Diagram of a proton exchange membrane fuel cell created using a surface engineering technique called “surface doping.” (Credit: Yu Huang Lab/UCLA)

Diagram of a proton exchange membrane fuel cell created using a surface engineering technique called “surface doping.” (Credit: Yu Huang Lab/UCLA)

Johns Hopkins engineers collaborated with researchers at the UCLA Henry Samueli School of Engineering and Applied Science to develop nanostructures that increase the efficiency and durability of fuel cells while lowering the cost to produce them.

Their findings were reported in the June 12 issue of Science. Dr. Tim Mueller, assistant professor of materials science and engineering, and Liang Cao, a Johns Hopkins University physics graduate student and advisee of Dr. Mueller, contributed to the research.

The team, led by UCLA researchers, focused on improving proton exchange membrane fuel cells (PEMFCs), which have shown great promise as a clean energy technology. In traditional car engines, the exhaust emitted contains pollutants and greenhouse gases. In PEMFCs, hydrogen fuel and oxygen from the air react to produce electricity, while the exhaust they create is water.

Platinum is typically used as a catalyst in PEMFCs, but the high cost of the metal has hindered fuel cell adoption. With eyes on both performance and cost efficiency, researchers used surface doping to add molybdenum to the surface of platinum-nickel nanostructures. The addition of this third metal made the alloy surface more stable and prevented the loss of nickel and platinum over time.

“The UCLA group had discovered experimentally that the molybdenum-doped nanoparticles were particularly good catalysts, and they were trying to understand why…We were able to build a computational model that provides insights into why these particles have such high activity and stability,” said Dr. Mueller. “It was a particularly challenging problem because there are four components in this system—nickel, platinum, molybdenum, and vacuum—and to my knowledge nobody had modeled such complex nanoparticles of this size with this level of accuracy before.”

The resulting nanostructures were found to be 81 times more efficient as catalysts than catalysts made from commercial platinum-carbon compounds. The platinum-nickel-molybdenum compound retained about 95% of its efficiency over time compared to the efficiency rate of 66% or less for platinum-nickel catalysts.

Yu Huang, associate professor of materials science and engineering, was the principal investigator of the research. The paper’s co-lead authors were Xiaoqing Huang, a postdoctoral scholar, and Zipeng Zhao, a graduate student; both are members of Huang’s research group.

Other authors included Yu Chen and Enbo Zhu, graduate students in Huang’s lab; UCLA chemistry and biochemistry graduate students Zhaoyang Lin and Mufan Li and their adviser, Professor Xiangfeng Duan; Aiming Yan, a UC Berkeley postdoctoral scholar in physics and her adviser, Professor Alex Zettl; and Y. Morris Wang, a researcher at Lawrence Livermore National Laboratory.

The research was supported by the Office of Naval Research, the National Science Foundation, and the U.S. Department of Energy.

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