, and the observed behavior can look like if the polarization has a negative effect.…”

“…Adsorption on BaO is believed to proceed through NO2 [22], whereas the chemisorption of NO is expected on Pt [29,36]. This means that when both, Pt and BaO nanoparticles are present, the adsorption and reduction of NO can proceed via different pathways.…”

The relationship of the catalytic activity and the open-circuit potential of Pt interfaced with YSZ

“…One can assume that, for propane oxidation, the key factor is not oxygen coverage but the propane one. shown the electrophilic behaviour of propene combustion [7,9] and SCR of NO by propene [10,11].…”

“…The system based on a platinum film deposited on yttria-stabilised zirconia (YSZ), an 0 2-conductor, has been intensively used in order to implement EPOC. Among these studies, much work concerns oxidation of light hydrocarbons such as methane, ethylene, propane, propene [3][4][5][6][7][8][9] and the NO reduction by propene in the presence of oxygen [10,11]. For instance, we have shown in a previous paper [9] that both propane and propene combustion on Pt/YSZ can be electrochemically promoted and that the two hydrocarbons exhibit opposite behaviours upon applied overpotentials.…”