Applications of the Electrochemical Promotion of Catalysis in Methanol Conversion Processes

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

“…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].…”

A Discussion on the Unique Features of Electrochemical Promotion of Catalysis (EPOC): Are We in the Right Path Towards Commercial Implementation?

“…Figure 6 shows a schematic of the proposed mechanism and an example of a dynamic experiment on H 2 production/storage and release. Under a methanol steam reforming reaction atmosphere (CH 3 OH/H 2 O = 4.4%/5.2%), the activity towards the production of H 2 was enhanced at 280 • C under the application of negative polarizations, due to the spill-over of potassium ions towards the catalyst surface [109], followed by a strong deactivation. The most interesting result dealt with the dynamic storage of the H 2 produced at these negative potentials.…”

Graphene Formation Mechanism by the Electrochemical Promotion of a Ni Catalyst

“…The phenomenon of the electrochemical promotion of catalysis (EPOC), discovered by Stoukides and Vayenas in 1981, constitutes an efficient way to enhance gas phase catalytic reaction rates. This phenomenon relies on the electrochemical activation of a catalyst film in contact with a solid electrolyte (e.g., Na + , K + , and O 2– ionic conductors) that, acting as a source of ions, modifies the surface state of the catalyst electrode and induces a nonfaradaic enhancement of gas phase catalytic activity and a decrease in reaction temperature. − Incidentally, some EPOC works have also reported an increase in the carbon formation rate as a side reaction during, for example, the steam reforming of CH 4 , the CO 2 hydrogenation, or during the methanol wet reforming reaction, the two former using yttria-stabilized zirconia (YSZ; i.e., O 2– conductor) and the latter using β-alumina (i.e., K + conductor) as solid electrolytes. However, the EPOC phenomenon has never been specifically applied for materials synthesis, an aspect that constitutes the main purpose of the present work aiming at synthesizing multilayer graphene at low temperatures and to unravel the basic mechanism involved in this process.…”

“…Although some insights on the mechanism of the EPOC phenomenon have been obtained in studies using surface science techniques, ,− the atomistic understanding of the involved processes is still rather elemental and, in most cases, relies on empirical analysis of electrocatalytic results supported with “ex situ” characterization of the catalysts. − ,, More recently, the near ambient pressure XPS (NAP-XPS) technique working “in operando” conditions has demonstrated to be quite useful to understand the EPOC mechanisms and interactions involved in various processes, for example, the role of a Rh catalyst film deposited on yttria-stabilized zirconia (YSZ) (i.e., O 2– ionic conductor) in promoting an ethylene–oxygen reaction or the interaction of potassium with the Ni electrode in a Ni/KβAl 2 O 3 /Au electrocatalytic cell . Herein, we have applied a similar operando approach to study the EPOC decomposition of methanol and the formation mechanism of graphene onto the surface of a similar Ni-catalyst electrode cell.…”