Jeffrey R. Potts

Graphene and Graphene Oxide: Synthesis, Properties, and Applications

There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphenes exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

Exploration of the active center structure of nitrogen-doped graphene-based catalysts for oxygen reduction reaction

We present two different ways to fabricate nitrogen-doped graphene (N-graphene) and demonstrate its use as a metal-free catalyst to study the catalytic active center for the oxygen reduction reaction (ORR). N-graphene was produced by annealing of graphene oxide (G-O) under ammonia or by annealing of a N-containing polymer/reduced graphene oxide (RG-O) composite (polyaniline/RG-O or polypyrrole/RG-O). The effects of the N precursors and annealing temperature on the performance of the catalyst were investigated. The bonding state of the N atom was found to have a significant effect on the selectivity and catalytic activity for ORR. Annealing of G-O with ammonia preferentially formed graphitic N and pyridinic N centers, while annealing of polyaniline/RG-O and polypyrrole/RG-O tended to generate pyridinic and pyrrolic N moieties, respectively. Most importantly, the electrocatalytic activity of the catalyst was found to be dependent on the graphitic N content which determined the limiting current density, while the pyridinic N content improved the onset potential for ORR. However, the total N content in the graphene-based non-precious metal catalyst does not play an important role in the ORR process.

Generation of B-doped graphene nanoplatelets using a solution process and their supercapacitor applications.

Chemically modified graphene (CMG) nanoplatelets have shown great promise in various applications due to their electrical properties and high surface area. Chemical doping is one of the most effective methods to tune the electronic properties of graphene materials. In this work, novel B-doped nanoplatelets (borane-reduced graphene oxide, B-rG-O) were produced on a large scale via the reduction of graphene oxide by a borane-tetrahydrofuran adduct under reflux, and their use for supercapacitor electrodes was studied. This is the first report on the production of B-doped graphene nanoplatelets from a solution process and on the use of B-doped graphene materials in supercapacitors. The B-rG-O had a high specific surface area of 466 m(2)/g and showed excellent supercapacitor performance including a high specific capacitance of 200 F/g in aqueous electrolyte as well as superior surface area-normalized capacitance to typical carbon-based supercapacitor materials and good stability after 4500 cycles. Two- and three-electrode cell measurements showed that energy storage in the B-rG-O supercapacitors was contributed by ion adsorption on the surface of the nanoplatelets in addition to electrochemical redox reactions.

Chemical structures of hydrazine-treated graphene oxide and generation of aromatic nitrogen doping

Chemically modified graphene platelets, produced via graphene oxide, show great promise in a variety of applications due to their electrical, thermal, barrier and mechanical properties. Understanding the chemical structures of chemically modified graphene platelets will aid in the understanding of their physical properties and facilitate development of chemically modified graphene platelet chemistry. Here we use (13)C and (15)N solid-state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy to study the chemical structure of (15)N-labelled hydrazine-treated (13)C-labelled graphite oxide and unlabelled hydrazine-treated graphene oxide, respectively. These experiments suggest that hydrazine treatment of graphene oxide causes insertion of an aromatic N(2) moiety in a five-membered ring at the platelet edges and also restores graphitic networks on the basal planes. Furthermore, density-functional theory calculations support the formation of such N(2) structures at the edges and help to elucidate the influence of the aromatic N(2) moieties on the electronic structure of chemically modified graphene platelets.

Chlorination of Reduced Graphene Oxide Enhances the Dielectric Constant of Reduced Graphene Oxide/Polymer Composites

14–19 ] The conductor-insulator composites are attracting much attention for potential applications of charge-storage capacitors, thin-fi lm transistors, and antistatic materials owing to their unique properties, i.e., a dramatic increase in dielectric constant in the conductor-insulator composite fi lms near the percolation threshold.