Acidic dissolution of transition metals from Pt based alloy catalysts for oxygen reduction reaction (ORR) is an unavoidable process during fuel cell operation. In this work we studied the effect of acid treatment of graphene-supported Pt 1 Ni x (x ) 0, 0.25, 0.5, 1, and 2) alloys on the kinetics of the ORR in both alkaline and acidic solutions together with the generation of OH radicals in alkaline solutions. The alloy nanoparticles were synthesized through coimpregnation and chemical reduction. The electronic and structural features of the alloy were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. The ORR performances were studied using cyclic voltammetry and rotating ring disk electrode techniques in 0.05 M H 2 SO 4 and 0.1 M NaOH, respectively. The alloy catalysts were more active than pure Pt toward ORR, and after acid treatment the ORR activity of Pt-Ni alloy was enhanced in both acidic and alkaline media. The maximum activity of the Pt-based catalysts was found with ca. 50 atom % Ni content in the alloys (Pt 1 Ni 1 @graphene). OH radicals were generated through dissociation of hydroperoxide at the catalysts' surface and detected by fluorescence technique using terephthalic acid as capture reagent, which readily reacts with OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. More OH radicals were found to be generated at Pt 1 Ni 1 @graphene catalyst. This work may be valuable in the design of electrocatalysts with higher ORR activity but lower efficiency of OH radical generation.

No abstract

A dependence of oxygen reduction reaction activity and generation of OH radicals upon the composition of Pt-Co alloy electrocatalyst supported on graphene was found in alkaline solutions.

No abstract

No abstract

Separation and purification of graphene oxide (GO) prepared from chemical oxidation of flake graphite and ultrasonication by capillary electrophoresis (CE) was demonstrated. CE showed the ability to provide high-resolution separations of GO fractionations with baseline separation. The GO fractionations after CE were collected for Raman spectroscopy, atomic force microscopy, and transmission electron microscopy characterizations. GO nanoparticles (unexfoliated GO) or stacked GO sheets migrated toward the anode, while the thin-layer GO sheets migrated toward the cathode. Therefore, CE has to be performed twice with a reversed electric field to achieve a full separation of GO. This separation method was suggested to be based on the surface charge of the GO sheets, and a separation model was proposed. This study might be valuable for fabrication of GO or graphene micro- or nanodevices with controlled thickness.

Fabricating ternary Pt-based alloys has emerged as a promising strategy to further enhance the catalytic performance of Pt catalyst in direct methanol fuel cell (DMFC) for both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR).Herein we reported for the first time the synthesis of ternary TeCuPt nanowires (NWs) by a Te-template-directed galvanic replacement reaction, in which Te NWs served as both sacrificial templates and reducing agents. Compared with binary TePt alloy and pure Pt catalysts, the ternary TeCuPt alloys exhibited a more positive half-wave potential and higher specific area/mass activity for ORR, and it also displayed a better CO tolerance ability and long-term stability for MOR. The enhanced catalytic performance for TeCuPt NWs was attributed to the electronic and geometric structure effects, originating from the Pt alloying with both Te and Cu components, which could weaken the binding strength between Pt surface atoms and intermediate species (e.g. OH*, CO*). Our studies demonstrated a new alternative ternary Pt-based catalyst

No abstract