Enhancing the catalytic activity and selectivity of the partial oxidation of methanol by electrochemical promotion

A Review of Surface Analysis Techniques for the Investigation of the Phenomenon of Electrochemical Promotion of Catalysis with Alkaline Ionic Conductors

“…Furthermore, some nitrogen (in red) was also noticed, homogeneously distributed on the catalyst surface, which was attributed to the K + -promotional effect on the ammonia formation via reaction of hydrogen and nitrogen, both of them present in the gas reaction atmosphere. The presence of potassium carbonate/bicarbonate species was also identified on the surface of a promoted Pt/K-βAl2O3 electrochemical catalyst employed in a methanol partial oxidation reaction [31]. In this study, these kinds of promoter-derived compounds were also detected ex situ by X-ray diffraction analysis after EPOC experiments, as shown in Figure 4.…”

“…In this study, these kinds of promoter-derived compounds were also detected ex situ by X-ray diffraction analysis after EPOC experiments, as shown in Figure 4. As in the case of the electropromoted Cu catalyst film, a poisoning effect derived from an excess of K + -derived surface species was found on this Pt film [31]. Furthermore, in both mentioned studies [31,32], the obtained electropromotional effect was completely reversible since all the promoter phases were decomposed The presence of potassium carbonate/bicarbonate species was also identified on the surface of a promoted Pt/K-βAl 2 O 3 electrochemical catalyst employed in a methanol partial oxidation reaction [31].…”

“…As in the case of the electropromoted Cu catalyst film, a poisoning effect derived from an excess of K + -derived surface species was found on this Pt film [31]. Furthermore, in both mentioned studies [31,32], the obtained electropromotional effect was completely reversible since all the promoter phases were decomposed and the alkali ions were transferred from the catalyst back to the solid electrolyte after applying a positive enough potential at Catalysts 2016, 6, 15 5 of 13 the end of the experiments. In this way, a clean, un-promoted catalyst surface, free of any promoter species, was achieved.…”

“…Urquhart et al used other K + -conductor solid electrolyte (K-βAl2O3) in Fischer-Tropsch reaction studies under both atmospheric [21] and high pressure [22], and de Lucas-Consuegra et al introduced the use of this kind of ion-conducting catalyst support for the electrochemical promotion of Pt in CO [23] and propylene [24] oxidation, as well as in NOx reduction reactions [25,26]. More recent alkaline electrochemical promotion studies on CO2 hydrogenation [27][28][29][30] and methanol conversion reactions [31][32][33] should Vayenas et al performed the first electrochemical promotion study with alkaline solid electrolyte (Na-βAl 2 O 3 ) in 1991 [8]. From this pioneer work, Na + -conductors have been widely employed in many catalytic systems such as ethylene [9,10], CO [11], propane [12] and propylene oxidation [13], NO reduction [14][15][16], Fischer Tropsch synthesis [17], or hydrogenation of benzene [18] and CO 2 [19].…”

“…Urquhart et al used other K + -conductor solid electrolyte (K-βAl 2 O 3 ) in Fischer-Tropsch reaction studies under both atmospheric [21] and high pressure [22], and de Lucas-Consuegra et al introduced the use of this kind of ion-conducting catalyst support for the electrochemical promotion of Pt in CO [23] and propylene [24] oxidation, as well as in NO x reduction reactions [25,26]. More recent alkaline electrochemical promotion studies on CO 2 hydrogenation [27][28][29][30] and methanol conversion reactions [31][32][33] should also be highlighted. Additionally, in order to understand the mechanism of the phenomenon of electrochemical promotion of catalysis with both anionic and cationic conductors, a wide variety of characterization techniques have been used in the fields of catalysis (e.g., TPD, TPO, or work function measurement), electrochemistry (e.g., cyclic/linear sweep voltammetry or impedance spectroscopy), and surface science (e.g., XPS, UPS, SPEM, or STM) [3].…”