Steam Reforming and Water-Gas Shift by Steam Permeation in a Protonic Ceramic Fuel Cell

We recently described a protonic ceramic fuel cell (PCFC) operating on dry methane that was made possible by the discovery of steam permeation reforming [W. G. Coors, J. Power Sources , 118 , 150 (2003)]. This paper presents new test results from a single PCFC operated in our laboratory on four different pure fuels, hydrogen, syngas, carbon monoxide, and methane, representative of the most important anode fuel mixtures expected in a fuel cell operating on natural gas. Except for hydrogen, some combination of steam reforming and water-gas shift reactions is necessary for complete conversion to carbon dioxide. The source of water vapor at the anode for these reactions was provided by ambipolar diffusion of water vapor through the electrolyte membrane. The fuel cell used a 10% yttrium-barium cerate (BCY10) protonic ceramic electrolyte membrane with platinum electrodes, and was tested between 650 and 800°C on each gas. Clear evidence for steam permeation reforming was obtained from the I-V curves of the cell operating on each fuel. The activation energy for the rate-limiting mechanism at constant current for each fuel was determined.