The use of a single porous mixed ion-electron conducting (MIEC) material as both the oxygen and fuel electrodes in reversible solid oxide cells is of increasing interest, primarily due to the resulting simplified cell design and lower manufacturing costs. In this work, La_0.3Sr_0.7Fe_0.7Cr_0.3O_3−δ (LSFCr-3) was studied in a 3-electrode half-cell configuration in air, pure CO₂ and in a 1 : 1 CO₂ : CO mixture, over a temperature range of 650–800 °C. A detailed analysis of the impedance (EIS) data, under both open circuit and polarized conditions, as well as the cyclic voltammetry response of LSFCr-3 has shown that it is very active in all of these environments, but with oxygen evolution being somewhat more facile that oxygen reduction, and CO₂ reduction more active than CO oxidation. Evidence for a chemical capacitance, associated with the Fe^3+/4+ redox process in LSFCr-3, was also obtained from the EIS and CV data in all gas environments.