Phosphine (PH 3 ) is present at ppm concentrations in coal syngas, a potential fuel source for solid oxide fuel cells (SOFCs). A mass spectrometer is used to monitor fuel mixtures of hydrogen and phosphine after exposure to two environments. In the first environment, the gas mixtures are passed through a heated zone in a tube furnace. In the second environment, the gas mixtures are passed across the anodes of operating SOFCs, both electrolyte-and anode-supported. Phosphine appears to react with residual oxygen in dry hydrogen at intermediate temperatures (400-600 • C) but is stable above 600 • C. Phosphine reacts with water in wet hydrogen mixtures and with a Ni/YSZ anode at temperatures above 400 • C. Evidence is presented for deposition of non-volatile contaminants following prolonged phosphine exposure. The contaminants react with dry hydrogen to generate PH 3 at 800 • C. Mass spectra of the anode exhaust of an electrolyte-supported SOFC show that a few torr of water, either present initially or electrochemically generated by fuel oxidation, is sufficient to suppress the phosphine signal. At all gas compositions and currents, no new mass signals were detected in the mass range of 45-100, suggesting that HPO, HPO 2 and HPO 3 are not products of phosphine reaction or electrochemical oxidation.

Phosphine (PH3) is present in part-per-million levels of coal syngas, a potential fuel for SOFCs. Previous studies have shown that the SOFC loses power and ultimately fails during prolonged exposure to ppm levels of phosphine in wet and dry fuels. A mass spectrometer was used to analyze fuel gases after passing the gases through a heated tube or after passing the gases across the anode of an operating SOFC. Phosphine appears to react with residual oxygen at intermediate temperatures in dry hydrogen, but does not react above 600ºC. At higher water concentrations, phosphine reacts at temperatures above 400ºC. Phosphine is detected in the exhaust gas of a SOFC using dry hydrogen while at open circuit, and disappears from the exhaust gas during current flow. No new compounds containing phosphorus were detected in the m/z range of 45-100, eliminating P2, HPO, HPO2 and HPO3 as possible reaction products.

A Study of Solid Oxide Fuel Cell Materials at High Temperature Using an Environmental Scanning Electron Microscope Solid oxide fuel cells (SOFCs) are promising energy conversion devices, but their economic viability depends on long term stability of the SOFC materials at the high operating temperatures. The in-situ study of materials degradation faces a great challenge because of the unavailability of analytical methods at those high temperatures. The traditional analytical techniques for degradation measurements are widely based on postmortem studies. The cells or cell materials are cooled down to room temperature and are then subjected to microscopy-based methods. Combining post-mortem analyses with cell modelling, several studies have reported the following microstructural degradations: (a) Lanthanum Strontium Manganite (LSM) particles, one of the most widely used cathode material, 'melt' or 'spread' at temperatures as low 850 0 C without the presence of a current flow on Yttrium Stabilized Zirconia (YSZ) surface, (b) the Ni particle shapes change during oxidation of nickel to NiO and as a result of reduction of NiO to Ni during redox cycling, (c) the formation of nickel phosphide particles on the Ni/YSZ anode surface due to the presence of PH 3 in coal syngas. However, these reports are limited due to the fact that analyses were done at room temperature rather at their high operating temperature. In this current study, cell materials were examined in-situ at high temperature using an Environmental Scanning Electron Microscope installed with a heating stage. High temperature images were collected for different cell materials such as silver paste, LSM particles, nickel oxide particles and secondary nickel phosphide phase formed on YSZ substrate. The images were analyzed by using ImageJ, an open source image processing software. An image analysis protocol was developed to analyze the cell materials images taken from 500 0 C to 1080 0 C. The image analysis provides both qualitative and quantitative insight of electrode/electrolyte interface. This novel approach of the SOFC materials study suggest that: (a) the absence of detectable microstructural changes in LSM particles as a function of temperature(no sign of 'melting'); (b) NiO particles do not shrink because of partial reduction of NiO to Ni under vacuum at high temperatures, (c) the nickel phosphide particles formed on the Ni/YSZ anode during PH 3 exposure are predominantly Ni 3 P and the particles melt between 900 0 C and 1000 0 C. Based on the findings this study suggests that : (a) the frequently reported increase in polarization resistance at the LSM/YSZ interface with temperature is most likely due to the cation migration rather than formation of new layers because of particle melting or migration, (b) partial reduction of nickel oxide on YSZ surface does not cause crack formation due to the volume reduction, (c) the low melting temperature of nickel Dedicated to my father MD Matiur Rahman and my mother Kohinoor Rahman. v ACKNOWLEDGEMENTS First, I want ...