Featured Research

from universities, journals, and other organizations

Collecting light with artificial moth eyes: Producing hydrogen with sunlight

Date:
June 18, 2014
Source:
Empa
Summary:
All over the world researchers are investigating solar cells which imitate plant photosynthesis, using sunlight and water to create synthetic fuels such as hydrogen. Researchers have developed such a photoelectrochemical cell, recreating a moth’s eye to drastically increase its light collecting efficiency. The cell is made of cheap raw materials – iron and tungsten oxide.

How the 'moth eye solar cell' functions: with the help of sunlight water molecules are split into oxygen and hydrogen.
Credit: Image courtesy of Empa

All over the world researchers are investigating solar cells which imitate plant photosynthesis, using sunlight and water to create synthetic fuels such as hydrogen. Empa researchers have developed such a photoelectrochemical cell, recreating a moth's eye to drastically increase its light collecting efficiency. The cell is made of cheap raw materials -- iron and tungsten oxide.

Rust -- iron oxide -- could revolutionise solar cell technology. This usually unwanted substance can be used to make photoelectrodes which split water and generate hydrogen. Sunlight is thereby directly converted into valuable fuel rather than first being used to generate electricity. Unfortunately, as a raw material iron oxide has its limitations. Although it is unbelievably cheap and absorbs light in exactly the wavelength region where the sun emits the most energy, it conducts electricity very poorly and must therefore be used in the form of an extremely thin film in order for the water splitting technique to work. The disadvantage of this is that these thin-films absorb too little of the sunlight shining on the cell.

Microspheres to collect the sunlight

Empa researchers Florent Boudoire and Artur Braun have now succeeded in solving this problem. A special microstructure on the photoelectrode surface literally gathers in sunlight and does not let it out again. The basis for this innovative structure are tiny particles of tungsten oxide which, because of their saturated yellow colour, can also be used for photoelectrodes. The yellow microspheres are applied to an electrode and then covered with an extremely thin nanoscale layer of iron oxide. When external light falls on the particle it is internally reflected back and forth, till finally all the light is absorbed. All the entire energy in the beam is now available to use for splitting the water molecules. In principle the newly conceived microstructure functions like the eye of a moth, explains Florent Boudoire.

The eyes of these night active creatures need to collect as much light as possible to see in the dark, and also must reflect as little as possible to avoid detection and being eaten by their enemies. The microstructure of their eyes especially adapted to the appropriate wavelength of light. Empa's photocells take advantage of the same effect. In order to recreate artificial moth eyes from metal oxide microspheres, Florent Boudoire sprays a sheet of glass with a suspension of plastic particles, each of which contains at its centre a drop of tungsten salt solution. The particles lie on the glass like a layer of marbles packed close to each other. The sheet is placed in an oven and heated, the plastic material burns away and each drop of salt solution is transformed into the required tungsten oxide microsphere. The next step is to spray the new structure with an iron salt solution and once again heat it in an oven.

"Capturing light" simulated on the computer

Now, one could interpret these mixing, spraying and burning processes as pure alchemy -- a series of steps that is eventually successful by pure chance. However in parallel to their practical experiments, the researchers have been running calculations modelling the process on their computers and have thus been able to simulate the "capturing of light" in the tiny spheres. The results of the simulation agree with the experimental observations, as project leader Artur Braun confirms. It is clear to see how much the tungsten oxide contributes to the photo current and how much is due to the iron oxide. Also, the smaller the microspheres the more light which lands on the iron oxide underneath the tiny balls. As a next step the researchers plan to investigate what the effect of several layers of microspheres lying on top of each other might be. The work on moth eye solar cells is still in progress.


Story Source:

The above story is based on materials provided by Empa. Note: Materials may be edited for content and length.


Journal Reference:

  1. Florent Boudoire, Rita Toth, Jakob Heier, Artur Braun, Edwin C. Constable. Photonic light trapping in self-organized all-oxide microspheroids impacts photoelectrochemical water splitting. Energy & Environmental Science, 2014; DOI: 10.1039/C4EE00380B

Cite This Page:

Empa. "Collecting light with artificial moth eyes: Producing hydrogen with sunlight." ScienceDaily. ScienceDaily, 18 June 2014. <www.sciencedaily.com/releases/2014/06/140618122109.htm>.
Empa. (2014, June 18). Collecting light with artificial moth eyes: Producing hydrogen with sunlight. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2014/06/140618122109.htm
Empa. "Collecting light with artificial moth eyes: Producing hydrogen with sunlight." ScienceDaily. www.sciencedaily.com/releases/2014/06/140618122109.htm (accessed July 24, 2014).

Share This




More Matter & Energy News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
Powered by NewsLook.com
Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
Powered by NewsLook.com
Boeing Ups Outlook on 52% Profit Jump

Boeing Ups Outlook on 52% Profit Jump

Reuters - Business Video Online (July 23, 2014) Commercial aircraft deliveries rose seven percent at Boeing, prompting the aerospace company to boost full-year profit guidance- though quarterly revenues missed analyst estimates. Bobbi Rebell reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins