Electrochemical Promotion of CH₄ Combustion over a Pd/CeO₂–YSZ Catalyst

Abstract

The phenomenon of electrochemical promotion of catalysis (EPOC) has been demonstrated on palladium supported catalysts using ceria and yttria‐stabilised zirconia as solid electrolyte. SEM, XRD, linear voltammetry and AC impedance spectroscopy have been used to study this double electrolyte system. Electrochemical catalysts were also used to promote the methane combustion reaction leading to one of the highest faradaic efficiency reported for this reaction (Λ = 764). Thus, the catalytic activity of palladium was found to increase over 450% via electrochemical transference of oxygen promoting ions from the solid electrolyte to the catalyst film.

Electrochemical Promotion of Nanostructured Palladium Catalyst for Complete Methane Oxidation

“…Figure 10 shows that there is an increase in catalytic rate as a function of temperature at all applied positive current values for 400, 425 and 450 • C. It can be noticed that upon application of small current of 1 µA, a significant rate increase was detected, resulting in a logarithmic-shape relationship of rate increase versus applied current. In addition, a highest value of~2400 was found for the apparent Faradaic efficiency, constructing that a very minimal current was able to result in a change of the Pd surface oxidation state and hence the adsorption strength of methane reactant [15,16,18,20]. Table 1 compares EPOC of methane oxidation on Pd/YSZ found in this work to previous studies carried out on Pd catalyst-electrode deposited on YSZ solid-electrolyte.…”

“…It can be noticed that upon application of small current of 1 μA, a significant rate increase was detected, resulting in a logarithmic-shape relationship of rate increase versus applied current. In addition, a highest value of ~2400 was found for the apparent Faradaic efficiency, constructing that a very minimal current was able to result in a change of the Pd surface oxidation state and hence the adsorption strength of methane reactant [15,16,18,20]. Similarly, the effect of temperature on closed-circuit reaction rate was tested at different galvanostatic conditions.…”

“…The addition of CeO 2 layer between the YSZ solid-electrolyte and Pd film catalyst increased the open-circuit catalytic rate but decreased the apparent Faradaic efficiency due to the higher electric resistance [18]. Another study on a Pd film catalyst prepared using commercial organometallic paste showed higher enhancement ratio (ρ = 5.6) and Faradaic efficiency (Λ = 579) at 560 • C; however, instability of the catalyst over time and rapid deactivation within 900 min of experiment was also noted [20]. Furthermore, the effect of CeO 2 layer was studied in [24].…”

“…The electrochemical promotion of complete methane oxidation was investigated on palladium catalysts prepared using various methods as summarized in Table 1 [15][16][17][18][19][20][21][22][23]. Electrochemical promotion of Pd thick film catalyst electrode prepared using wet impregnation was investigated in the temperature range of 470-600 • C [18].…”

Ionically Conducting Ceramics as Active Catalyst Supports

“…Combustion of alkanes is the most intensively studied family of oxidation reactions, first because it is related to clean energy production and second because effective catalysts (noble metals) and their activity temperature window are suitable for the O 2– ionic conductivity level of ceramics such as YSZ (Figure ). EPOC of methane deep oxidation has been extensively investigated during the past few years over a wide temperature window (250–600 °C) using Pd films deposited on YSZ with organometallic paste or by wet impregnation. − In the temperature range 470–600 °C and under oxidizing conditions, the catalytic activity of the impregnated Pd film on YSZ for methane oxidation can be increased over 160% under positive polarization . Even in excess of oxygen and at lower temperature (320 °C), EPOC can affect the catalytic oxidation of methane when a small concentration of ethylene is cofed in the reaction mixture.…”