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A full understanding of ion transport in porous carbon electrodes is essential for achieving effective energy storage in their applications as electrochemical supercapacitors. It is generally accepted that pores in the size range below 0.5 nm are inaccessible to electrolyte ions and lower the capacitance of carbon materials. Here, nitrogen-doped carbon with ultra-micropores smaller than 0.4 nm with a narrow size distribution, which represents the first example of electrode materials made entirely from ultra-microporous carbon, is prepared. An in situ electrochemical quartz crystal microbalance technique to study the effects of the ultra-micropores on charge storage in supercapacitors is used. It is found that ultra-micropores smaller than 0.4 nm are accessible to small electrolyte ions, and the area capacitance of obtained sample reaches the ultrahigh value of 330 µF cm , significantly higher than that of previously reported carbon-based materials. The findings provide a better understanding of the correlation between ultra-micropore structure and capacitance and open new avenues for design and development of carbon materials for the next generation of high energy density supercapacitors.

The unique heterostructure MoOx@N-doped MoS2−x was performed in situ by electrochemical oxidation, which showed remarkable OER activity.

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In this work, Ti3SiC2, layered ternary transition metal carbide called MAX phase, was invoked as the anode material for lithium‐ion batteries. Oxygen‐doped Ti3SiC2, named O‐Ti3SiC2, was produced by calcination in air. The initial reversible capacity was ∼70 mAh g−1 at 10 C, which increased to ∼180 mAh g−1 after 3000 cycles. The capacity was four times higher than original Ti3SiC2, showing a suitable electrochemical performance.

Carbonaceous materials are considered to be the most promising anode materials of Potassium‐ion batteries (PIBs). However, for most carbon‐based PIBs anode materials reported so far, they usually deliver low reversible capacities, insufficient cycle life and poor rate capability. In this work, we report a novel P/N co‐doped carbon nanotube (PNCNTs) material as the anode material for PIBs. The material with fully exposed active edges and open fast ion/electron transfer structure can effectively shorten the K+ transfer distance. Furthermore, the P/N co‐doping provides abundant electrochemical active adsorption sites and extended interlayer spacing, which facilitates the rapid insertion/removal of K+, increases the surface charge capacity and maintains the structural stability of the electrode material. As expected, when used as the anode material for PIBs, PNCNTs exhibited a high specific capacity (612.2 mA h g−1 at 100 mA g−1), excellent rate capability (190, 183 and 165 mA h g−1 at 0.5, 1.0, and 2.0 A g−1 after 500 cycles, respectively) as well as remarkable long‐term cycling stability (162 mA h g−1 at 2.0 A g−1 after 1400 cycles). Through further kinetic analysis and a simple first‐principles calculation, we revealed the dominated capacity‐controlled absorption mechanism of potassium storage in PNCNTs.

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