(Invited) Structured Carbon Nanostructures Derived from Graphene Oxide for Catalysis

Abstract

Carbon Nanostructures are at the heart of numerous energy conversion and storage applications including catalysis, fuel cells, super capacitors, and batteries. However, current technologies are marred with issues such as long-term durability under high potentials (e.g., fuel cells), low energy/power density (super capacitors), and metal intercalation issues (batteries). Research efforts worldwide have been focused on developing carbon nanostructures and especially graphene/graphene oxide materials with superior structural and functional properties for fuel cell applications. State-of-the-art devices have typically been synthesized from highly heterogeneous precursors and amorphous carbon materials. Catalysts derived from graphene and graphene-oxide (GO) are more homogeneous and possess properties, such as good chemical stability, excellent conductivity, and more importantly, can be functionalized in a controlled manner. These unique properties have led to explosion in research in areas of graphitic materials as catalyst support/material for ORR. In this study, we report the synthesis of highly ordered carbon nanostructures derived from GO. Despite the widely known fact of the presence of residual water between the graphene oxide layers, only a few reports exist about the role of intercalated water. We control the density of functional groups and inter-lamellar spacing of GO materials using low temperature drying treatments. The synthesized graphene oxide structures were subjected to reduction and nitrogen doping in different conditions to obtain an optimum oxygen reduction reaction catalyst. In this report, we focus on the affect of pre-treatment on the structure and function of the catalyst systems. We further demonstrate that the structure formed following the effective removal of intercalated water is crucial in the formation of active sites due to nano-confinement of water. Towards the end, we demonstrate a systematic shift in half wave potential and a significant decrease in peroxide production obtained depending upon the graphene oxide pretreatment. Acknowledgment Financial support from the Los Alamos National Laboratory Laboratory-Directed Research and Development (LDRD) Program is gratefully acknowledged.