In situ Van der Pauw measurements of the Ni/YSZ anode during exposure to syngas with phosphine contaminant

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.

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“…As in previous studies, [3][4][5][6][7][8][9][10][11][12][13] this coating yields XRD spectra consistent with nickel phosphide phases.…”

Section: Resultssupporting

confidence: 71%

Mass Spectrometry of SOFC Fuel Mixtures Containing Phosphine

Finklea

Zhang

Jony

et al. 2015

J. Electrochem. Soc.

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“…Periodic impedance measurements revealed a slight increase in the ohmic resistance and a significant increase in the polarization resistance accompanying the power degradation. The resistivity of the anode, obtained via in-situ Van der Pauw measurements of the anode, did not increase significantly during the degradation [2]. Post-mortem SEM analysis revealed the severe nickel migration to the surface of the anode and into pores in the anode structure, Figure 5, mostly in a form of Ni 3 P as verified by XRD analysis.…”

Section: Effect Of Phosphorusmentioning

confidence: 80%

Overview of SOFC Anode Interactions with Coal Gas Impurities

Marina

Pederson

Gemmen³

et al. 2010

ECS Trans.

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An overview of the results of SOFC anode interactions with phosphorus, arsenic, selenium, sulfur, antimony, and hydrogen chloride as single contaminants or in combinations is discussed. Tests were performed using both anode- and electrolyte-supported cells in synthetic and actual coal gas for periods greater than 1000 hours. Post-test analyses were performed to identify reaction products formed and their distribution, and compared to phases expected from thermochemical modeling. The ultimate purpose of this work is to establish maximum permissible concentrations for impurities in coal gas, to aid in the selection of appropriate coal gas clean-up technologies.

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“…The furnace and gas handling system details have been described in previous studies [4,5]. The furnace temperature was increased to 800 • C at the rate of 2 • C min −1 , while exposing the anode to a dry H 2 (30 sccm)-N 2 (200 sccm) gas mixture and the cathode to air (200 sccm).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The effect of syngas contaminants on the Ni/YSZ anode has been a popular research subject [1]. Volatile phosphorus species in syngas, particularly phosphine (PH 3 ), are known to cause irreversible and immediate degradation of the performance of the Ni/YSZ anode [2][3][4][5][6][7]. The degradation of Ni/YSZ anode performance due to the presence of PH 3 at ppm levels could be the result of two different mechanisms: (i) the loss of Ni (loss of TPB length) in the active layer of the anode via nickel migration out of the anode active layer due to facile reactions between Ni and P and (ii) the production of Ni-P compounds resulting in a decrease in the number of active Ni sites in catalytic anode layer.…”

Section: Introductionmentioning

confidence: 99%