Platinum

About: Platinum is a research topic. Over the lifetime, 49675 publications have been published within this topic receiving 1150035 citations. The topic is also known as: Pt & element 78.

Structural Changes of γ-Al2O3-Supported Catalysts in Hot Liquid Water

Abstract: The structural changes of γ-Al2O3, Ni/γ-Al2O3, and Pt/γ-Al2O3 catalysts under aqueous phase reforming conditions (liquid water at 200 °C and autogenic pressure) are examined over the course of 10 h. The changes are characterized by X-ray diffraction, NMR spectroscopy, N2 physisorption, pyridine adsorption followed by IR spectroscopy, and electron microscopy. It is demonstrated that γ-alumina is converted into a hydrated boehmite (AlOOH) phase with significantly decreased acidity and surface area. For metal-free γ-alumina, the transformation is completed within 10 h, whereas the presence of nickel and platinum particles significantly retards the formation of boehmite. In the beginning of the treatment, the surface area of γ-alumina increases, suggesting surface pitting and formation of small boehmite particles on the surface of γ-alumina. This process is followed by the formation of a compact crystalline boehmite phase. It is proposed that the metal particles affect the kinetics of this transformation by b...

Different Sized Platinum Nanoparticles Supported on Carbon: An XPS Study on These Methanol Oxidation Catalysts

Abstract: Different sized platinum nanoparticles on carbon supports have been prepared using PtCl4 (catalyst Ia) and H2PtCl6 (catalyst IIa) as starting materials and 1-hexanethiol as a surfactant and then heated to 200 °C (catalyst Ib and catalysts IIb), 300 °C (catalyst Ic and catalysts IIc), and 400 °C (catalyst Id and catalysts IId) for 4 h under argon gas. All the catalysts showed a face-centered cubic (fcc) crystal structure as determined by X-ray diffraction. X-ray diffractograms and transmission electron microscopy results reveal that the platinum nanoparticles are homogeneously dispersed on the carbon support, exhibit narrow particle size distribution, and show no appreciable aggregation. The average platinum particle size as determined from XRD data was found to be ∼2.00, ∼2.56, ∼4.23, ∼4.52, ∼2.13, ∼2.77, ∼4.29, and ∼4.62 nm for catalysts Ia−d and IIa−d, respectively. X-ray photoelectron spectra of all the catalysts indicated that most (>70%) of the platinum nanoparticles have an oxidation state of zero a...

A molecule-like PtAu 24 (SC 6 H 13 ) 18 nanocluster as an electrocatalyst for hydrogen production

Abstract: The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. Here, we report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanocluster. The catalytic activity of the resulting bimetallic nanocluster, PtAu24(SC6H13)18, for the hydrogen production is found to be significantly higher than reported catalysts. It is even better than the benchmarking platinum catalyst. The molecule-like bimetallic nanocluster represents a class of catalysts that bridge homogeneous and heterogeneous catalysis and may provide a platform for the discovery of finely optimized catalysts. Volcano plots for electrocatalytic hydrogen production show the best catalysts as those ensuring the hydrogen binding step is thermodynamically neutral. Here, the authors report fabrication of a highly active thermoneutral electrocatalyst via doping of a single platinum atom into a gold nanocluster.

Effect of CeO2 loading on the surface and catalytic behaviors of CeO2-Al2O3-supported Pt catalysts

Abstract: Pt catalysts supported on mixed CeO2-Al2O3 carriers with different CeO2 loading (0.5–10.3 wt.%) were prepared by wetness impregnation method. The catalysts were characterized by SBET, X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and thermogravimetric analysis (TG). It was shown that pretreatment temperature and the concentration of CeO2 in the support influences significantly on the morphology of Pt. XRD showed the formation of nanocrystallites of Pt on the surface of alumina and low-loaded CeO2 (≤6 wt.%) samples at higher temperature of calcination (1073 K). Amorphous Pt was observed in all reduced samples. XPS spectra showed the presence of interaction between Pt and Ce, which leads to easy surface reduction of both, ceria and platinum, as revealed by TPR patterns. The effect of CeO2 loading on the catalytic behavior of supported Pt catalysts in the reaction of CO2 reforming of CH4 was determined. Addition of cerium oxide results in improvement of catalytic performance for the reforming of methane with CO2. Pt catalyst with 1 wt.% of CeO2 exhibited the highest specific activity and stability, due to the increase in the metal–support interface area, caused by the higher Pt dispersion.