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Hybrid electric storage systems that combine capacitive and faradaic materials need to be well designed to benefit from the advantages of batteries and supercapacitors. The ultimate capacitive material is graphite (GR), yet high capacitance is usually not achieved due to restacking of its sheets. Therefore, an appealing approach to achieve high power and energy systems is to embed a faradaic 2D material in between the graphite sheets. Here, a simple one‐step approach was developed, whereby a faradaic material [layered double hydroxide (LDH)] was electrochemically formed inside electrochemically exfoliated graphite. Specifically, GR was exfoliated under negative potentials by CoII and, in the presence of MnII, formed GR‐CoMn‐LDH, which exhibited a high areal capacitance and energy density. The high areal capacitance was attributed to the exfoliation of the graphite at very negative potentials to form a 3D foam‐like structure driven by hydrogen evolution as well as the deposition of CoMn‐LDH due to hydroxide ion generation inside the GR sheets. The ratio between the CoII and MnII in the CoMn‐LDH was optimized and analyzed, and the electrochemical performance was studied. Analysis of a cross‐section of the GR‐CoMn‐LDH confirmed the deposition of LDH inside the GR layers. The areal capacitance of the electrode was 186 mF cm−2 at a scan rate of 2 mV s−1. Finally, an asymmetric supercapacitor was assembled with GR‐CoMn‐LDH and exfoliated graphite as the positive and negative electrodes, respectively, yielding an energy density of 96.1 μWh cm−3 and a power density of 5 mW cm−3. [ABSTRACT FROM AUTHOR]

The synthesis of multi‐carbon products through electrochemical CO2 reduction reactions has attracted great interest from researchers. Herein, nitrogen‐ and carbon‐doped copper nanocatalyst (NC−Cu) containing abundant Cu−N−C active sites was prepared by thermal decomposition of the complexes containing copper and melamine. The NC−Cu catalyst exhibited an ideal current density of 22 mA cm−2 at −0.93 V versus reversible hydrogen electrode (vs. RHE) in CO2‐saturated 0.5 M KHCO3 medium, with ethanol as the predominant product at −0.93 V (vs. RHE) and a maximum Faraday efficiency of 31 %. The current density of the catalyst remained almost unchanged after 20 h of electrolysis, indicating its excellent stability. The excellent catalytic ability is attributed to the abundant Cu−N−C active sites of NC−Cu with 3D porous microstructure. [ABSTRACT FROM AUTHOR]

Cobalt‐glycolate (Co‐glycolate) is a kind of layered coordination polymer with abundant electrochemically active sites but low conductivity. The fabrication of heterostructures is a novel strategy to enhance the electrical conductivity. Herein, Co‐glycolate serves as a host substrate for the in situ growth of guest ZIF‐67 to build MOFs‐on‐CPs heterostructures (named Co‐glycolate /ZIF‐67) via a simple ligand‐exchange method as an anode for lithium‐ion batteries. A heterojunction interface with distorted lattice between the Co‐glycolate phase and the ZIF‐67 phase can be observed. Theoretical calculations and experimental results simultaneously prove that the formed heterojunction reduces the band gap and enhances the conductivity. Compared with both single components, optimized Co‐glycolate/ZIF‐67 shows a higher capacity and better cycling and rate performances due to the improved charge‐transfer rate of the heterostructure. Its specific capacity remains at 652 mAh g−1 after 800 cycles at 1 A g−1. These excellent electrochemical properties can be due to the smaller size, rough surface, and strong combination of a unique heterostructure as well as to the greatly reduced band gap of the individual components. A lithium‐storage mechanism for Co‐glycolate/ZIF‐67 was proposed. This work provides a new strategy for building MOFs‐on‐CPs heterostructures to improve the electrochemical performance of metal‐glycolate‐based electrode materials for energy‐storage and conversion systems. [ABSTRACT FROM AUTHOR]

Heterostructured composites, inheriting the integrated properties of the individual components due to the synergistic effect, have engendered great attention in materials science and energy storage. However, conventional biphasic heterostructures not only optimize the performance of the composites but also aggregate the inevitable drawbacks, which can be addressed with the construction of the triphasic heterostructures by introducing an appropriate intermediate phase, significantly. Herein, a two‐dimensional (2D) double‐heterostructures MoSe2‐TiO2‐MXene anode is architected for Li‐ion storage, which combines the advantages of the high theoretical capacity of MoSe2 and metallic conductivity of MXene. Besides, the in‐situ derived TiO2 can alleviate the irreversible phase transition of MoSe2, arising from the low electronic/ionic conductivities, through electronic coupling effects. Meanwhile, the intermediate phase of TiO2 can further prevent the restacking issue of MXene, thus sustaining its high conductivity. Finally, the three‐dimensional (3D) printing technology is employed to further improve the kinetics of the electrodes for Li‐ion capacitors (LICs), which deliver the power density of 5563 W kg−1 at an energy density of 51 Wh kg−1, and a remarkable cycling stability for 20 000 cycles at 1 A g−1. This work deepens the understanding of the influence of heterostructured engineering on the design of high‐energy/power storage devices. [ABSTRACT FROM AUTHOR]