EES Blog

Seth Darling and co-workers from the USA describe methods to achieve better consistency in high performance of organic solar cells in their recent EES paper.

Batch-to-batch variation in performance of organic solar cells is a well-known problem, for which the underlying causes have been unclear so far. Trace impurities from residual catalyst material, used to synthesise the polymers in these devices, are known to affect device performance. Before now, no technique has been developed for identifying and quantifying impurities, even though they can cause issues with irreproducible optoelectronic function.

The group from Argonne National Laboratory, The University of Chicago and Northwestern University have shown that synchrotron-based X-ray fluorescence can detect and quantify trace concentrations of metal impurities in organic solar cell systems. They have also identified the threshold concentration at which performance degrades and the mechanism for the degradation.

Read the details in their paper today:

Detection and role of trace impurities in high-performance organic solar cells
Maxim P. Nikiforov, Barry Lai, Wei Chen, Si Chen, Richard D. Schaller, Joseph Strzalka, Jörg Maser and Seth B. Darling
DOI: 10.1039/C3EE40556G

Yang Shao-Horn, from MIT, and her co-workers report a novel and interesting study of oxygen reduction reaction (ORR) electrocatalysis on epitaxial perovskite thin films of different Mn valance states.

They were able to demonstrate conclusively that Mn³⁺, not Mn⁴⁺ or Mn²⁺, is the active species for ORR. They also revealed that the substrate can greatly alter the ORR activities of oxide films of a few nanometers in thickness by interfacial charge transfer.

Their findings are very important for the future design of nanostructured catalysts for electrochemical conversion and storage.

Alkaline fuel cells and metal–air batteries are promising carbon-neutral energy sources. However, these devices suffer from efficiency loss due to the slow ORR kinetics, and the cost of precious metal catalysts required to catalyze the ORR. LaMnO₃-based oxides have previously been  found to be among the most active for the ORR with activities comparable to that of Pt. However, ambiguity has existed until now as to which Mn valence state on the surface is responsible for the high ORR activity.

Read this HOT article today:

Oxygen electrocatalysis on (001)-oriented manganese perovskite films: Mn valency and charge transfer at the nanoscale
Kelsey A. Stoerzinger, Marcel Risch, Jin Suntivich, W. M. Lü, Jigang Zhou, Michael D. Biegalski, Hans M. Christen, Ariando, T. Venkatesan and Yang Shao-Horn
DOI: 10.1039/C3EE40321A

George Zhao and co-authors from Australia and China have written an excellent review of graphene-based electrode materials for electrochemical energy storage.

Read this timely summary of the field today:

Stephen Foster and Sajeev John demonstrate numerically that photonic crystal dye-sensitized solar cells (DSSCs) can provide at least a factor of one-third enhancement in solar light absorption and power conversion efficiency relative to their conventional counterparts in their recent EES paper.

Their design, which consists of a lattice of modulated-diameter TiO₂ nanotubes filled with TiO₂ nanoparticles and interstitial regions filled with electrolyte, has the potential of optimizing both light trapping and electron collection.

Read this HOT article today:

Light-trapping in dye-sensitized solar cells
Stephen Foster and Sajeev John
DOI: 10.1039/C3EE40185E

Scientists from Korea present a major step forward in the field of capacitive deionization (CDI) in their recent EES Communication. They cleverly substituted the fixed carbon electrodes used in typical CDI processes with a suspension of active carbon nanoparticles, achieving excellent desalination efficiency.

CDI is a promising water-treatment method. It has the advantage of being more energy efficient that other processes, such as reverse osmosis. However, CDI is not traditionally used for the desalination of salty water, because it requires a discharging step. After the adsorption of a certain amount of ions on the carbon electrodes in the CDI cell, the cell voltage is reduced and the electrodes are shortcircuited.  The new method presented in this Communication  avoids the need for a discharging step, and therefore allows easy scale-up  by simply increasing the number of flow-electrodes used.

Read this HOT Communication today:

Desalination via a new membrane capacitive deionization process utilizing flow-electrodes
Sung-il Jeon, Hong-ran Park, Jeong-gu Yeo, SeungCheol Yang, Churl Hee Cho, Moon Hee Han and Dong Kook Kim
DOI: 10.1039/C3EE24443A

Shi Su and co-authors from Australia have prepared carbon composite monoliths with superior CO₂ adsorption properties and hierarchical macroporous-microporous structures.

They prepared the monoliths by mixing a commercial phenolic resin with a small amount of carbon nanotubes followed by carbonization and physical activation with CO₂.  Their method is simple and low-cost, and may pave the way for more general use of carbon nanotubes in hierarchically porous structured composites for energy and environmental applications.

Read more in this HOT Communication:

Carbon nanotube modified carbon composite monoliths as superior adsorbents for carbon dioxide capture
Yonggang Jin, Stephen C. Hawkins, Chi P. Huynh and Shi Su
DOI: 10.1039/C3EE24441E

Scientists from Pacific Northwest National Laboratory have designed a low-cost Na–ZnCl₂ battery with a planar β′′-Al₂O₃ solid electrolyte. They found that the ZnCl₂-based chemical reactions were complex with multiple electrochemical reactions including liquid-phase formation occurring at temperatures above 253 °C. Their Na-ZnCl₂ battery performs impressively, and offers several advantages over Na-NiCl₂ batteries.

Read this HOT article today:

A novel low-cost sodium–zinc chloride battery
Xiaochuan Lu, Guosheng Li, Jin Y. Kim, John P. Lemmon, Vincent L. Sprenkle and Zhenguo Yang
DOI: 10.1039/C3EE24244G