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Edward Sabolsky
Multi-functional and Energy Ceramics Group
Benjamin M. Statler College of Engineering and Mineral Resources
WVU Home | Mechanical and Aerospace Engineering

Fuel Cells

Nano-Catalyst Infiltration Enhancement of Porous Solid Oxide Fuel Cell Electrodes Using Catechol Surfactants

Wet nano-catalyst infiltration of porous Solid Oxide Fuel Cell (SOFC) electrodes is a recognized process to enhance electrochemical performance. Simple infiltration protocols includes multiple pipet deposition steps of aqueous salt solutions onto the SOFC electrodes. In the current work, it was found that this labor-intensive and time-consuming process could be simplified through the use of a bio-adhesive (or bio-derived surfactant). The surfactant-assisted impregnation protocol, however, could allow homogenous incorporation of a nano-catalyst within the electrode in a single salt solution deposition step with lower electrode overpotential and enhanced long-term stability.

In this project, bio-inspired catechol-based surfactants were used to act as a wetting and local chelating agent which adhered within the 3-D electrode architectures. The work initially assessed the use of polymerized dopamine (PDA) and/or nor-epinephrine (pNE) neurotransmitters as the bio-template layer for metal oxide or hydroxide deposition. The adhered bio-template on the pore walls was shown to provide higher nano-catalyst loading by avoiding segregation of the precipitate within the porous structure, which typically results in the migration and distribution of the solute near the surface during the drying process.

Additionally, we aimed to monitor the growth kinetics of the catechol surfactants in order to understand the nano-catalyst deposition morphology. The work investigated the deposition of these layers on YSZ substrates by Atomic Force Microscopy (AFM), which would act as an ideal surface to characterize (over the 3-D electrode layers). The result showed that the polymerization method and surfactant type had a significant effect on the adhered layer thickness, which varied from 30 to 500 nm within 24 hours of immersion time. In addition, the effect of these surfactants on the chelation and precipitation of metal oxide nano-catalyst from precursor solutions were also studied. The optimal conditions were resolved from the surfactant coating studies which were used to infiltrate nano-ceria (CeO 2) based nano-catalyst into the electrodes of anode-supported SOFC button cells.

The final studies of this work investigated the effect of the critical nano-catalyst infiltrant concentration on fuel cell performance. Commercial button cells were infiltrated with norepinephrine (pNE) and then impregnated with different molarities of cerium salt solution for both electrodes by dip-coating method. The infiltrated cells displayed up to 35% reduction in polarization over the baseline cell with high electrochemical stability during 300 hours of testing at 750°C.

SEM of anode-supported solid-oxide button fuel cell  
(a) SEM of anode-supported solid-oxide button fuel cell (b) pNE assisted ceria infiltration to the anode active area.

Anodes

One major issue limiting the application of SOFCs to clean coal technologies is the degradation of the anode upon exposure to trace amounts of impurities that exist within coal-derived syngas. Specifically, H 2S and PH 3 have been shown to have an immediate effect on cell performance for cells with Ni-based anodes. The nickel reacts to form various nickel-phosphide and -sulfide phases that inhibit catalytic activity. Thus, our work focuses on developing mixed-conducting oxides as alternate anodes that show stable long-term performance. Our studies not only exam the effect of the impurities in the new anodes and traditional cermet anodes, but the role that fuel delivery configuration has on cell performance and degradation.