Rice University engineers have created a device that absorbs light, converts it into electricity, and then uses the electricity to split water molecules and generate hydrogen. Photo courtesy Gustavo Raskoksy/Rice University

A team of Rice University engineers have developed a scalable photoelectrochemical cell that converts sunlight into clean hydrogen at a record-setting pace.

The lab led by Aditya Mohite, an associate professor at Rice, published the findings in a study in Nature Communications late last month, in collaboration with the National Renewable Energy Laboratory, which is backed by the Department of Energy. In it, the team details how they created a device that absorbs light, converts it into electricity, and then uses the electricity to split water molecules and generate hydrogen.

Austin Fehr, a chemical and biomolecular engineering doctoral student at Rice and one of the study’s lead authors, says in a statement that the device "could open up the hydrogen economy and change the way humans make things from fossil fuel to solar fuel."

The device has a high solar-to-hydrogen conversion efficiency rate of 20.8 percent, which has yet to be reached with this type of technology, according to a release from Rice. In addition to its speed, this device is groundbreaking because it uses low-cost metal-halide perovskite semiconductors to power the reaction.

A photoreactor developed by Rice University’s Mohite research group and collaborators achieved a 20.8 percent solar-to-hydrogen conversion efficiency. Photo courtesy Gustavo Raskoksy/Rice University

“Using sunlight as an energy source to manufacture chemicals is one of the largest hurdles to a clean energy economy,” Fehr says in the statement. “Our goal is to build economically feasible platforms that can generate solar-derived fuels. Here, we designed a system that absorbs light and completes electrochemical water-splitting chemistry on its surface.”

To create the device the Mohite lab turned their existing solar cell into a reactor to split water into oxygen and hydrogen. However they continued running into issues with the semiconductors being "extremely unstable in water," according to Rice.

After two years of trials and errors, the team uncovered that by adding two layers of barriers to the semiconductors they were able to reach these record-breaking efficiency rates.

The team has also shown uses for their double barrier design with different semiconductors and for different reactions.

“We hope that such systems will serve as a platform for driving a wide range of electrons to fuel-forming reactions using abundant feedstocks with only sunlight as the energy input,” Mohite says in the statement.

The device joins another game-changing product shared in a Rice research study in recent weeks. Last month, a Rice University lab led by Haotian Wang, the William Marsh Rice Trustee Chair and an associate professor at Rice, shared their findings on how their simple plug-and-play device removes carbon dioxide from air capture to induce a water-and-oxygen-based electrochemical reaction.

Rice also recently opened registration for its 20th anniversary of Energy Tech Venture Day. Click here to register for the event on Sept. 21.

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Engie signs deal to supply wind power for Texas data center

wind deal

Houston-based Engie North America, which specializes in generating low-carbon power, has sealed a preliminary deal to supply wind power to a Cipher Mining data center in Texas.

Under the tentative agreement, Cipher could buy as much as 300 megawatts of clean energy from one of Engie’s wind projects. The financial terms of the deal weren’t disclosed.

Cipher Mining develops and operates large data centers for cryptocurrency mining and high-performance computing.

In November, New York City-based Cipher said it bought a 250-acre site in West Texas for a data center with up to 100 megawatts of capacity. Cipher paid $4.1 million for the property.

“By pairing the data center with renewable energy, this strategic collaboration supports the use of surplus energy during periods of excess generation, while enhancing grid stability and reliability,” Engie said in a news release about the Cipher agreement.

The Engie-Cipher deal comes amid the need for more power in Texas due to several factors. The U.S. Energy Information Administration reported in October that data centers and cryptocurrency mining are driving up demand for power in the Lone Star State. Population growth is also putting pressure on the state’s energy supply.

Last year, Engie added 4.2 gigawatts of renewable energy capacity worldwide, bringing the total capacity to 46 gigawatts as of December 31. Also last year, Engie signed a new contract with Meta (Facebook's owner) and expanded its partnership with Google in the U.S. and Belgium.

Houston researchers make headway on developing low-cost sodium-ion batteries

energy storage

A new study by researchers from Rice University’s Department of Materials Science and NanoEngineering, Baylor University and the Indian Institute of Science Education and Research Thiruvananthapuram has introduced a solution that could help develop more affordable and sustainable sodium-ion batteries.

The findings were recently published in the journal Advanced Functional Materials.

The team worked with tiny cone- and disc-shaped carbon materials from oil and gas industry byproducts with a pure graphitic structure. The forms allow for more efficient energy storage with larger sodium and potassium ions, which is a challenge for anodes in battery research. Sodium and potassium are more widely available and cheaper than lithium.

“For years, we’ve known that sodium and potassium are attractive alternatives to lithium,” Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Engineering at Rice, said in a news release. “But the challenge has always been finding carbon-based anode materials that can store these larger ions efficiently.”

Lithium-ion batteries traditionally rely on graphite as an anode material. However, traditional graphite structures cannot efficiently store sodium or potassium energy, since the atoms are too big and interactions become too complex to slide in and out of graphite’s layers. The cone and disc structures “offer curvature and spacing that welcome sodium and potassium ions without the need for chemical doping (the process of intentionally adding small amounts of specific atoms or molecules to change its properties) or other artificial modifications,” according to the study.

“This is one of the first clear demonstrations of sodium-ion intercalation in pure graphitic materials with such stability,” Atin Pramanik, first author of the study and a postdoctoral associate in Ajayan’s lab, said in the release. “It challenges the belief that pure graphite can’t work with sodium.”

In lab tests, the carbon cones and discs stored about 230 milliamp-hours of charge per gram (mAh/g) by using sodium ions. They still held 151 mAh/g even after 2,000 fast charging cycles. They also worked with potassium-ion batteries.

“We believe this discovery opens up a new design space for battery anodes,” Ajayan added in the release. “Instead of changing the chemistry, we’re changing the shape, and that’s proving to be just as interesting.”

ExxonMobil lands major partnership for clean hydrogen facility in Baytown

power deal

Exxon Mobil and Japanese import/export company Marubeni Corp. have signed a long-term offtake agreement for 250,000 tonnes of low-carbon ammonia per year from ExxonMobil’s forthcoming facility in Baytown, Texas.

“This is another positive step forward for our landmark project,” Barry Engle, president of ExxonMobil Low Carbon Solutions, said in a news release. “By using American-produced natural gas we can boost global energy supply, support Japan’s decarbonization goals and create jobs at home. Our strong relationship with Marubeni sets the stage for delivering low-carbon ammonia from the U.S. to Japan for years to come."

The companies plan to produce low-carbon hydrogen with approximately 98% of CO2 removed and low-carbon ammonia. Marubeni will supply the ammonia mainly to Kobe Power Plant, a subsidiary of Kobe Steel, and has also agreed to acquire an equity stake in ExxonMobil’s low-carbon hydrogen and ammonia facility, which is expected to be one of the largest of its kind.

The Baytown facility aims to produce up to 1 billion cubic feet daily of “virtually carbon-free” hydrogen. It can also produce more than 1 million tons of low-carbon ammonia per year. A final investment decision is expected in 2025 that will be contingent on government policy and necessary regulatory permits, according to the release.

The Kobe Power Plant aims to co-fire low-carbon ammonia with existing fuel, and reduce CO2 emissions by Japan’s fiscal year of 2030. Marubeni also aims to assist the decarbonization of Japan’s power sector and steel manufacturing industry, chemical industry, transportation industry and various others sectors.

“Marubeni will take this first step together with ExxonMobil in the aim of establishing a global low-carbon ammonia supply chain for Japan through the supply of low-carbon ammonia to the Kobe Power Plant,” Yoshiaki Yokota, senior managing executive officer at Marubeni Corp., added in the news release. “Additionally, we aim to collaborate beyond this supply chain and strive towards the launch of a global market for low-carbon ammonia. We hope to continue to actively cooperate with ExxonMobil, with a view of utilizing this experience and relationship we have built to strategically decarbonize our power projects in Japan and Southeast Asia in the near future.”