Support Effects of Carbon on Pt Catalysts

Surfactant/organic solvent free single-step engineering of hybrid graphene-Pt/TiO2 nanostructure: Efficient photocatalytic system for the treatment of wastewater coming from textile industries

In this study, hybrid graphene-Pt/TiO₂ nanostructure were synthesized by single-step, inexpensive and surfactant/organic solvent free route; hydrothermal technique. The physicochemical properties of hybrid graphene-Pt/TiO₂ nanostructure were carefully analyzed by multiple techniques, including X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The synthesized hybrid nanostructures were utilized as photocatalyst for the degradation of methylene blue (MB) dye under natural environment at average ambient temperature and mean daily global solar radiation, of about 22–25 °C and 374.9 mWh/cm², respectively. The activity performance indicated considerable degradation of methylene blue (MB) dye and was in the following order Gr (13%), TiO₂ (60%) and hybrid graphene-Pt/TiO₂ nanostructure (90%) over 21 min under the natural light illumination. The physiochemical characterization suggests that, the tightly attached metalized TiO₂ nanoparticles (Pt-TiO₂) on the high surface area graphene sheets improved utilization of visible light and increased separation and transfer of photo-excited electron (ē) hole (h⁺) pairs. Notably, the hybrid graphene-Pt/TiO₂ nanostructure exhibited an excellent cyclic stability for methylene blue (MB) dye removal. Finally, the kinetic behavior indicated that the photocatalytic degradation reaction of the dye obeyed the pseudo-first order (Langmuir-Hinshelwood) kinetics model.

In Situ Assembly of Ultrathin PtRh Nanowires to Graphene Nanosheets as Highly Efficient Electrocatalysts for the Oxidation of Ethanol

One-dimensional (1D) anisotropic platinum-based nanowires are promising electrocatalysts in polymer electrolyte membrane fuel cells owing to the inherent structural merits. Herein, we report an in situ growth of ultrathin PtRh nanowires (diameters of 2-3 nm) on graphene nanosheets via the oriented attachment pathway. Mechanistic studies reveal that graphene nanosheets play a critical role in the nucleation and growth of PtRh nanowires. The resulting hybrid of PtRh nanowire decorated graphene nanosheets shows outstanding activity and durability toward ethanol electro-oxidation. It exhibits a specific current density of 2.8 mA cm^-2 and a mass-normalized current density of 1 A mg^-1 metal, which are 5.4 and 3.1 times those of the state-of-the-art Pt/C catalyst, respectively. After 2000 cyclic tests, it maintains 86% of the initial electrochemically active surface area, which is larger than that of 63% obtained from the Pt/C catalyst. The superior performance is attributed to the combination of the advantageous 1D morphological motif with the synergistic effects of PtRh alloys and graphene nanosheet support.

Synthesis of ultrafine Pt nanoparticles stabilized by pristine graphene nanosheets for electro-oxidation of methanol

In this study, the pristine graphene nanosheets (GNS) derived from chemical vapor deposition process were employed as catalyst support. In spite of the extremely hydrophobic GNS surface, ultrafine Pt nanoparticles (NPs) were successfully assembled on the GNS through a surfactant-free solution process. The evolution of Pt NPs in the GNS support was studied using transmission electron microscopy. It was found that the high-energy surface sites in the GNS, such as edges and defects, played a critical role on anchoring and stabilizing Pt nuclei, leading to the formation of Pt NPs on the GNS support. The concentration of the Pt precursor, i.e., H2PtCl6 solution had significant effects on the morphology of Pt/GNS hybrids. The resulting Pt/GNS hybrids were examined as catalysts for methanol electro-oxidation. It was indicated that the electrochemical active surface area and catalytic activity of the Pt/GNS hybrids were highly dependent on Pt loadings. The superior activity of the catalysts with low Pt loadings was attributed to the presence of Pt subnanoclusters as well as the strong chemical interaction of Pt NPs with the GNS support.

Electrocatalytic activity of Pt subnano/nanoclusters stabilized by pristine graphene nanosheets

Outstanding electrocatalytic activity of Pt subnano/nanoclusters stabilized by pristine graphene nanosheets.