packaging, account for a large fraction of the total weight of the device, the use of thin electrodes results in a signifi cantly lower energy density than what could be attained using thicker electrodes. [ 3 ] Therefore, the development of thick electrodes for supercapacitors represents an important direction for making high-energy supercapacitors for practical applications.We recently developed a class of pseudocapacitive anode materials for asymmetric supercapacitors composed of interpenetrating networks of carbon nanotubes (CNTs) and V 2 O 5 nanowires. [ 16 ] The CNTs and nanowires were intimately intertwined into a hierarchically porous structure, enabling effective electrolyte access to the electrochemically active materials without limiting charge transport. Such composites exhibited high specifi c capacitance ( > 300 F g − 1 ) at high current density (1 A g − 1 ) in aqueous electrolyte. In this paper we report the fabrication of high energy density asymmetric supercapacitors containing thick-fi lm electrodes (over 100 μ m thick) of the CNT/V 2 O 5 nanowire composite in combination with an organic electrolyte, which allows for a higher initial cell potential. The excellent conductivity, high specifi c capacitance, and large voltage window of the CNT/V 2 O 5 nanocomposite enable the fabrication of devices with an energy density as high as 40 Wh kg − 1 at a power density of 210 W kg − 1 . Even at a high power density of 6 300 W kg − 1 , the device possesses an energy density of nearly 7.0 Wh kg − 1 . Moreover, the resulting devices exhibit excellent cycling stability. This work demonstrates that the nanowire composite approach is an effective strategy towards high-energy and high power density supercapacitors. Figure 1 A shows a representative scanning electron microscopy (SEM) image of a nanocomposite with 18 wt% of CNTs, demonstrating a continuous fi brous structure (Figure 1 A). The intertwined networks of the CNTs and nanowires exhibit an electrical conductivity of ≈ 3.0 S cm − 1 , which is 80 times higher than that of V 2 O 5 nanowires (0.037 S cm − 1 ). Figure 1 B is a transmission electron microscopy (TEM) image of a V 2 O 5 nanowire with a diameter of around 50 nm. The high-resolution TEM (HRTEM) image (inset) suggests the nanowire contains a layered crystalline structure; the small nanowire dimension allows effective Li + diffusion. Moreover, nitrogen sorption isotherms ( Figure S1, Supporting Information) and higher resolution SEM images of the etched composite fi lm (Figure 1 A, inset) show that the composite possesses a hierarchically porous structure; the presence of large pores enables rapid electrolyte transport while the small pores effectively increase the surface area available for electrochemical reactions. These small pores are responsible for the surface area of 125 m 2 g − 1 determined for the composite.An ideal electrical energy storage device provides both high energy and power density. [ 1 , 2 ] Supercapacitors exhibit signifi cantly higher power densities compared to batteries and ...

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Despite the maximized metal dispersion offered by single-atom catalysts, further improvement of intrinsic activity can be hindered by the lack of neighboring metal atoms in these systems. Here we report the use of isolated Pt 1 atoms on ceria as “seeds” to develop a Pt-O-Pt ensemble, which is well-represented by a Pt 8 O 14 model cluster that retains 100% metal dispersion. The Pt atom in the ensemble is 100–1000 times more active than their single-atom Pt 1 /CeO 2 parent in catalyzing the low-temperature CO oxidation under oxygen-rich conditions. Rather than the Pt-O-Ce interfacial catalysis, the stable catalytic unit is the Pt-O-Pt site itself without participation of oxygen from the 10–30 nm-size ceria support. Similar Pt-O-Pt sites can be built on various ceria and even alumina, distinguishable by facile activation of oxygen through the paired Pt-O-Pt atoms. Extending this design to other reaction systems is a likely outcome of the findings reported here.

Hierarchically porous graphite particles are synthesized using a continuous, scalable aerosol approach. The unique porous graphite architecture provides the particles with high surface area, fast ion transportation, and good electronic conductivity, which endows the resulting supercapacitors with high energy and power densities. This work provides a new material platform for high‐performance supercapacitors with high packing density, and is adaptable to battery electrodes, fuel‐cell catalyst supports, and other applications.