Showing papers in "Energy and Environmental Science in 2012"
TL;DR: In this paper, a review of Na-ion battery materials is presented, with the aim of providing a wide view of the systems that have already been explored and a starting point for the new research on this battery technology.
Abstract: Energy production and storage have become key issues concerning our welfare in daily life. Present challenges for batteries are twofold. In the first place, the increasing demand for powering systems of portable electronic devices and zero-emission vehicles stimulates research towards high energy and high voltage systems. In the second place, low cost batteries are required in order to advance towards smart electric grids that integrate discontinuous energy flow from renewable sources, optimizing the performance of clean energy sources. Na-ion batteries can be the key for the second point, because of the huge availability of sodium, its low price and the similarity of both Li and Na insertion chemistries. In spite of the lower energy density and voltage of Na-ion based technologies, they can be focused on applications where the weight and footprint requirement is less drastic, such as electrical grid storage. Much work has to be done in the field of Na-ion in order to catch up with Li-ion technology. Cathodic and anodic materials must be optimized, and new electrolytes will be the key point for Na-ion success. This review will gather the up-to-date knowledge about Na-ion battery materials, with the aim of providing a wide view of the systems that have already been explored and a starting point for the new research on this battery technology.
3,017 citations
TL;DR: In this paper, the authors report new insights into the electrochemical reduction of CO2 on a metallic copper surface, enabled by the development of an experimental methodology with unprecedented sensitivity for the identification and quantification of CO 2 electroreduction products.
Abstract: We report new insights into the electrochemical reduction of CO2 on a metallic copper surface, enabled by the development of an experimental methodology with unprecedented sensitivity for the identification and quantification of CO2 electroreduction products. This involves a custom electrochemical cell designed to maximize product concentrations coupled to gas chromatography and nuclear magnetic resonance for the identification and quantification of gas and liquid products, respectively. We studied copper across a range of potentials and observed a total of 16 different CO2 reduction products, five of which are reported here for the first time, thus providing the most complete view of the reaction chemistry reported to date. Taking into account the chemical identities of the wide range of C1–C3 products generated and the potential-dependence of their turnover frequencies, mechanistic information is deduced. We discuss a scheme for the formation of multicarbon products involving enol-like surface intermediates as a possible pathway, accounting for the observed selectivity for eleven distinct C2+ oxygenated products including aldehydes, ketones, alcohols, and carboxylic acids.
2,184 citations
TL;DR: In this article, the authors show that 2 and 5 times higher energy densities are required to meet the performance goals of a future generation of plug-in hybrid-electric vehicles (PHEVs) with a 40-80 mile all-electric range, and all-EVs with a 300-400 mile range, respectively.
Abstract: The escalating and unpredictable cost of oil, the concentration of major oil resources in the hands of a few politically sensitive nations, and the long-term impact of CO2 emissions on global climate constitute a major challenge for the 21st century. They also constitute a major incentive to harness alternative sources of energy and means of vehicle propulsion. Today's lithium-ion batteries, although suitable for small-scale devices, do not yet have sufficient energy or life for use in vehicles that would match the performance of internal combustion vehicles. Energy densities 2 and 5 times greater are required to meet the performance goals of a future generation of plug-in hybrid-electric vehicles (PHEVs) with a 40–80 mile all-electric range, and all-electric vehicles (EVs) with a 300–400 mile range, respectively. Major advances have been made in lithium-battery technology over the past two decades by the discovery of new materials and designs through intuitive approaches, experimental and predictive reasoning, and meticulous control of surface structures and chemical reactions. Further improvements in energy density of factors of two to three may yet be achievable for current day lithium-ion systems; factors of five or more may be possible for lithium–oxygen systems, ultimately leading to our ability to confine extremely high potential energy in a small volume without compromising safety, but only if daunting technological barriers can be overcome.
2,105 citations
TL;DR: In this article, two different ways to fabricate nitrogen-doped graphene (N-graphene) and demonstrate its use as a metal-free catalyst to study the catalytic active center for the oxygen reduction reaction (ORR).
Abstract: We present two different ways to fabricate nitrogen-doped graphene (N-graphene) and demonstrate its use as a metal-free catalyst to study the catalytic active center for the oxygen reduction reaction (ORR). N-graphene was produced by annealing of graphene oxide (G-O) under ammonia or by annealing of a N-containing polymer/reduced graphene oxide (RG-O) composite (polyaniline/RG-O or polypyrrole/RG-O). The effects of the N precursors and annealing temperature on the performance of the catalyst were investigated. The bonding state of the N atom was found to have a significant effect on the selectivity and catalytic activity for ORR. Annealing of G-O with ammonia preferentially formed graphitic N and pyridinic N centers, while annealing of polyaniline/RG-O and polypyrrole/RG-O tended to generate pyridinic and pyrrolic N moieties, respectively. Most importantly, the electrocatalytic activity of the catalyst was found to be dependent on the graphitic N content which determined the limiting current density, while the pyridinic N content improved the onset potential for ORR. However, the total N content in the graphene-based non-precious metal catalyst does not play an important role in the ORR process.
2,008 citations
TL;DR: In this article, the potential applications of nanostructured and nanoporous graphitic carbon nitrides (g-C3N4) materials have been developed for a wide range of new applications.
Abstract: Graphitic carbon nitrides (g-C3N4) are becoming increasingly significant due to the theoretical prediction of their unusual properties and promising applications ranging from photocatalysis, heterogeneous catalysis, to fuel cells. Recently, a variety of nanostructured and nanoporous g-C3N4 materials have been developed for a wide range of new applications. This feature article gives, at first, an overview on the synthesis of g-C3N4 nanomaterials with controllable structure and morphology, and secondly, presents and categorizes applications of g-C3N4 as multifunctional metal-free catalysts for environmental protection, energy conversion and storage. A special emphasis is placed on the potential applications of nanostructured g-C3N4 in the areas of artificial photocatalysis for hydrogen production, oxygen reduction reaction (ORR) for fuel cells, and metal-free heterogeneous catalysis. Finally, this perspective highlights crucial issues that should be addressed in the future in the aforementioned exciting research areas.
1,507 citations
TL;DR: In this paper, the authors present the electrocatalytic properties of a highly conductive MoS2 hybrid material, and demonstrate that the origin of the HER activity is closely related to the amount of edges in the layered MOS2.
Abstract: This perspective covers the use of molybdenum disulfide and related compounds, generally termed MoSx, as electro- or photoelectrocatalysts for the hydrogen evolution reaction (HER). State of the art solutions as well as the most illustrative results from the extensive electro- and photoelectrocatalytic literature are given. The research strategies currently employed in the field are outlined and future challenges pointed out. We suggest that the key to optimising the HER activity of MoS2 is divided into (1) increasing the catalytic activity of the active site, (2) increasing the number of active sites of the catalyst, and (3) improving the electrical contact to these sites. These postulations are substantiated by examples from the existing literature and some new results. To demonstrate the electrocatalytic properties of a highly conductive MoS2 hybrid material, we present the HER activity data for multi-wall MoS2 nanotubes on multi-wall carbon nanotubes (MWMoS2@MWCNTs). This exemplifies the typical data collected for the electrochemical HER. In addition, it demonstrates that the origin of the activity is closely related to the amount of edges in the layered MoS2. The photoelectrocatalytic HER is also discussed, based on examples from literature, with an emphasis on the use of MoSx as either (1) the co-catalyst providing the HER activity for a semiconductor, e.g. Mo3S+4on Si or (2) MoS2 as the semiconductor with an intrinsic HER activity. Finally, suggestions for future catalyst designs are given.
1,189 citations
TL;DR: In this article, the authors focus on catalysts made of cobalt (Co), nickel (Ni), and iron (Fe) elements for water reduction and water oxidation and discuss different series of catalysts that can be applied in electrocatalytic and photocatalytic water spitting.
Abstract: This article reviews recent significant advances in the field of water splitting. Catalysts play very important roles in two half reactions of water splitting - water reduction and water oxidation. Considering potential future applications, catalysts made of cheap and earth abundant element(s) are especially important for economically viable energy conversion. This article focuses only on catalysts made of cobalt (Co), nickel (Ni) and iron (Fe) elements for water reduction and water oxidation. Different series of catalysts that can be applied in electrocatalytic and photocatalytic water spitting are discussed in detail and their catalytic mechanisms are introduced. Finally, the future outlook and perspective of catalysts made of earth abundant elements will be discussed.
1,152 citations
TL;DR: Nanomaterials in various shapes/morphologies, such as nanoparticles, tubes, wires, fibres etc., function as adsorbents and catalysts and their composites with polymers are used for the detection and removal of gases (SO2, CO, NOx, etc.), contaminated chemicals (arsenic, iron, manganese, nitrate, heavy metals, etc.).
Abstract: This article gives an overview of the application of nanomaterials in environmental remediation. In the area of environmental remediation, nanomaterials offer the potential for the efficient removal of pollutants and biological contaminants. Nanomaterials in various shapes/morphologies, such as nanoparticles, tubes, wires, fibres etc., function as adsorbents and catalysts and their composites with polymers are used for the detection and removal of gases (SO2, CO, NOx, etc.), contaminated chemicals (arsenic, iron, manganese, nitrate, heavy metals, etc.), organic pollutants (aliphatic and aromatic hydrocarbons) and biological substances, such as viruses, bacteria, parasites and antibiotics. Nanomaterials show a better performance in environmental remediation than other conventional techniques because of their high surface area (surface-to-volume ratio) and their associated high reactivity. Recent advances in the fabrication of novel nanoscale materials and processes for the treatment of drinking water and industrial waste water contaminated by toxic metal ions, radionuclides, organic and inorganic solutes, bacteria and viruses and the treatment of air are highlighted. In addition, recent advances in the application of polymer nanocomposite materials for the treatment of contaminants and the monitoring of pollutants are also discussed. Furthermore, the research trends and future prospects are briefly discussed.
1,144 citations
TL;DR: In this article, Minnich et al. reviewed the progress made in thermoelectrics over the past two years on charge and heat carrier transport, strategies to improve the thermiolectric figure of merit, with new discussions on device physics and applications.
Abstract: This review is an update of a previous review (A. J. Minnich, et al., Energy Environ. Sci., 2009, 2, 466) published two years ago by some of the co-authors, focusing on progress made in thermoelectrics over the past two years on charge and heat carrier transport, strategies to improve the thermoelectric figure of merit, with new discussions on device physics and applications, and assessing challenges on these topics. Understanding of phonon transport in bulk materials has advanced significantly as the first-principles calculations are applied to thermoelectric materials, and experimental tools are being developed. Some new strategies have been developed to improve electron transport in thermoelectric materials. Fundamental questions on phonon and electron transport across interfaces and in thermoelectric materials remain. With thermoelectric materials reaching high ZT values well above one, the field is ready to take a step forward and go beyond the materials' figure of merit. Developing device contacts and module fabrication techniques, developing a platform for efficiency measurements, and identifying applications are becoming increasingly important for the future of thermoelectrics.
1,049 citations
TL;DR: In this article, the authors show that complex multi-shelled micro-nano-materials show significant material advantages in many applications over conventional simple hollow structures, and discuss the possible application of these novel materials for power generation and storage.
Abstract: Hollow micro-/nano-structured materials are now playing an important role in cutting edge innovations for energy conversion and storage technologies such as solar cells, fuel cells, lithium ion batteries and super capacitors. These materials show great promise in addressing growing environmental concerns for cleaner power sources at a time of increasing global demand for energy. In this perspective, we show that complex multi-shelled micro-/nano-materials show significant material advantages in many applications over conventional simple hollow structures. We also summarize the vast array of synthetic strategies used to create multi-shelled hollow structures, and discuss the possible application of these novel materials for power generation and storage. Finally, the emergent challenges and future developments of multi-shelled hollow structures are further discussed.
1,039 citations
TL;DR: In this paper, the authors provide an overview of the fundamentals underlying the reduction of oxygen on platinum and its alloys, and report the ORR activity of Pt5La for the first time, which shows a 3.5-to 4.5fold improvement in activity over Pt in the range 0.9 to 0.87 V.
Abstract: The high cost of low temperature fuel cells is to a large part dictated by the high loading of Pt required to catalyse the oxygen reduction reaction (ORR). Arguably the most viable route to decrease the Pt loading, and to hence commercialise these devices, is to improve the ORR activity of Pt by alloying it with other metals. In this perspective paper we provide an overview of the fundamentals underlying the reduction of oxygen on platinum and its alloys. We also report the ORR activity of Pt5La for the first time, which shows a 3.5- to 4.5-fold improvement in activity over Pt in the range 0.9 to 0.87 V, respectively. We employ angle resolved X-ray photoelectron spectroscopy and density functional theory calculations to understand the activity of Pt5La.
TL;DR: In this paper, the authors provide an overview on the recent development of solution processed organic, inorganic, and hybrid interfacial materials for bulk-heterojunction polymer solar cells.
Abstract: This article provides an overview on the recent development of solution processed organic, inorganic, and hybrid interfacial materials for bulk-heterojunction polymer solar cells. The introduction of proper interfacial materials to optimize the electronic and electrical properties between the interfaces of the light-harvesting active layer and the charge-collecting electrode has become an important criterion to improve the performance of polymer solar cells. The electronic processes at these interfaces play a critical role in determining the efficiency for photon-to-electricity conversion. An ideal interface requires the formation of Ohmic contact with minimum resistance and high charge selectivity to prevent charge carriers from reaching the opposite electrodes. For long-term stability of polymer solar cells, interfaces with matched surface energy are required to prevent interfacial dewetting and delamination. Several classes of interfacial materials including inorganic metal oxides, crosslinkable charge-transporting materials, conjugated polymer electrolytes, self-assembled functional molecules, and graphene-based materials are highlighted and the integration of these interfacial materials with new low bandgap polymers and fullerene derivatives as active materials in different device architectures is also discussed.
TL;DR: In this article, the authors present the recent technological and theoretical advances related to the CeO2-based nanomaterials, with a focus on the synthesis from one dimensional to mesoporous ceria as well as the properties from defect chemistry to nano-size effects.
Abstract: The controllable synthesis of nanostructured CeO2-based materials is an imperative issue for environment- and energy-related applications. In this review, we present the recent technological and theoretical advances related to the CeO2-based nanomaterials, with a focus on the synthesis from one dimensional to mesoporous ceria as well as the properties from defect chemistry to nano-size effects. Seven extensively studied aspects regarding the applications of nanostructured ceria-based materials are selectively surveyed as well. New experimental approaches have been demonstrated with an atomic scale resolution characterization. Density functional theory (DFT) calculations can provide insight into the rational design of highly reactive catalysts and understanding of the interactions between the noble metal and ceria support. Achieving desired morphologies with designed crystal facets and oxygen vacancy clusters in ceria via controlled synthesis process is quite important for highly active catalysts. Finally, remarks on the challenges and perspectives on this exciting field are proposed.
TL;DR: In this article, the state of research for heterogeneous and homogeneous formic acid dehydrogenation catalysts is reviewed in detail and an outlook on necessary development steps is presented.
Abstract: Formic acid has recently been suggested as a promising hydrogen storage material. The basic concept is briefly discussed and the recent advances in the development of formic acid dehydrogenation catalysts are shown. Both the state of research for heterogeneous and for homogeneous catalyst systems are reviewed in detail and an outlook on necessary development steps is presented. Formic acid is considered as one of the most promising materials for hydrogen storage today. There are a number of highly active and robust homogeneous catalysts that selectively decompose formic acid to H2 and CO2 near to room temperature. Although the activity and selectivity of heterogeneous catalysts have not yet reached the level of homogeneous systems, this gap is closing.
TL;DR: In this article, the authors compare the status of three main lines of CCS technologies with respect to efficiency, energy consumption, and technical feasibility as well as the implications of the CCS on the efficiency and structure of the energy supply chain.
Abstract: While Carbon Capture and Storage (CCS) technologies are being developed with the focus of capturing and storing CO2 in huge quantities, new methods for the chemical exploitation of carbon dioxide (CCU) are being developed in parallel. The intensified chemical or physical utilization of CO2 is targeted at generating value from a limited part of the CO2 stream and developing better and more efficient chemical processes with reduced CO2 footprint. Here, we compare the status of the three main lines of CCS technologies with respect to efficiency, energy consumption, and technical feasibility as well as the implications of CCS on the efficiency and structure of the energy supply chain.
TL;DR: In this article, a review of the recent progress and advances in the development of C/LiFePO4 composite materials is presented, based on selected reports from peer-reviewed journal publications.
Abstract: Olivine-structured LiFePO4 has been the focus of research in developing low cost, high performance cathode materials for lithium ion batteries. Various processes have been developed to synthesize LiFePO4 or C/LiFePO4 (carbon coating on LiFePO4), and some of them are being used to mass produce C/LiFePO4 at the commercial or pilot scale. Due to the low intrinsic electronic and ionic conductivities of LiFePO4, the decrease of particle size and the nano-layer of carbon coating on LiFePO4 particle surfaces are necessary to achieve a high electrochemical performance. Significant progress has been made in understanding and controlling phase purity, particle size and carbon coating of the C/LiFePO4 composite material in the past. However, there are still many challenges in achieving a high quality product with high consistency. In this review, we summarize some of the recent progress and advances based on selected reports from peer-reviewed journal publications. Several typical synthesis methods and the effect of carbon coating quality on the properties of C/LiFePO4 composite are reviewed. An insight into the future research and further development of C/LiFePO4 composite is also discussed.
TL;DR: In this paper, the authors focus on a new type of quantum dots, graphene quantum dots (GQDs), and summarize the significant advances achieved by them and other groups in the past few years on both the experimental and theoretical fronts.
Abstract: In this perspective, we focus on a new type of quantum dots, graphene quantum dots (GQDs). Due to quantum confinement and edge effects, GQDs have presented extraordinary properties, attracting extensive attention from scientists in the fields of chemistry, physics, materials, biology, and other interdisciplinary sciences. Herein, we summarize the significant advances achieved by us and other groups in the past few years on both the experimental and theoretical fronts. Synthetic strategies, unique optical and electronic properties, and the promise of GQDs in energy-related devices, such as photovoltaic devices, fuel cells, and light-emitting diodes, are systematically discussed.
TL;DR: In this paper, the authors reviewed the latest advances in the exploration and development of Ti-based compounds, such as Li4Ti5O12, Li2Ti3O7, TiO2-B and H2Ti 3O7 as high performance anode materials for Li-ion batteries.
Abstract: Li-ion batteries are one of the most promising electrochemical power sources to be widely used in portable electronics, electric vehicles, and stationary energy storage systems. Ti-based materials have been intensively investigated as important anodes for Li-ion batteries due to their high safety and excellent cycling stability. The present work reviews the latest advances in the exploration and development of Ti-based compounds, such as Li4Ti5O12, Li2Ti3O7, TiO2-B and H2Ti3O7, as high performance anode materials for Li-ion batteries. The relationship between the preparation, composition, structure, morphology and electrochemical performance are summarized and analyzed. Further, the related advancements and challenges in practical energy applications are discussed.
TL;DR: In this article, an advanced electrode for high-performance electrochemical capacitors has been designed by growing ultrathin mesoporous Co3O4 nanosheet arrays on the Ni foam support.
Abstract: An advanced electrode for high-performance electrochemical capacitors has been designed by growing ultrathin mesoporous Co3O4 nanosheet arrays on the Ni foam support. This unique 3D electrode manifests exceptional supercapacitive performance with ultrahigh specific capacitance at high current densities and excellent cycling stability.
TL;DR: In this article, the authors provide an overview on recently developed carbon material technology synthesised from the hydrothermal carbonisation (HTC) approach, with a particular focus on the carbon formation mechanism, perspectives on large scale production, nanostructuring, functionalisation and applications.
Abstract: This perspective review paper provides an overview on recently developed carbon material technology synthesised from the hydrothermal carbonisation (HTC) approach, with a particular focus on the carbon formation mechanism, perspectives on large scale production, nanostructuring, functionalisation and applications. Perceptions on how this technology will be developed especially with regard to application fields where the use of HTC-derived materials could be extended will also be introduced and discussed.
TL;DR: In this article, localized surface plasmons and their effects on semiconductors, particularly in terms of energy transfer, scattering, and hot electron transfer, are reviewed, and the relevant physics, device geometries, and research progress in this area are discussed.
Abstract: The study of the optoelectronic effects of plasmonic metal nanoparticles on semiconductors has led to compelling evidence for plasmon-enhanced water splitting. We review the relevant physics, device geometries, and research progress in this area. We focus on localized surface plasmons and their effects on semiconductors, particularly in terms of energy transfer, scattering, and hot electron transfer.
TL;DR: A review of the application of metal-organic frameworks in the field of electrochemistry can be found in this article, where the authors discuss the potential of MOFs for rechargeable batteries, supercapacitors and fuel cells.
Abstract: Metal–organic frameworks (MOFs) have received huge attention in the last years as promising porous materials with unrivalled degree of tunability for a wide range of applications including gas storage or separation, catalysis, drug delivery and imaging. The present review appraises the application of MOFs in the field of electrochemistry. From materials for rechargeable batteries, supercapacitors and fuel cells to electrocatalysis or corrosion inhibition, MOFs or MOF-derived materials are gaining momentum in this field. For real breakthroughs, combining their electrochemical properties with appropriate electronic and ionic conductivity will be required.
TL;DR: In this article, a hierarchical nanostructures composed of carbon coated α-Fe2O3 hollow nanohorns on carbon nanotube (CNT) backbones have been constructed by direct growth and thermal transformation of β-FeOOH nanospindles on CNTs, followed by carbon nanocoating.
Abstract: Novel hierarchical nanostructures composed of carbon coated α-Fe2O3 hollow nanohorns on carbon nanotube (CNT) backbones have been constructed by direct growth and thermal transformation of β-FeOOH nanospindles on CNTs, followed by carbon nanocoating. When evaluated as a potential anode material for lithium-ion batteries, such hierarchical structures exhibit superior lithium storage capabilities by virtue of their advantageous structural features.
TL;DR: In this article, single-crystalline nanoneedle arrays of NiCo2O4 were grown on conductive substrates such as Ni foam and Ti foil through a simple solution method together with a post-annealing treatment.
Abstract: In this work, we have successfully grown single-crystalline nanoneedle arrays of NiCo2O4 on conductive substrates such as Ni foam and Ti foil through a simple solution method together with a post-annealing treatment. Remarkably, the NiCo2O4–Ni foam binder-free electrode exhibits greatly improved electrochemical performance with very high capacitance and excellent cycling stability.
TL;DR: In this paper, the effect of electronic density of states (DOS) distortions on the thermopower of thermoelectric semiconductors has been investigated and the authors have discussed the conditions for DOS distortions to increase the thermopelectric power of the semiconductor.
Abstract: Distortions of the electronic density of states (DOS) are a potent mechanism to increase the thermopower of thermoelectric semiconductors, thereby increasing their power factor. We review band-structure engineering approaches that have been used to achieve this, resonant impurity levels, dilute Kondo effects, and hybridization effects in strongly correlated electron systems. These can increase the thermoelectric power of metals and semiconductors through two mechanisms: (1) the added density of states increases the thermopower in a nearly temperature-independent way; (2) resonant scattering results in a strong electron energy filtering effect that increases the thermopower at cryogenic temperatures where the electron–phonon interactions are weaker. Electronic structure calculation results for Tl:PbTe and Ti:PbTe are contrasted and identify the origin of the thermopower enhancement in Tl:PbTe. This leads to a discussion of the conditions for DOS distortions to produce thermopower enhancements and illustrates the existence of an optimal degree of delocalization of the impurity states. The experimentally observed resonant levels in several III–V, II–VI, IV–VI and V2-VI3 compound semiconductor systems are reviewed.
TL;DR: In this paper, superhydrophobic and superoleophilic graphene-based sponges are demonstrated as efficient absorbents for a broad range of oils and organic solvents with high selectivity, good recyclability, and excellent absorption capacities up to 165 times their own weight.
Abstract: Superhydrophobic and superoleophilic graphene-based sponges are demonstrated as efficient absorbents for a broad range of oils and organic solvents with high selectivity, good recyclability, and excellent absorption capacities up to 165 times their own weight. The findings show promise for large-scale removal of organic contaminants, especially in the field of oil spillage cleanup.
TL;DR: In this paper, the authors survey the research progress in hydrogen generation from liquid-phase chemical hydrogen storage materials and their regeneration, and present a review of these materials in hydrogen storage.
Abstract: In the search for future energy supplies, the application of hydrogen as an energy carrier is seen as a prospective issue. However, the implementation of a hydrogen economy is suffering from several unsolved problems. Particularly challenging is the storage of appropriate amounts of hydrogen. In this context one of the promising hydrogen storage techniques relies on liquid-phase chemical hydrogen storage materials, in particular, aqueous sodium borohydride, ammonia borane, hydrazine, hydrazine borane and formic acid. The use of these materials in hydrogen storage provides high gravimetric and volumetric hydrogen densities, low potential risk, and low capital investment because it is largely compatible with the current transport infrastructure. In this review, we survey the research progresses in hydrogen generation from these liquid-phase chemical hydrogen storage materials and their regeneration.
TL;DR: The results demonstrate that GAC can promote DIET and suggest that stimulation of metabolism in methanogenic digesters can be attributed, at least in part, to the high conductivity of GAC providing better interspecies electrical connections than those that can be forged biologically.
Abstract: Granular activated carbon (GAC) is added to methanogenic digesters to enhance conversion of wastes to methane, but the mechanism(s) for GAC's stimulatory effect are poorly understood. GAC has high electrical conductivity and thus it was hypothesized that one mechanism for GAC stimulation of methanogenesis might be to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens. Metabolism was substantially accelerated when GAC was added to co-cultures of Geobacter metallireducens and Geobacter sulfurreducens grown under conditions previously shown to require DIET. Cells were attached to GAC, but did not aggregate as they do when making biological electrical connections between cells. Studies with a series of gene deletion mutants eliminated the possibility that GAC promoted electron exchange via interspecies hydrogen or formate transfer and demonstrated that DIET in the presence of GAC did not require the electrically conductive pili and associated c-type cytochrome involved in biological interspecies electrical connections. GAC also greatly stimulated ethanol metabolism and methane production in co-cultures of G. metallireducens and Methanosarcina barkeri. Cells were attached to GAC, but not closely aggregated, suggesting little opportunity for biological electrical contacts between the species. GAC also enhanced methane production in samples from a methanogenic digester in which Methanosaeta were the predominant methanogens. The results demonstrate that GAC can promote DIET and suggest that stimulation of metabolism in methanogenic digesters can be attributed, at least in part, to the high conductivity of GAC providing better interspecies electrical connections than those that can be forged biologically.
TL;DR: In this paper, the authors proposed a simple yet robust film treatment method with methanol having only one hydroxyl group to enhance the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by four orders of magnitude.
Abstract: We proposed a simple yet robust film treatment method with methanol having only one hydroxyl group to enhance the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by four orders of magnitude. Different methods of film treatment: immersing PEDOT:PSS film in the methanol solution; dropping methanol on the film; and a combination of these are employed and the results are compared. The conductivity of PEDOT:PSS films was enhanced from 0.3 S cm−1 to 1362 S cm−1 after film treatment with methanol. Other alcohols like ethanol and propanol were also used to treat the PEDOT:PSS film and showed inferior conductivity enhancement compared to methanol. The conductivity enhancement was greatly affected by the hydrophilicity and dielectric constant of the alcohols used. The mechanism of conductivity enhancement was investigated through various characterization techniques including FTIR, XPS and AFM. Removal of the insulator PSS from the film, and morphology and conformational changes are the mechanisms for the conductivity enhancement. The treated films also showed high transmittance and low sheet resistance desirable for a standalone electrode. ITO-free polymer solar cells were fabricated using PEDOT:PSS electrodes treated with methanol and showed almost equal performance to ITO electrodes.
TL;DR: In this paper, the binary EC:PC solvent mixture has emerged as the best solvent formulation and has been used to test the performance of Na/hard carbon cells with both NaClO4 and NaPF6 as dissolved salts.
Abstract: Electrolytes are essential for the proper functioning of any battery technology and the emerging Na-ion technology is no exception. Hence, a major focus on battery research is to identify the most appropriate formulation so as to minimize interface reactions and enhance both cell performances and safety aspects. In order to identify suitable electrolyte formulations for Na-ion chemistry we benchmarked various electrolytes containing diverse solvent mixtures (cyclic, acyclic carbonates, glymes) and Na-based salts having either F-based or perchlorate anions and measured viscosity, ionic conductivity, and thermal and electrochemical stability. The binary EC:PC solvent mixture has emerged as the best solvent formulation and has been used to test the performance of Na/hard carbon cells with both NaClO4 and NaPF6 as dissolved salts. Hard carbon electrodes having reversible capacities of 200 mA h g−1 with decent rate capability and excellent capacity retention (>180 cycles) were demonstrated. Moreover, DSC heating curves demonstrated that fully sodiated hard carbon cycled in NaPF6–EC:PC exhibits the highest exothermic onset temperature and nearly the lowest enthalpy of reaction, thus making this electrolyte most attractive for the development of Na-ion batteries.