Clive H. Yen

One-pot synthesis of B-doped three-dimensional reduced graphene oxide via supercritical fluid for oxygen reduction reaction

There has been a great deal of interest recently in three-dimensional (3D) graphene based materials, as they exhibit large surface areas, unique electronic properties, and other attractive features. Particularly, 3D graphene doped with heteroatoms catalysts show high electrocatalytic activity toward oxygen reduction reaction (ORR), which can be used as metal-free catalysts. Most of the existing synthesis strategies of 3D graphene invariably involve multiple steps and procedures are often energy intensive and time-consuming. In this paper, we reported a one-pot and green method to synthesize boron-doped 3D reduced graphene oxide (B-3DrGO) using the supercritical carbon dioxide (ScCO2) technique. The resulting products exhibit hierarchical porous structures, leading to a high specific surface area of 541 m2 g−1. A high content of B (2.9 at%) was detected in the product, suggesting that B-doping was efficient using this technique. The B-3DrGO displays electrocatalytic activity toward ORR, which is comparable to the commercially available Pt/C (20 wt%) catalyst, in addition to their superior durability and resistance to the crossover effect. Moreover, the supercritical fluid technique, which uses non-flammable, essentially nontoxic, inexpensive, and environmentally benign CO2, is a new and green approach for the synthesis of heteroatom doped 3D graphene.

Recyclable and Ligandless Suzuki Coupling Catalyzed by Carbon Nanotube-Supported Palladium Nanoparticles Synthesized in Supercritical Fluid

Abstract Carbon nanotube–supported palladium nanoparticles prepared by a supercritical fluid deposition method show high activities for catalyzing Suzuki coupling reactions, and the catalysts can be recycled and reused at least six times without losing activity.

Cu(II) extraction by supercritical fluid carbon dioxide from a room temperature ionic liquid using fluorinated β-diketones

Copper(II) can be extracted in supercritical CO2 from a room temperature ionic liquid using CO2-philic fluorinated β-diketonate ligands; thanks to the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIMTf2N) ionic liquid properties, there is no need to add modifiers to the neat supercritical CO2 to reach high extraction efficiencies.

The separation of lanthanides and actinides in supercritical fluid carbon dioxide

Supercritical fluid carbon dioxide presents an attractive alternative to conventional solvents for recovery of the actinides and lanthanides. Carbon dioxide is a good solvent for fluorine and phosphate-containing ligands, including the traditional tributylphosphate ligand used in process-scale uranium separations. Actinide and lanthanide oxides may even be directly dissolved in carbon dioxide containing the complexes formed between these ligands and mineral acids, obviating the need for large volumes of acids for leaching and dissolution, and the corresponding organic liquid–liquid solvent extraction solutions. Examples of the application of this novel technology for actinide and lanthanide separations are presented.

Making ultrafine and highly-dispersive multimetallic nanoparticles in three-dimensional graphene with supercritical fluid as excellent electrocatalyst for oxygen reduction reaction

Three-dimensional (3D) graphene showed an advanced support for designing porous electrode materials due to its high specific surface area, large pore volume, and excellent electronic property. However, the electrochemical properties of reported porous electrode materials still need to be improved further. The current challenge is how to deposit desirable nanoparticles (NPs) with controllable structure, loading and composition in 3D graphene while maintaining the high dispersion. Herein, we demonstrate a modified supercritical fluid (SCF) technique to address this issue by controlling the SCF system. Using this superior method, a series of Pt-based/3D graphene materials with the ultrafine-sized, highly dispersive and controllable composition multimetallic NPs were successfully synthesized. Specifically, the resultant Pt40Fe60/3D graphene showed a significant enhancement in electrocatalytic performance for the oxygen reduction reaction (ORR), including a factor of 14.2 enhancement in mass activity (1.70 A mgPt−1), a factor of 11.9 enhancement in specific activity (1.55 mA cm−2), and higher durability compared with that of Pt/C catalyst. After careful comparison, the Pt40Fe60/3D graphene catalyst shows the higher ORR activity than most of the reported similar 3D graphene-based catalysts. The successful synthesis of such attractive materials by this method also paves the way to develop 3D graphene in widespread applications.