High Temperature Carbonized Grass as a High Performance Sodium Ion Battery Anode

Hard carbon is currently considered the most promising anode candidate for room temperature sodium ion batteries because of its relatively high capacity, low cost, and good scalability. In this work, switchgrass as a biomass example was carbonized under an ultrahigh temperature, 2050 °C, induced by Joule heating to create hard carbon anodes for sodium ion batteries. Switchgrass derived carbon materials intrinsically inherit its three-dimensional porous hierarchical architecture, with an average interlayer spacing of 0.376 nm. The larger interlayer spacing than that of graphite allows for the significant Na ion storage performance. Compared to the sample carbonized under 1000 °C, switchgrass derived carbon at 2050 °C induced an improved initial Coulombic efficiency. Additionally, excellent rate capability and superior cycling performance are demonstrated for the switchgrass derived carbon due to the unique high temperature treatment

Nanocellulose-based Translucent Diffuser for Optoelectronic Device Applications with Dramatic Improvement of Light Coupling

Nanocellulose is a biogenerated and biorenewable organic material. Using a process based on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)/NaClO/NaBr system, a highly translucent and light-diffusive film consisting of many layers of nanocellulose fibers and wood pulp microfibers was made. The film demonstrates a combination of large optical transmittance of ∼90% and tunable diffuse transmission of up to ∼78% across the visible and near-infrared spectra. The detailed characterizations of the film indicate the combination of high optical transmittance and haze is due to the film’s large packing density and microstructured surface. The superior optical properties make the film a translucent light diffuser and applicable for improving the efficiencies of optoelectronic devices such as thin-film silicon solar cells and organic light-emitting devices

High Temperature Carbonized Grass as a High Performance Sodium Ion Battery Anode

Hard carbon is currently considered the most promising anode candidate for room temperature sodium ion batteries because of its relatively high capacity, low cost, and good scalability. In this work, switchgrass as a biomass example was carbonized under an ultrahigh temperature, 2050 °C, induced by Joule heating to create hard carbon anodes for sodium ion batteries. Switchgrass derived carbon materials intrinsically inherit its three-dimensional porous hierarchical architecture, with an average interlayer spacing of 0.376 nm. The larger interlayer spacing than that of graphite allows for the significant Na ion storage performance. Compared to the sample carbonized under 1000 °C, switchgrass derived carbon at 2050 °C induced an improved initial Coulombic efficiency. Additionally, excellent rate capability and superior cycling performance are demonstrated for the switchgrass derived carbon due to the unique high temperature treatment

Highly Transparent and Flexible Nanopaper Transistors

Renewable and clean “green” electronics based on paper substrates is an emerging field with intensifying research and commercial interests, as the technology combines the unique properties of flexibility, cost efficiency, recyclability, and renewability with the lightweight nature of paper. Because of its excellent optical transmittance and low surface roughness, nanopaper can host many types of electronics that are not possible on regular paper. However, there can be tremendous challenges with integrating devices on nanopaper due to its shape stability during processing. Here we demonstrate for the first time that flexible organic field-effect transistors (OFETs) with high transparency can be fabricated on tailored nanopapers. Useful electrical characteristics and an excellent mechanical flexibility were observed. It is believed that the large binding energy between polymer dielectric and cellulose nanopaper, and the effective stress release from the fibrous substrate promote these beneficial properties. Only a 10% decrease in mobility was observed when the nanopaper transistors were bent and folded. The nanopaper transistor also showed excellent optical transmittance up to 83.5%. The device configuration can transform many semiconductor materials for use in flexible green electronics

Natural Cellulose Fiber as Substrate for Supercapacitor

Cellulose fibers with porous structure and electrolyte absorption properties are considered to be a good potential substrate for the deposition of energy material for energy storage devices. Unlike traditional substrates, such as gold or stainless steel, paper prepared from cellulose fibers in this study not only functions as a substrate with large surface area but also acts as an interior electrolyte reservoir, where electrolyte can be absorbed much in the cellulose fibers and is ready to diffuse into an energy storage material. We demonstrated the value of this internal electrolyte reservoir by comparing a series of hierarchical hybrid supercapacitor electrodes based on homemade cellulose paper or polyester textile integrated with carbon nanotubes (CNTs) by simple solution dip and electrodeposited with MnO₂. Atomic layer deposition of Al₂O₃ onto the fiber surface was used to limit electrolyte absorption into the fibers for comparison. Configurations designed with different numbers of ion diffusion pathways were compared to show that cellulose fibers in paper can act as a good interior electrolyte reservoir and provide an effective pathway for ion transport facilitation. Further optimization using an additional CNT coating resulted in an electrode of paper/CNTs/MnO₂/CNTs, which has dual ion diffusion and electron transfer pathways and demonstrated superior supercapacitive performance. This paper highlights the merits of the mesoporous cellulose fibers as substrates for supercapacitor electrodes, in which the water-swelling effect of the cellulose fibers can absorb electrolyte, and the mesoporous internal structure of the fibers can provide channels for ions to diffuse to the electrochemical energy storage materials

Dynamics of a Water Nanodrop through a Holey Graphene Matrix: Role of Surface Functionalization, Capillarity, and Applied Forcing

Nanoporous graphene has emerged as an excellent material for desalination and water purification. Holey graphene (HG) is a special form of nanoporous graphene, where multilayers of nanoporous graphene get arranged in spatially separated stacks. In this paper, we employ molecular dynamics simulations to unravel the dynamics of a water drop in presence of an applied force <i>F</i> in such holey graphene architecture, which is characterized by the presence of either hydrophilic functionalization (HIF) or hydrophobic functionalization (HOF) of the edges of the holes. For realistic values of <i>F</i>, the consideration of water drop makes the capillary effects important, which in turn interplays with the wettability of the surface functionalization to ensure that the HG with the HOF causes both an enhanced flux and an enhanced permeated water volume. We relate these phenomena to the augmented water-hydrophilic-edge attraction that arrests the dewetting of water from the graphene stacks and slows the speed of water flowing past the graphene edges. Finally, we discover a time interval when a quasi-steady flux of water comes out of the HG for either types of functionalization and therefore attempts a Darcy’s law-like description of the water flux only to witness a capillarity-induced breakdown of Darcy’s law with the flux being proportional to <i>F</i>^α, where α_HOF > α_HIF > 1

Interfacial Oxygen Stabilizes Composite Silicon Anodes

Silicon can store Li⁺ at a capacity 10 times that of graphite anodes. However, to harness this remarkable potential for electrical energy storage, one has to address the multifaceted challenge of volume change inherent to high capacity electrode materials. Here, we show that, solely by chemical tailoring of Si-carbon interface with atomic oxygen, the cycle life of Si/carbon matrix-composite electrodes can be substantially improved, by 300%, even at high mass loadings. The interface tailored electrodes simultaneously attain high areal capacity (3.86 mAh/cm²), high specific capacity (922 mAh/g based on the mass of the entire electrode), and excellent cyclability (80% retention of capacity after 160 cycles), which are among the highest reported. Even at a high rate of 1C, the areal capacity approaches 1.61 mAh/cm² at the 500th cycle. This remarkable electrochemical performance is directly correlated with significantly improved structural and electrical interconnections throughout the entire electrode due to chemical tailoring of the Si-carbon interface with atomic oxygen. Our results demonstrate that interfacial bonding, a new dimension that has yet to be explored, can play an unexpectedly important role in addressing the multifaceted challenge of Si anodes

Dynamics of a Water Nanodrop through a Holey Graphene Matrix: Role of Surface Functionalization, Capillarity, and Applied Forcing

Nanoporous graphene has emerged as an excellent material for desalination and water purification. Holey graphene (HG) is a special form of nanoporous graphene, where multilayers of nanoporous graphene get arranged in spatially separated stacks. In this paper, we employ molecular dynamics simulations to unravel the dynamics of a water drop in presence of an applied force <i>F</i> in such holey graphene architecture, which is characterized by the presence of either hydrophilic functionalization (HIF) or hydrophobic functionalization (HOF) of the edges of the holes. For realistic values of <i>F</i>, the consideration of water drop makes the capillary effects important, which in turn interplays with the wettability of the surface functionalization to ensure that the HG with the HOF causes both an enhanced flux and an enhanced permeated water volume. We relate these phenomena to the augmented water-hydrophilic-edge attraction that arrests the dewetting of water from the graphene stacks and slows the speed of water flowing past the graphene edges. Finally, we discover a time interval when a quasi-steady flux of water comes out of the HG for either types of functionalization and therefore attempts a Darcy’s law-like description of the water flux only to witness a capillarity-induced breakdown of Darcy’s law with the flux being proportional to <i>F</i>^α, where α_HOF > α_HIF > 1

Dynamics of a Water Nanodrop through a Holey Graphene Matrix: Role of Surface Functionalization, Capillarity, and Applied Forcing

Nanoporous graphene has emerged as an excellent material for desalination and water purification. Holey graphene (HG) is a special form of nanoporous graphene, where multilayers of nanoporous graphene get arranged in spatially separated stacks. In this paper, we employ molecular dynamics simulations to unravel the dynamics of a water drop in presence of an applied force <i>F</i> in such holey graphene architecture, which is characterized by the presence of either hydrophilic functionalization (HIF) or hydrophobic functionalization (HOF) of the edges of the holes. For realistic values of <i>F</i>, the consideration of water drop makes the capillary effects important, which in turn interplays with the wettability of the surface functionalization to ensure that the HG with the HOF causes both an enhanced flux and an enhanced permeated water volume. We relate these phenomena to the augmented water-hydrophilic-edge attraction that arrests the dewetting of water from the graphene stacks and slows the speed of water flowing past the graphene edges. Finally, we discover a time interval when a quasi-steady flux of water comes out of the HG for either types of functionalization and therefore attempts a Darcy’s law-like description of the water flux only to witness a capillarity-induced breakdown of Darcy’s law with the flux being proportional to <i>F</i>^α, where α_HOF > α_HIF > 1

Dynamics of a Water Nanodrop through a Holey Graphene Matrix: Role of Surface Functionalization, Capillarity, and Applied Forcing

Nanoporous graphene has emerged as an excellent material for desalination and water purification. Holey graphene (HG) is a special form of nanoporous graphene, where multilayers of nanoporous graphene get arranged in spatially separated stacks. In this paper, we employ molecular dynamics simulations to unravel the dynamics of a water drop in presence of an applied force <i>F</i> in such holey graphene architecture, which is characterized by the presence of either hydrophilic functionalization (HIF) or hydrophobic functionalization (HOF) of the edges of the holes. For realistic values of <i>F</i>, the consideration of water drop makes the capillary effects important, which in turn interplays with the wettability of the surface functionalization to ensure that the HG with the HOF causes both an enhanced flux and an enhanced permeated water volume. We relate these phenomena to the augmented water-hydrophilic-edge attraction that arrests the dewetting of water from the graphene stacks and slows the speed of water flowing past the graphene edges. Finally, we discover a time interval when a quasi-steady flux of water comes out of the HG for either types of functionalization and therefore attempts a Darcy’s law-like description of the water flux only to witness a capillarity-induced breakdown of Darcy’s law with the flux being proportional to <i>F</i>^α, where α_HOF > α_HIF > 1