Micro-solid oxide fuel cells running on reformed hydrocarbon fuels

Micro‐solid oxide fuel cell (micro‐SOFC) systems are predicted to have a high energy density and specific energy and are potential power sources for portable electronic devices. A micro‐SOFC system is under development in the frame of the ONEBAT project [1‐3]. In this presentation, we report on the fabrication and characterization of a sub‐system assembly consisting of a startup heater and a micro‐reformer bonded to a Si chip with electrochemically‐active micro‐SOFC membranes. A functional carrier including fluidic channels for gas feed and integrated heaters was bonded to a microreformer with an overall size of 12.7 mm x 12.7 mm x 1.9 mm [4‐7]. As a catalyst, a foam‐like material made of ceria‐zirconia nanoparticles doped with rhodium was used to fill the 58.5 mm3 reformer cavity. This micro‐reformer allows for high methane and butane conversion of > 90 % with a hydrogen selectivity of > 80 % at 550 °C in the reformer [7, 8]. A silicon chip with 30 free‐standing micro‐SOFC membranes (390 μm x 390 μm) with a thickness of less than 500 nm was bonded to the carrier‐reformer assembly described above. The micro‐SOFC membrane consisted of an yttria‐ stabilized zirconia thin film electrolyte. Both Pt‐based and ceramic‐based electrode materials were tested regarding the thermal stability and carbon poisoning at temperatures below 600 °C. The functional‐carrier mirco‐reformer micro‐SOFC assembly was electrochemically tested with hydrocarbon fuel between 300 °C and 600 °C. The fuel cell performance and the microstructural evolution of the anode are discussed as well.