A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 3 5 SMART SUPERCAPACITOR SETS RECORDS A team of scientists from Clemson University, South Carolina, and the Indian Institute of Science designed a smart supercapacitor using an innovative stack of metal oxides — vanadium pentoxide and zinc oxide — that can efficiently harvest energy from sunlight and simultaneously store it. The research could eventually lead to self-charging consumer electronics such as health monitoring devices. Zinc oxide has been widely used in light-dependent charge transfer appli- cations such as photovoltaics due to its low cost, high carrier mobility, long carrier diffusion, ease of synthesis on substrates, and nontoxicity. It features electron transporting and hole- blocking characteristics and readily generates photoexcited electrons upon light irradiation. However, zinc oxide has a wide band gap that restricts its utility to a narrow light spectrum, requiring a creative strategy to improve its performance. The researchers stacked vanadium pentoxide and zinc oxide to create a unique heterostructure, one that improved on the ability of traditional materials to convert light into electrical energy. In a test to measure its ability to store harvested light, the new device beat the previous record by a factor of RESEARCH TRACKS / FEEDBACK A new supercapacitor made of vanadium pentoxide and zinc oxide harvests and stores energy from sunlight. four. “We’ve come up with a two-in-one device that not only harvests light more efficiently but also stores it as electrical energy, unlike the other systems that exist right now,” says Clemson post-doctoral fellow Mihir Parekh. “The materials we chose allowed us to engineer the band gap so that the light-to-electricity conversion was very efficient.” The team found that the device showed excellent electrochemical performance and stability for over 5000 cycles. clemson.edu. MIXED MOLECULES BUILD BETTER BATTERIES Researchers from Florida State University (FSU) and Lawrence Berkeley National Laboratory developed a new strategy to build solid-state batteries that are less reliant on specific elements, especially expensivemetals with supply chain issues. The team demonstrated that a mix of various solid-state molecules could result in a more conductive battery that was less dependent on a large quantity of one individual element. For example, instead of creating a battery made with germanium, which rarely appears naturally in high CELEBRATING WOMEN AVIATORS The editorial about women in air and space (AM&P, March 2023) reminded me of an audiobook I enjoyed several years ago, “Fly Girls: How Five Daring Women Defied All Odds and Made Aviation History” by Keith O’Brien. It covered many interesting topics, including the fact that Amelia Earhart was once an aeronautics advisor at Purdue University. The Museum of Flight in Seattle also includes some interesting history about women pilots and flight attendants and is well worth a visit. Patrick Mizik, P.E. Haldex Brake Products Corp. FEEDBACK We welcome all comments and suggestions. Send letters to joanne.miller@asminternational.org. Scanning transmission electron microscope images reveal the elemental distribution in a “disordered” solid electrolyte. Top row: titanium (Ti), zirconium (Zr), and tin (Sn); bottom row: hafnium (Hf), phosphorus (P), and oxygen (O); scale bar 50 nanometers. Courtesy of Yan Zeng and Gerd Ceder/ Berkeley Lab. concentrations, the researchers created a mixture of titanium, zirconium, tin, and hafnium. “There’s no hero element here,” explains FSU scientist Bin Ouyang. “It’s a collective of diverse elements that make things work. What we found is that we can get this highly conductive material as long as different elements can assemble in a way that atoms can move around quickly. And there are many situations that can lead to these so-called atom diffusion highways, regardless of which elements it may contain.” fsu.edu.
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