Reversible poisoning of nickel/zirconia solid oxide fuel cell anodes by hydrogen chloride in coal gas

The performance of anode-supported solid oxide fuel cells (SOFC) was evaluated in synthetic coal gas containing HCl in the temperature range 650–850 °C. Exposure to up to 800 ppm HCl resulted in reversible poisoning of the Ni/zirconia anode by chlorine species adsorption, the magnitude of which decreased with increased temperature. Performance losses increased with the concentration of HCl to ∼100 ppm, above which losses were insensitive to HCl concentration. Neither cell potential, nor current density had any effect on the extent of poisoning. No evidence was found for long-term degradation that can be attributed to HCl exposure. Similarly, no evidence of microstructural changes or formation of new solid phases as a result of HCl exposure was found. From thermodynamic calculations, solid nickel chloride phase formation was shown to be highly unlikely in coal gas containing HCl. The presence of HCl at even the highest anticipated concentrations in coal gas would minimally increase the volatility of nickel.