Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Rice researchers demo solar water-splitting technology

07.09.2015

Process uses light-harvesting nanoparticles, captures energy from 'hot electrons'

Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules.


Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules.

Credit: I. Thomann/Rice University

The technology, which is described online in the American Chemical Society journal Nano Letters, relies on a configuration of light-activated gold nanoparticles that harvest sunlight and transfer solar energy to highly excited electrons, which scientists sometimes refer to as "hot electrons."

"Hot electrons have the potential to drive very useful chemical reactions, but they decay very rapidly, and people have struggled to harness their energy," said lead researcher Isabell Thomann, assistant professor of electrical and computer engineering and of chemistry and materials science and nanoengineering at Rice. "For example, most of the energy losses in today's best photovoltaic solar panels are the result of hot electrons that cool within a few trillionths of a second and release their energy as wasted heat."

Capturing these high-energy electrons before they cool could allow solar-energy providers to significantly increase their solar-to-electric power-conversion efficiencies and meet a national goal of reducing the cost of solar electricity.

In the light-activated nanoparticles studied by Thomann and colleagues at Rice's Laboratory for Nanophotonics (LANP), light is captured and converted into plasmons, waves of electrons that flow like a fluid across the metal surface of the nanoparticles.

Plasmons are high-energy states that are short-lived, but researchers at Rice and elsewhere have found ways to capture plasmonic energy and convert it into useful heat or light. Plasmonic nanoparticles also offer one of the most promising means of harnessing the power of hot electrons, and LANP researchers have made progress toward that goal in several recent studies.

Thomann and her team, graduate students Hossein Robatjazi, Shah Mohammad Bahauddin and Chloe Doiron, created a system that uses the energy from hot electrons to split molecules of water into oxygen and hydrogen. That's important because oxygen and hydrogen are the feedstocks for fuel cells, electrochemical devices that produce electricity cleanly and efficiently.

To use the hot electrons, Thomann's team first had to find a way to separate them from their corresponding "electron holes," the low-energy states that the hot electrons vacated when they received their plasmonic jolt of energy. One reason hot electrons are so short-lived is that they have a strong tendency to release their newfound energy and revert to their low-energy state.

The only way to avoid this is to engineer a system where the hot electrons and electron holes are rapidly separated from one another. The standard way for electrical engineers to do this is to drive the hot electrons over an energy barrier that acts like a one-way valve. Thomann said this approach has inherent inefficiencies, but it is attractive to engineers because it uses well-understood technology called Schottky barriers, a tried-and-true component of electrical engineering.

"Because of the inherent inefficiencies, we wanted to find a new approach to the problem," Thomann said. "We took an unconventional approach: Rather than driving off the hot electrons, we designed a system to carry away the electron holes. In effect, our setup acts like a sieve or a membrane. The holes can pass through, but the hot electrons cannot, so they are left available on the surface of the plasmonic nanoparticles."

The setup features three layers of materials. The bottom layer is a thin sheet of shiny aluminum. This layer is covered with a thin coating of transparent nickel-oxide, and scattered atop this is a collection of plasmonic gold nanoparticles -- puck-shaped disks about 10 to 30 nanometers in diameter.

When sunlight hits the discs, either directly or as a reflection from the aluminum, the discs convert the light energy into hot electrons. The aluminum attracts the resulting electron holes and the nickel oxide allows these to pass while also acting as an impervious barrier to the hot electrons, which stay on gold. By laying the sheet of material flat and covering it with water, the researchers allowed the gold nanoparticles to act as catalysts for water splitting. In the current round of experiments, the researchers measured the photocurrent available for water splitting rather than directly measuring the evolved hydrogen and oxygen gases produced by splitting, but Thomann said the results warrant further study.

"Utilizing hot electron solar water-splitting technologies we measured photocurrent efficiencies that were on par with considerably more complicated structures that also use more expensive components," Thomann said. "We are confident that we can optimize our system to significantly improve upon the results we have already seen."

###

Robatjazi is a graduate student in electrical and computer engineering, Bahauddin is a graduate student in physics and astronomy and Doiron is a graduate student in applied physics. The research was supported by the Welch Foundation and a National Science Foundation CAREER Award.

High-resolution IMAGES are available for download at:

http://news.rice.edu/wp-content/uploads/2015/08/0901-ELECTRO-team-lg.jpg
CAPTION: Rice University researchers (clockwise from left) Chloe Doiron, Hossein Robatjazi, Shah Mohammad Bahauddin and Isabell Thomann.
CREDIT: Jeff Fitlow/Rice University

http://news.rice.edu/wp-content/uploads/2015/08/0901-ELECTRO-color-lg.jpg
CAPTION: Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules.
CREDIT: I. Thomann/Rice University

http://news.rice.edu/wp-content/uploads/2014/06/0616_THOMANN-Isabell3-lg.jpg
CAPTION: Isabell Thomann
CREDIT: Jeff Fitlow/Rice University

A copy of the Nano Letters paper, "Direct Plasmon-Driven Photoelectrocatalysis," is available at: http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b02453

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,888 undergraduates and 2,610 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go here.

Media Contact

Jade Boyd
jadeboyd@rice.edu
713-348-6778

 @RiceUNews

http://news.rice.edu 

Jade Boyd | EurekAlert!

More articles from Materials Sciences:

nachricht Let the good tubes roll
19.01.2018 | DOE/Pacific Northwest National Laboratory

nachricht Method uses DNA, nanoparticles and lithography to make optically active structures
19.01.2018 | Northwestern University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>