The design of noble-metal-free catalysts for oxygen reduction reaction (ORR) is very important to the commercialization of fuel cells. Here, we use a Co-modified montmorillonite (Co-MMT) as a flat template to prepare Co- and N-doped nanocarbon ORR catalysts derived from carbonization of polyaniline at controlled temperatures. The use of flat template can hinder the agglomeration of polyaniline during pyrolysis process and optimize the N-rich active site density on the surface. The addition of transition metal Co in the flat MMT template can largely promote the formation of Co–N sites in prepared catalyst, facilitating the effective improvement of catalytic activity towards the ORR with a direct four-electron transfer pathway. The excellent ORR activity may be mainly attributed to high contents of graphitic N, pyridinic-N, and Co-N configurations. This study opens a new way to rationally design cheap and active ORR catalysts by using simple flat compound as a direct template.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1804-z) contains supplementary material, which is available to authorized users.

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Shock-induced depolarization of the ferroelectrics could generate a depoling current, which has been utilized widely in the energy conversion devices, such as explosive-driven ferroelectric generators and high pulsed power sources. Among all these ferroelectrics, the lead zirconate/titanate ferroelectric ceramic received most of the attention due to their high energy density and low depolarization pressure, especially Pb(Zr0.95Ti0.05)O3 (PZT 95/5). The dynamic permittivity of PZT 95/5 under the shock compression is critical for their applications, which determines the efficiency of the energy conversion. However, to reveal the dynamic permittivity of the ferroelectrics is challenging, the depolarization process during the shock compression is not only short (∼μs) but also coupled with a high electrical field. In this study, the dynamic permittivity of the PZT 95/5 ceramic in shock compression under high electrical fields has been investigated by using a designed oscillation circuit. The experimental results show that the relative permittivity of PZT 95/5 is about 500 at the initial shock compression, and it is only about 220 after shock transit. This decrease would be explained by the PZT 95/5 phase transition under high pressure. In addition, it is found that the permittivity of poled PZT 95/5 is more sensitive to the electrical field than depoled PZT 95/5, and the damping resistances of poled PZT 95/5 could also be influenced by electric fields.