There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

TiO2 photocatalysis and related surface phenomena

The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited

A surface science perspective on TiO2 photocatalysis

Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Fundamentals and Catalytic Applications of CeO2-Based Materials

The morphology of amorphous solid water grown by vapor deposition was found to depend strongly on the angular distribution of the water molecules incident from the gas phase. Systematic variation of the incident angle during deposition using a collimated beam of water led to the growth of nonporous to highly porous amorphous solid water. The physical and chemical properties of amorphous solid water are of interest because of its presence in astrophysical environments. The ability to control its properties in the laboratory may shed light on some of the outstanding conflicts related to this important material.

https://science.sciencemag.org/content/sci/283/5407/1505.full.pdf

Controlling the morphology of amorphous solid water

The interaction of water and methanol with well-defined (1 × 1) terminated surfaces of anatase-TiO2(101) were investigated with temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). For water, three desorption states were observed in the TPD spectra at 160, 190, and 250 K. The three desorption peaks were assigned to multilayer water, water adsorbed to 2-fold-coordinated O, and water adsorbed to 5-fold-coordinated Ti, respectively. The TPD spectra for methanol were more complicated. For methanol, five desorption peaks were observed in the TPD spectra at 135, 170, 260, 410, and 610 K. The five desorption peaks were assigned to multilayer methanol, methanol adsorbed to 2-fold-coordinated O, methanol adsorbed to 5-fold-coordinated Ti, methoxy adsorbed to 5-fold-coordinated Ti, and methoxy adsorbed to Ti at step edges, respectively. The XPS results indicated that the adsorbed water and methanol were predominantly bound to the surface in a molecular state, with no evidence for diss...

Experimental Investigation of the Interaction of Water and Methanol with Anatase−TiO2(101)

Thermally-driven processes on rutile TiO2(1 1 0)-(1 × 1): A direct view at the atomic scale

The adsorption of N2 was used to investigate the porosity/morphology of thin films of amorphous solid water. Molecular beams were used to vapor deposit amorphous solid water films on a Pt(111) crystal at a variety of incident growth angles. The amount of N2 adsorbed by the amorphous solid water depends very sensitively on the growth angle and thermal history of the film. For normal and nearly normal incidence growth, the water films are relatively dense and smooth and adsorb only a small amount of N2. For larger growth angles, the films are porous and adsorb large quantities of N2 with apparent surface areas as high as ∼2700 m2/g. The physical and chemical properties of amorphous solid water are of interest because of its presence in astrophysical environments. The observations have important implications for laboratory studies which use vapor deposited amorphous solid water films as analogs for astrophysical icy bodies such as comets.

Control of amorphous solid water morphology using molecular beams. I. Experimental results

Identical regions of partially reduced TiO2(110) surfaces with bridge-bonded oxygen vacancy (BBOV) concentrations of ∼10% ML (1 ML = 5.2 × 1014 cm-2) were imaged using scanning tunneling microscopy (STM) before and after dosing H2O at ambient temperature (∼300 K). Atomically resolved images confirm that H2O adsorbs dissociatively on the BBOV sites, producing two hydroxyl species, one positioned at BBOV and denoted OHV and the other, denoted OHB, formed by protonation at either of the two nearest-neighbor bridge-bonded oxygen atoms. Hydrogen hopping along the [001] direction is observed at ambient temperature, with a strong preference for OHB (∼10×) hydrogen motion. This powerful imbalance demonstrates the inequality of OHV and OHB and suggests differences in their charge and/or binding configuration.

Zdenek Dohnálek

Papers

Controlling the morphology of amorphous solid water

Experimental Investigation of the Interaction of Water and Methanol with Anatase−TiO2(101)

Thermally-driven processes on rutile TiO2(1 1 0)-(1 × 1): A direct view at the atomic scale

Control of amorphous solid water morphology using molecular beams. I. Experimental results

Imaging water dissociation on TiO2(110): Evidence for inequivalent geminate OH groups.