Zhenhua Zeng

Heterogeneous catalysts are widely used to promote chemical and electrochemical reactions. Although it is known that chemical reactions usually happen on catalyst surfaces, only specific surface sites have high  activity. Thus, identifying active sites and maximizing their presence lies at the heart of catalysis research.

My research focuses on identifying active sites in hydrogen fuel cells and water electrolysis, including the hydrogen evolution and oxidation reaction reactions (HER/HOR) at the metal/oxide interfaces, the oxygen reduction reaction (ORR) on transition metal surfaces and the oxygen evolution reaction (OER) on transition metal oxides. In the presentation, I will delve into the active sites of ORR on Pt group metal surfaces and the active sites of OER on Ni-based oxyhydroxides.

For ORR on Pt group metal surfaces, 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, I 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, I 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. I will demonstrate strategies to enhance ORR activity by leveraging this effect, such as varying terrace widths,¹ the thickness of 2D nanosheets² and external stress.³

Regarding OER on Ni-based oxyhydroxides, despite over five decades of reseach, the atomic-scale strutures of the active phases remain elusive, hindering the identification of active sites. I will first provide direct atomic-scale insights into their crystal structures and structural transformations, shedding light on unique active sites: synergistic dual-metal reaction centers. There center are characterized by switching active sites during OER, and through simple surface Fe doping and the formation of dual Fe-Fe center, they increases OER activity by over two orders of magnitude. This fundamental understanding not only elucidates the high OER activity of Ni (oxy)hydroxides with Fe-doping,⁴ but also provides principles for developing OER catalysts with further improved performance.^{5, 6}

Dr. Zeng is a research assistant professor in the David School of Chemical Engineering and Tarpo Department of Chemistry at Purdue University. His research focuses on first-principles-based modeling of hydrogen fuel cells, water electrolysis, surface sciences and heterogeneous catalysis. He works closely with the U.S. Department of Energy and industry partners, such as 3M, Honda and Toyota to advance zero-emission and clean energy technology.

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.

Dr. Zeng has published over 60 peer-reviewed papers (10k+ 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.

• Time: 11:00 AM
• Location: 206 Furnas Hall