Calcium-Modified Ni-SDC Anodes in Solid Oxide Fuel Cells for Direct Dry Reforming of Methane

Abstract

Direct internal reforming is one of the promising methods of utilizing hydrocarbon fuels in solid oxide fuel cells (SOFCs). Among direct internal reforming technologies, dry reforming of methane (DRM) is attracting attention as an alternative to steam reforming of methane. In this study, a cermet material composed of nickel and samarium-doped ceria (Ni-SDC) was investigated as an SOFC anode for the direct internal DRM operation. Compared to a conventional nickel-yttria-stabilized zirconia (Ni-YSZ) anode, the Ni-SDC anode showed superior current-voltage characteristics. However, poor carbon balances were recorded in anode outlet gas analysis, indicating coke formation on the Ni-SDC anode. The addition of calcium to the Ni-SDC anode was also tested. Measured anode outlet gas compositions suggested that the calcium addition suppressed coke formation, while the power generation performance of the pristine Ni-SDC anode was maintained. Microscopic observations showed that a certain part of the calcium additive existed as CaO particles on the anode surface, which could be responsible for the improved coking resistance.

Promotion of Hydrogen Oxidation and Methane Dry Reforming Over Ni-SDC Anode by Basic Oxide Additives

“…The obtained SDC powder was mixed with NiO at the desired ratio, followed by calcination at 1300°C for 5 h in air, in order to obtain cermet powders. The formation of SDC was confirmed by X-ray diffraction measurements, which was reported previously (15). Standard anode cermet of Ni-YSZ was prepared by mixing NiO (Wako Pure Chemical Industries, Ltd., Japan) and YSZ (TZ-8YS; Tosoh Corp., Japan) at a desired ratio, followed by calcination at 1300°C for 5 h in air.…”

“…With these preparation methods, the alkaline-earth metal elements could have resided in the grain boundaries in the cermet particles, leading to the increase in the ohmic resistance. Recently we reported calcium-modified Ni-SDC cermet anodes prepared by impregnating Ni-SDC cermet powders with an aqueous solution of calcium nitrate (15). The addition of Ca to Ni-SDC anodes improved the activity not only for hydrogen oxidation, but also for DRM reaction.…”

BaCe 0.8Fe 0.1Ni 0.1O 3− δ -impregnated Ni–GDC by phase-inversion as an anode of solid oxide fuel cells with on-cell dry methane reforming

“…Studies have been conducted to improve the long-term performance stability of cells for on-cell DRM, such as adding Fe or Mo-Au into NiO-(Gd0.6Ce0.4)2O3.2 [18] and CaO into NiO-Ce0.8Sm0.2O1.9 [19] cermet anodes. However, this approach will reduce the overall electrocatalytic activity of the anode while enhancing its resistance to carbon deposition.…”

A comprehensive review of solid oxide fuel cells operating on various promising alternative fuels

“…Although the simpler apparatus of the SOFC system towards dry reforming can be achieved due to the fact that carbon dioxide is easier to handle than steam [51], dry reforming may pose more serious degradation threats to the anode than steam reforming from the perspective of carbon tolerance [52]. Despite these, as the major components of biogas, the utilization of methane and carbon dioxide from renewable resources could be a very promising route to achieve the carbon-neutral electric power generation [53].…”