Summary A new template‐free controlled method is reported herein to prepare the novel hollow carbon nanospheres with dual active sites of FeN4 and FeC3 by in situ growth reaction on graphene nanosheets, labeled as HCN‐FNFCG. As‐prepared HCN‐FNFCG nanomaterials possess hierarchically porous FeN4/FeC3 shells with structures of microporous, mesoporous, and macroporous properties. Moreover, the hierarchically porous HCN‐FNFCG nanomaterials with dual active sites of FeN4 and FeC3 have not been reported before. The HCN‐FNFCG nanomaterials, as oxygen reduction reaction (ORR) catalysts, are first studied systematically toward cathodic ORR of fuel cell. The measurements have illustrated that HCN‐FNFCG‐650 has the best ORR performances among these HCN‐FNFCG nanomaterials studied. The onset potential of HCN‐FNFCG‐650 has reached 1.095 V in alkaline electrolyte, and its maximum current density is 6.48 mA cm−2. Additionally, the HCN‐FNFCG‐650 has also displayed small electrochemical impedance, its Tafel‐slope value is 44.25 mV dec−1, much lower than that of the 20% Pt/C (69.57 mV dec−1). And its value of current density is still maintained 92.83% of the initial value after 9000‐second continuous tests. High tolerance against methanol crossover is also exhibited for HCN‐FNFCG‐650. This novel method of template‐free synthesis can provide a promising strategy for preparing hollow nanospheres with hierarchically porous shells. And it can be used to design ORR electrocatalysts, electrode materials, or other applications.

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The node's energy of wireless sensor networks is limited, so saving energy and prolonging network's lifetime is very important. A multi-hop routing protocol based on grid optimization (MhRPGO) is proposed to improve network's performance in wireless sensor networks. The clustering topology based on grid is used in the network layer, and grid optimization algorithm is adopted to optimize the node's number of neighbor grids in order to equal the number of nodes in different grids. The residual energy and location information of node is used to select cluster head so as to balance the energy consumption of network, and the cluster head replacement mechanism is adopted to replace the old cluster head when its energy is below the energy threshold. The simulation results show that MhRPGO is able to improve clustering feature of network, equally consume network's energy, significantly reduce the number of lost packets which is due to the death of cluster head, and extend the network's lifetime.

In order to solve the hot spot problem of multi-hop network, a redundancy deployment strategy based on energy balance is proposed to improve network performance in wireless sensor networks. In this paper, the clustering topology based on grid is adopted in network layer, and an energy balance model based on redundant nodes rotation dormancy is proposed to deploy more redundant nodes for grids which are closer to base station. By adopting this method, the energy consumption of network can be balanced and the hot spot problem can be improved. The simulation results show that the redundancy deployment strategy proposed in this paper is able to balance the energy consumption of network, improve the hot spot problem of multi-hop network effectively, and extend the network's lifetime.

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