EES Blog

Scientists in the US and South Korea have used molecular simulations to study over 130,000 hypothetical MOFs to expand their knowledge of potential CO₂ capture materials. The team calculated the adsorption properties, which allowed them to define structure-property relationships for structural characteristics (pore size, surface area, pore volume), and chemical characteristics (i.e. functional groups), building up a roadmap to act as a shortcut to future porous material design.

Many researchers have been looking at different types of compounds for CO₂ capture and metal-organic frameworks (MOFs) seem to be the most promising. Until now, there have been no clear correlations between material properties (pore size, surface area and pore volume).

Read the ‘HOT’ EES paper today:

Structure-Property Relationships of Porous Materials for Carbon Dioxide Separation and Capture
Christopher E Wilmer, Omar K. Farha, Youn-Sang Bae, J T Hupp and Randall Q Snurr
Energy Environ. Sci., 2012, DOI: 10.1039/C2EE23201D

Researchers in the US have used cyanobacteria (blue-green algae) to covert CO₂ into valuable organic chemicals.

Good conversion rates of 65% were obtained and the authors say that the system could be developed to harvest a range of organic compounds from phototrophs (organisms that carry out photon capture to produce energy, like algae). They add that the tool will facilitate future research on photosynthetic production of biofuels and chemicals and new insights into mechanisms for using cyanobacteria for carbon re-distribution.

Read the ‘HOT’ EES article:

Photo-catalytic conversion of carbon dioxide to organic acids by a recombinant cyanobacterium incapable of glycogen storage
Damian Joseph Carrieri, Troy Paddock, Pinching Maness, Michael Seibert and Jianping Yu
Energy Environ. Sci., 2012, DOI: 10.1039/C2EE23181F

A new method of variable temperature spectroelectrochemistry to measure the conduction band energy of nanoparticle TiO₂ has been developed by scientists in the US. Spectroelectrochemistry combines reaction-oriented electrochemistry with species-focused spectroscopy.

Nanostructured semiconductors such as TiO₂ are important for dye-sensitised solar cells and photocatalysis. Measuring the conduction and valence band energy of semiconductors is one of the most important physical parameters. However, these are currently problematic to measure; there is no reliable method. The new method is quick, makes a minimal number of assumptions and is remarkably versatile. The team says that they expect it could be used with a variety of porous semiconductor materials.

Read the EES ‘HOT’ Communication:

Conduction Band Energy Determination by Variable Temperature Spectroelectrochemistry
Jesse Ondersma and Thomas Hamann
Energy Environ. Sci., 2012, DOI: 10.1039/C2EE22926A

Scientists in the US, Mexico and China have developed semi-transparent organic photovoltaic (OPV) cells with high performance, tuneable transparency and excellent colour perception and rendering properties.

The performance of semi-transparent OPV devices is much lower than their opaque counterparts, and much needs to be done to study and optimise their properties. The team has made semi-transparent OPVs using a low bandgap polymer. By tuning the thickness of the reflective metal electrode, they achieve power conversion efficiencies of 4.25–7.56% and transparency from 2–36%.

They say that their cells have significantly improved performance compared to other semi-transparent OPVs with similar transparencies. The colour rendering indices (CRIs)* of their devices are close to 100, the best values ever reported. (* CRI = quantitative measure of the ability of a light source to reproduce the colours of various objects faithfully in comparison with an ideal or natural light source.)

Polymer solar cells are of interest due to their roll-to-roll fabrication and associated low cost. Semi-transparent OPV devices are a promising candidate for power-generating window applications, as they can be integrated with conventional elements in buildings and vehicles.

Read the ‘HOT’ EES article:

Semi-transparent polymer solar cells with 6% PCE, 25% average visible transmittance and color rendering index close to 100 for power generating window applications
Kung-Shih Chen, Jose Francisco Salinas, Hin-Lap Yip, Jianhui Hou and A Jen
Energy Environ. Sci., 2012, DOI: 10.1039/C2EE22623E

Dye-sensitised solar cells (DSSCs) have been attracted increasing interest recently as an alternative to conventional silicon-based solar cells, owing to their relatively high conversion efficiencies and low manufacturing costs.

In DSSC devices, dye aggregation on the TiO₂ electrode is one of the most serious problems, which leads to a reduced device performance. Conventional solutions involve cumbersome optimisation processes and increased production costs, so a simple solution for the problem is required.

Scientists in Japan and China have reported an aggregation-free branch-type organic dye with a twisting pi-conjugate architecture. They compare it with an analogue dye possessing a planar molecular structure. The influences of deoxycholic acid co-adsorption are investigated, and it is found that the twisting dye has excellent potential as an aggregation-free dye.

Read the ‘HOT’ EES article hot off the press:

Aggregation-free branch-type organic dye with a twisted molecular architecture for dye-sensitized solar cells
Youhei Numata, Ashraful Islam, Han Chen and Liyuan Han
Energy Environ. Sci., 2012, Accepted Manuscript
DOI: 10.1039/C2EE22506A

Scientists in China and the US have demonstrated a thermoelectric material with excellent thermal and chemical stability up to high temperatures; it’s a promising material for converting wasted heat into electricity, they say.

The material is an oxyselenide – BiCuSeO. A high ZT ~1.1 at 923K in BiCuSeO system is achieved via Ba heavily doping and refining grain sizes (200~400 nm), which is higher than any thermoelectric oxides. Excellent thermal and chemical stability up to 923 K and high thermoelectric performance confirm that BiCuSeO system is promising for thermoelectric power generation applications.

Read the ‘HOT’ EES Communication:

High thermoelectric figure of merit ZT>1 in Ba heavily doped BiCuSeO oxyselenides
Li-Dong Zhao, Jing Li, Jiehe Sui, yanling pei, celine barreteau, David Berardan, Nita Dragoe, Wei Cai and Jiaqing He
Energy Environ. Sci., 2012, Accepted Manuscript
DOI: 10.1039/C2EE22622G

Scientists in the US have investigated the influence of a polymer’s crystallinity [P(VDF-TrFE)] on its function in ferroelectric photovoltaic devices by comparing crystalline and amorphous phases.

 The team’s results showed that the highly crystalline polymer film is needed for enhanced power conversion efficiency, because only crystalline P(VDF-TrFE) is ferroelectric.

 The method, they say, could be applied to many other devices, such as organic solar cells with low bandgap polymers, tandem solar cells, organic light emitting diodes, organic field effect transistors and organic bistable memories.

 Read the ‘HOT’ EES article today:

Understanding the effect of ferroelectric polarization on power conversion efficiency of organic photovoltaic devices
Y Yuan et al, Energy Environ. Sci., 2012, DOI: 10.1039/c2ee22098a