AbstractDegradation of the Ni/yttria‐stabilised zirconia (YSZ) anode of the solid oxide fuel cell has been evaluated in the coal syngas containing different PH3 concentrations in the temperature range from 750 to 900 °C. Thermodynamic equilibrium calculations show that PH3 in the coal syngas gas is converted mostly to P2O3 at 750–900 °C. The phosphorous impurity reacts with the Ni‐YSZ anode to form phosphates. The P‐impurity poisoning leads to the deactivation of the Ni catalyst and to the reduction in the electronic conductivity of the anode. The impurity poisoning effect on the anode is exacerbated by increase in the temperature and/or the PH3 concentration.