Comparative studies between classic and wireless electrochemical promotion of a Pt catalyst for ethylene oxidation

Abstract

A comparative study between a classic and a wireless electrochemical promotion experiment was undertaken as a tool towards the better understanding of both systems. The catalytic modification of a platinum catalyst for ethylene oxidation was studied. The catalyst was supported on yttria-stabilised-zirconia (YSZ), a known pure oxide ion conductor, for the classic experiment and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d -a mixed oxide ion electronic conductor-was used for the wireless experiment. The two systems showed certain similarities in terms of the reaction classification (in both cases electrophobic behaviour was observed) and the promotion mechanism. Significant difference was observed in the time scales and the reversibility of the induced rate modification.

Hydration, CO2 stability and wireless electrochemical promotion studies on yttria-doped Ba (Ce, Zr) O3 perovskites

“…It is interesting to note that the phenomenon is rapidly reversed upon re-introduction of the Arsweep. This is very different from the behaviour previously [18][19][20][21][22] but similar to that observed for the case of a mixed protonic electronic conductor (Sr 0.97 Ce 0.9 Yb 0.1 O 3 − α ) [23] used for the modification of Pt catalytic activity for ethylene oxidation. In the case of the mixed oxygen-electronic conductor, the catalytic rate remained to the promoted state upon re-introduction of the inert gas sweep, while in the case of the mixed protonoxygen ion conductor, there was also a rapid restoration.…”

“…Upon introduction of the H 2 /H 2 O flow on the sweep side of the reactor, a chemical potential difference of hydrogen species across the membrane is created. This will act as the driving force for these species to migrate across the membrane and spillover on the catalyst surface to impose a similar modification to the catalytic rate as in classic EPOC [18][19][20]. The effect on the catalytic rate (promotion or poisoning) depends on the nature of the promoting species (electronegative and electropositive) and the adsorption status of the reactants.…”

“…In addition, for supports with mixed ionic and electronic conductivity (such as BCZY), a wireless configuration has also been proposed by Poulidi et al [18][19][20][21][22][23] utilising a chemical potential difference of the promoting species across a dense membrane supporting the catalyst. Wireless EPOC has been observed using both mixed oxygen ion and electronic conductors [18][19][20][21][22] or mixed protonic and electronic conductors [23] in different reactor configurations. In this work, the most promising composition of BCZY evaluated in terms of stability under CO 2 environments was used for the wireless EPOC of CO oxidation on a Pt catalyst.…”

Influence of impurities and catalyst surface characteristics on the oxygen charge transfer reaction in the Pt/YSZ system

“…The sintered YSZ pellets were polished with SiC paper and washed with isopropyl alcohol in an ultrasonic cleaner and then rinsed with deionised (DI) water and dried. The electrochemical cell used in the current work was of the single chamber type and consisted of a three electrode system (working, reference and counter electrodes) [10]. The working electrode used in the current work was platinum (Pt) catalyst that was deposited on the prepared YSZ pellets on one side of the pellet by using a brush and then sintered by using a specific sintering program.The ESL catalyst was sintered at 980 o C for 10 and 60 minutes, the Metalor catalyst at 800 o C for 2 hours and the Heraeus catalyst at 850 o C for 5 minutes.The two different sintering times for the ESL catalyst were used in order to investigate the effect of sintering time on impurity levels (e.g.…”

Recent developments and trends in the electrochemical promotion of catalysis (EPOC)

“…Poulidi et al in recent studies [67,68,92] introduce the term of wireless EPOC. The concept is based on the utilization of fuel cell type configurations and the control of oxygen chemical potential difference across the solid electrolyte.…”