Detection of CO in H2-rich gases with a samarium doped ceria (SDC) sensor for fuel cell applications

Abstract

International audienceAn original sensor has been studied in order to detect low CO concentration in h2-rich atmosphere for pem (protonic exchange membrane) fuel cell applications. The SCD (samarium doped ceria) sensor is a potentiometric sensor working with an electrode dissymmetry Au/Pt. The originality of this sensor is mainly working with the two electrodes in the same atmosphere without a reference cell. The Δ (emf) response, defined by the difference between the emf (electromotive force) value under carrier gas and the emf value under CO, is correlated with the CO concentration. Experiments have been carried out on a laboratory testing bench, either with a large measurement cell equipped with a hot plate and two mobile gold points as electrical contacts or in a small cell with self-heated sensors supplied with a platinum heater on the reverse side of the substrate. Responses to low CO concentrations (0-4000 ppm v/v) in H2-rich gases (5% v/v) varies between 25 and 100 mV, but saturation is observed beyond 400 ppm v/v of CO. In wet atmosphere, the sensitivity is partially reduced but the sensor response remains perfectly usable. At the moment no satisfying model can be used to explain the experimental results. Nevertheless, the performances of these SCD sensors appear sufficiently good to satisfy the fuel cell application

Structures and vibrational spectroscopy of partially reduced gas-phase cerium oxide clusters

“…28,29 The clusters studied in the present work are not fully oxidized, i.e., there are Ce atoms in the lower oxidation state than +IV. There is lively interest in partially reduced ceria [30][31][32][33][34][35] which arises from a broad range of industrial applications 36,37 including heterogeneous catalysis. 30,38,39 Partially reduced ceria is formed when oxygen defects are created which leaves electrons in Ce 4f states.…”

CO-Sensing Properties of Diode-Type Gas Sensors Employing Anodized Titania and Noble-Metal Electrodes under Hydrogen Atmosphere

“…The solubility of hydrogen into Pt is extremely smaller than that into Pd [29], but H 2 molecules easily and largely adsorb on the Pt surface [30]. In addition, CO molecules are well known to strongly adsorb on the Pt surface [2][3][4][5][6][7][8][9][10][11][12][13][14][15], especially at around 100 • C (temperatures at which PEMFCs generally operate) under H 2 -based reducing atmospheres. Therefore, the strongly adsorbed CO species probably interrupted the dissociatively adsorption of H 2 molecules, to increase the work function of Pt and the height of Schottky barrier at the M/TiO 2 interface, and thus to decrease the magnitude of current.…”

“…Various types of gas sensors, such as chemiresistor-type sensors using oxides [2][3][4][5][6], polymers [7], or metal salts [8][9][10], electrochemical sensors [11][12][13], and solid-electrolyte sensors [14,15], have been developed to detect CO sensitively and selectively, under reducing atmosphere. However, none of the sensors have CO-sensing properties sufficient to quantify the concentration of residue CO left in the reformed gas.…”

Application of advanced morphology Au–X (X=YSZ, ZrO2) composites as sensing electrode for solid state mixed-potential exhaust NOx sensor

“…A recent development of such a sensor is reported in [4]. Most of these sensors are composed of a solid electrolyte based on yttria-stabilized zirconia (YSZ) [4][5][6][7][8][9][10], but other electrolyte may be used: ␤-alumina (2Na 2 O-11Al 2 O 3 ) [11] or samaria-doped-ceria (SDC) [12]. Two electrodes, a reference one and a sensing one are associated with the electrolyte.…”