Abstract
We have conducted a study on the preferential CO oxidation in hydrogen-rich stream (PROX) coupling catalysis and electrochemistry, i.e., by using an electrochemical catalyst (Pt/K-βAl2O3). It was shown that PROX activity and selectivity of a Pt catalyst can be strongly enhanced by electrochemical pumping of potassium ions from the solid electrolyte support. The observed promotional effect was attributed to a decrease in the CO and H2 chemisorption and to an increase in the O2 chemisorption which led to a relative increase in the CO oxidation reaction vs. the H2 oxidation. The electrochemical promotion allowed decreasing the operating temperature window of the Pt catalyst and attenuating the inhibiting effect of H2 on both catalytic activity and selectivity. In addition some of the catalytic results were supported by in situ electrochemical characterization techniques such as cyclic voltammetry and open circuit potential measurements. Finally a very interesting permanent NEMCA effect was shown. It demonstrated the high stability of the formed promoting species and the potential for a further development of NEMCA effect in PROX real configurations.
Highlights
The polymer electrolyte membrane fuel cell (PEMFC) has come to be regarded as one of the most promising candidates for utilizing hydrogen to produce heat and electricity, especially for electric vehicles, residential co-generation systems and portable power supplies for small devices [1]
We propose the use of solid electrolytes as electroactive catalyst supports as a novel approach to improve the catalytic properties of Pt for the preferential CO oxidation (PROX) reaction through the concept of electrochemical promotion
This explanation is in good agreement with the previous work of Kuriyama et al [15] who demonstrated that the chemical addition of potassium on Pt under PROX conditions weakened the interaction between Pt and CO modifying the CO adsorption sites
Summary
The polymer electrolyte membrane fuel cell (PEMFC) has come to be regarded as one of the most promising candidates for utilizing hydrogen to produce heat and electricity, especially for electric vehicles, residential co-generation systems and portable power supplies for small devices [1]. We propose the use of solid electrolytes as electroactive catalyst supports as a novel approach to improve the catalytic properties of Pt for the PROX reaction through the concept of electrochemical promotion. This phenomenon known as NEMCA (Non-Faradaic Electrochemical Modification of Catalytic Activity) effect is based on the improvement of the catalytic properties of a heterogeneous catalyst by the electrochemical pumping of promoter ions from the solid electrolyte support [17,18,19,20] Until now, this phenomenon has been demonstrated in more than 80 catalytic systems with several important technological possibilities, in industrial product selectivity and in exhaust gas treatment [21,22]. The catalytic experiments were supported by different in situ characterization techniques (open circuit potential measurements and cyclic voltammetry), which provided useful information on the competitive chemisorption of the reactants under different conditions
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