Interaction of nickel-based SOFC anode with trace species in coal derived synthesis gas
EMSL Project ID
38790
Abstract
Solid oxide fuel cells (SOFC) utilizing nickel-based anodes have been widely studied at scales spanning micro (interfaces) to macro (system integration). In particular, SOFC have been investigated in the U.S. in anticipation of integration into central power generation facilities fueled with carbon based fuels. Aspects of macro-scale system design will impact the conditions at the SOFC micro-scale, particularly at the critical anode/electrolyte interface, where the primary oxidation electrochemistry occurs. The generation of trace coal materials in the combustion system and their subsequent interaction with the fuel cell anode is a topic of focused investigation. Trace materials contained in synthesis gas interact with the SOFC anode in one of three broad classes: I) Physical blockage of anode pores; II) Adsorption of material onto active locations; and III) Generation of secondary solid solutions and phases. Class III interactions are frequently irreversible and ultimately destructive to the fuel cell operation. In nickel-based SOFC anodes, trace species containing the elements arsenic, phosphorus, and antimony are expected to generate undesirable secondary solid phases. Carbon is also postulated to produce an unwanted solid solution with the nickel. The trace material interactions tend to produce SOFC performance degradation although specific details of the degradative processes are documented only for limited cases. In the proposed study, a thorough investigation is made of the anodic composition and microstructure of SOFC samples that have been exposed to simulated and direct coal-derived synthesis gas at various cell power densities and gas exposure durations. Secondary phase formation and material segregation will be examined in the anode bulk and at the triple phase region (TPR) proximal to the anode/electrolyte interface. Microstructural alteration will be examined at the critical TPR and proximal anode zone. Depending on the trace material exposure and operating conditions of a particular sample, searches for specific postulated structures and secondary phases will be conducted. To complete the proposed research, investigation of the anode/electrolyte interface is requested using Time-of-Flight Secondary Ion Mass Spectrometry (SIMS), Tunneling Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM) coupled with an Electron Backscattered Diffraction (EBSD) system. As the proposer has basic knowledge of various techniques of microscopy and microanalysis, it is suggested that in the most productive effort the proposer will collaborate with an EMSL researcher that will coordinate collection of data and generate comprehensive analysis. To that end, the proposer suggests that funds of at least $15k be made available from the propose's agency to support the effort. Results from the investigation will be leveraged for two primary purposes. First, anode susceptibility to the primary trace materials as a function of operating potential will be characterized. The analysis will be used to tune predictions for cell lifetime as a function of the trace material exposure and operating power density. Second, the information will be used to suggest alterations to anode composition and microstructure that will enhance anodic tolerance to trace material exposure under typical operating conditions.
Project Details
Project type
Exploratory Research
Start Date
2010-03-02
End Date
2011-03-06
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Hackett GA, KR Gerdes, X Song, Y Chen, V Shutthanandan, MH Engelhard, Z Zhu, S Thevuthasan, and R Gemmen. 2012. "Performance of solid oxide fuel cells operated with coal syngas provided directly from a gasification process." Journal of Power Sources 214:142-152. doi:10.1016/j.jpowsour.2012.04.050