New Nanoporous metals are superior catalysts for chemical reactions due to their large surface area and high electrical conductivity, making them perfect candidates for applications such as electrochemical reactors, sensors, and actuators.
In a study published today in the journal Science Advances, Lawrence Livermore National Laboratory (LLNL) researchers, along with their counterparts at Harvard University, report on the hierarchical 3-D printing of nanoporous gold, a proof of concept that researchers say could revolutionize the design of chemical reactors.
“If you consider traditional machining processes, it’s time-consuming and you waste a lot of materials—also, you don’t have the capability to create complex structures,” said LLNL postdoctoral researcher Zhen Qi, a co-author on the paper. “By using 3-D printing we can realize macroporous structures with application-specific flow patterns. By creating hierarchical structures, we provide pathways for fast mass transport to take full advantage of the large surface area of nanoporous materials. It’s also a way to save materials, especially precious metals.”
Combining 3-D printing through extrusion-based direct ink writing and an alloying and dealloying process, researchers were able to engineer the nanoporous gold into three distinct scales, from the micro scale down to the nanoscale, reporting the hierarchical structure “dramatically improves mass transport and reaction rates for both liquid and gases.” With the ability to manipulate the catalyst’s surface area to generate electrochemical reactions through 3-D printing, researchers said the development could have a major impact on electrochemical plants, which today rely primarily on thermal energy.
“By controlling the multiscale morphology and surface area of 3-D porous materials, you can start to manipulate the mass transport properties of these materials,” said LLNL researcher Eric Duoss. “With hierarchal structures, you have channels that can handle transfer of reactants and products for different reactions. It’s like transportation systems, where you go from seven-lane expressways down to multiple lane highways to thoroughfares and side streets, but instead of transporting vehicles we’re transporting molecules.”
Achieving the finished product required several steps. LLNL researcher Cheng Zhu and former postdoc Wen Chen created inks made of gold and silver microparticles. After printing, the 3-D parts were put into a furnace to allow the particles to coalesce into a gold-silver alloy. Then they put the parts into a chemical bath that removed the silver (a process called “dealloying”) to form porous gold within each beam or filament.
Read more: Hierarchical 3-D printing of nanoporous gold
thumbnail courtesy of phys.org