Pla, D.; Salleras, M.; Morata, A.; Garbayo, I.; Gerboles, M.; Sabaté, N.; Divins, N.; Casanovas, A.; Llorca, J.; Tarancón, A. Lab on a chip Vol. 16, num. 15, p. 2900-2910 DOI: 10.1039/c6lc00583g Data de publicació: 2016 Article en revista
A novel design of a silicon-based micro-reformer for onboard hydrogen generation from ethanol is presented in this work. The micro-reactor is fully fabricated with mainstream MEMS technology and consists of an active low-thermal-mass structure suspended by an insulating membrane. The suspended structure includes an embedded resistive metal heater and an array of ca. 20k vertically aligned through-silicon micro-channels per square centimetre. Each micro-channel is 500 mu m in length and 50 mu m in diameter allowing a unique micro-reformer configuration that presents a total surface per projected area of 16 cm(2) cm(-2) and per volume of 320 cm(2) cm(-3). The walls of the micro-channels become the active surface of the micro-reformer when coated with a homogenous thin film of Rh-Pd/CeO2 catalyst. The steam reforming of ethanol under controlled temperature conditions (using the embedded heater) and using the micro-reformer as a standalone device are evaluated. Fuel conversion rates above 94% and hydrogen selectivity values of ca. 70% were obtained when using operation conditions suitable for application in micro-solid oxide fuel cells (micro-SOFCs), i.e. 750 degrees C and fuel flows of 0.02 ml(L) min(-1) (enough to feed a one watt power source).
Almar, L.; Tarancón, A.; Andreu, T.; Torrell, M.; Hu, Y.; Dezanneau, G.; Morata, A. Sensors and actuators B. Chemical Vol. 216, p. 41-48 DOI: 10.1016/j.snb.2015.04.018 Data de publicació: 2015-09-01 Article en revista
Mesoporous materials have been studied as high performance sensing materials due to their singular microstructure and extremely high surface-to-volume ratio. However, the lack of stability of these nanostructures is assumed as one of the major drawbacks toward their application in real devices. In this work, this limitation is overcome by the synthesis of thermally stable mesoporous gadolinium doped ceria. Humidity sensors were fabricated and tested under different (i.e. humidity and temperature) conditions. The mesoporous layers were attached to the substrate at 900 °C preserving mesoporous structure intact. This process at high temperature provides the layer with a mechanical strength and allows self-cleaning cycles at high temperatures if required. The humidity sensing mechanism is presented and discussed in detail by means of impedance spectroscopy. An ionic type of conduction mechanism is corroborated. Fast response and recovery, as well as very low hysteresis and no drift are observed.
It was also shown that the response of the devices can be straightforwardly tuned by changing layer thickness or pore size, allowing to fulfill sensing needs of different applications. All the mentioned properties joined to the simplicity of the fabrication and the flexibility of the used fabrication route for synthesizing any other metal oxide make this kind of devices a potential group for developing high performance and fast gas sensors.