ZnO-promoted surface diffusion on NiO-Ce0.8Sm0.2O1.9 anode for solid oxide fuel cell

Abstract

Ni1-xZnxO-Ce0.8Sm0.2O1.9 is studied as an anode material for solid oxide fuel cells with hydrogen and methanol as fuels. After reduction, Zn is incorporated into the lattice of Ni when x is less than 0.5, while NiZn alloy accompanied with ZnO is formed when x reaches 0.8. The electrochemical oxidation process of H2 on the anode is investigated with a symmetric cell under various H2 partial pressures. The addition of Zn increases the electron cloud density of Ni and thus weakens the adsorbing strength of H on Ni, accelerating the surface diffusion of H species, which is the rate determining step when the content of Zn is lower than 0.5. ZnO in the reduced Ni0·2Zn0·8O- Ce0.8Sm0.2O1.9 anode facilitates H spillover, resulting in the variation of the rate determining step and the highest activity of the anode. The cell with Ni0·2Zn0·8O- Ce0.8Sm0.2O1.9 anode shows the highest performance with both H2 and methanol fuels at 700 °C. ZnO also improves coking resistance of NiO-Ce0.8Sm0.2O1.9 anode.