Preparation and electrochemical properties of Nd_{2 - x}Sr_xFeO_{4 + d} {hbox{N}}{{hbox{d}}_{{{2} - x}}}{hbox{S}}{{hbox{r}}_x}{hbox{Fe}}{{hbox{O}}_{{{4} + delta }}} cathode materials for intermediate-temperature solid oxide fuel cells

摘要

Cathodic materials Nd_{2 - x}Sr_xFeO_{4 + d} {hbox{N}}{{hbox{d}}_{{{2} - x}}}{hbox{S}}{{hbox{r}}_x}{hbox{Fe}}{{hbox{O}}_{{{4} + delta }}} (x = 0.5, 0.6, 0.8, 1.0) with K₂NiF₄-type structure, for use in intermediate-temperature solid oxide fuel cells (IT-SOFCs), have been prepared by the glycine–nitrate process and characterized by XRD, SEM, AC impedance spectroscopy, and DC polarization measurements. The results have shown that no reaction occurs between an Nd_{2 - x}Sr_xFeO_{4 + d} {hbox{N}}{{hbox{d}}_{{{2} - x}}}{hbox{S}}{{hbox{r}}_x}{hbox{Fe}}{{hbox{O}}_{{{4} + delta }}} electrode and an Sm_0.2Gd_0.8O_1.9 electrolyte at 1,200 °C, and that the electrode forms a good contact with the electrolyte after sintering at 1,000 °C for 2 h. In the series Nd_{2 - x}Sr_xFeO_{4 + d} {hbox{N}}{{hbox{d}}_{{{2} - x}}}{hbox{S}}{{hbox{r}}_x}{hbox{Fe}}{{hbox{O}}_{{{4} + delta }}} (x = 0.5, 0.6, 0.8, 1.0), the composition Nd_1.0Sr_1.0FeO_{4 + d} {hbox{N}}{{hbox{d}}_{{{1}.0}}}{hbox{S}}{{hbox{r}}_{{{1}.0}}}{hbox{Fe}}{{hbox{O}}_{{{4} + delta }}} shows the lowest polarization resistance and cathodic overpotential, 2.75 Ω cm2 at 700 °C and 68 mV at a current density of 24.3 mA cm−2 at 700 °C, respectively. It has also been found that the electrochemical properties are remarkably improved the increasing Sr content in the experimental range.