Big Step for Next-Generation Fuel Cells and Electrolyzers (http://newscenter.lbl.gov/news-releases/2014/02/27/next-generation-fuel-cells-and-electrolyzers-researchers-at-berkeley-and-argonne-national-labs-develop-highly-promising-new-class-of-nanocatalyst/)
A big step in the development of next-generation fuel cells and water-alkali electrolyzers has been achieved with the discovery of a new class of bimetallic nanocatalysts that are an order of magnitude higher in activity than the target set by the
"We report the synthesis of a highly active and durable class of electrocatalysts by exploiting the structural evolution of platinum/nickel bimetallic nanocrystals," says
Yang, who also holds appointments with the
Fuel cells and electrolyzers can help meet the ever-increasing demands for electrical power while substantially reducing the emission of carbon and other atmospheric pollutants. These technologies are based on either the oxygen reduction reaction (fuel cells), or the hydrogen evolution reaction (electrolyzers). Currently, the best electrocatalyst for both reactions consists of platinum nanoparticles dispersed on carbon. Though quite effective, the high cost and limited availability of platinum makes large-scale use of this approach a major challenge for both stationary and portable electrochemical applications.
"Intense research efforts have been focused on developing high-performance electrocatalysts with minimal precious metal content and cost," Yang says. "In an earlier study, the ANL scientists showed that forming a nano-segregated platinum skin over a bulk single-crystal platinum/nickel alloy enhances catalytic activity but the materials cannot be easily integrated into electrochemical devices. We needed to be able to reproduce the outstanding catalytic performance of these materials in nanoparticulates that offered high surface areas."
Yang and his colleagues at
"In contrast to other synthesis procedures for hollow nanostructures that involve corrosion induced by harsh oxidizing agents or applied potential, our method proceeds spontaneously in air," Yang says. "The open structure of our platinum/nickel nanoframes addresses some of the major design criteria for advanced nanoscale electrocatalysts, including, high surface-to-volume ratio, 3-D surface molecular accessibility, and significantly reduced precious metal utilization."
In electrocatalytic performance tests at ANL, the platinum/nickel nanoframes when encapsulated in an ionic liquid exhibited a 36-fold enhancement in mass activity and 22-fold enhancement in specific activity compared with platinum nanoparticles dispersed on carbon for the oxygen reduction reaction. These nanoframe electrocatalysts, modified by electrochemically deposited nickel hydroxide, were also tested for the hydrogen evolution reaction and showed that catalytic activity was enhanced by an order-of-magnitude over platinum/carbon catalysts.
"Our results demonstrate the beneficial effects of the hollow nanoframe's open architecture and surface compositional profile," Yang says. "Our technique for making these hollow nanoframes can be readily applied to other multimetallic electrocatalysts or gas phase catalysts. I am quite optimistic about its commercial viability."
Other co-authors of the Science paper in addition to Yang and Stamenkovic are
This research was funded by the
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