TEM study of TiO2 nanocrystals with different particle size and shape

Gao, Ying; Elder, S.A

doi:10.1016/s0167-577x(00)00033-1

Cited by 83 publications

(61 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Particle morphology can also be controlled with pH. At low pH, predominantly truncated bipyramids are found, [24][25][26] ) surfaces. 16 At basic pH, the order of stability of the exposed surfaces is reversed, and the {100} facet becomes the most stable (surface energy 1.53 J m ) facets.…”

Section: Introductionmentioning

confidence: 99%

Tuning TiO₂nanoparticle morphology in graphene–TiO₂hybrids by graphene surface modification

Sordello

Zeb

et al. 2014

Nanoscale

View full text Add to dashboard Cite

We report the hydrothermal synthesis of graphene (GNP)-TiO2 nanoparticle (NP) hybrids using COOH and NH2 functionalized GNP as shape controller. Anatase was the only TiO2 crystalline phase nucleated on the functionalized GNP, whereas traces of rutile were detected on unfunctionalized GNP. X-Ray Photoelectron spectroscopy (XPS) showed C-Ti bonds on all hybrids, thus confirming heterogeneous nucleation. GNP functionalization induced the nucleation of TiO2 NPs with specific shape and crystalline facets exposed. COOH functionalization directed the synthesis of anatase truncated bipyramids, bonded to graphene sheets via the {101} facets, while NH2 functionalization induced the formation of belted truncated bipyramids, bonded to graphene via the {100} facets. Belted trunc ated bipyramids formed on unfuctionalized GNP too, however the NPs were more irregular and rounded. These effects were ascribed to pH variations in the proximity of the functionalized GNP sheets, due to the high density of COOH or NH 2 groups. Because of the different reactivity of anatase {100} and {101} crystalline facets, we hypothesize that the hybrid materials will behave differently as photocatalysts, and that the COOH-GNP-TiO2 hybrids will be better photocatalysts for water splitting and H2 production .

show abstract

Section: Introductionmentioning

confidence: 99%

Tuning TiO₂nanoparticle morphology in graphene–TiO₂hybrids by graphene surface modification

Sordello

Zeb

et al. 2014

Nanoscale

View full text Add to dashboard Cite

show abstract

“…Although TEM studies on anatase nanocrystals known to date indicate some of the crystal facets present, [15][16][17][18]21] they are not able to describe the three-dimensional shape in a quantitative manner. Herein, we present for the first time a method that combines geometric estimations by TEM and the elucidation of detailed three-dimensional shapes by a Wulff-type construction.…”

mentioning

confidence: 99%

Direct Measurement of Size, Three‐Dimensional Shape, and Specific Surface Area of Anatase Nanocrystals

et al. 2007

View full text Add to dashboard Cite

At the heart of photocatalysis lies the recognition that chemical reactions are catalyzed on specific surfaces of catalyst particles. Because of the specific structure of such particles and the coordination of exposed surface atoms, the reactivity of different surfaces and their mechanisms for bonding to adsorbed molecules can vary dramatically. [1,2] Information about the size and shape of titanium dioxide (TiO 2 ) nanocrystals and, in particular, about the abundance and relative surface areas of specific crystal facets is highly desirable for the development of sophisticated photocatalytic experiments that are based on powdery materials. Unfortunately, for real catalysts, the kind of crystal facets that are exposed and their relative abundances are often not known. Profound knowledge about the relationship between processing conditions and the abundance of specific crystal facets would allow for tailoring improved catalysts that show predominantly those surfaces that are catalytically most active for specific reactions. The discovery of the decomposition of water on TiO 2 electrodes [3] stimulated many further investigations and opened up the research area of photocatalysis. Today, titanium dioxide is by far the most important photocatalyst material. It is commercially available as powders in two crystalline modifications, anatase and rutile, with surface areas ranging from 10 to more than 300 m 2 g À1. There is some evidence that the surface energy densities of anatase are generally lower than those of rutile. [4][5][6] However, theoretical predictions of the relative stability of perfect rutile and anatase surfaces do not give a coherent picture. Depending on the quantum-chemical method, the calculated rutile (110) surface energy density is found to be smaller [7] or larger [8,9] than those of all anatase low-index surfaces. Calculations based on classical pair potentials [6,10] disagree as to the relative stability of different anatase surfaces. All of these theoretical calculations are for perfect clean TiO 2 surfaces. A study for water-covered surfaces predicts anatase (101) and anatase (100) to be more stable than rutile (110), depending on the coverage with hydrogen or oxygen. [5] In another theoretical study of rutile and anatase nanoparticles of 2-6 nm diameter, [11] it was concluded that anatase particles have smaller surface energy densities than rutile up to a diameter of 2.5 nm. Consequently, for small crystals that show high surface-tovolume ratios, it is advantageous to adopt the anatase modification, and large titania crystals are thermodynamically favored if they have the rutile structure. The rutile-to-anatase transition occurs at particle sizes of a few tens of nanometers, and it depends on temperature, grain size, nanocrystal morphology, impurity content, reaction atmosphere, and synthesis conditions. [5,12]

show abstract

“…In previous reported works, the (101) anatase surface is found to dominate the structure of nanosized anatase crystallites, due to its energetic preference supported by both computational and experimental work [3,4,[9][10][11]. Therefore, the (101) anatase surface is labeled as the majority surface.…”

mentioning

confidence: 82%

“…2 Computational methodology Several computational results have been reported for anatase nanoparticles which predict the structures and energetics for different sizes and shapes [9,[21][22][23][24][25]]. An interesting computational work by Posternak et al verified that water dissociation occurs on under-coordinated Ti atoms at where exists strong acidity to stabilize the anion generated by deprotonation [26].…”

mentioning

confidence: 99%

The reactive sites in faceted anatase nanoparticles

Wang

Lewis

2011

Physica Status Solidi (b)

View full text Add to dashboard Cite

Considering both (001) and (101) surfaces, we construct two models of anatase nanoparticles with size ranging between 182 and 774 atoms. We choose nanoparticles where the majority surface (101) decreases in surface percentage as the size of the nanoparticle increases; the minority surface (001) decreases correspondingly. Upon optimization, significant structural changes occur in the edged Ti atoms which are junctures between the (001) and (101) facets; original four-coordinated Ti atoms become three coordinated upon optimization. Analyzing the electronic properties, we observe frontier orbitals occurring as small peaks in the band gap region approximately 1 eV lower than the conduction band. We find that these mid-gap peak states are highly localized at the edged Ti atoms. Therefore, we propose that these edged Ti atoms are a key to understanding the reactivity properties exhibited in anatase nanoparticles.

show abstract

TEM study of TiO2 nanocrystals with different particle size and shape

Cited by 83 publications

References 9 publications

Tuning TiO₂nanoparticle morphology in graphene–TiO₂hybrids by graphene surface modification

Tuning TiO₂nanoparticle morphology in graphene–TiO₂hybrids by graphene surface modification

Direct Measurement of Size, Three‐Dimensional Shape, and Specific Surface Area of Anatase Nanocrystals

The reactive sites in faceted anatase nanoparticles

Contact Info

Product

Resources

About

TEM study of TiO2 nanocrystals with different particle size and shape

Cited by 83 publications

References 9 publications

Tuning TiO2nanoparticle morphology in graphene–TiO2hybrids by graphene surface modification

Tuning TiO2nanoparticle morphology in graphene–TiO2hybrids by graphene surface modification

Direct Measurement of Size, Three‐Dimensional Shape, and Specific Surface Area of Anatase Nanocrystals

The reactive sites in faceted anatase nanoparticles

Contact Info

Product

Resources

About

Tuning TiO₂nanoparticle morphology in graphene–TiO₂hybrids by graphene surface modification

Tuning TiO₂nanoparticle morphology in graphene–TiO₂hybrids by graphene surface modification