February 13, Yanguang Li, Stanford University
Advanced Electrocatalysts Based on Nano-Carbon Materials for Energy Applications
Abstract: Oxygen electrocatalysts are important for a range of energy applications including fuel cells, metal air batteries and water electrolysis. Precious metal electrocatalysts (e.g. Pt, IrOx and RuOx) display high catalytic activity. To increase scalability and reduce costs, non-precious metal catalysts with high activity and durability at low costs have been actively pursued. In this talk, I will highlight some of my research in the past two years. First of all, I will present a Co3O4-graphene hybrid material as a bi-functional electrocatalyst for oxygen reduction and evolution (ORR/OER) in alkaline electrolytes . While Co3O4 nanocrystals or N-doped graphene sheets alone has little catalytic activity for ORR, their hybrid exhibits an unexpected, surprisingly high activity close to the Pt standard, accompanied a superior stability in alkaline electrolytes. The same hybrid is also highly active for OER. The unusual catalytic activity is believed to result from the covalent coupling between Co3O4 nanocrystals and graphene sheets. Secondly, I will introduce a carbon nanotube-nanographene complex with Fe and N impurities as an ORR electrocatalyst in acids . A unique oxidation condition is identified to partially unzip the outer wall of the few-walled carbon nanotubes and to form numerous nanographene pieces attached to the mostly intact inner walls. These defective nanographene sheets facilitate the formation of catalytic sites comprising of iron and nitrogen species, as revealed by annular dark field imaging and electron energy loss spectroscopy mapping at atomic resolution. At last, I will briefly talk about high performance primary and rechargeable Zn-air batteries based on the hybrid electrocatalysts I have developed very recently . The primary Zn-air battery demonstrates an ultrahigh peak power density ~265 mW/cm2 and energy density > 700 Wh/kg. The rechargeable Zn-air battery in a tri-electrode configuration exhibits an unprecedented small charge-discharge voltage polarization, high reversibility and stability over long charge and discharge cycles.
Biography: Dr. Yanguang Li is working at the interface of chemistry, materials science and electrochemistry towards the development of nanostructured materials for energy conversion and storage. Currently as a postdoctoral scholar at Stanford University, his research interest focuses on the synthesis of nanoscale inorganic materials covalently coupled with graphene or carbon nanotubes for high-performance and low-cost electrocatalysts and batteries. He has published over 20 research papers on international journals, including Nat. Mater., Nat. Nanotechnol., Nat. Commun., J. Am. Chem. Soc., Nano. Lett., Adv. Mater., ect.
Faculty Host: Soumendra Basu
Student Host: Debangshu Mukherjee