# Catalytic versus Electrocatalytic Layer for Oxidative Coupling of Methane on Solid Oxide Fuel Cells

Vanessa Bezerra Villela, Elizabeth Vera, Franck Fournet Fayard, Laurent

Dessemond, Steil M.C., Fabio Fonseca

► To cite this version:

Vanessa Bezerra Villela, Elizabeth Vera, Franck Fournet Fayard, Laurent Dessemond, Steil M.C., et al.. Catalytic versus Electrocatalytic Layer for Oxidative Coupling of Methane on Solid Oxide Fuel Cells. 18th International Congress on Catalysis, Jul 2024, Lyon, France. hal-04889262

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Submitted on 15 Jan 2025

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# Catalytic versus Electrocatalytic Layer for Oxidative Coupling of Methane on Solid Oxide Fuel Cells

V. B. Vilela¹,², E. Vera², F. F. Fayard², L. Dessemond², M. C. Steil²*, and F. C. Fonseca¹

¹Nuclear and Energy Research Institute, IPEN-CNEN, São Paulo, 05505-000, SP, Brazil

²Univ. Grenoble-Alpes, Univ. Savoie Mont-Blanc, CNRS, Grenoble INP (Institute of Engineering and Management), LEPMI, 38000, Grenoble, France

*marlu-cesar.steil@lepmi.grenoble-inp.fr

## Introduction

Light olefins such as ethylene (C2) serve as important building blocks for a large range of applications like polymers, lubricants, cosmetics, etc, and their production represent a crucial challenge for the fabrication of more sustainable petrochemicals.¹ Methane, a widely available feedstock, can be converted to C2+ hydrocarbons indirectly via syngas, however it is energetically and economically expensive.² In this sense, oxidative coupling of methane (OCM) represents a more viable route for the direct conversion of methane into higher value hydrocarbons, such as ethylene.

The use of solid oxide fuel cells (SOFC) for the performance of electrochemically aided catalytic reactions has gained interest because of the larger availability of green electrons from renewable sources. Therefore, the electrocatalytic oxidative coupling of methane (EOCM) can allow to selectively tune the active oxygen for the reaction and thus increase the selectivity of the desired products.³ Here we study the OCM on two different anode architectures of a SOFC: a classical perovskite-MIEC electrocatalytic anode (La₀.7Sr₀.2Fe₀.8Co₀.₂O₃) and a double-layered anode composed of NiO/YSZ coupled with a catalytic layer of La₀.5Ce₀.₅O₁.₇₅ (Figure 1).

## Materials and Methods

La₀.₅Ce₀.₅O₁.₇₅ (LCO) was prepared by the combustion method (with excess urea) while La₀.₇Sr₀.₂Fe₀.₈Co₀.₂O₃ (LSFO) was prepared by an EDTA-citrate method. The powders were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscope (SEM). The electrolyte-supported single cells were prepared using a YSZ-8 substrate. The electrode layers were deposited by screen printing on each side of the electrolyte. The cell with LSFO was symmetric. For the double-layered anode cell, a La₀.₆₅Sr₀.₃MnO₃ (LSM)/YSZ cermet was used as cathode and the anode was based on a NiO/YSZ cermet, upon which a LCO catalytic layer was spray-coated.

The single cell was set up in a three-atmosphere test bench comprised of two alumina tubes (anode and cathode side) using a gold ring-and-glass for sealing. The EOCM tests were conducted at 800 °C under different reaction conditions. The outlet gases were analyzed by gas chromatography and the electrochemical measurements were performed with a impedancemeter/potentiostat.

## Results and Discussion

XRD diffractograms of the powders showed single-phase crystalline structures. For LCO, Raman spectroscopy showed the presence of bands associated with the formation of

oxygen vacancies while SEM images evidenced a porous microstructure. The catalytic tests on powder LCO demonstrated that it is active for C₂ hydrocarbons production, with a higher production of COx but a fair selectivity for C₂H₄. Additionally, no coke formation was observed even after 20h of reaction. Then, the EOCM was tested on the different cells by varying the O²-/CH₄ ratio. The CH₄ conversion (X) presented a slight increase when increasing the ratio. Regarding the C₂ selectivity (S) and yield (Y), a maximum was observed at 0.12. The formation rate of carbon oxides (CO + CO₂) increased with the ratio, which was attributed to an increase on the amount of O²- species that favored the COx products.

<table><caption>Table 1. Summary of the EOCM performance of the LCO/NiO-YSZ/YSZ/LSM cell.</caption><thead><tr><th>O²-/CH₄</th><th>XCH₄</th><th>SC₂</th><th>YC₂</th><th>SCOₓ</th><th>YCOₓ</th><th>SH₂</th><th>YH₂</th><th>C₂H₄/C₂H₆</th><th>CO/CO₂</th></tr></thead><tbody><tr><td>0.06</td><td>65%</td><td>3%</td><td>2%</td><td>8%</td><td>5%</td><td>81%</td><td>54%</td><td>0.7</td><td>0.18</td></tr><tr><td>0.12</td><td>67%</td><td>7%</td><td>5%</td><td>16%</td><td>10%</td><td>74%</td><td>60%</td><td>0.9</td><td>0.03</td></tr><tr><td>0.30</td><td>68%</td><td>4%</td><td>3%</td><td>23%</td><td>16%</td><td>70%</td><td>63%</td><td>0.7</td><td>0.04</td></tr></tbody></table>

Finally, the EOCM was also tested on the symmetric LSFO/YSZ/LSFO cell. The differences found were attributed to the different secondary reactions controlling the COx formation.

<figure><img src="image_2.png" /><figcaption>Figure 1. EOCM process on the different types of architectures: electrocatalytic perovskite-MIEC (left) and double-layered (right) anode cells.</figcaption></figure>

## Significance

The influence of different anode-architectures was evaluated for the enhancement of electrocatalytic oxidative coupling of methane. An innovative double-layered anode showed fair performances for the EOCM.

## References

1. The Future of Petrochemicals – Analysis - IEA, https://www.iea.org/reports/the-future-of-petrochemicals

2. P. Schwach, et al, Chem Rev, 2017, 117, 8497.

3. V. V. Thyssen et al, Chem Rev, 2022, 122, 3966.