MEMS-based fuel reformer integrated with catalytic combustor using carbon nanotubes as catalyst supports

Abstract

Recently, PEMFCs have received a great attention as an attractive power source for portable devices due to its low operating temperature and high performance. Therefore, several researchers are attempting to supply pure hydrogen to PEMFC safely. Among these trials, researches on the methanol steam-reforming are on the rise due to its high energy density and low reforming temperature. In this work, we have successfully integrated all the components of a micromachined fuel processor on one-chip system. To realize this system, we have developed a coating method of the commercial catalyst into microchannels for methanol-steam-reforming. And for the first time, carbon nanotubes(CNTs) have been used as support of Pt catalyst for catalytic-combustor. The proposed system is composed of vaporizer, steam-reformer and catalytic-combustor. The chemical reaction of methanol-steam-reforming are occurred in the steam-reformer. The catalytic-combustor generates heat by using a small portion of the hydrogen produced in the reformer as a fuel, air as an oxidant. The heat generated from the catalytic-combustion can heat up two micro channels which are closely intertwined. One channel is a vaporizer and the other is a reaction channel. In this scheme, we can enhance the resident time of reactants with catalyst to assure high reforming rate. Methanol-steam-reforming has several catalytic reactions which are strongly dominated by catalysts and supports. Among these catalytic reactions, the catalytic combustion of hydrogen requires the catalyst with high activity and the catalyst support with large surface area, thermal mechanical stability, and inertness to undesired reactions. Pt on CNTs is very promising candidate from these aspects. And, the preparation procedure for CNT supports can be achieved at relatively low temperature $(<200~250^\circ C)$ which allows to use PDMS as a combustor chamber. We have chosen PDMS material as the structural material for the catalytic c...