Paul H. Matter

Non-precious metal oxygen reduction catalysts for PEM fuel cells

Proton Exchange Membrane Fuel Cells (PEMFCs) are being considered as a potential alternative energy conversion device for mobile power applications. Since the electrolyte of a PEM fuel cell can function at low temperatures (typically at 80 °C), PEMFCs are unique from the other commercially viable ty...

Amperometric NO x Sensor Based on Oxygen Reduction

A novel ceria-based amperometric NO_x and NH₃ sensor was investigated. The sensor consisted of gadolinium-doped ceria electrolyte membrane with (La_0.60Sr_0.40) (Co_0.20Fe_0.80)O_3-δ (LSCF) electrodes applied to opposite sides. The assembly operated in combustion exhaust streams with higher sensitivity to both NO_x and NH₃, less dependence on oxygen partial pressure, and faster response than previously reported. The sensor had an operational temperature range of 200 °C-550 °C and was resistant to common exhaust gas contaminants, such as steam, CO₂, and sulfur oxides. Electrochemical testing and in-situ DRIFTS studies showed NOx adsorption on the sensor causing accelerated kinetics for oxygen reduction reaction (ORR) whereby adsorbed NOx species acted as a catalyst for an alternative ORR pathway, thus enabling an amperometric sensing mechanism.

Development Status for a Combined Solid Oxide Co-Electrolyzer and Carbon Formation Reactor System for Oxygen Regeneration

A critical component in spacecraft life support loop closure is the removal of carbon dioxide (CO2, produced by the crew) from the cabin atmosphere and chemical reduction of this CO2 to recover the oxygen. In 2015, we initiated development of an oxygen recovery system for life support applications consisting of a solid oxide co-electrolyzer (SOCE) and a carbon formation reactor (CFR). The SOCE electrolyzes a combined stream of carbon dioxide (CO2) and water (H2O) gas mixtures to produce synthesis gas (e.g., CO and H2 gas) and pure dry oxygen as separate products. This SOCE is being developed from a NASA GRC solid oxide fuel cell and stack design originally developed for aeronautics longduration power applications. The CFR, being developed by pHMatter LLC, takes the CO and H2 output from the SOCE, and converts it primarily to solid carbon (C(s)) and H2O and CO2. Although the solid carbon accumulates in the CFR, the innovative design allows easy removal of the carbon product, requiring minimal crew member (CM) time and low resupply mass (1.0 kg/year/CM) for replacement of the solid carbon catalyst, a significant improvement over previous Bosch reactor approaches. In this work, we will provide a status of our Phase I efforts in the development and testing of both the SOCE and CFR prototype units, along with an initial assessment of the combined SOCE-CFR system, including a mass and power projections, along with an estimate of the oxygen recovery rate.