February AMP_Digital

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 | F E B R U A R Y / M A R C H 2 0 1 9 1 1 X-RAYS REVEAL NANOPARTICLE GROWTH Contributing to the worldwide search for fuel cell cathode materials, researchers at the University of Akron, Ohio, developed a new method of syn- thesizing catalysts from a combination of metals—platinum and nickel—that form octahedral-shaped nanoparticles. While scientists have identified this catalyst as one of the most efficient replacements for pure platinum, they have not fully understood why it grows in an octahedral shape. To better under- stand the growth process, the scientists collaborated with multiple institutions including Brookhaven National Lab (BNL) and its NSLS-II. Using the ultrabright x-rays at NSLS-II and the advanced capabilities gas pressures higher than what is usu- ally possible in conventional XPS exper- iments. uakron.edu . of NSLS-II’s In situ and Operando Soft X-ray Spectroscopy (IOS) beamline, the researchers revealed the chemical char- acterization of the catalyst’s growth pathway in real time. “We used a re- search technique called ambient-pres- sure x-ray photoelectron spectroscopy (AP-XPS) to study the surface composi- tion and chemical state of the metals in the nanoparticles during the growth reaction,” says Iradwikanari Waluyo, lead scientist at IOS. Using this technique, the scien- tists observed an interesting synergis- tic effect between platinum and nickel that plays a significant role in the devel- opment of the nanoparticle’s octahe- dral shape as well as its reactivity. The findings depended on the advanced capabilities of IOS, where the research- ers were able to run the experiments at From left, Mingyuan Ge, Iradwikanari Waluyo, and Adrian Hunt at the IOS beamline, where they are studying the growth pathway of an efficient catalyst for hydrogen fuel cells. Courtesy of BNL.