The role of sintering time on reversibility of Ni(s)?NiO(s) electrodes for high temperature solid oxide electrolyte galvanic cells

Abstract

The reversibility of solid electrolyte galvanic cells such as $${\text{Mo/Ni(s)}}--{\text{NiO(s)/CSZ/Fe(s)}}--{\text{Fe}}_{{\text{1}}--\delta } {\text{O(s)/Mo}}$$ has been studied with respect to the sintering time of the active powders. Pellets from short (7h) and long (14h) sintering times have been prepared and assembled to give the above cells. Each of them has been thermally cycled and only the cells containing Ni(s)-NiO(s) electrodes prepared with a long sintering time give emf versus T curves which are independent of cycle. These values are in close agreement with the literature. For the cell reaction $${\text{NiO(s)}} + (1 - \delta ){\text{Fe(s) = Ni(s)}} + {\text{Fe}}_{1 - \delta } {\text{O(s)}}$$ the free energy change $$\Delta G = - (27.85 \pm 0.06) - (0.02157 \pm 0.00004)T{\text{ kJ mol}}^{ - {\text{1}}} $$ has been found in the temperature range 977–1350 K.