EES Blog

Credit: Foreign Policy magazine

We are delighted to announce that Energy and Environmental Science authors Florent Boudoire, Rita Toth, Jakob Heier, Artur Braun and Edwin C. Constable have been listed among Foreign Policy magazine’s “100 Leading Global Thinkers of 2014” for their work on advancing solar technology using rust and moth eyes.

The researchers are based at the Swiss Federal Laboratories for Materials Science and Technology and the University of Basel, Switzerland and were honoured in the innovators section. The Foreign Policy editors noted on their work that ‘The advance opens up a new method for hydrogen-fuel production and could let the next generation of solar technologies take wing.’

For further information take a look at the Global Thinkers website and make sure to read the original EES article!

Photonic light trapping in self-organized all-oxide microspheroids impacts photoelectrochemical water splitting
Florent Boudoire, Rita Toth, Jakob Heier, Artur Braun and Edwin C. Constable
Energy Environ. Sci., 2014,7, 2680-2688

 Abigail Hallowes writes about an EES article in Chemistry World

Researchers from the US have optimised a photoelectrochemical cell (PEC) so that it can continuously split water into clean burning hydrogen and oxygen for over 2200 hours – the equivalent to one year of outdoor operation.

In order for PECs to be a competitive energy provider, they should efficiently covert solar into chemical energy, whilst remaining stable for years of continuous operation. The condition of the electrodes in PECs is a major concern as they immediately start to corrode once immersed in the electrolyte. Previous PEC researchers have only been able to produce systems that are either stable for 4–100 hours but inefficient, or efficient but only stable for a few minutes; they have not been able to incorporate both required properties.

Scanning-electron micrograph image of a microwire array with its protective coating

 
Electrode instability is brought on when the energy required to excite an electron is within the same energy range that causes electrode corrosion; photocorrosion then becomes competitive with water splitting. In these cases, it is most likely that photocorrosion is thermodynamically more favourable which therefore leads to unstable electrodes. Now, a team led by Nathan Lewis at the California Institute of Technology have drastically increased PEC stability whilst achieving a 100% Faradaic efficiency for oxygen evolution.
 
Their approach increased the electrochemically active sites versus the surface area of the electrode through the use of silicon microwire arrays; this led to a decrease in the effective current density at the electrode–electrolyte interface, increasing the energy required for photocorrosion, which decreased the rate of photocorrosion. They also coated the arrays in a protective but conductive layer, to act as a corrosion-resistant barrier while maintaining efficient charge transfer to the reaction sites, as well as with an oxygen evolution catalyst to promote water oxidation.
 
Brian Seger, a photoelectrochemist at the Technical University of Denmark, explains that water splitting provides some very corrosive conditions so stability has been a large hurdle in this field: ‘The fact that the Lewis group could test their device for three months with no noticeable corrosion indicates that this hurdle is surmountable.’
 
Materials scientist, Dongyuan Zhao, of Fudan University, China, describes the work was a breakthrough and says it ‘shows great potential for industrial application.’

Interested to find out more? Read the full article by Abigail Hallowes in Chemistry World.

Read the original article in Energy and Environmental Science:

Stabilization of Si microwire arrays for solar-driven H2O oxidation to O2(g) in 1.0 M KOH(aq) using conformal coatings of amorphous TiO2
Matthew R. Shaner,ab   Shu Hu,ab   Ke Sunab and   Nathan S. Lewis
Energy Environ. Sci., 2015, Advance Article
DOI: 10.1039/C4EE03012E

A low-cost, high-efficiency technique for fabricating perovskite solar cells – ultra-sonic spray-coating – has been developed by a team of researchers in the UK. It represents a significant step towards commercialising perovskite solar cells.

David Lidzey, head of the research group at the University of Sheffield behind the study, explains that there has been ‘interest in developing solar cell materials that are easy to process, efficient and have less embodied energy than current technologies.’

Thin-film solar cells using perovskite semi-conductors have become a promising form of photovoltaic device achieving power conversion efficiencies of up to 15–19%, surpassing the efficiencies of amorphous silicon and organic semi-conductor photovoltaics.

Perovskite films can be fabricated by depositing precursor materials from solution. However, there have been few reports detailing the application of scalable solution-processing techniques to create these films.

In this study, an ultra-sonic spray-coating of methylamine iodide and lead chloride created a thin film of a perovskite precursor under ambient conditions. The film was then thermally annealed into a CH3NH3PbI3–ᵪClᵪ perovskite structure prior to inclusion within a solar cell with a planar heterojunction architecture.

Interested to find out more? Read the full article by Vicki Marshall in Chemistry World.

Read the original article in Energy and Environmental Science:

Efficient planar heterojunction mixed-halide perovskite solar cells deposited via spray-deposition
Alexander T. Barrows, Andrew J. Pearson, Chan Kyu Kwak, Alan D. F. Dunbar, Alastair R. Buckley and David G. Lidzey
Energy Environ. Sci., 2014, Advance Article
DOI: 10.1039/C4EE01546K