Fig. 7.

(A) Calculated ECSA, MA, SA at 0.9 V vs. RHE of Pt₃Co/C before and after stability tests, after a series of annealing temperatures for 2 h. (B) Normalized retention of MA, SA, and ECSA on the left axis and half-wave potential shift on the right axis of Pt₃Co/C after annealing at different temperatures. Normalized retention was calculated based on the ratio of the initial activity/surface areas to that after durability tests (2,000 cycles in cyclic voltammetry at 100 mV/sec in 0.1 M HClO₄ over the potential at the range from 0.6 to 1.0 V vs. RHE). The best durability was achieved at around 750 °C, corresponding to the optimal degree of ordering.