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Fabulous functionalised fibres for fuel cells

17 Feb 2011

A remarkable new electrode design represents a significant leap in microbial fuel cell (MFC) technology. Fuel cells using the new cathode have more than two times the power density of current commercially available cathodes.

SEM image of the surface of the CNT–textile composite

The porous textile fibre network is critical for cathode performance

MFCs are a promising technology that is able to act as both a renewable energy source and wastewater treatment method. They use the catalytic activity of microbes to oxidise organic matter in wastewater using oxygen, generating electrical energy. However, fuel cell performance is often limited by the cathode performance.

Continuing work previously published, the researchers have developed a new aqueous electrode (i.e. designed to work when submerged in an electrolyte purged with oxygen) in which they deposit platinum nanoparticles onto a carbon nanotube–textile composite.

The electrode allows a maximum MFC power density of 837 mW m⁻²; using a commercial carbon cloth–Pt electrode only obtains a density of 391 mW m⁻².

This enhanced performance is attributed to the cathode’s superior design:

the network of textile fibres allows a much larger electrochemically active surface area;
the network also contains macroscale pores for fast access of electrolyte;
a glacial acetic acid treatment during synthesis provided the electrode with an hydrophilic surface.

Read more about this exciting new work now:

Nano-structured textiles as high-performance aqueous cathodes for microbial fuel cells
Xing Xie, Mauro Pasta, Liangbing Hu, Yuan Yang, James McDonough, Judy Cha, Craig S. Criddle and Yi Cui
Energy Environ. Sci., 2011, Advance Article, DOI: 10.1039/C0EE00793E

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Breakthrough for bacterial hydrogen production

11 Feb 2011

Breakthrough for bacterial hydrogen production

by Philippa Ross

Scientists in China have developed a device that can produce hydrogen from organic materials using bacteria at temperatures below 25 degrees Celsius.

Normally, hydrogen production by bacterial metabolism is reduced at lower temperatures because it slows down the enzymes that catalyse the reactions. Now, Defeng Xing and his team at the Harbin Institute of Technology have optimised hydrogen production from organic matter between 4 and 9 degrees Celsius by using a microbial electrolysis cell (MEC). This eliminates the cost of heating and could enable hydrogen production to be carried out at high latitudes and mountainous regions where the air temperature is below 10 degrees Celsius.

MECs generate hydrogen directly upon applying an electric current to bacteria. Bacteria consume acetic acid, which is produced from fermenting plant matter and release protons, electrons and CO_2. Addition of an electric current enables the protons and electrons to join together to make hydrogen gas and the higher the current, the more hydrogen is produced.

Breakthrough for bacterial hydrogen production

‘In order to achieve a high yield of hydrogen in MECs, it’s essential that both the electron transfer and hydrogen recovery processes are highly efficient,’ explains Xing.

Methanogenesis, or methane formation, is a common problem in MECs, which occurs at higher temperatures as a result of bacterial anaerobic respiration. This can reduce the efficiency of electron transfer to the cathode, reducing the overall output of hydrogen. However, at temperatures below 10 degrees Celsius, no methane was produced since the growth of the methane producing organisms was inhibited and the yield of hydrogen produced is comparable to that at temperatures above 25 degrees Celsius.

Sarah Strycharz-Glaven, an expert in microbial fuel cells at the Naval Research Laboratory in Washington DC is impressed with the group’s findings but acknowledges that there is some progress to be made. ‘The authors will need to increase the efficiency of hydrogen production under colder conditions to compete with MECs operating at ambient conditions,’ she says.

The group aim to do this by increasing hydrogen recovery and exploring new electrode materials. In the future they hope that MEC technology could be considered for biohydrogen production in cold environments.

Read the Energy & Environmental Science article now:

Hydrogen production, methanogen inhibition and microbial community structures in psychrophilic single-chamber microbial electrolysis cells
Lu Lu, Nanqi Ren, Xin Zhao, Huan Wang, Di Wu and Defeng Xing
Energy Environ. Sci., 2011, Advance Article, DOI: 10.1039/C0EE00588F

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Could urea be the future source of hydrogen?

10 Feb 2011

Energy & Environmental Science Perspective

This ‘HOT’ feature article reviews the potential of urea ((NH₂)₂CO) as a hydrogen carrier for fuel cells and the feasibility of utilising the enormous natural resource of urea that already exists.

Urea is a cheap and readily available resource, and has the advantage over other chemicals of being non-toxic and stable, and therefore easy to transport and store.

The authors say that urea “could be a solution to long-term future sustainable hydrogen supply” and conclude that urea is a realistic sustainable route and could be exploited if sufficient research is undertaken.

Read this ‘HOT’ Perspective today:
Urea as a hydrogen carrier: a perspective on its potential for safe, sustainable and long-term energy supply
Andrew N. Rollinson, Jenny Jones, Valerie Dupont and Martyn V. Twigg
Energy Environ. Sci., 2011, DOI: 10.1039/C0EE00705F

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The true cost of getting energy from the sun

08 Feb 2011

US scientists have proposed a new method to compare the cost of solar energy technology with traditional sources as current methods may not give a realistic result

Seth Darling and colleagues from the Argonne National Laboratory in Illinois have used a simulation that gives distributions of values for variable parameters such as weather, solar panel performance, operating costs and inflation to more accurately reflect the overall cost.

‘For solar energy to make a significant dent in the overall energy mix, its cost will have to be similar to or lower than traditional sources such as fossil fuels,’ says Darling, ‘but to make this comparison, you need to know how to calculate the cost.’

Monte Carlo simulation

‘The results indicate that the real discount rate is the most relevant factor,‘ says José Goldemberg, an expert on energy and environmental issues from the University of São Paulo, Brazil.

Darling hopes that stakeholders in the energy community will adopt his approach. The biggest challenge, he says, is getting performance data from diverse geographic locations.

‘We hope that partnerships between the solar energy industry, utility providers and national laboratories will focus on collecting the data and making it accessible to those interested in exploring the potential of solar energy,’ he concludes.

Read more of the Chemistry World feature here…

View the Energy Environmental Science Analysis article:

Assumptions and the levelized cost of energy for photovoltaics
Seth B. Darling, Fengqi You, Thomas Veselka and Alfonso Velosa
Energy Environ. Sci., 2011, DOI: 10.1039/c0ee00698j

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A simple and efficient way to reduce CO2

04 Feb 2011

With increasing concerns over global warming and the urgent need to reduce CO₂ emissions, scientists in China have developed a new simple and efficient strategy for the reduction of CO_2.

They demonstrate a carbon cycle which is driven simply by the oxidation and reduction of commonly available metals, such as iron.

The cycle begins with the high-yield reduction of CO₂to formic, via the oxidation of a zero-valent metal under hydrothermal conditions. The metal oxide can then be converted back to the metal using a bio-derived chemical such as glycerin, which is readily available from renewable resources.

reduce co2

The production of formic acid in the cycle is also an added bonus, as this can be used to power fuel cells, which can be applied to small, portable electronics such as cell phones and laptop computers.

This new energy system has many advantages over current methods to reduce CO₂ (such as water-splitting) as it has high yields, no waste products, does not require expensive catalysts or harsh reagents and, as the overall cycle is exothermic, it is expected to have minimal energy requirements.

Read the ‘HOT’ Communication today:

High-yield reduction of carbon dioxide into formic acid by zero-valent metal/metal oxide redox cycles
Fangming Jin, Ying Gao, Yujia Jin, Yalei Zhang, Jianglin Cao, Zhen Wei and Richard L. Smith Jr
Energy Environ. Sci., 2011, DOI: 10.1039/C0EE00661K

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EES paper featured on Green Car Congress website

04 Feb 2011

An Energy & Environmental Science paper has been highlighted on the Green Car Congress website.

The work by Hugh O’Neill and colleagues at the Oak Ridge National Laboratory demonstrates a novel approach for developing a new class of smart materials with architectures that are dependent on the assembly of interacting components. These could have important implications in self-repair and control of energy transfer in photoconversion devices.

Read the Energy & Environmental Science paper today:

Supramolecular assembly of biohybrid photoconversion systems
Mateus B. Cardoso, Dmitriy Smolensky, William T. Heller, Kunlun Hong and Hugh O’Neill
Energy Environ. Sci., 2011, 4, 181-188
DOI: 10.1039/C0EE00369G

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Energy & Environmental Science Issue 2 now online

02 Feb 2011

February’s issue of Energy & Environmental Science is now published online – take a look at this great issue today

This issue’s very artistic outside front cover* highlights the crucial role of electrode buffer layers for the overall performance of polymer solar cells, as discussed in the Review by Nadia Camaioni and colleagues.

The role of buffer layers in polymer solar cells
Riccardo Po, Chiara Carbonera, Andrea Bernardi and Nadia Camaioni
Energy Environ. Sci., 2011, 4, 285-310

The inside front cover (equally as impressive artwork!) features the work of Amanda Barnard, looking at the photocatalytic activity or potential free radical toxicity of titania at the nanoscale.

Mapping the photocatalytic activity or potential free radical toxicity of nanoscale titania
Amanda S. Barnard
Energy Environ. Sci., 2011, 4, 439-443

*Image adapted by Dr Maddalena Pezzani from Graur Razvan Ionut / FreeDigitalPhotos.net (image of sky), Sapere.it (image of hieroglyphic carvings), and Konarka Power Plastic(R) by George Disario (PV module). Image reproduced by permission of Dr Nadia Camaioni from Energy Environ. Sci., 2011, 4, 285.

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Bridging the gap in energy storage materials

01 Feb 2011

Perspective article – nanostructured carbon-based electrodes could be the answer…

The fast evolution of portable electronic devices and micro-electro-mechanical systems (MEMS) requires energy sources that have high power, high energy, long cycle life, and the adaptability to various substrates.

Two excellent candidates are lithium-ion batteries, which can store high energy on a gravimetric and volumetric basis but have relatively low power, and electrochemical capacitors (ECs) which are ideal for high power applications, but are limited for energy storage. There is now a need to develop materials with both high power and energy storage capabilities.

Nanostructured carbon-based electrodes

Currently, the excellent performance of nanostructured electrodes with thickness of a few microns can be integrated on Si chips or flexible plastic substrates, suggesting promising energy sources for portable electronic devices and micro-electro-mechanical systems (MEMS). If these nanostructured electrodes can be successfully scaled up to a thickness of hundreds of microns without losing performance, they could be promising for incorporation into electric vehicles, heavy machinery, and load-leveling applications.

Read the feature review today:
Nanostructured carbon-based electrodes: bridging the gap between thin-film lithium-ion batteries and electrochemical capacitors
Seung Woo Lee, Betar M. Gallant, Hye Ryung Byon, Paula T. Hammond and Yang Shao-Horn
Energy Environ. Sci., 2011, DOI: 10.1039/C0EE00642D

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Biomass for Biofuels: The use of ionic liquids

31 Jan 2011

New Energy and Environmental Science mini review

Advances on biomass pretreatment using ionic liquids: An overview

Haregewine Tadesse and Rafael Luque

Energy and Environmental Science, DOI: 10.1039/c0ee00667j

With increasing pressure on non-renewable energy and chemical sources due to the Earth’s swelling population and dwindling supplies, research into renewable and environmentally friendly feedstocks is of critical importance. In this Energy and Environmental Science review, the authors Tadesse and Luque set out the current state of affairs in an area of research which sits at the interface of two important areas of science: ionic liquids and biofuels.

The conversion of biomass into useful fuels and chemicals is a complex process. It is of utmost importance that a strategy for this conversion is developed which is low cost, efficient, and minimises the use of volatile organic solvents. A critical step in this process is the pre-treatment of the biomass. In this review the discussion revolves around lignocellulosic biomass, which includes materials like corn stalk and wheat straw. The pre-treatment step removes or weakens the strong linkages between cell wall components in the plant structure, making the biomass easier to break down and improving the eventual yield of useful products. The key point, as set out by the authors, is as follows:

The depolymerization or hydrolysis of lignocellulosics into intermediates that are more susceptible to chemical or biological transformations is a prerequisite step for the production of biofuels and chemicals.

The solvent systems that are currently used for pre-treatment present various difficulties and drawbacks, for example their volatility and the generation of poisonous gases. An exciting alternative to these systems has emerged in the form of ionic liquids, molten ion solutions which melt at temperatures less that 100 °C. These are considered as promising solvents in many areas of chemistry due to their high solvation capacity, negligible vapour pressure and highly tuneable properties.

To read more on this topic, including thorough explanation and detailed analysis of this exciting field of research, click here.

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Pig power for batteries

18 Jan 2011

Scientists in China have developed an electrode for lithium-sulfur batteries using pig bones as a cheap and renewable carbon source.

Pig and battery Lithium-sulfur batteries are promising rechargeable batteries because of their high energy storage capacity and low cost, but their use has been hindered by their short life cycle and loss of active sulfur through electrochemical reactions in the battery. Porous carbon materials can help as the sulfur is trapped in the pores, preventing it reacting further, but their preparation involves many synthetic steps.

Now, Yaqin Huang and his team from the Beijing University of Chemical Technology have discovered a porous carbon source in pig bone.

“The development of rechargeable batteries that can be coupled to renewable sources is becoming more important for clean and efficient energy storage,” explains Huang.

Leela Mohana Reddy, an expert in lithium ion batteries and supercapacitors at Rice University, Texas, US, comments that, “pig bone based porous carbon has great potential in the development of novel cathode materials for building the next generation of energy storage devices.”

Read more of the Chemistry World article…

Read the Energy & Environmental Science article today:

Pig bone derived hierarchical porous carbon and its enhanced cycling performance of lithium–sulfur batteries
Shaochen Wei, Hao Zhang, Yaqin Huang, Weikun Wang, Yuzhen Xia and Zhongbao Yu
Energy Environ. Sci., 2011, DOI: 10.1039/c0ee00505c

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EES Blog

Archive for the ‘Hot Article’ Category

Fabulous functionalised fibres for fuel cells

Breakthrough for bacterial hydrogen production

Breakthrough for bacterial hydrogen production

Could urea be the future source of hydrogen?

The true cost of getting energy from the sun

A simple and efficient way to reduce CO2

EES paper featured on Green Car Congress website

Energy & Environmental Science Issue 2 now online

Bridging the gap in energy storage materials

Biomass for Biofuels: The use of ionic liquids

Pig power for batteries

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