Energy & Environmental Science (Energ Environ Sci )

Publisher: Royal Society of Chemistry (Great Britain)

Description

The journal recognises the complexity of issues and challenges relating to energy and environmental science and therefore particularly welcomes work of an interdisciplinary nature across both the (bio) chemical and (bio)physical sciences and chemical engineering disciplines.

  • Impact factor
    11.65
  • 5-year impact
    12.46
  • Cited half-life
    1.80
  • Immediacy index
    3.09
  • Eigenfactor
    0.06
  • Article influence
    3.46
  • Website
    Energy & Environmental Science website
  • Other titles
    Energy & environmental science, Energy and environmental science, EES
  • ISSN
    1754-5706
  • OCLC
    232359932
  • Material type
    Document, Periodical, Internet resource
  • Document type
    Internet Resource, Computer File, Journal / Magazine / Newspaper

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: The application of ferroelectric materials (i.e. solids that exhibit spontaneous electric polarisation) in solar cells has a long and controversial history. The developments include the first observations of the anomalous photovoltaic effect (APE) and the bulk photovoltaic effect (BPE). The recent success of inorganic and hybrid perovskite structured materials (e.g. BiFeO3, CsSnI3, CH3NH3PbI3) in solar cells emphasises that polar or ferroelectric semiconductors can be used in conventional photovoltaic architectures. We review developments in this field, with a particular emphasis on the materials known to display the APE/BPE (e.g. ZnS, CdTe, SbSI) and the theories developed to explain the experimental observations. Critical analysis is complemented with first-principles calculation of the underlying electronic structure. In addition to discussing the implications of a ferroelectric absorber layer, and the solid state theory of polarisation (Berry phase analysis), design principles and opportunities for high-efficiency ferroelectric photovoltaics are presented.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: Conceptually new research on dye-sensitized photoelectrochemical cells (DS-PECs), through which solar-driven water splitting to generate solar fuel in the form of hydrogen is realized, has attracted growing interest in the past few years. DS-PECs are based on the configurations of dye-sensitized solar cells (DSCs), but with an aim to drive the water splitting two half reactions at physically separated two compartments (electrodes) rather than to generate electrical power. Herein, we review some of the recent advances in the design and construction of functional DS-PECs for visible light-driven water splitting together with some comments on the performance of these devices. Future challenges towards the developments of more efficient dye-sensitized photoelectrochemical devices are addressed in the end.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: The aprotic lithium-oxygen cell is based on the reversible reduction of oxygen on a cathode host to form lithium peroxide, and has received much attention in the last few years owing to its promise to offer increased electrochemical energy density beyond that provided by traditional Li-ion batteries. Carbon has been extensively utilized as a host, but it reacts with Li2O2 to form an insulating layer of lithium carbonate resulting in high overpotentials on charge. Establishing a stable, and conductive interface at the porous cathode is a major challenge that has motivated a search for non-carbonaceous cathode materials. Very few suitable materials have been discovered so far. Here we report on the synthesis of the metallic Magnéli phase Ti4O7 with a crystallite size between 10-20 nm, and show that a cathode fabricated from this material greatly reduces the overpotential compared to carbon. Oxidation of lithium peroxide on charge starts just above 3 V, comparable to gold and TiC, and the majority (~65%) of oxygen release occurs in the 3-3.5 V window vs Li+/Li as determined by on-line electrochemical mass spectrometry. Ti4O7 is much lighter and lower cost than gold, easy to prepare, and provides a controlled interface. X-ray photoelectron spectroscopy measurements show that a conductive, self-passivating substoichiometric metal oxide layer is formed at the surface which is important for stability.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: Photoelectrochemical reduction of CO2 to CO was driven by a TiO2-protected Cu2O photocathode paired with a rhenium bipyridyl catalyst. Efficient and selective CO evolution was demonstrated as stable over several hours. The use of protic solution additives to overcome severe semiconductor-to-catalyst charge transfer limitations provided evidence of a modified catalytic pathway.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: Batteries that shuttle multi-valent ions such as Mg2+ and Ca2+ ions are promising candidates for achieving higher energy density than available with current Li-ion technology. Finding electrode materials that reversibly store and release these multi-valent cations is considered a major challenge for enabling such multi-valent battery technology. In this paper, we use recent advances in high-throughput first-principles calculations to systematically evaluate the performance of compounds with the spinel structure as multivalent intercalation cathode materials, spanning a matrix of five different intercalating ions and seven transition metal redox active cation. We estimate the insertion voltage, capacity, thermodynamic stability of charged and discharged states, as well as the intercalating ion mobility and use these properties to evaluate promising directions. Our calculations indicate that the Mn2O4 spinel phase based on Mg and Ca are feasible cathode materials. In general, we find that multivalent cathodes exhibit lower voltages compared to Li cathodes; the voltages of Ca spinels are ~ 0.2V higher than those of Mg compounds (versus their corresponding metals), and the voltages of Mg compounds are ~1.4 V higher than Zn compounds; consequently, Ca and Mg spinels exhibit the highest energy densities amongst all the multivalent cation species. The activation barrier for the Al3+ ion migration in the Mn2O4 spinel is very high (~1400 meV for Al3+ in the dilute limit); thus, the use of an Al based Mn spinel intercalation cathode is unlikely. Amongst the choice of transition metals, Mn-based spinel structures rank highest when balancing all the considered properties.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: A particularly suitable reactor concept for the continuous dehydrogenation of perhydro-N-ethylcarbazole in the context of hydrogen and energy storage applications is described. The concept addresses the fact that dehydrogenation is a highly endothermic gas evolution reaction. Thus, for efficient dehydrogenation a significant amount of reaction heat has to be provided to a reactor that is essentially full of gas. This particular challenge is addressed in our study by the use of a catalyst coated (Pt on alumina), structured metal reactor obtained by Selective Electron Beam Melting. The so-obtained reactor was tested both as single tube set-up and as Hydrogen Release Unit (HRU) with ten parallel reactors. The HRU realized in stationary operation a hydrogen release capacity of 1.75 kWtherm (960 Wel at subsequent fuel cell) with up to 1.12 gH2 min-1 gPt-1 and a power density of 3.84 kWel liter-1 of HRU reactor.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: We report a perovskite promoted iron oxide as a highly effective redox catalyst in a hybrid solar-redox scheme for methane partial oxidation and water-splitting. In contrast to previously reported ferrite materials, which typically exhibit 20% or lower steam to hydrogen conversion, La0.8Sr0.2FeO3-δ (LSF) promoted Fe3O4 is capable of converting more than 67% steam with high redox stability. Both experiments and a defect model indicate that the synergistic effect of reduced LSF and metallic iron phases is attributable to the exceptional steam conversion. To further enhance such a synergistic effect, a layered reverse-flow reactor concept is proposed. Using such a concept, over 77% steam to hydrogen conversion is achieved at 930 °C, which is 15% higher than the maximum conversion predicted by second law for unpromoted iron (oxides). When applied to the hybrid solar-redox scheme for liquid fuels and hydrogen co-generation, significant improvements in energy conversion efficiency can be achieved with reduced CO2 emissions.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: The development of high-performance capacitive energy storage devices is of critical importance to address an ever-increasing electricity need. The energy density of a film capacitor is determined by the dielectric constant and breakdown strength of dielectric materials. With the highest dielectric constant among the known polymers, poly(vinylidene fluoride)-based ferroelectric terpolymers are of great potential for high energy density capacitors. However, their energy storage capability has long been limited by the relatively low breakdown strength. Here we demonstrate remarkable improvements in the energy density and charge–discharge efficiency of the ferroelectric terpolymers upon the incorporation of ultra-thin boron nitride nanosheets (BNNSs). It is found that BNNSs function as a robust scaffold to hamper the onset of electromechanical failure and simultaneously as an efficient insulating barrier against electrical conduction in the resulting polymer nanocomposites, resulting in greatly enhanced breakdown strength. Of particular note is the improved thermal conductivity of the terpolymer with the introduction of BNNSs; this is anticipated to benefit the stability and lifetime of polymer capacitors. This work establishes a facile, yet efficient approach to solution-processable dielectric materials with performance comparable or even superior to those achieved in the traditionally melt-extruded ultra-thin films.
    Energy & Environmental Science 12/2014;
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    ABSTRACT: Three low bandgap conjugated polymers based on 7-fluorinated isoindigo (IID1F) and dithieno[3,2-b;6,7-b]carbaole (DTC), i.e., poly[N-dodecyldithieno[3,2-b;6,7-b]carbazole-alt-7-fluoro-N,N-di(2-octyldodecyl)isoindigo] (P1), poly[N-dodecyldithieno[3,2-b;6,7-b]carbazole-alt-7-fluoro-N,N-di(3-octyltridecyl)isoindigo] (P2) and poly[N-dodecyldithieno[3,2-b;6,7-b]carbazole-alt-7-fluoro-N,N-di(4-octyltetradecyl)isoindigo] (P3), were synthesized. All three polymers are soluble in non-chlorinated solvent o-xylene owing to region-random distribution of F-atoms along the conjugated backbone. The position of the alkyl-branching point has a negligible influence on energy levels and absorption spectra of the polymers, but has a small effect on their charge transport properties. Bulk heterojunction (BHJ) polymer solar cells (PSCs) of the polymers were fabricated with phenyl-C61-butyric acid methyl ester (PC61BM) as electron acceptor. When o-xylene was used as solvent, all three polymers delivered power conversion efficiencies (PCEs) above 7%. P2 exhibited the best device performance with a PCE of 7.5%. The devices processed with o-xylene showed higher device efficiency than those fabricated with o-dichlorobenzene (o-DCB) since the films of polymer:PC61BM blends prepared with o-xylene exhibited better morphology and higher and more balanced charge-carrier mobilities, leading to less recombination loss and higher fill factor (FF).
    Energy & Environmental Science 11/2014;
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    ABSTRACT: The search of hydrogen storage materials capable of efficiently storing hydrogen in a compact and light weight package is one of the most difficult challenges for the coming hydrogen economy. The liquid chemical hydrides with high gravimetric and volumetric hydrogen densities offer the hope of overcoming the challenges associated with hydrogen storage. Moreover, the liquid-phase nature of these hydrogen storage systems provides the distinguished advantages of easy recharging and the availability of the current liquid fuel infrastructures for recharging. In this review, we briefly survey the research progresses in the development of diverse liquid-phase chemical hydrogen storage materials, including organic and inorganic chemical hydrides, with emphases on the syntheses of active catalysts for catalytic hydrogen generation and storage. Moreover, the advantages and drawbacks of each storage system are discussed.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: In the search for alternatives to conventional Pt electrocatalysts, we have synthesized ultrathin, ternary PtRuFe nanowires (NW), possessing different chemical compositions in order to probe their CO tolerance as well as electrochemical activity as a function of composition for both (i) the methanol oxidation reaction (MOR) and (ii) the formic acid oxidation reaction (FAOR). As-prepared ‘multifunctional’ ternary NW catalysts exhibited both higher MOR and FAOR activity as compared with mono-metallic Pt NWs, binary Pt7Ru3 and Pt7Fe3 NWs, and commercial catalyst control samples. In terms of synthetic novelty, we utilized a sustainably mild, ambient wet-synthesis method never previously applied to the fabrication of crystalline, pure ternary systems in order to fabricate ultrathin, homogeneous alloy PtRuFe NWs with a range of controlled compositions. These NWs were subsequently characterized using a suite of techniques including XRD, TEM, SAED, and EDAX in order to verify not only the incorporation of Ru and Fe into the Pt lattice but also their chemical homogeneity, morphology, as well as physical structure and integrity. Lastly, these NWs were electrochemically tested in order to deduce the appropriateness of conventional explanations such as (i) the bi-functional mechanism as well as (ii) the ligand effect to account for our MOR and FAOR reaction data. Specifically, methanol oxidation appears to be predominantly influenced by the Ru content, whereas formic acid oxidation is primarily impacted by the corresponding Fe content within the ternary metal alloy catalyst itself.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: Interfacing α-Fe2O3 photoanodes with the water-oxidation electrocatalyst Co-Pi is known to enhance their photon-to-current conversion efficiencies by reducing electron-hole recombination near their surfaces, particularly at cathodic potentials, but the mechanism by which Co-Pi modification achieves this enhancement remains poorly understood. Conflicting experimental observations have been recorded with respect to the role of Co-Pi thickness and even the participation of Co-Pi in catalysis, raising important general questions concerning the fundamental properties of catalyst-modified PEC water-oxidation photoanodes for solar energy conversion. Here, we report results from electrochemical, spectroscopic, and microscopic measurements on mesostructured Co-Pi/α-Fe2O3 composite photoanodes that reveal evolving pathways of water oxidation with increasing Co-Pi thickness. These results highlight major fundamental differences between structured and planar Co-Pi/α-Fe2O3 composite photoanodes and help to reconcile previously conflicting mechanistic interpretations.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: Room temperature Na-ion secondary battery has been under focus lately due to its feasibility to compete against already well-established Li-ion secondary battery. Although there are many obstacles to overcome before Na-ion battery becomes commercially available, recent research discoveries corroborate that some of the cathode materials for Na-ion battery have indeed indisputable advantages over its Li-ion counterparts. In this publication, a comprehensive review of layered oxides (NaTMO2, TM = Ti, V, Cr, Mn, Fe, Co, Ni, and mixture of 2 or 3 elements) as a viable Na-ion battery cathode is presented. Unary systems are well characterized not only for their electrochemical performance but also for their structural transitions during the cycle. Binary systems are investigated in order to address issues regarding low reversible capacity, capacity retention, operating voltage, and structural stability. In consequence, some materials already have reached energy density of 520 mW h g-1, which is comparable to that of LiFePO4. Furthermore, some ternary system retained more than 72% of its capacity along with over 99.7% Coulombic efficiency for 275 cycles. The goal of this review is to present the development of Na layered oxide materials in the past as well as state of the art today in order to emphasize compatibility and durability of layered oxide as a powerful candidate for Na-ion battery cathode material.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: All photovoltaic solar cells transmit photons with energies below the absorption threshold (bandgap) of the absorber material, which are therefore usually lost for the purpose of solar energy conversion. Upconversion (UC) devices can harvest this unused sub-threshold light behind the solar cell, and create one higher energy photon out of (at least) two transmitted photons. This higher energy photon is radiated back towards the solar cell, thus expanding the utilization of the solar spectrum. Key requirements for UC units are a broad absorption and high UC quantum yield under low-intensity incoherent illumination, as relevant to solar energy conversion devices, as well as long term photostability. Upconversion by triplet-triplet annihilation (TTA) in organic chromophores has proven to fulfil the first two basic requirements, and first proof-of-concept applications in photovoltaic conversion as well as photo(electro)chemical energy storage have been demonstrated. Here we review the basic concept of TTA-UC and its application in the field of solar energy harvesting, and assess the challenges and prospects for its large-scale application, including the long term photostablity of TTA upconversion materials.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: Thermal energy was shown to be efficiently converted into electrical power in a thermally regenerative ammonia-based battery (TRAB) using copper-based redox couples [Cu(NH3)42+/Cu and Cu2+/Cu]. Ammonia addition to the anolyte (2 M ammonia in a copper-nitrate electrolyte) of a single TRAB cell produced a maximum power density of 115 ± 1 W m–2 (based on projected area of a single copper mesh electrode), with an energy density of 453 Wh m–3 (normalized to the total electrolyte volume, under maximum power production condition). Adding a second cell doubled both the voltage and maximum power production. Increasing the anolyte ammonia concentration to 3 M further improved power density to 136 ± 3 W m–2. Volatilization of ammonia from the spent anolyte by heating (simulating distillation), and re-addition of this ammonia to the spent catholyte chamber with subsequent operation of this chamber as the anode (to regenerate copper on the other electrode), produced a power density of 60 ± 3 W m–2, with an average energy recovery of ~29% (energy captured versus energy in the starting solutions). Power was restored to 126 ± 5 W m–2 through acid addition to the regenerated catholyte to decrease pH and dissolve Cu(OH)2 precipitates, suggesting that an inexpensive acid or a waste acid could be used to improve performance. These results demonstrated that TRABs using ammonia-based electrolytes and inexpensive copper electrodes can provide a practical method for efficient conversion of low-grade thermal energy into electricity.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: Rational design of non-noble metal catalysts with the electrocatalytic activity comparable or even superior to Pt is extremely important for the future fuel cell-based renewable energy device. Herein, we demonstrate a new concept that metal-organic framework (MOF) can be used as a novel precursor to in-situ encapsulate Co@Co3O4@C core@bishell nanoparticles (NPs) into a highly ordered porous carbon matrix (CM) (denoted as Co@Co3O4@C-CM).The central cobalt ions from MOF are used as metal source to produce Co metal cores, which are later transformed into fancy Co@Co3O4 nanostructure via a controlled oxidation. The most notable feature of our Co@Co3O4@C-CM is that the highly ordered CM can provide much better transport pathway than the disordered pure MOF derived nanostructure that can facilitate the mass transport of O2 and electrolyte. As a result, the well-designed Co@Co3O4@C-CM derived from MOF shows almost identical activity but superior stability and methanol tolerance for ORR relatively to the commercial Pt/C in alkaline medium. Our work first reports the novel Co@Co3O4@C nanostructure from MOF and also reveals the important role of the introduction of highly ordered carbon matrix into MOF derived catalyst on enhancing the ORR activity and stability. To the best of our knowledge, Co@Co3O4@C-CM is the most efficient non-noble metal nanocatalyst ever reported for ORR.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: Global greenhouse gas (GHG) emission targets can only be met by significantly decarbonising road transport. The only long term way to do this is via the electrification of powertrains combined with the production of low carbon electricity or hydrogen. Current assumptions and models, such as the IEA BLUE Map, demonstrate that this is technically possible, but assume growth in demand for transport services will only double by 2035 and triple by 2050, largely driven by growth in developing economies. However, another transport revolution, automated vehicles, could drive growth in transport services significantly further, which without electrification will have a large negative impact on efforts to curb transport related emissions. In contrast, it is shown in this paper that automated vehicles could significantly improve the economics of electric vehicles, and therefore make the electrification of powertrains more likely, which could help reduce emissions. Despite this uncertainty, little work has been done on understanding how these factors will affect each other, particularly the timing and uptake of automated vehicles and their effect on future transport related GHG emissions and economics, yet the impact on transport policy, infrastructure and society will be profound and should be of interest to policy makers, the automotive and energy industries, and society as a whole.
    Energy & Environmental Science 11/2014;
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    ABSTRACT: We report new p-type FeNb1-xTixSb (0.04≤ x ≤0.24) half-Heusler thermoelectric materials with a maximum zT of 1.1 at 1100K, which is twice higher than the ZrCoSb half-Heusler alloys. The electrical properties are optimized by a tradeoff between band effective mass and mobility via a band engineering approach. High content of Ti up to x=0.2 optimizes the power factor and reduces lattice thermal conductivity. In view of abundantly available elements, good stability and high zT, FeNb1-xTixSb alloys can be great promising for high temperature power generation.
    Energy & Environmental Science 11/2014;