Design and development of a catalyst microsystem for the detection of carbon monoxide in hydrogen fuels

The viability and fabrication of a catalytic micro-system for the detection of CO in H2 fuel is discussed in detail. Technology utilizing the measurement of temperature changes from the exothermic oxidation of CO as a transduction method is proposed. CuOx-CeO2 is shown as a suitable catalyst substrate for selective CO detection, showing 100% selectivity to CO oxidation (relative to H2 oxidation) down to 200 ppm CO at 333 K. The high selectivity of CuOx-CeO2 is shown to be a result of both competitive adsorption effects as well as the ability of the oxidized catalyst to inhibit H2 dissociation. Pt/CeO2 is studied as another potential catalyst substrate for CO detection due to its higher activity per gram, but is found to have substantial selectivity losses at low CO concentrations (∼20% selective at 333 K for 100 ppm CO). Selectivity loss in Pt/CeO2 catalysts is explained by a loss of CO coverage at low concentrations, and also the ability of Pt to dissociate H2 at a very fast rate. Device design and fabrication are discussed. The micro-system functions properly as a calorimeter, showing a very clear signal for the oxidation of H2 on a Pt/CeO2 catalyst. However, CO detection with CuOx-CeO2 proves to challenge the device sensitivity, and potential improvements on device sensitivity are discussed