Electrochemical catalysts for hydrocarbon combustion

Abstract

International audienceTwo series of electrochemical catalysts were prepared from sputtered Pt thin films onto two kinds of electrolyte membranes, 8 mol% Y2O3-stabilized ZrO2 (YSZ), an O2− conducting oxide and Na3Zr2Si2PO12 (NASICON), a Na+ one; respectively. The thickness of the Pt films varied from 8 to 120 nm. Therefore, the Pt loading was extremely low. The catalytic activity of Pt/YSZ and Pt/NASICON systems has been investigated between 200 and 500 °C for propane and propene, respectively. In spite of the low Pt loading, the Pt/YSZ electrochemical catalysts exhibited high activity for propane combustion. Furthermore, the catalytic activity can be in-situ controlled by applying electrical polarisation with high Faradaic efficiency (103). The catalytic rate of propene deep oxidation on Pt/NASICON electrochemical catalyst was found to be limited by the number of active sites, which is low on very thin Pt films. Moreover, initial anodic polarisation indicate that Na+ ions are already present on the top surface of Pt, probably proceeding from the preliminary stabilisation treatment of Pt in the reactive mixture. Nevertheless, polarisation allows the tuning of the catalytic activity of the electrochemical catalysts for propene oxidation. Finally, for both kinds of electrochemical catalysts, our results have evidenced that the measurement of the open-circuit voltage during catalytic process can be an indicator of the hydrocarbon conversion

Towards a new definition of EPOC parameters for anionic electrochemical catalysts: case of propene combustion

“…Indeed, polarization inducing the migration of O 2-ions from the electrolyte to the Pt surface strengthens the Pt-C 3 H 6 chemical bonds (electron-donor) and weakens the Pt-O bonds (electron-acceptor) [5,11,34]. Considering that at low temperatures, C 3 H 6 is strongly adsorbed on the Pt surface (low oxygen coverage) as already shown in previous studies [11][12][13][21][22][23], positive polarization inhibits oxygen adsorption, thus, as predicted by the Langmuir-Hinshelwood model, decreasing propene conversion.…”

“…The selected reaction was propene combustion in excess oxygen and the electrochemical catalyst was Pt/ YSZ. Previous studies [13,[21][22][23] have demonstrated that a negative voltage, above 340°C, could promote propene deep oxidation on a Pt/YSZ electrochemical catalyst.…”

Electrochemical promotion of deep oxidation of methane on Pd/YSZ

“…One can assume that this last had a so thin Pd layer that it did not cover the entire surface of the pellet. Billard and Vernoux [24] already reported that low thickness Pt catalysts did not cover all the YSZ support. Therefore, the catalytic activity was very low.…”

Electrochemical promotion of Pt impregnated catalyst for the treatment of automotive exhaust emissions

“…This phenomenon has been applied to improve the behaviour of a wide variety of catalyst in a large number of important catalytic reactions [4]. Recently the NEMCA effect has been successfully applied in environmental catalysis such as in the combustion of hydrocarbons [5][6][7][8][9][10], the oxidation of CO [11,12] and the selective reduction of NO [13][14][15][16][17]. However, apart from previous work of Marwood and Vayenas [18], there have been no further studies of electrochemical promotion on the reduction of nitrous oxide (N 2 O).…”