Development of an efficient hydrogen evolution reaction (HER) catalyst composed of earth-abundant elements is scientifically and technologically important for the water splitting associated with the conversion and storage of renewable energy. Herein we report a new class of Co-C-N complex bonded carbon (only 0.22 at% Co) for HER with a self-supported and three-dimensional porous structure that shows an unexpected catalytic activity with low overpotential (212 mV at 100 mA cm(-2)) and long-term stability, better than that of most traditional-metal catalysts. Experimental observations in combination with density functional theory calculations reveal that C and N hybrid coordination optimizes the charge distribution and enhances the electron transfer, which synergistically promotes the proton adsorption and reduction kinetics.

Prussian blue analogs with an open framework are ideal cathodes for Na‐ion batteries. A superior high‐rate and highly stable monoclinic nickel hexacyanoferrate (NiHCF‐3) is synthesized via a facile one‐step crystallization‐controlled co‐precipitation method. It gives a high specific capacity of 85.7 mAh g−1, nearly to its theoretical value. It also exhibits an excellent rate capability with a high capacity retention ratio of 78% at 50 C and a stable cycling performance over 1200 cycles. Through the ex situ X‐ray diffraction and pair distribution function measurements, it is found that the monoclinic structure with distorted framework is greatly related to the high Na content. The electronic structure studies by density functional theory (DFT) calculation demonstrate that NiHCF‐3 deformation promotes the framework conductivity and improves the electrochemical activity of Fe, which results in an ultrahigh‐rate performance of monoclinic phase. Furthermore, the high‐quality monoclinic (NiHCF‐3) exhibits excellent compatibility with both hard carbon and NaTi2(PO4)3 anodes in full cells, which shows great prospects for the application in the large‐scale energy storage systems.

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Hard carbon (HC) is one of the most promising anode materials for sodium-ion batteries (SIBs) due to its suitable potential and high reversible capacity. At the same time, the correlation between carbon local structure and sodium-ion storage behavior is not clearly understood. In this paper, the two series of HC materials with perfect spherical morphology and tailored microstructures were designed and successfully produced using resorcinol formaldehyde (RF) resin as precursor. Via hydrothermal self-assembly and controlled pyrolysis, RF is a flexible precursor for high-purity carbon with a wide range of local-structure variation. Using these processes, one series of five representative RF-based HC nanospheres with varying degrees of graphitization were obtained from an RF precursor at different carbonization temperatures. The other series of HC materials with various microscopic carbon layer lengths and shapes was achieved by carbonizing five RF precursors with different cross-linking degrees at a single carbonization condition (1300 °C and 2 h). On the basis of the microstructures, unique electrochemical characteristics, and atomic pair distribution function (PDF) analyses, we proposed a new model of “three-phase” structural for HC materials and found triregion Na-ion storage behavior: chemi-/physisorption, intercalation between carbon layers, and pore-filling, derived from the HC phases, respectively. These results enable new understanding and insight into the sodium storage mechanism in HC materials and improve the potential for carbon-based SIB anodes.