Nanyang Technological University, Singapore
Dr. Lianxi Zheng received his BE degree in Electronic Engineering from Southeast University in China, and his Ph.D. in Physics from The University of Hong Kong. He has worked in Los Alamos National Laboratory as a director’s postdoctoral fellow, CNT Technologies Inc. as a research scientist, and Nanyang Technological University as an assistant professor. He has made many significant contributions in the area of carbon nanotube, among which is his invention of a chemical-vapor-deposition method to make word-record long (40mm) CNTs. This technology was ranked as one of the top 50 technologies that have significantly impacted, or are expected to impact, the state of the art in nanotechnology, by Nanotech Briefs (NASA’s technical magazine) in 2005. During his career, he has gained several awards, including 2 Nano 50 Award from NASA, applied 3 US patents on CNT preparation, and published over 80 journal papers. He has been the treasurer and committee member of IEEE Nanotechnology Chapter (Singapore section), and a member of the editor board of several scientific journals.
Single layer graphene exhibits a theoretical specific surface area as high as 2630 m2g-1 and has an intrinsic capacitance around 21μFcm-2, making it excellent candidate for electrochemical capacitor applications. However, a major challenge in the field of energy storage devices by adopting graphene as electrode materials still remains to achieve highly porous structures with good quality in large scale production, because single layer graphene must be collected into various assemblies, in which the restacking due to the strong sheet-sheet van der Waals interactions is unavoidable. Thermal-related exfoliation production of graphene has been believed to be a promising strategy for practical applications, but the needed high temperature and special experimental environment hinder this method from wide adoption. In this study, an actuation triggered thermal exfoliation process is realized at a very low temperature of 200oC and atmospheric pressure. The underlying mechanism is found to be similar to corn popping and attributed to the thermally-stimulated actuation and water molecules escape. It is found that after the exfoliation process, the resultant popped graphene oxide exhibits highly porous structures with the oxygen-containing groups being effectively removed, and has a specific capacitance of 120 Fg-1 without any retention after 1500 CV cycles, demonstrating good electrochemical capacitance performance with excellent stability. The popping-like process can effectively reduce graphene oxide into 3D porous graphene structures in one single-step process. This process is mild, short in time, environmental friendly and most importantly providing a scalable and easy method to produce large amount graphene-based assembly for potential capacitor applications.