EES Blog

Graphene oxide may be a better choice as an electrode for supercapacitors than graphene because it exhibits higher capacitance, shorter processing time and is cheaper than graphene, say researchers from China.

Supercapacitors are promising energy storage devices for electric vehicles because of their high power densities and long cyclic lives.

Graphene, a two-dimensional nanosheet of graphite, has been the material of choice for supercapacitors because it possesses superior electrical conductivity, a high theoretical surface area and chemical tolerance. But, owing to the unavoidable aggregation of graphene nanosheets, the surface area is usually much lower than the theoretical one and its capacitance is generally in the range 100–200 F g^-1.

Graphene oxide is an intermediate during the synthesis of graphene. Despite the fact that some graphene oxide-based nanocomposites have performed well in supercapacitors, it has been said that graphene oxide is not suitable as an electrode material because of its poor conductivity, but the team contradict this with their findings.

Read the article in full:
What Is the Choice for Supercapacitors: Graphene or Graphene Oxide?
B Xu, S Yue, Z Sui, X Zhang, S Hou, G Cao and Y Yang
Energy Environ. Sci., 2011, DOI: 10.1039/c1ee01198g

Link to journal article

Metabolite-based mutualism between Pseudomonas aeruginosa PA14 and Enterobacter aerogenes enhances current generation in bioelectrochemical systems
Arvind Venkataraman, Miriam A. Rosenbaum, Sarah D. Perkins, Jeffrey J. Werner and Largus T. AngenentEnergy Environ. Sci., 2011
DOI: 10.1039/c1ee01377g

A way to avoid bubble formation in photoelectrolysis systems – which split water into hydrogen and oxygen – so that water vapour can be electrolysed at room temperature at current densities in excess of those produced by the best photoelectrolysis systems has been developed by US scientists.

The formation of hydrogen through water electrolysis is one viable approach for solar fuel production on a global scale. Although photovoltaic modules can be connected to conventional electrolysers to split water, photoelectrolysis systems, in which sunlight is absorbed and the energy directly converted to decompose water to hydrogen and oxygen, have the potential to be more inexpensive and efficient.

An efficient photoelectrolyser, however, tends to limit its own performance by the formation of copious bubbles of gaseous products that inhibit the process by reflecting light and slowing the transfer of water to the catalyst reaction sites. Without concentrators, the intensity of the solar photon flux limits photoelectrolysers to far lower current densities than are used in conventional electrolysers.

Read this paper hot off the press! 

Reference:
J M Spurgeon and N S Lewis, Energy Environ. Sci., 2011
DOI: 10.1039/c1ee01203g

The world’s first spent nuclear fuel repository concept (Swedish KBS-3) has been illustrated by a team from Sweden.

The researchers looked at what happens when canisters containing spent fuel are breached at the early stages of disposal. In deoxygenated synthetic groundwater (2 mM NaHCO3), under radiation, leaching rates of fission products (137Cs, 90Sr and 99Tc) and actinides (238U, 237Np) from a spent fuel segment were found to be around 10-6 and 10-7 per day, respectively.

The team found that a cast-iron canister surface could immobilise 238U, 90Sr, 99Tc and 237Np dissolved from spent fuel, but a copper surface could not. In the presence of the oxidative species generated from water radiolysis, the corrosion rates of waste canister materials, copper and cast-iron were found to be 1 and 30 mm per year, respectively. The observation of insignificant dissolution of spent fuel in the leaching solution equilibrated with 0.1 atm H2 is explained by the reducing effects of H2 in the presence of fission-product alloy particles (Mo–Tc–Ru–Rh–Pd) as catalysts and dissolved Fe(II) in groundwater.

Reference:
Environmental behaviors of spent nuclear fuel and canister materials
D Cui, J Low and K Spahiu
Energy Environ. Sci., 2011, DOI: 10.1039/c0ee00582g

An Energy & Environmental Science paper has featured today on ACS Noteworthy Chemistry – check it out today!

Very low temperature membrane-free desalination by directional solvent extraction
Anurag Bajpayee, Tengfei Luo, Andrew Muto and Gang Chen
Energy Environ. Sci., 2011, 4, 1672-1675
DOI: 10.1039/C1EE01027A

This article was also featured in Chemistry World  – read the article:

Simple salt removal to get fresh water

US scientists have used a silicon photoanode substrate to process cobalt metal thin films to form a cobalt-based water oxidation catalyst (Co–Pi).

The Co–Pi loaded electrodes show significant improvement (x 100) over bare silicon photoanodes. Integrating chemical electrocatalysts for water splitting and photoanode materials to achieve light assisted water oxidation for the generation of solar fuels is a longstanding challenge.

The team’s results demonstrate the importance of material selection and device engineering to harness the solar spectrum towards catalytic chemical fuel production. The robust and abundant silicon electrode and direct processing of the cobalt metal produce an improved light assisted water oxidation device.

Reference:
Photo-assisted water oxidation with cobalt-based catalyst formed from thin-film cobalt metal on silicon photoanodes
Elizabeth R. Young, Ronny Costi, Sarah Paydavosi, Daniel G. Nocera and Vladimir Bulović
Energy Environ. Sci., 2011, DOI: 10.1039/C1EE01209F

Read it today!