Biomass‐Derived 3D Carbon Aerogel with Carbon Shell‐Confined Binary Metallic Nanoparticles in CNTs as an Efficient Electrocatalyst for Microfluidic Direct Ethylene Glycol Fuel Cells

Flexible and 3D carbon aerogels (CAs) composed of carbon nanotubes (CNTs) with carbon shell‐confined binary palladium–nickel (Pd_x–Ni_y) nanocatalysts on carbon fibers (Pd_x–Ni_y/NSCNT/CA) have been developed through a facile chemical vapor deposition method. The 3D porous carbon network and the synergistic effect of carbon shell‐confined bimetal nanoparticles of rationally constructed aerogels facilitate enhanced electrocatalytic and antipoisoning activities toward ethylene glycol (EG) oxidation reaction compared to the commercial Pt/C catalyst. With the 3D morphological features and direct growth of Pd–Ni bimetallic nanoparticles encapsulated CNTs on carbon fibers, the Pd₅₂–Ni₄₈/NSCNT/CA delivers a maximum microfluidic direct ethylene glycol fuel cell (µDEGFC) power density and durability of, respectively, 62.8 mW cm^?2 and 60 h. The superior performance observed, with Pd₅₂–Ni₄₈/NSCNT/CA amongst the catalysts reported in the literature, opens an exciting research avenue towards powering next‐generation, portable electronics.     

The effects of slip velocity on a micropolar fluid through a porous channel with expanding or contracting walls

In this paper, a simple mathematical model depicting blood flow in the deforming porous channel is developed with an emphasis on the permeability property of the blood vessel and slip boundary based on Beavers and Joseph slip condition. In this study, the blood is represented by a micropolar fluid. With such an ideal model, the governing equations are reduced to ordinary ones by introducing suitable similar transformations. Homotopy analysis method is employed to obtain the expressions for velocity and microrotation fields. Graphs are sketched for some values of parameters such as slip coefficient and expansion ratio, and the associated dynamic characteristics are analysed in detail.     

Porous Electrode Materials for Lithium‐Ion Batteries – How to Prepare Them and What Makes Them Special

Numerous benefits of porous electrode materials for lithium ion batteries (LIBs) have been demonstrated, including examples of higher rate capabilities, better cycle lives, and sometimes greater gravimetric capacities at a given rate compared to nonporous bulk materials. These properties promise advantages of porous electrode materials for LIBs in electric and hybrid electric vehicles, portable electronic devices, and stationary electrical energy storage. This review highlights methods of synthesizing porous electrode materials by templating and template‐free methods and discusses how the structural features of porous electrodes influence their electrochemical properties. A section on electrochemical properties of porous electrodes provides examples that illustrate the influence of pore and wall architecture and interconnectivity, surface area, particle morphology, and nanocomposite formation on the utilization of the electrode materials, specific capacities, rate capabilities, and structural stability during lithiation and delithiation processes. Recent applications of porous solids as components for three‐dimensionally interpenetrating battery architectures are also described.     

Assignment of ferriheme resonances for high- and low-spin forms of nitrophorin 3 by H and C NMR spectroscopy and comparison to nitrophorin 2: Heme pocket structural similarities and differences

Nitrophorin 3 (NP3) is the only one of the four major NO-binding heme proteins found in the saliva of the blood-sucking insect Rhodnius prolixus (also called the Kissing Bug) for which it has not been possible to obtain crystals of diffraction quality for structure determination by X-ray crystallography. Thus we have used NMR spectroscopy, mainly of the hyperfine-shifted ferriheme substituent resonances, to learn about the similarities and differences in the heme pocket and the iron active site of NP3 as compared to NP2, which has previously been well-characterized by both X-ray crystallography and NMR spectroscopy. Only one residue in the heme pocket differs between the two, F27 of NP2 is Y27 for NP3; in both cases this residue is expected to interact strongly with the 2-vinyl side chain of the B heme rotational isomer or the 4-vinyl of the A heme rotational isomer. Both the high-spin (S = 5/2) aquo complex, NP3-H₂O, and the low-spin (S = 1/2) N-methylimidazole (NMeIm) complex of NP3 have been studied. It is found that the chemical shifts of the protons of both forms are similar to those of the corresponding NP2 complexes, but with minor differences that indicate a slightly different angle for the proximal histidine (H57) ligand plane. The B heme rotational isomer is preferred by both NP3 and NP2 in both spin states, but to a greater extent when phenylalanine is present at position 27 (A:B = 1:8 for NP2, 1:6 for NP3-Y27F, 1:4 for NP3, and 1:3 for NP2-F27Y). Careful analysis of the 5Me and 8Me shifts of the A and B isomers of the two high-spin nitrophorins leads to the conclusion that the heme environment for the two isomers differs in some way that cannot be explained at the present time. The kinetics of deprotonation of the aquo ligand of the high-spin complexes of NP2 and NP3 are very different, with NP2 giving well-resolved high-spin aquo and “low-spin” hydroxo proton NMR spectra until close to the end of the titration, while NP3 exhibits broadened ¹H NMR spectra indicative of an intermediate-rate of exchange on the NMR timescale between the two forms throughout the titration. The heme methyl shifts of NP2-OH are similar in magnitude and spread to those of NP2-CN, while those of metmyoglobin-hydroxo complexes are much larger in magnitude but not spread. It is concluded that the hydroxo complex of NP2 is likely S = 1/2 with a mixed(d_xy)²(d_xz, d_yz)³/(d_xy)¹(d_xz, d_yz)⁴ electron configuration, while those of metMb-OH are likely S = 1/2,3/2 mixed spin systems.     

Highly ordered mesoporous carbons as electrode material for the construction of electrochemical dehydrogenase- and oxidase-based biosensors

In this work, the excellent catalytic activity of highly ordered mesoporous carbons (OMCs) to the electrooxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H(2)O(2)) was described for the construction of electrochemical alcohol dehydrogenase (ADH) and glucose oxidase (GOD)-based biosensors. The high density of edge-plane-like defective sites and high specific surface area of OMCs could be responsible for the electrocatalytic behavior at OMCs modified glassy carbon electrode (OMCs/GE), which induced a substantial decrease in the overpotential of NADH and H(2)O(2) oxidation reaction compared to carbon nanotubes modified glassy carbon electrode (CNTs/GE). Such ability of OMCs permits effective low-potential amperometric biosensing of ethanol and glucose, respectively, at Nafion/ADH-OMCs/GE and Nafion/GOD-OMCs/GE. Especially, as an amperometric glucose biosensor, Nafion/GOD-OMCs/GE showed large determination range (500-15,000mumoll(-1)), high sensitivity (0.053nAmumol(-1)), fast (9+/-1s) and stable response (amperometric response retained 90% of the initial activity after 10h stirring of 2mmoll(-1) glucose solution) to glucose as well as the effective discrimination to the possible interferences, which may make it to readily satisfy the need for the routine clinical diagnosis of diabetes. By comparing the electrochemical performance of OMCs with that of CNTs as electrode material for the construction of ADH- and GOD-biosensors in this work, we reveal that OMCs could be a favorable and promising carbon electrode material for constructing other electrochemical dehydrogenase- and oxidase-based biosensors, which may have wide potential applications in biocatalysis, bioelectronics and biofuel cells.     

Ultra‐High Surface Area Activated Porous Asphalt for CO2 Capture through Competitive Adsorption at High Pressures

This study reports an improved method for activating asphalt to produce ultra‐high surface area porous carbons. Pretreatment of asphalt (untreated Gilsonite, uGil ) at 400 °C for 3 h removes the more volatile organic compounds to form pretreated asphalt ( uGil‐P ) material with a larger fraction of higher molecular weight π‐conjugated asphaltenes. Subsequent activation of uGil‐P at 900 °C gives an ultra‐high surface area (4200 m² g^?1) porous carbon material ( uGil‐900 ) with a mixed micro and mesoporous structure. uGil‐900 shows enhanced room temperature CO₂ uptake capacity at 54 bar of 154 wt% (35 mmol g^?1). The CH₄ uptake capacity is 37.5 wt% (24 mmol g^?1) at 300 bar. These are relevant pressures in natural gas production. The room temperature working CO₂ uptake capacity for uGil‐900 is 19.1 mmol g^?1 (84 wt%) at 20 bar and 32.6 mmol g^?1 (143 wt%) at 50 bar. In order to further assess the reliability of uGil‐900 for CO₂ capture at elevated pressures, the authors study competitive sorption of CO₂ and CH₄ on uGil‐900 at pressures from 1 to 20 bar at 25 °C. CO₂/CH₄ displacement constants are measured at 2 to 40 bar, and found to increase significantly with pressure and surface area.     

From Ionogels to Biredox Ionic Liquids: Some Emerging Opportunities for Electrochemical Energy Storage and Conversion Devices

Ionic liquids (ILs) continue to receive attention for applications in electrochemistry because of their unique properties as charge carriers (electrolytes) and redox shuttles (solar cells) and their ability to promote energy storage either electrostatically (supercapacitors) or chemically (secondary batteries). More specifically, the confinement of ILs in nanopores or the adsorption at surfaces, are considered a promising strategy for all solid‐state energy storage and conversion devices. Upon such immobilization, one benefits from the specific properties of ILs (large electrochemical window, relatively high ionic conductivity, task‐specific functionalities, etc.) combined with surface and confinement effects that can be tuned by playing with the porosity and chemical nature of the host. Here, some emerging applications of ILs in electrochemistry are first discussed: silica‐based ionogels as solid electrolytes and systems that involve carbon host substrates, as typical electrode materials in electrical double layer capacitors and lithium secondary batteries. Also, a non‐exhaustive, yet a comprehensive picture of the confinement and surface effects at play in such applications is presented. Then, the confinement of task‐specific ILs such as protonic ILs, IL lithium salts, and biredox ILs, is discussed, which paves the way for promising perspectives. Finally, some concluding remarks are reported and directions for future work are suggested.     

Amphicharge‐Storable Pyropolymers Containing Multitiered Nanopores

In this study, hierarchically nanoporous pyropolymers (HN‐PPs) including numerous redox‐active heteroatoms are fabricated from polyaniline nanotubes by heating with KOH. In the large operating voltage range 1.0–4.8 V versus Li⁺/Li, HN‐PPs store amphicharges by a pseudocapacitive manner of Li‐ion (mainly <3.0 V) and electrochemical double layer formation of anion (primarily >3.0 V). Through these surface‐driven charge storage behaviors, HN‐PPs achieve a significantly high specific capacity of ≈460 mA h g^?1 at 0.5 A g^?1, maintaining specific capacities of 140 mA h g^?1 at a high specific current of 30 A g^?1 and 305 mA h g^?1 after 2000 cycles at 3 A g^?1. Furthermore, asymmetric energy storage devices based on HN‐PPs deliver a high specific energy of 265 W h kg^?1 and high specific power of 5081 W kg^?1 with long‐term cycling performance.     

General Controlled Sulfidation toward Achieving Novel Nanosheet‐Built Porous Square‐FeCo2S4‐Tube Arrays for High‐Performance Asymmetric All‐Solid‐State Pseudocapacitors

A significant advance toward the design and fabrication of a novel hierarchical supercapacitor electrode consisting of FeCo₂S₄‐tubes with well‐defined square cross‐section and intersecting nanosheets built porous shells on a 3D porous Ni backbone via controlled sulfidation is reported. This general method allows template‐free synthesis of metal sulfides tubular structures with polygonal cross‐sections and also fine control over the nanostructure leading to both maximized porosity and saturation sulfidation. New insights into concentration and time dependent sulfidation reaction kinetics are proposed. The FeCo₂S₄ electrode achieves a specific capacitance reaching 2411 F g^‐1 at 5 mA cm^‐2 and good rate capability, which are superior over those for nanotube arrays of other ternary transition metal sulfides. This is attributed to rich redox reactions, the highly porous but robust architecture as well as high electrical conductivity. Especially such porous shells effectively avoid “dead volume”, thus improve the utilization ratio of the electrode material. Asymmetric solid‐state device applying the FeCo₂S₄ as positive electrode and N‐doped graphene hydrogel film as negative electrode has a high cell voltage of 1.6 V and thus delivers considerably higher energy density of 76.1 W h kg^‐1 (at 755 W kg^‐1) than those reported for similar devices.