Active Sites for the Oxygen Reduction Reaction on Pt in Hydrogen Fuel Cells: A DFT Perspective

Guest Speaker：Research Scientist Zhenhua Zeng, Purdue University, US

Inviter: Assoc.Prof. Wenpei Gao

Date&Time: Mon.  24. June. 10:00-11:30

Venue: Yiucheng Lecture Hall (500), Xu Zuyao Building

Biography:

Dr. Zhenhua Zeng obtained his a BS degree in Applied Physics and a Master’s degree in Materials Science from Hunan University (China). He obtained his Ph.D. degree in Physical Chemistry from the Dalian Insitute of Chemical Physics, the Chinese Academy of Sciences.

He had his first postdoctoral training at the Technical University of Denmark. Then, he moved to Argonne National Laboratory.

Currently, Dr. Zeng is a Research Scientist in the David School of Chemical Engineering a Purdue University. His research focuses on first-principles-based modeling of hydrogen fuel cells and water electrolysis. He works closely with the U.S. Department of Energy and industry partners, such as 3M, GM, Honda, Nikola and Toyota to advance green hydrogen energy technologies.

Dr. Zeng has published 50+ peer-reviewed papers (7000+ citations), including those in Nature and Science as a corresponding author. He has supervised over 20 postdocs, graduate students, undergraduate students, and high school students. He was a winner of the 2019-2020 ECS Toyota Young Investigator Fellowships.

Abstract:

For the oxygen reduction reaction (ORR) on Pt, the classic model categorizes active sites based on surface motifs, such as terraces and steps. However, this simplistic approach often leads to orders of magnitude errors in catalyst activity predictions and qualitative uncertainties of active sites, thus limiting opportunities for catalyst design. Using stepped Pt(111) surfaces and ORR as examples, we will illustrate that the root cause of larger errors and uncertainties is such a simplified categorization overlooks atomic site-specific reactivity driven by surface stress release. Specifically, we will show how surface stress release at steps introduces inhomogeneous strain fields, resulting in distinct electronic structures and reactivity for terrace atoms with identical local coordination. This phenomenon leads to a cluster of active sites flanking both sides of the step edge. We will demonstrate strategies to enhance ORR activity in hydrogen PEM fuel cells by leveraging this effect, such as varying terrace widths, adjusting the thickness of 2D nanosheets, controlling external stress and circumventing irreversible strain relaxation