The electrocatalytic activity toward oxygen reduction reaction is studied on the perovskite oxide La1?xSrxMn O3, as prepared under different firing temperatures. X-ray diffraction shows that three different crystal phases featuring tetragonal, cubic, and orthorhombic symmetries form with increasing crystallinities. The electrocatalytic activity is characterized by cyclic voltammetry and linear sweeping voltammetry for the three phases of La1?xSrxMn O3. We find that the tetragonal phase has the best catalytic activity among the three crystal phases, with the largest onset potential of 0.147 V. The synergistic effect between the volume per unit cell and crystallinity is indicated to account for the good catalytic activity of the tetragonal phase.
