Archive for the ‘Hot Article’ Category

Revealing electron transfer in current-producing bacteria

Researchers from Japan and the USA have found the first clue to the electron transfer mechanism in a species of current-producing bacteria.

Some bacteria can generate electrical energy from its metabolic systems, and they are used in microbial fuel cells and bioremediation processes. Geobacter sulfurreducens is the most efficient current-producing bacteria found so far, but there is no conclusive mechanism for electron transfer from the bacteria to the electrode.

In this paper, Ryuhei Nakamura et al. the authors identify self-secreted flavin as the electron shuttle involved in this extracellular electron transfer (EET). For this bacteria, free-floating flavin in the solution does not contribute to EET, as changing the solution to a fresh one did not impact current production. Instead, electron transfer occurs through flavin bound to c-type cytochromes (c-Cyts) on the outer membrane.

The authors confirmed flavin secretion by spectroscopy and mass chromatography, and voltammetry showed that current production was influenced by the amount of flavin present. The importance of c-Cyts was revealed by a mutant comparison experiment, in which a mutant lacking several major c-Cyts produced less current than the wild type.

Extracellular electron transfer (EET) is a key step in current production from bacteria, and understanding the mechanisms involved can lead to optimization of microbial fuel cells.

by Bhavin Siritanaratkul

For more information read this Energy & Environmental Science article:

Uptake of self-secreted flavins as bound cofactors for extracellular electron transfer in Geobacter species
Akihiro Okamoto, Koichiro Saito, Kengo Inoue, Kenneth H. Nealson, Kazuhito Hashimoto and Ryuhei Nakamura
DOI: 10.1039/C3EE43674H

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A Neutral Solution: Reliable PEC H2 Production at Near Neutral pH

In an exciting breakthrough in photoelectrochemical (PEC) solar generator development, a new report describes a methodology for robust H2 production in a near neutral environment.

Robust production of purified H2 in a stable, self-regulating, and continuously operating solar fuel generator

The development of practical, sustainable solar fuel generators comes with many challenges. Not only do the materials and components used need to be cost-effective and abundant, but the devices also need to be able to consistently produce purified fuels over long periods of time under environmentally benign conditions. A challenge to meeting all of these requirements has been in the creation of devices that are stable using either strong acid or basic electrolytes. A recent EES paper by Modestino et al. describes the development of a controlled recirculating stream across reactions sites to yield continuous solar-hydrogen generation in near neutral pH electrolytes.

In this report, researchers from the Joint Center for Artificial Photosynthesis and collaborating institutions describe alternate ion transport pathways that allow for operation under a near neutral pH. By creating a recirculation scheme to balance the concentration across the membrane in a membrane-separated photoelectrochemical (PEC) system, the authors achieved robust production of separated product streams (pure hydrogen and oxygen) via their ion-transport membrane components.

Designing a PEC device that operates using neutral pH electrolytes enables the use of catalytic and light absorbing components that would degrade in acidic or basic environments. The methodology described in this paper can provide researchers with a platform to experiment with different materials and hopefully optimize solar-to-hydrogen efficiency. It will be interesting to see the implementation of this methodology in future research, and if this approach ultimately provides a good solution to one major obstacle in the creation of scalable, sustainable, and robust solar fuel generators.

Read more in the full EES article here:

Robust production of purified H2 in a stable, self-regulating, and continuously operating solar fuel generator
Miguel A. Modestino, Karl A. Walczak, Alan Berger, Christopher M. Evans, Sophia Haussener, Carl Koval, John S. Newman, Joel W. Ager and Rachel A. Segalman
Energy Environ. Sci., 2014,7, 297-301
DOI: 10.1039/C3EE43214A

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This week’s HOT articles

Take a look at this week’s selection! These articles are available free for a limited time: Graphical abstract: Uptake of self-secreted flavins as bound cofactors for extracellular electron transfer in Geobacter species

Transforming an oxygen-tolerant [NiFe] uptake hydrogenase into a proficient, reversible hydrogen producer
Bonnie J. Murphy, Frank Sargent and Fraser A. Armstrong
DOI: 10.1039/C3EE43652G, Paper

Uptake of self-secreted flavins as bound cofactors for extracellular electron transfer in Geobacter species
Akihiro Okamoto, Koichiro Saito, Kengo Inoue, Kenneth H. Nealson, Kazuhito Hashimoto and Ryuhei Nakamura
DOI: 10.1039/C3EE43674H, Communication

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This week’s HOT article

Take a look at this week’s selection! This article is available free for a limited time: Graphical abstract: Spin caloritronics

Spin caloritronics
Stephen R. Boona, Roberto C. Myers and Joseph P. Heremans
DOI: 10.1039/C3EE43299H, Review Article

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This week’s HOT article

Take a look at this week’s selection! This article is available free for a limited time: Graphical abstract: Light harvesting vesicular donor–acceptor scaffold limits the rate of charge recombination in the presence of an electron donor

Light harvesting vesicular donor–acceptor scaffold limits the rate of charge recombination in the presence of an electron donor
Rijo T. Cheriya, Ajith R. Mallia and Mahesh Hariharan
DOI: 10.1039/C3EE43293A, Paper

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This week’s HOT articles

Take a look at this week’s selection! These articles are available free for a limited time: Graphical abstract: From lab to fab: how must the polymer solar cell materials design change? – an industrial perspective

Efficient decommissioning and recycling of polymer solar cells: justification for use of silver
Roar R. Søndergaard, Nieves Espinosa, Mikkel Jørgensen and Frederik C. Krebs
DOI: 10.1039/C3EE43746A, Communication

Large scale deployment of polymer solar cells on land, on sea and in the air
Nieves Espinosa, Markus Hösel, Mikkel Jørgensen and Frederik C. Krebs
DOI: 10.1039/C3EE43212B, Analysis

Towards sustainable wastewater treatment by using microbial fuel cells-centered technologies
Wen-Wei Li, Han-Qing Yu and Zhen He
DOI: 10.1039/C3EE43106A, Perspective

Visible light driven photocatalysis mediated via ligand-to-metal charge transfer (LMCT): an alternative approach to solar activation of titania
Guan Zhang, Gonu Kim and Wonyong Choi
DOI: 10.1039/C3EE43147A, Minireview

From lab to fab: how must the polymer solar cell materials design change? – an industrial perspective
Riccardo Po, Andrea Bernardi, Anna Calabrese, Chiara Carbonera, Gianni Corso and Andrea Pellegrino
DOI: 10.1039/C3EE43460E, Perspective

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This week’s HOT article

Take a look at this week’s selection! This article is available free for a limited time:Graphical abstract: Formamidinium lead trihalide: a broadly tunable perovskite for efficient planar heterojunction solar cells

Formamidinium lead trihalide: a broadly tunable perovskite for efficient planar heterojunction solar cells
Giles E. Eperon, Samuel D. Stranks, Christopher Menelaou, Michael B. Johnston, Laura M. Herz and Henry J. Snaith
DOI: 10.1039/C3EE43822H, Communication

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Multi-shelled hematite microspheres: high-performance anode materials for the Li-ion battery

Researchers from the University of Science and Technology Beijing, China, have developed a novel technique for the fabrication of multi-shelled α-Fe2O3 microspheres. The spheres, when tested as anode materials for Li-ion batteries (LIB), give ultra-high specific capacity values of up to 1702 mAhg-1, which is about 5 times higher than that of graphite (372 mAhg-1) – the currently employed material for LIB anodes.

The performance of the current generation of LIBs is fundamentally limited by the properties of their material components. The charge stored per gram, or specific capacity, of the anode is one such limiting factor; with graphite restricted to a maximum capacity of 372 mAhg-1. Numerous other materials are capable of exceeding this value, however they typically suffer from poor rechargeability (or cycle stability) owing to the fact they expand/contract considerably upon charge/discharge cycling – which causes the electrodes to crumble.

One such material is α-Fe2O3, or hematite, which, as well as being low-cost, abundant and non-toxic, has a high theoretical capacity of 1000 mAhg-1, however it suffers from a destructive volume change of about 90 % upon cycling. A group led by Dan Wang has managed to overcome this problem by preparing α-Fe2O3 as hollow, thin-shelled, concentric microspheres, which are capable of buffering the mechanical stresses upon cycling and therefore prevent crumbling.

In their paper, they reported stable reversible capacities as high as 1702 mAhg-1, which is record-breaking performance for additive-free α-Fe2O3 – and even beats the maximum theoretical capacity of 1000 mAhg-1. What’s more, the materials also display excellent high-current performance; maintaining a high capacity of about 1100 mAhg-1 at a current rate of 1 Ag-1. The authors attributed this excellent performance to the novel concentric shell structure of the hollow microspheres, which is capable of buffering mechanical stresses whilst providing a high surface area for rapid Li-ion transfer kinetics.

So could Dan Wong’s α-Fe2O3 spheres the next big thing for Li-ion batteries? He-matite just be on to something…

Interested? Read the full article here:

α-Fe2O3 multi-shelled hollow microspheres for lithium ion battery anodes with superior capacity and charge retention

Simeng Xu, Colin M. Hessel, Hao Ren, Ranbo Yu, Quan Jin, Mei Yang, Huijun Zhao and Dan Wang
Energy Environ. Sci., 2014, Advance Article
DOI: 10.1039/C3EE43319F

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This week’s HOT articles

Take a look at this week’s selection! These articles are available free for a limited time:Graphical abstract: Graphene oxide derivatives as hole- and electron-extraction layers for high-performance polymer solar cells

Photoelectrochemistry of core–shell tandem junction n–p+-Si/n-WO3 microwire array photoelectrodes
Matthew R. Shaner, Katherine T. Fountaine, Shane Ardo, Rob H. Coridan, Harry A. Atwater and Nathan S. Lewis
DOI: 10.1039/C3EE43048K, Paper

Graphene oxide derivatives as hole- and electron-extraction layers for high-performance polymer solar cells
Jun Liu, Michael Durstock and Liming Dai
DOI: 10.1039/C3EE42963F, Review Article

α-Fe2O3 multi-shelled hollow microspheres for lithium ion battery anodes with superior capacity and charge retention
Simeng Xu, Colin M. Hessel, Hao Ren, Ranbo Yu, Quan Jin, Mei Yang, Huijun Zhao and Dan Wang
DOI: 10.1039/C3EE43319F, Communication

Ultra-long anatase TiO2 nanowire arrays with multi-layered configuration on FTO glass for high-efficiency dye-sensitized solar cells
Wu-Qiang Wu, Yang-Fan Xu, Cheng-Yong Su and Dai-Bin Kuang
DOI: 10.1039/C3EE42167H, Communication

Energy demand and emissions of the non-energy sector
Vassilis Daioglou, Andre P. C. Faaij, Deger Saygin, Martin K. Patel, Birka Wicke and Detlef P. van Vuuren
DOI: 10.1039/C3EE42667J, Analysis

π-Extended low bandgap polymer based on isoindigo and thienylvinylene for high performance polymer solar cells
Eui Hyuk Jung and Won Ho Jo
DOI: 10.1039/C3EE42297F, Communication

High performance silicon-based anodes in solid-state lithium batteries
Rinlee B. Cervera, Naoki Suzuki, Tsuyoshi Ohnishi, Minoru Osada, Kazutaka Mitsuishi, Takayoshi Kambara and Kazunori Takada
DOI: 10.1039/C3EE43306D, Communication

Metal–organic frameworks as solid magnesium electrolytes
M. L. Aubrey, R. Ameloot, B. M. Wiers and J. R. Long
DOI: 10.1039/C3EE43143F, Communication

Enhancing SOFC cathode performance by surface modification through infiltration
Dong Ding, Xiaxi Li, Samson Yuxiu Lai, Kirk Gerdes and Meilin Liu
DOI: 10.1039/C3EE42926A, Review Article

Towards optimisation of photocurrent from fullerene excitons in organic solar cells
Stoichko D. Dimitrov, Zhenggang Huang, Florent Deledalle, Christian B. Nielsen, Bob C. Schroeder, Raja Shahid Ashraf, Safa Shoaee, Iain McCulloch and James R. Durrant
DOI: 10.1039/C3EE42607F, Paper

Self-supported Li4Ti5O12 nanosheet arrays for lithium ion batteries with excellent rate capability and ultralong cycle life
Shuai Chen, Yuelong Xin, Yiyang Zhou, Yurong Ma, Henghui Zhou and Limin Qi
DOI: 10.1039/C3EE42646G, Paper

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Notes from the Non-Energy Sector: A Broad Model for Emissions Reduction

In a new broad analysis researchers model the impact of fossil fuels for non-energy purposes vs. lower-emission alternatives, such as the use of biomass.

In research and popular media, much attention is focused on the impact of fossil fuels used for energy purposes. In a new EES paper, researchers focus instead on the non-energy uses of fossil fuels, their impact, and lower-emissions alternatives. Non-energy uses are defined as “fuels that are used as raw materials […] and are not consumed as a fuel or transformed into another fuel,” and primarily include feedstock for chemical production of ethylene, methanol, and ammonia, and oil products like waxes and lubricants. Coal, gas, and oil usage for non-energy purposes currently account for up to 7% of global CO2 emissions.

In their paper, Daioglou et al. present a global model for emissions reduction in non-energy processes, called the Non-Energy Demand and Emissions Model, or NEDE. This model projects that the global demand of non-energy processes will more than double over the next 100 years. Their analysis explores the alternative of using biomass for feedstock chemical production, promoting fuel switching in climate policy, and post-consumer waste management such as mechanical recycling and cascading processes. By comparing current usage and feedstock substitution costs, and by projecting based on economic, population, and fuel price developments, the model predicts that substituting fossils fuels, particularly coal, with biomass for non-energy purposes could significantly reduce emissions. Post-consumer waste management processes are currently too inefficient to significantly reduce emissions; however, climate policy that promotes fuel switching through carbon taxation can help to implement emissions-reducing practices.

It is interesting that Daioglou et al. point out that there are currently a lack of broad studies on the emission reduction potential of using biomass in non-energy processes, as was apparently pointed out in the recent Special Report on Renewable Energy Sources of the Intergovernmental Panel on Climate Change. Speaking as someone outside of this field of research, I would say that lowering emissions of non-energy processes certainly takes a back seat in the media to the use of fossil fuels for energy purposes. While the relative impact of non-energy processes may seem small by comparison, if the NEDE model is correct then analyses such as this one will grow increasingly important. As the authors note, there is still much research to be done to determine if biomass is optimal for reducing emissions for non-energy purposes, but his broad analysis is certainly a good start.

Read more in the full EES article here:

Energy Demand and Emissions of the Non-Energy Sector
Vassilis Daioglou, Andre Faaij, Deger Saygin, Birka Wicke, Martin Patel and Detlef Peter van Vuuren
Energy Environ. Sci., 2013, Accepted Manuscript
DOI: 10.1039/C3EE42667J

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