Jin-Yu Ye

ELECTROCHEMICAL PREPARATION OF A POLYPARAPHENYLENE FILM AND A POLYPARAPHENYLENE POLYACRYLAMINE FUNCTIONAL FILM

Abstract We have first found the way to obtain a uniform and flexible polyparaphenylene (PPP) film by electrochemical polymerization of benzene in concentrated sulphuric acid with an anhydrous Lewis acid as catalyst. It is evident that concentrated sulphuric acid plays an important role in the electrochemical polymerization of benzene. It protonates benzene into benzenium. The rotation of the working electrode is an important condition for obtaining uniform and flexible PPP films. The thickness of the PPP film can be controlled by the electricity used for polymerization and the amounts and kinds of catalysts employed. The colour of the PPP film changes from transparent yellow to black, depending on the thickness. The PPP film is electroactive in concentrated sulphuric acid. The stable polymer film (PPP) is a suitable underlayer for polyacrylamine (PAA) formation by the electrochemical polymerization method. This PPP/PAA film has high potential for applications in the extraction of trace metal ions, ion exchange and in catalysis.

A new method of STM tip fabrication for in-situ electrochemical studies

Abstract A new method of STM tip fabrication utilizing the electrophoresis technique and the ability of mercury to expand and shrink upon changing the temperature is introduced, and experimental details for tip etching and tip plating are described. Tips electrophoretically plated in 601 water-soluble electrophoretic varnish at 40 V for more than 30 min show good insulation behavior with exposed tip electrode disk radii around 0.8 μm. The apices of the plated tips remain undestroyed and clean after undergoing the mercury-touching procedure and the electrophoretic process. The characterization of ultramicroelectrode behaviors and the STM imaging capability of the plated tips are demonstrated.

A NEW ELECTROCHEMICAL SCANNING TUNNELING MICROSCOPE

Abstract A new in-situ electrochemical scanning tunneling microscope (ECSTM) has been designed in our laboratory with the following main features: (1) The normal electrochemical current at the tip during scanning can be automatically corrected by a newly designed special feedback loop and computer program. (2) The tip-sample bias potential and the individual electrode potential of tip or sample can be adjusted, scanned or cycled by computer according to the requirement. (3) Driving and adjusting the tip to a nanometer distance from the sample surface can be carried out by a computer-controlled motor. A preliminary example of application to electrochemical systems is presented.

Oxygen Reduction Reaction Activity on Pt{111} Surface Alloys

PtM overlayers (where M=Fe, Co or Ni) supported on Pt{111} are prepared via thermal annealing in either a nitrogen/water or hydrogen ambient of dilute aqueous droplets containing M(Z+) cations directly attached to the electrode. Two different PtM phases are detected depending on the nature of the post-annealing cooling environment. The first of these consists of small (<20 nm), closely packed microcrystals comprised of a central metallic core and a shell (several monolayers thick) of mixed metal oxides/hydroxides. The second type of PtM phase is prepared by cooling in a stream of hydrogen gas. Although this second phase also consists of numerous microcrystals covering the Pt{111} electrode surface, these are both flatter than before and moreover are entirely metallic in character. A positive shift in the onset of PtM oxide formation correlates with increased activity towards the oxygen reduction reaction (ORR), which we ascribe to the greater availability of platinum metallic sites under ORR conditions.

Cyclic Penta-Twinned Rhodium Nanobranches as Superior Catalysts for Ethanol Electro-oxidation

Developing active and durable electro-catalysts toward ethanol oxidation reaction (EOR) with high selectivity toward the C-C bond cleavage is an important issue for the commercialization of direct ethanol fuel cell. Unfortunately, current ethanol oxidation electro-catalysts (e.g., Pt, Pd) still suffer from poor selectivity for direct oxidation of ethanol to CO2, and rapid activity degradation. Here we report a facile route to the synthesis of a new kind of cyclic penta-twinned (CPT) Rh nanostructures that are self-supported nanobranches (NBs) built with 1-dimension CPT nanorods as subunits. Structurally, the as-prepared Rh NBs possess high percentage of open {100} facets with significant CPT-induced lattice strains. With these unique structural characteristics, the as-prepared CPT Rh NBs exhibit outstanding electrocatalytic performance toward EOR in alkaline solution. Most strikingly, the selectivity of complete conversion ethanol to CO2 on the CPT Rh NBs is measured to be as high as 14.5 ± 1.1% at -0.15 V, far exceeding that for single-crystal tetrahedral nanocrystals, icosahedral nanocrystals, and commercial Rh black, as well as majority of reported values for Pt or Pd-based electro-catalysts. By combining with density functional theory calculation, the effects of different structural features of Rh on EOR are definitively elucidated. It was found that the large amount of open Rh (100) facets dominantly contribute to the outstanding activity and exceptionally high selectivity, while the additional tensile strain on (100) planes can further boost the catalytic activity by enhancing the adsorption strength and lowering the reaction barrier of dehydrogenation process of ethanol. As a proof of concept, the present work shows that rationally optimizing surface and electronic structure of electro-catalysts by simultaneously engineering their surface and bulk structures is a promising strategy to promote the performance of electro-catalysts.