Developing a facile and cost-efficient method to synthesize carbon-based nanomaterials possessing excellent structural and functional properties has become one of the most attractive topics in energy conversion and storage fields. In this study, density functional theory calculation results reveal the origin of high oxygen reduction reaction (ORR) activity predominantly derived from the synergistic effect of intrinsic defects and heteroatom dopants (e.g., N, S) that modulate the bandgap and charge density distribution of carbon matrix. Under the guidance of the first-principle prediction, by using ultralight biomass waste as precursor of C, N, and S elements, a defect-rich and N/S dual-doped cheese-like porous carbon nanomaterial is successfully designed and constructed. Herein, the intrinsic defects are artfully generated in terms of alkaline and ammonia activation. The electrochemical measurements display that such a material owns a comparable ORR activity (E = 0.835 V) to the commercial Pt/C catalyst, along with splendid durability and methanol tolerance in alkali media. Furthermore, as cathode catalyst, it displays a high Zn-air battery performance. The excellent ORR activity of the catalyst can be attributed to its unique 3D porous architecture, abundant intrinsic defects, and high-content active heteroatom dopants in the carbon matrix.

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In order to quickly obtain the voltage value of each node after the power system line is disconnected, a fast and accurate calculation method of breaking voltage based on Taylor series expansion is proposed in this study, which can calculate the value of nodal voltage of the system in a short time. At first, a breaking parameter is introduced into the admittance of the disconnected line, and a nonlinear disconnection function is constructed about the breaking parameter. After the line is disconnected, the voltage of each node and the admittance matrix of each node are functions of the relevant parameters, and then, the Taylor series is used to expand. The voltage of each node of the system before breaking is considered as the initial value of the Taylor series, and the first, second, and third derivatives of the node voltage with respect to the parameter are considered as the correction term; the voltage of each node of the system is calculated after the line is disconnected. Finally, the simulation results of the IEEE 14-node system are used to verify the correctness of the proposed method.