To enhance the oxygen reduction reaction (ORR) activity of spinel Co 3 O 4 , in this work, a novel strategy of cerium (Ce) modification is developed via the co-precipitation and followed annealing method. The Ce modification not only diminishes the critical size, but also increases the surface content of Co 3 + and elevates the conductivity of the Co 3 O 4 electrocatalysts, working together to enhance the ORR activity. Moreover, the adsorptive CeO 2 on the surface of Co 3 O 4 further promotes the ORR activity by the synergistic effect between CeO 2 and Co 3 O 4 . Typically, the optimized 0.5 % CeÀ Co 3 O 4 exhibits a half-wave potential of 0.665 V versus reversible hydrogen electrode (RHE) and low Tafel slope of À 60 mV dec À 1 as well as long-term stability.

The high compensation degree series compensation has a broad development prospects in long distance and large-capacity UHV transmission lines. But it is generating secondary arc current contains low frequency components with high amplitude when the single-phase grounding fault occurs in the series compensated transmission line, which is not conducive to rapid arc extinguishing. To solve this problem, this paper based on the mechanism of generating secondary arc by series compensation transmission lines, and using ATP – EMTP electromagnetic transient program to establish the simulation model of UHV series compensation device. And the suppression effects of small resistance short connection fault series compensation and linkage bypass series compensation measures on secondary arc current and recovery voltage under different series compensation layout mode are studied respectively. The results show that the attenuation speed of the secondary arc current is related to the series compensation arrangement modes and the time when the series compensation device is short connected or bypassed. Series compensation device short connected or bypassed before circuit breaker tripping which can accelerate the arc extinction speed, and the suppression effect is better when the series compensated double platform segmentation layout is distributed on both sides of the line. The results can be used as a reference for the engineering design of UHV with large capacity and long distance and high compensation series compensation transmission lines.