ADVANCED MATERIALS & PROCESSES | MARCH 2024 5 FROM SOLAR ENERGY TO HYDROGEN Researchers from the University of California, Davis and Martin Luther University in Germany developed a new method to accurately measure photovoltage—an essential step toward finding the best conditions to make fuel from sunlight and water. Scientists can already determine the electric energy output of solar cells by using wires that connect the cell and a measuring device. However, this energy output is harder to measure in solar fuel electrodes that are in contact with water because pure water is not electrically conductive. In the new study, the team found that the photovoltage of such solar fuel electrodes can be measured in a contactless way. They did this by using a gold Kelvin probe that hovers over the illuminated device and picks up the information wirelessly. The researchers conducted contactless photovoltage measurements on bismuth vanadate, a semiconductor for water oxidation, and on copper gallium selenide, a semiconductor for hydrogen generation from water. They covered the semiconductors with water solutions and a glass slide, then placed the microscopy slide under the Kelvin probe. The team discovered that the photovoltage depends not only on the semiconductor, but also on the color of RESEARCH TRACKS / FEEDBACK ERRATA In the July/August 2023 issue, the article “Identification of Sustainable Tonewoods for Acoustic Guitars Using Materials Selection Software” by James D. Cotton and John D. Wolodko stated that the ANSYS Granta Selector database contains 498 tree species. The actual number is 214 when reduced for separate longitudinal and transverse entries and engineered wood products. This has been corrected online in the digital edition available at asminternational.org. FEEDBACK We welcome all comments and suggestions. Send letters to joanne.miller@asminternational.org. A semitransparent gold Kelvin probe measures the photovoltage of an illuminated semiconductor film in contact with an electrode and a water solution. Courtesy of UC Davis. the light, the light intensity, and the chemical properties of the water solution. They say this information will enable scientists to identify the best conditions for the direct conversion of solar energy into hydrogen and other fuels. ucdavis.edu. FAST-CHARGING LITHIUM BATTERIES With funding from the U.S. DOE’s Basic Energy Sciences Program, scientists at Cornell University, Ithaca, N.Y., developed a lithium battery that can charge in less than five minutes while maintaining stable performance over numerous cycles. The new technology could help alleviate the range anxiety common among those who worry electric vehicles cannot travel long distances without a lengthy recharge. Lithium-ion batteries are among the most popular means of powering electric vehicles because they are lightweight, yet they take hours to charge. The Cornell team identified indium as a promising material for fast-charging batteries, as it features two crucial characteristics as a battery anode: an extremely low migration energy barrier and a modest exchange current density. The combination of those qualities is essential for fast charging and longduration storage. The new technology paired with wireless induction charging Charging an EV in less than five minutes could help alleviate range anxiety. Courtesy of DOE/NREL. on roadways would shrink the size and cost of batteries, making electric transportation more feasible. The indium anodes are not perfect however. “While this result is exciting, in that it teaches us how to get to fast-charge batteries, indium is heavy,” says researcher Lynden Archer. “Therein lies an opportunity for computational chemistry modeling, perhaps using generative AI tools, to learn what other lightweight materials chemistries might achieve the same intrinsically low Damköhler numbers.” cornell.edu.
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