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Heterostructure construction is an efficient method for reinforcing K+ storage of transition metal selenides. The spontaneously developed internal electric fields give a strong boost to charge transport and significantly reduce the activation energy. Nevertheless, perfection of the interfacial region based on the energy level gradient and lattice matching degree is still a great challenge. Herein, rich vacancies and ultrafine CoSe2–FeSe2 heterojunctions with semicoherent phase boundary are simultaneously obtained, which possess unique electronic structures and abundant active sites. When employed as anodes for potassium‐ion batteries (PIBs), CoSe2–FeSe2@C composites display a reversible potassium storage of 401.1 mAh g−1 at 100 mA g−1 and even 275 mAh g−1 at 2 A g−1. Theoretical calculation also reveals that the potassium‐ion diffusion can be dramatically promoted by the controllable CoSe2–FeSe2 heterojunction.

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Accelerated testing that targets specific mechanisms of chemical and mechanical durability, and tests that target both failure mechanisms at the same time can be an effective tools to advance membrane technologies for PEM fuel cells. Such tests should be accelerated to reduce development times, with conditions relevant to the given application. In studies of membrane mechanical durability, uniform membrane degradation was obtained by using careful test design. When conducting a combined mechanism accelerated test, the relative balance of the two mechanisms should be considered. Too much mechanical stress in the test can overwhelm improvements in the chemical durability of the materials and vise versa. Customer screening and more realistic testing conditions are used to verify accelerated test conclusions. Test results indicate that combinations of these test protocols enable the dependable selection of more mechanically and chemically durable membranes and also provide quantitative data to assist understanding of degradation mechanisms in fuel cells under various operation conditions.

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Herein, the quantum dots-assisted self-assembly MoSe2-MoO3 with a porous structure is synthesized via a MOFs-directed strategy involving a thermal-induced reaction with Se. As an anode material for sodium ion batteries,...

In order to advance membrane technologies for PEM fuel cells, it is critical to establish an effective testing matrix, which includes tests that target specific mechanisms of chemical and mechanical durability, as well as tests that can challenge the membrane with combined failure mechanisms. Furthermore, the tests should be both accelerated and realistic. In studies of membrane chemical durability, it was discovered that using regular test cells resulted in highly non-uniform membrane degradation in the active area. This compromised the quantitative value of the data and prevented the use of average fluoride release rate over the entire cell as an accurate measure of the chemical degradation rate of the membrane. Therefore, a homogeneous environment was needed for more quantitative studies of membrane chemical durability. Among various options, operation at OCV using standard test cells and operation under a load using high gas stoichiometries with a uniform test cell were chosen. Test results indicate that combinations of these test protocols enable the dependable selection of more chemically durable membranes and also provide quantitative data to assist understanding of degradation mechanisms in fuel cells under various operation conditions.