Seminar on Engineering Multifunctional Catalysts for Sustainable Catalysis

Division Director, Institute of Sustainability for Chemicals, Energy & Environment, A*STAR

Adjunct Assistant Professor, School of Mechanical & Aerospace Engineering, NTU

Venue: The Arc - Learning Hub North, LHN TR+08 (LHN-B2-08)

Multifunctional catalysts with atomically dispersed active centers have been designed. However, how to precisely construct active catalytic sites with precisely defined coordination environment having favorable electronic structure at the atomic level remains challenging. What’s more challenging is how to mass produce advanced catalysts with highly dispersed active centers. Single-atom catalysts (SACs) with symmetric charge distribution are not electron-conducting and thus limits the transfer rates. Therefore, breaking the symmetry of electronic density by axially introducing an additional coordinating atom shall improve the catalytic performance. We describe how we achieved multifunctional catalysts with asymmetric electronic structures that lead to good catalytic performance for CO₂ reduction and water splitting. [1-2] In addition, we show how we produced advanced catalysts through high-throughput mechanochemistry method. Ni-N₄-O coordination abundantly anchored on high-surface nitrogen-doped porous graphitic carbon was designed and synthesized.[3] In-depth experimental and theoretical studies reveal that the axial M-O coordination introduces asymmetry to the catalytic center, leading to lower Gibbs free energy for the rate-limiting step, stronger binding with *COOH, and weaker association with *CO in CO₂ reduction. Another SAC achieved electronic regulation of Co active center by near-range coordination with N and long-range interaction with S, and exhibited excellent and stable trifunctional electrocatalytic activity for water splitting. The demonstrated strategies can be applied to make various asymmetrically coordinated SACs (M-N4-O/S) to enrich the family of SACs for various catalytic applications.

References

1. Huang, M., et al, Template-Sacrificing Synthesis of Ni-N₄-O Single Atom Catalysts for Highly Efficient CO₂ Electrocatalytic Reduction, ACS Nano,16, 2, 2110, 2022.
2. Zhang, Z., et al, Dispersed Cobalt Trifunctional Electrocatalysts with Tailored Coordination Environment for Flexible Rechargeable Zn–Air Battery and Self-Driven Water Splitting, Adv. Energy Mater., 2002896, 2020.
3. Tang, R., et al, Single-metal catalytic sites via high-throughput mechanochemistry enable selective and efficient CO2 photoreductionAppl Catal B-Environ,121661, 2022
4. Tang, R., et al, A Ball Milling Method for Highly Dispersed Ni Atoms on g-C3N4 to Boost CO₂ Photoreduction, J. Colloid Interface Sci, in press, 2022.

Dr. Lili Zhang received her B. Eng. and Ph.D. degree from Chemical and Biomolecular Engineering, National University of Singapore (NUS) in 2004 and 2011, respectively. She worked as a process engineer in Micron between 2004 and 2006, and a research engineer from 2010 to 2011 at NUS. Then she continued her research in Professor Ruoff’s group at The University of Texas at Austin from 2011 to 2012 as a research fellow. Now Dr. Zhang is the Division Director of Catalysis and Green Process Engineering in the Institute of Sustainability for Chemicals, Energy and Environment (ISCE²), A*STAR, Singapore. Dr. Zhang expertise in sustainable processes, electrocatalysis, waste upcycling, low emission H₂ production and carbon-based materials and their applications. She is Global Highly Cited Researcher with more than 20,000 citations (H-index: 50, by Web of Science) and her research interest is advanced materials for clean energy solutions, fundamental materials chemistry and physics, electrochemistry, and reaction mechanistic study.