Fundamentals of electro- and thermochemistry in the anode of solid-oxide fuel cells with hydrocarbon and syngas fuels

High fuel flexibility of solid-oxide fuel cells (SOFCs) affords the possibility to use relatively cheap, safe, and readily available hydrocarbon (e.g., CH4) or coal syngas (i.e., CO-H-2 mixtures) fuels. Utilization of such fuels would greatly lower fuel cost and increase the feasibility of SOFC commercialization, especially for near-term adoption in anticipation of the long-awaited so-called hydrogen economy. Current SOFC technology has shown good performance with a wide range of hydrocarbon and syngas fuels, but there are still significant challenges for practical application. In this paper, the basic operating principles, state-of-the-art performance benchmarks, and SOFC-relevant materials are summarized. More in-depth reviews on those topics can be found in Kee and co-workers [Combust Sci and Tech 2008; 180:1207-44 and Proc Combust Inst 2005; 30:2379-404] and McIntosh and Gorte [Chem Rev 2004; 104:4845-65]. The focus of this review is on the fundamentals and development of detailed,electro- and thermal (or simply, electrothermal) chemistry within the SOFC anode, including electrochemical oxidation mechanisms for H-2, CO, CH4, and carbon, as well as the effects of carbon deposition and sulfur poisoning. The interdependence of heterogeneous chemistry, charge-transfer processes, and transport are discussed in the context of SOFC membrane-electrode assembly modeling. (C) 2013 Elsevier Ltd. All rights reserved.