Synthesis and catalytic properties of metal nanoparticles: Size, shape, support, composition, and oxidation state effects

Doped and undoped hematite (α-Fe2O3) thin film electrodes for photoelectrochemical hydrogen production have been prepared using reactive magnetron sputtering. We present an extensive characterization of the photoelectrochemical, structural, electrical, and optical properties of the α-Fe2O3 films to assess the mechanisms by which the dopants influence photoelectrode performance. The Si-doped and Ti-doped α-Fe2O3 exhibited much higher photoelectrochemical activity than the undoped material. The Ti-doped α-Fe2O3 showed the largest photocurrent as well as the lowest onset potential, the highest electrical conductivity, the lowest activation energy, and the highest charge carrier density. The crystallographic orientation of the films does not appear to be a dominant factor affecting the photocurrent. The changes in conductivity with doping are insufficient to explain the observed changes in the photoelectrochemical activity. The proposed mechanism for the enhanced photocurrent is reduction of recombination due...

Enhancement of Photoelectrochemical Hydrogen Production from Hematite Thin Films by the Introduction of Ti and Si

Tailoring the chemical reactivity of nanomaterials at the atomic level is one of the most important challenges in catalysis research. In order to achieve this elusive goal, fundamental understanding of the geometric and electronic structure of these complex systems at the atomic level must be obtained. This article reports the influence of the nanoparticle shape on the reactivity of Pt nanocatalysts supported on γ-Al(2)O(3). Nanoparticles with analogous average size distributions (∼0.8-1 nm), but with different shapes, synthesized by inverse micelle encapsulation, were found to display distinct reactivities for the oxidation of 2-propanol. A correlation between the number of undercoordinated atoms at the nanoparticle surface and the onset temperature for 2-propanol oxidation was observed, demonstrating that catalytic properties can be controlled through shape-selective synthesis.

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Shape-dependent catalytic properties of Pt nanoparticles.

High-pressure catalytic reactions over single-crystal metal surfaces

Adsorbate-induced restructuring of surfaces

https://escholarship.org/content/qt5px951h0/qt5px951h0.pdf?t=p0jury

The oscillatory behavior of the CO oxidation reaction at atmospheric pressure over platinum single crystals: surface analysis and pressure dependent mechanisms

Single crystals of germanium-substituted Fe2O3 have been grown using chemical vapour transport with tellurium tetrachloride and their crystallographic, electrical, magnetic and photoelectronic properties have been studied. Germanium-substituted Fe2O3 crystallized with the corundum structure and is an extrinsic n-type semiconductor with a room-temperature resistivity of ca. 5 Ω cm and an impurity ionization energy of 0.12 eV. Low-temperature susceptibility measurements suggest that insertion of GeIV leads to reduction of FeIII to FeII without spinel-phase inclusion. Photoelectrochemical measurements and determinations of the flatband potential by different techniques suggest that the behaviour of Fe2O3 photoanodes may be influenced by energy levels in the bandgap near the conduction band.

Preparation, characterization and photoelectronic properties of germanium-substituted Fe2O3 single crystals

Chemical interactions between molecules in excited electronic, vibrational, or rotational states and surfaces is a new field of catalytic science. Until recently, catalysis of chemical reactions has only been considered for molecules in their thermodynamic ground states. Most of the surface reactions to be catalyzed were exothermic or thermodynamically downhill. In carrying out endothermic reactions, the only source of energy considered has been the addition of heat. This also assured that the molecules maintained an equilibrium energy distribution throughout the reaction.

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J. E. Turner

Papers

The oscillatory behavior of the CO oxidation reaction at atmospheric pressure over platinum single crystals: surface analysis and pressure dependent mechanisms

Preparation, characterization and photoelectronic properties of germanium-substituted Fe2O3 single crystals

The catalyzed photodissociation of water