According to Planck's law, the emittance of a non-reflective black object - a blackbody - defines the maximum level of thermal emittance from an arbitrary object. Planck's law has been challenged in recent decades by predictions and successful demonstrations of the radiative heat transfer between objects separated by nanoscale gaps that deviate significantly from the law predictions. Researchers have now demonstrated another way to modify the object thermal emission spectrum and to force it to deviate from the one predicted by Planck's law.
Counter intuitive to our idea of 'perfection equals best performance', researchers have shown that defects in nanocarbons could provide a breakthrough for increasing the quantum capacitance. By subjecting graphene layers to a reactive-ion etching process, the team has poked holes into graphene to create holey graphene, which can change the microscopic distribution of electrons and thereby increase the quantum capacitance of graphene by at least fourfold.
The commonly used separators in battery systems are porous polymer membranes, which separate the two electrodes while having little impact on the transportation of ions through the membrane. Polysulfides generated in a lithium-sulfur system can also diffuse freely through the membranes and react with a metal lithium anode, which results in the degradation of the battery's performance. If a novel, ion-selective but highly permeable separator can be developed, the shuttling of polysulfides and self-discharge would be effectively prevented, and both the energy density and power density of lithium-sulfur batteries could be significantly improved.
Supercapacitors offer an alternative source of energy to replace rechargeable batteries for various applications, such as mobile electronics and electric vehicles. Among the various types of supercapacitors, carbon nanotube based devices have shown an order of magnitude higher performance in terms of energy and power densities. The bottleneck for transferring this technology to the marketplace, however, is the lack of efficient and scalable nanomanufacturing methods. Researchers have now developed a new scalable method to to directly spraycoat CNT-based supercapacitor electrodes.
Energy-scavenging fabrics based on nano-sized generators that have piezoelectric properties could eventually lead to wearable 'smart' clothes that can power integrated electronics and sensors through ordinary body movements. Researchers have now demonstrated a new type of fully flexible, very robust and wearable triboelectric nanogenerator with high power-generating performance and mechanical robustness. This was achieved by applying a bottom-up nanostructuring approach where a silver-coated textile and polydimethylsiloxane (PDMS) nanopatterns based on ZnO nanorod arrays were used as active triboelectric materials.
Researchers have created a free-standing carbon nanotube paper electrode with high sulfur loading for lithium-sulfur batteries employing a bottom-up strategy to design and fabricate a hierarchical structure. This new fabrication method does not employ aluminum foil or binders, thereby fully utilizing the advantage of a Li-S system with high specific capacity. This proof-of-concept experiment indicates that the rational design of the nanostructured electrode offers the possibility to efficiently use the active materials at practical loading.
Researchers have demonstrated a unique coaxial carbon nanocable material with pristine carbon nanotubes as the core and nitrogen-doped wrinkled carbon layer as the shell. The active sites rendered by the surface enriched dopant atoms on the carbon nanocables are accessible and effective to catalyze the oxygen involved electrochemical reactions. These coaxial nanocables afford higher ORR/OER current compared with the routine bulk doped nitrogen-doped carbon nanotubes.
Graphene and graphene-based materials have attracted great attention in energy storage applications for batteries and supercapacitors owing to their unique properties of high mechanical flexibility, large surface area, chemical stability, superior electric and thermal conductivities that render them great choices as alternative electrode materials for electrochemical energy storage systems. A recent review article summarizes the progress in graphene and graphene-based materials for four energy storage systems, i.e., lithium-ion batteries, supercapacitors, lithium-sulfur batteries and lithium-air batteries.