EES Blog

Paul Dauenhauer and coworkers’ paper on an improved methodology for the study of cellulose pyrolysis has been highlighted in Nature Chemistry. This is an important step in the realization of efficient biofuel production.

Read the full EES paper today:

Revealing pyrolysis chemistry for biofuels production: Conversion of cellulose to furans and small oxygenates
Matthew S. Mettler, Samir H. Mushrif, Alex D. Paulsen, Ashay D. Javadekar, Dionisios G. Vlachos and Paul J. Dauenhauer
DOI: 10.1039/C1EE02743C

HOT EES communication

The recombination of charges before they reach the electrode in a solar cell has been identified as one of the key reasons for a loss of efficiency in these systems. Tracey Clarke and coworkers have developed a new switch-based time resolved technique for studying the recombination process. This allowed the researchers to overcome the resistance-dependence limitations of typical time-of-flight experiments.

Read the full HOT EES communication:

Non-Langevin bimolecular recombination in a silole-based polymer:PCBM solar cell measured by time-resolved charge extraction and resistance-dependent time-of-flight techniques
Tracey M. Clarke, Jeff Peet, Patrick Denk, Gilles Dennler, Christoph Lungenschmied and Attila J. Mozer
DOI: 10.1039/C1EE02434E

Platinum has been the electrode material of choice for the oxygen reduction reaction which takes place in fuel cells. However it is expensive, and previous research using alloys of Pt with Co, Ni and Fe have required high Pt ratios.

Now researchers working at the Brookhaven National Laboratory have synthesized nanoparticles with a carbon-supported IrNi core and a surface monolayer of platinum. These nano-electocatalysts have an approximately 3 times higher Pt mass activity than currently available commercial Pt/C electrocatalysts.

Read the full details of this HOT EES paper:

Bimetallic IrNi core platinum monolayer shell electrocatalysts for the oxygen reduction reaction
Kurian A. Kuttiyiel, Kotaro Sasaki, YongMan Choi, Dong Su, Ping Liu and Radoslav R. Adzic
DOI: 10.1039/C1EE02067F

Marta Hatzell, Younggy Kim and Bruce Logan at work in the lab. Photograph by Robert Davis

Microbial fuel cells (MFCs) are a potential “green” energy source of the future, using organic matter in water to produce electricity. However, the voltages obtained from MFCs are generally too small to be useful.

Now Bruce Logan and his co-workers at Penn State University have shown that MFC voltages can be increased while maintaining continuous power production.

They introduced two sets of capacitors that are alternately charged and discharged into their circuit. The capacitors were charged in parallel by the MFCs, but linked in series while discharging thus preventing a phenomenon known as voltage reversal which can cause an overall decrease  in the voltage achieved. Impressively, the system also had negligible energy losses compared to those reported up to now.

Read the full details of this HOT EES paper:

Capturing power at higher voltages from arrays of microbial fuel cells without voltage reversal
Younggy Kim, Marta C. Hatzell, Adam J. Hutchinson and Bruce E. Logan
Energy Environ. Sci., 2011
DOI: 10.1039/C1EE02451E

Producing supercapacitors with energy densities similar to those of traditional batteries is currently a hot topic in energy research as they have great potential for use in electric vehicles. Graphene has been identified as promising supercapacitor material.

In this HOT article Ruoff et al. report for the first time the interfacial capacitance of a single sheet of graphene, and show that the greater charge can be stored on a single side of the graphene sheet than can be stored simultaneously on both sides. This means that an increase in the graphene surface area does not result in a linear increase in energy storage capacity, as was previously thought.

Read this exciting article in full:

Interfacial capacitance of single layer graphene
Meryl D. Stoller, Carl W. Magnuson, Yanwu Zhu, Shanthi Murali, Ji Won Suk, Richard Piner and Rodney S. Ruoff
Energy Environ. Sci., 2011
DOI: 10.1039/C1EE02322E

An exciting article in Energy and Environmental Science has been highlighted in this week’s Editor’s Choice in Science. The article by Teixeira et al. describes their studies into the way cellulose behaves at high temperatures.

You can read the article on our website:

Aerosol generation by reactive boiling ejection of molten cellulose
Andrew R. Teixeira, Kyle G. Mooney, Jacob S. Kruger, C. Luke Williams, Wieslaw J. Suszynski, Lanny D. Schmidt, David P. Schmidt and Paul J. Dauenhauer
Energy Environ. Sci., 2011
DOI: 10.1039/C1EE01876K

Or why not look at our EES blog post about this exciting work.

Scientists from China and the US have produced glass that responds to its environmental temperature, making it a promising material for energy efficient windows. On cold days, the windows would prevent heat escaping and on hot days, the windows would reflect infrared radiation, keeping the room inside cool.

Vanadium dioxide (VO₂) has long been recognised as a potential candidate material for making ‘smart windows’ because it can change from a transparent semiconductive state at low temperatures, allowing infrared radiation through, to an opaque metallic state at high temperatures, while still allowing visible light to get through. VO₂ has its drawbacks, however: it’s not a very good insulator and can only be made at very high temperatures of 420-500°C.

Zhong Lin Wang at the Georgia Institute of Technology, Atlanta, and co-workers at the   Shanghai Institute of Ceramics Chinese Academy of Sciences and the Graduate University of Chinese Academy of Sciences in Beijing, have created a system with improved insulating ability by combining a layer of VO₂ with a transparent fluorine-doped tin oxide (FTO) layer coated on glass. As an added benefit, the  FTO layer enhances the crystallinity of the VO₂ film – an important factor for improving the material’s performance and reducing its cost – and lowers the synthesis temperature to 390°C.

‘Buildings and maintaining man-made structures use 30-40 per cent of the primary energy supply, mainly for heating, cooling, ventilation and lighting. Effective control of the energy exchange between the interior and exterior of buildings through windowpanes is a key area in saving energy,’ says Yanfeng Gao, one of the researchers. ‘We conducted this research to create a film that can combine the functions of low emissivity and thermochromic coatings.’

Materials expert Seeram Ramakrishna, from the National University of Singapore, sees advantages to the group’s approach. However, he also feels that improvements could be made to optimise the system. The work ‘doesn’t attempt to bring down the transition temperature of VO₂ to room temperature, which would be desirable if it is to have practical technological applications,’ he says.

Gao now hopes to realise his dream of seeing the smart windows go into mass production.

Heather Montgomery

Read this HOT Energy and Environmental Science article:

Solution-based fabrication of vanadium dioxide on F:SnO2 substrates with largely enhanced thermochromism and low-emissivity for energy-saving applications
Zongtao Zhang, Yanfeng Gao, Hongjie Luo, Litao Kang, Zhang Chen, Jing Du, Minoru Kanehira, Yuzhi Zhang and Zhong Lin Wang
DOI: 10.1039/C1EE02092G