Solid Hybrid materials abound. But flowing versions of them are new actors in the materials science landscape and in particular for energy applications. This paper presents a new way to deliver ...nanostructured hybrid materials for energy storage, namely, in the form of nanofluids. We present here the first example of a hybrid electroactive nanofluid (HENFs) combining capacitive and faradaic energy storage mechanisms in a single fluid material. This liquid electrode is composed of reduced graphene oxide and polyoxometalates (rGO‐POMs) forming a stable nanocomposite for electrochemical energy storage in novel Nanofluid Flow Cells. Two graphene based hybrid materials (rGO‐phosphomolybdate, rGO‐PMo12 and rGO‐phosphotungstate, rGO‐PW12) were synthesized and dispersed with the aid of a surfactant in 1 M H2SO4 aqueous electrolyte to yield highly stable hybrid electroactive nanofluids (HENFs) of low viscosity which were tested in a home‐made flow cell under static and continuous flowing conditions. Remarkably, even low concentration rGO‐POMs HENFs (0.025 wt%) exhibited high specific capacitances of 273 F/g(rGO‐PW12) and 305 F/g(rGO‐PMo12) with high specific energy and specific power. Moreover, rGO‐POM HENFs show excellent cycling stability (∼95 %) as well as Coulombic efficiency (∼77–79 %) after 2000 cycles. Thus, rGO‐POM HENFs effectively behave as real liquid electrodes with excellent properties, demonstrating the possible future application of HENFs for dual energy storage in a new generation of Nanofluid Flow Cells.
This study offers a kinetic exploration of the Hydrogen Evolution Reaction (HER) in an acidic environment using a catalyst of MoS x modified with electrodeposited platinum atoms (Pt-MoS x ). Scanning ...electron microscopy and high-resolution transmission electron microscopy images revealed a two-dimensional network structure of Pt-MoS x . The linear sweep voltammetries in a 0.5 mol/L H2SO4 solution demonstrated a high catalytic activity of the modified catalyst: an onset potential for hydrogen reduction reaction much more positive than that observed for MoS x , high mass activity (16.5 A/mg at an overpotential of −50 mV), a turnover frequency of 50 H2/s per surface site at a kinetic current density of 10 mA/cm2, and an overpotential of −39 mV. Based on classical models, including the Butler–Volmer equation, Kouteck-Levich equation, and Langmuir isotherm, essential kinetic parameters were obtained. The models in the frequency domain allowed the determination of the surface concentration of molecular hydrogen and the proposition of a transfer function for both dc frequency and infinite rotating disk speed conditions, enabling the determination of the exchange current density (8.51 × 10–4 A/cm2) and Tafel slope (40 mV/dec); the latter value suggested that the reaction proceeds through a Volmer–Heyrovsky pathway, predominantly limited by the Heyrovsky step. Based on the observed electrocatalytic behavior and the measured and calculated parameters, our findings suggest that the electrodeposition of small amounts of Pt on MoS x may represent a promising strategy for molecular hydrogen production.
Nanofabrication using a “bottom‐up” approach of hybrid electrode materials into a well‐defined architecture is essential for next‐generation miniaturized energy storage devices. This paper describes ...the design and fabrication of reduced graphene oxide (rGO)/polyoxometalate (POM)‐based hybrid electrode materials and their successful exploitation for asymmetric supercapacitors. First, redox active nanoclusters of POMs phosphomolybdic acid (PMo12) and phosphotungstic acid (PW12) were uniformly decorated on the surface of rGO nanosheets to take full advantage of both charge‐storing mechanisms (faradaic from POMs and electric double layer from rGO). The as‐synthesized rGO‐PMo12 and rGO‐PW12 hybrid electrodes exhibited impressive electrochemical performances with specific capacitances of 299 (269 mF cm−2) and 370 F g−1 (369 mF cm−2) in 1 m H2SO4 as electrolyte at 5 mA cm−2. An asymmetric supercapacitor was then fabricated using rGO‐PMo12 as the positive and rGO‐PW12 as the negative electrode. This rGO‐PMo12∥rGO‐PW12 asymmetric cell could be successfully cycled in a wide voltage window up to 1.6 V and hence exhibited an excellent energy density of 39 Wh kg−1 (1.3 mWh cm−3) at a power density of 658 W kg−1 (23 mW cm−3).
Twins, but not twins: Polyoxometalates (POMs) can exhibit high energy density for supercapacitors (SCs) due to rapid and reversible multielectron redox reactions. On the other hand, the energy storing capacity can be also increased by extending the operating voltage boundary of the device by creating an asymmetric SC. Both of these strategies are combined herein: reduced graphene oxide (rGO) is combined with either PMo12 to be used as positive electrode or with PW12, which is used as negative electrode.
This paper aims to explain the macroeconomic volatility due to microeconomic shocks to one or several sectors, recognizing the non-symmetrical relation in the interaction among the Ecuadorian ...economic sectors. To grasp the economic structure of this emerging economy, a statistical analysis of network data is applied to the respective input-output matrix of Ecuador from 1975 until 2012. We find periods wherein the production of domestic inputs is concentrated in a few suppliers; for example, in 2010, the concentration significantly affects sectors and their downstream providers, thus influencing aggregate volatility. Compared to the US productive structure, this emerging economy presents fewer sectors and degree distributions with less extreme fat-tail behavior. In this simpler economy, we continue to find a link between microeconomic shocks and aggregate volatility. Two new theoretical propositions are introduced to formalize our results.
Building of hierarchical core-shell hetero-structures is currently the subject of intensive research in the electrochemical field owing to its potential for making improved electrodes for ...high-performance micro-supercapacitors. Here we report a novel architecture design of hierarchical MnO2@silicon nanowires (MnO2@SiNWs) hetero-structures directly supported onto silicon wafer coupled with Li-ion doped 1-Methyl-1-propylpyrrolidinium bis(trifluromethylsulfonyl)imide (PMPyrrBTA) ionic liquids as electrolyte for micro-supercapacitors. A unique 3D mesoporous MnO2@SiNWs in Li-ion doped IL electrolyte can be cycled reversibly across a voltage of 2.2 V and exhibits a high areal capacitance of 13 mFcm(-2). The high conductivity of the SiNWs arrays combined with the large surface area of ultrathin MnO2 nanoflakes are responsible for the remarkable performance of these MnO2@SiNWs hetero-structures which exhibit high energy density and excellent cycling stability. This combination of hybrid electrode and hybrid electrolyte opens up a novel avenue to design electrode materials for high-performance micro-supercapacitors.
This review deals with recent progress on the development of nanocomposite materials formed by conducting organic polymers (COPs) and carbon nanotubes (CNs), both from a fundamental and applied point ...of view. The combination of the unique properties of CNs with COPs makes of these materials interesting multifunctional systems with great potential in many applications such as supercapacitors, sensors, photovoltaic cells and photodiodes, optical limiting devices, solar cells, high-resolution printable conductor, electromagnetic absorbers, and, last but not least, advanced transistors.
Transitions from marine to intertidal and terrestrial habitats resulted in a significant adaptive radiation within the Panpulmonata (Gastropoda: Heterobranchia). This clade comprises several groups ...that invaded the land realm independently and in different time periods, e.g., Ellobioidea, Systellomatophora, and Stylommatophora. Thus, mitochondrial genomes of panpulmonate gastropods are promising to screen for adaptive molecular signatures related to land invasions.
We obtained three complete mitochondrial genomes of terrestrial panpulmonates, i.e., the ellobiid Carychium tridentatum, and the stylommatophorans Arion rufus and Helicella itala. Our dataset consisted of 50 mitogenomes comprising almost all major panpulmonate lineages. The phylogenetic tree based on mitochondrial genes supports the monophyly of the clade Panpulmonata. Terrestrial lineages were sampled from Ellobioidea (1 sp.) and Stylommatophora (9 spp.). The branch-site test of positive selection detected significant non-synonymous changes in the terrestrial branches leading to Carychium (Ellobiodea) and Stylommatophora. These convergent changes occurred in the cob and nad5 genes (OXPHOS complex III and I, respectively).
The convergence of the non-synonymous changes in cob and nad5 suggest possible ancient episodes of positive selection related to adaptations to non-marine habitats. The positively selected sites in our data are in agreement with previous results in vertebrates suggesting a general pattern of adaptation to the new metabolic requirements. The demand for energy due to the colonization of land (for example, to move and sustain the body mass in the new habitat) and the necessity to tolerate new conditions of abiotic stress may have changed the physiological constraints in the early terrestrial panpulmonates and triggered adaptations at the mitochondrial level.
The current recession has caused a large number of companies to reevaluate their valuable resources and ways to preserve and invest those resources. Given the relevance of employees as key ...stakeholders, developing a socially responsible orientation in human resource management for taking care of workers and their needs must be an essential process for business success. This study, based on stakeholder theory and a social integrative approach, examines the main drivers and barriers in the implementation of socially responsible actions in human resource management. The research uses a quantitative analysis based on questionnaires responded to by 85 human resource managers from large Spanish companies. We conclude that there are two significant drivers of socially responsible actions in human resource management (HRM): access to public subsidies and the improvement of the working environment. The main significant barriers highlighted by human resource managers are conflicts in decisions with boards and/or management teams and the lack of employees’ acceptance. The professional implications of the research are discussed at the end of the paper.
The Biological Magnetic Resonance Data Bank (BioMagResBank or BMRB), founded in 1988, serves as the archive for data generated by nuclear magnetic resonance (NMR) spectroscopy of biological systems. ...NMR spectroscopy is unique among biophysical approaches in its ability to provide a broad range of atomic and higher-level information relevant to the structural, dynamic, and chemical properties of biological macromolecules, as well as report on metabolite and natural product concentrations in complex mixtures and their chemical structures. BMRB became a core member of the Worldwide Protein Data Bank (wwPDB) in 2007, and the BMRB archive is now a core archive of the wwPDB. Currently, about 10% of the structures deposited into the PDB archive are based on NMR spectroscopy. BMRB stores experimental and derived data from biomolecular NMR studies. Newer BMRB biopolymer depositions are divided about evenly between those associated with structure determinations (atomic coordinates and supporting information archived in the PDB) and those reporting experimental information on molecular dynamics, conformational transitions, ligand binding, assigned chemical shifts, or other results from NMR spectroscopy. BMRB also provides resources for NMR studies of metabolites and other small molecules that are often macromolecular ligands and/or nonstandard residues. This chapter is directed to the structural biology community rather than the metabolomics and natural products community. Our goal is to describe various BMRB services offered to structural biology researchers and how they can be accessed and utilized. These services can be classified into four main groups: (1) data deposition, (2) data retrieval, (3) data analysis, and (4) services for NMR spectroscopists and software developers. The chapter also describes the NMR-STAR data format used by BMRB and the tools provided to facilitate its use. For programmers, BMRB offers an application programming interface (API) and libraries in the Python and R languages that enable users to develop their own BMRB-based tools for data analysis, visualization, and manipulation of NMR-STAR formatted files. BMRB also provides users with direct access tools through the NMRbox platform.
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