Study on a Novel Double-Layer Anode for Solid Oxide Fuel Cells Based on CO2 Dry Reforming of Methane

Abstract

Solid oxide fuel cell (SOFC) is an energy conversion device that converts chemical energy in fuels into electric energy directly with the advantages of high efficient, clean, and wide fuel adaptability. Most hydrocarbons such as natural gas, ethane and bio-oil can be used as fuels in SOFC. When a hydrocarbon fuel, such as methane (CH4), is directly used for IT-SOFCs without prereforming by adding oxygen, steam or carbon dioxide, it is electrochemically oxidized on the triple-phase boundaries (TPB) with a strong tendency of carbon deposition in the traditional Ni-based anode. In this paper, we introduce an extra internal reforming layer on the surface of anode-support. The layer of a LaCrO3 based perovskite with exsolved Ni nanoparticles catalyst (La0.6Sr0.2Cr0.85Ni0.15O3 showed high stability in reducing atmosphere and excellent catalytic performance. Based on this, two types of anode-supported cell are fabricated by tape casting, screen printing and sintering processes. The first one is a conventional anode supported cell with a configuration of Ni-GDC/GDC/GDC-LSCF (cell 1); and the other contains a reforming layer mixed with La0.6Sr0.2Cr0.85Ni0.15O3 and SDC which was a well coking resistant promoters (cell 2). When CH4–CO2 was used as the fuel, which was supposed to yield syngas with the H2–CO ratio close to unity, the polarization resistance of the cell 1 reach at 0.247 Ω cm2 whereas the value of cell 2 is 0.082Ω cm2 at 750 °C. These results implied that both the physical and the chemical properties of the TPB have been altered drastically during internal dry reforming since that Ni-based anode show poor catalytic performance in reforming and are prone to coking. Consequently, the maximum power density for cell 1 was 470 mW cm-2 and the cell suffered from degradations during a 1 h galvanostatic operation at 1 A cm-2. The performances of the cell 2 are significantly increased above the level of the cell 1, demonstrating a peak power density at 929 mW cm-2 at 750 °C and a stable cell voltage at 1 A cm-2 and 750 °C for 48 h. Carbon deposition in the anode region of the tested cell 2 is not detected, as the La0.6Sr0.2Cr0.85Ni0.15O3 is a more active and stable catalyst than the Ni-based anode-support for dry reforming. Finally we demonstrated the strong interaction between the exsolved nanoparticles and the substrate could prevent coking deposition and proposed a promising configuration of double-layer anode for solid oxide fuel cells with on-cell reforming. Figure 1