Spectroscopic insights on the active site structures of M-N-C catalysts for oxygen and CO2 reduction reactions
Date: 2021/07/28 - 2021/07/28
Academic Seminar: Spectroscopic insights on the active site structures of M-N-C catalysts for oxygen and CO2 reduction reactions
Speaker: Dr. Jingkun Li, faculty of the School of Chemical Engineering and Technology, Tianjin University
Time: 9:00a.m.-10:00a.m. July 28th, 2021 (Beijing Time)
Location: Room 454, Longbin Building
Abstract
Developing highly efficient precious group metal-free (PGM-free) electrocatalysts for fuel cells and electrolyzers is a high-reward solution for boosting their wide-spread applications. However, the rational design and controllable synthesis of PGM-free catalysts are severely hindered by the lack of understanding of the dynamic evolution of active sites during pyrolysis and operation under potential bias. Herein, this presentation will discuss a variety of operando/in situ characterization techniques to systematically elucidate the dynamic evolution of active sites, and thus to unveil the correlations between synthesis, active site structures, and the activity/selectivity of M-N-C catalysts. Despite the complexity of the class of M-N-C materials, important implications have been achieved: 1) revealing the dynamic changes in M-N bond distances and/or the reconstructions of M-N4 sites under working conditions, elucidating the redox mechanisms for oxygen reduction reaction, and unveiling the demetallation of M-N4 sites responsible for the deactivation of M-N-C catalysts; 2) coupling the time-resolved X-ray absorption spectroscopy with a house-designed high-temperature furnace to monitor the atomic-level structural evolution of M-N4 sites during pyrolysis, where gaseous metal atoms are captured by nitrogen defects in the carbon matrix. This further directs the development of a novel synthetic approach (non-contact pyrolysis) based on chemical vapor deposition, leading to an enhanced effective site density and catalytic activity; 3) engineering the micro/macro-porous structures of M-N-C catalysts via electrospinning to facilitate the mass transportation of reactants and products during electrolysis, and thus to promote the implementation of M-N-C in fuel cells and Chlor-alkali electrolyzers.
Biography
Dr. Jingkun Li was born in China in 1987. She obtained her Bachelor’s degree from Hefei University of Technology (2009, Applied Chemistry), Master’s degree from Shanghai Jiao Tong University (2011, Chemical Engineering), and PhD degree from Northeastern University (2017, Chemistry), under the supervision of Prof. Sanjeev Mukerjee. Until 2019, she was a postdoctoral research fellow at the CNRS - Université de Montpellier in France, in the group of Dr Frédéric Jaouen. Then she joined the faculty of the School of Chemical Engineering and Technology, Tianjin University. Her research interest focuses on the design, synthesis, ex situ and in situ/operando characterizations of novel catalysts based on Earth-abundant elements for catalyzing O2 electroreduction in proton-exchange-membrane fuel cells, as well as for catalyzing CO2 electroreduction to valuable chemical products. In particular, her research on charge transfer dynamics at both two- and three-dimensional electrochemical interfaces encompasses materials development, in situ synchrotron spectroscopy and electro-analytical methods. Her research has led to 30+ papers, including 14 papers as (co-)first and/or corresponding author (Nat. Catal, Energy Environ. Sci., J. Am. Chem. Soc., Angew. Chem. Int. Ed., Chem, ACS Catal., ACS Appl. Energy Mater., etc.).