NH3 adsorption on anatase-TiO2(101)

Koust, Stig; Adamsen, Kræn C.; Kolsbjerg, Esben L.; Li, Zheshen; Hammer, Bjørk; Wendt, Stefan; Lauritsen, Jeppe V.

doi:10.1063/1.5021407

Cited by 15 publications

(14 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Using thermogravimetric analysis (TGA) a total organic mass fraction of ~40% was measured (Supplementary Materials, Figure S3). Assuming a 0.2 nm 2 molecular footprint of OLAM [31] and a spherical particle shape with a diameter of 5 nm, the total amount of OLAM corresponded roughly to a monolayer coverage of the TNDs’ surface (Supplementary Materials, Figure S4). However, a precise determination of the particle size via transmission electron microscopy (TEM) was difficult because the TNDs aggregated on the TEM substrates and occasionally observed isolated nanocrystals showed only faint imaging contrast.…”

Section: Resultsmentioning

confidence: 99%

Elasticity of Cross-Linked Titania Nanocrystal Assemblies Probed by AFM-Bulge Tests

et al. 2019

View full text Add to dashboard Cite

In order to enable advanced technological applications of nanocrystal composites, e.g., as functional coatings and layers in flexible optics and electronics, it is necessary to understand and control their mechanical properties. The objective of this study was to show how the elasticity of such composites depends on the nanocrystals’ dimensionality. To this end, thin films of titania nanodots (TNDs; diameter: ~3–7 nm), nanorods (TNRs; diameter: ~3.4 nm; length: ~29 nm), and nanoplates (TNPs; thickness: ~6 nm; edge length: ~34 nm) were assembled via layer-by-layer spin-coating. 1,12-dodecanedioic acid (12DAC) was added to cross-link the nanocrystals and to enable regular film deposition. The optical attenuation coefficients of the films were determined by ultraviolet/visible (UV/vis) absorbance measurements, revealing much lower values than those known for titania films prepared via chemical vapor deposition (CVD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed a homogeneous coverage of the substrates on the µm-scale but a highly disordered arrangement of nanocrystals on the nm-scale. X-ray photoelectron spectroscopy (XPS) analyses confirmed the presence of the 12DAC cross-linker after film fabrication. After transferring the films onto silicon substrates featuring circular apertures (diameter: 32–111 µm), freestanding membranes (thickness: 20–42 nm) were obtained and subjected to atomic force microscopy bulge tests (AFM-bulge tests). These measurements revealed increasing elastic moduli with increasing dimensionality of the nanocrystals, i.e., 2.57 ± 0.18 GPa for the TND films, 5.22 ± 0.39 GPa for the TNR films, and 7.21 ± 1.04 GPa for the TNP films.

show abstract

Section: Resultsmentioning

confidence: 99%

Elasticity of Cross-Linked Titania Nanocrystal Assemblies Probed by AFM-Bulge Tests

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Moreover, they introduced oxygen adatoms and thereupon observed a second desorption species that was shifted to higher temperature. However, in any case, they did not detect remaining carbon or nitrogen above 400 K. In addition, there are a number of publications reporting the chemistry of ammonia on different TiO 2 surfaces. ,− In brief, ammonia adsorbs molecularly on the Ti 5c sites and fully desorbs up to 400 K without remaining nitrogen detectable in XPS . The desorption energy as well as the pre-exponential coefficient of the desorption varies widely with the coverage. , …”

Section: Introductionmentioning

confidence: 92%

Multidentate Interaction of Methylamine with Rutile TiO₂ (110)

et al. 2021

View full text Add to dashboard Cite

Aiming for a comprehensive expertise of the adsorption and activation of small organic molecules on transition metal oxides, the chemistry of methylamine on rutile TiO 2 (110) is examined combining surface science experiments with firstprinciples calculations. Besides the physisorption of a methylamine multilayer, three types of methylamine adsorbates were ascertained: adsorption via hydrogen bonding toward bridging oxygen atoms, adsorption of methylamine at one individual Ti 5c site, and an adsorbate occupying two Ti 5c sites in an unprecedented multidentate bonding geometry. In all three adsorbate classes, multiple interactions with the TiO 2 substrate as well as intermolecular dispersion forces are identified to be crucial to explain the molecule−surface interaction and concomitant adsorption geometries. While the Ti−N bond surely makes the largest contribution to the molecules' adsorption energy, smaller forces such as hydrogen bonds between NH−O and CH−O moieties are shown to be the central key for understanding the chemistry of methylamine on titania surfaces. Comparing different adsorption geometries, these multidentate adsorption motifs can boost the thermal stability in relation to ordinary adsorption, in the case of the adsorbate occupying two Ti 5c sites by more than 100 K or several tens of kJ per mol being thermally stable up to more than 500 K. Surprisingly, the multidentate adsorption is remarkably sensitive to the adsorption conditions and especially does not occur for elevated adsorption temperatures. Curiously enough, low adsorption temperatures thus yield high-temperature desorption species. Our findings are particularly important for the understanding of (photo-)chemical reactions, which usually requires an extensive knowledge of adsorbate-substrate interactions and the bonding situation toward the catalysts surface.

show abstract

“…The classical surface science approach has employed SPM techniques in UHV or under ambient conditions, introducing the molecules of interest on well‐defined model surfaces. This classical approach has allowed researchers to study the interactions between these model surfaces and even smallest adsorbed species, such as OH, NH 3 , or O 2 , which are of great relevance for future energy technologies. However, for the complete understanding of the molecular adsorbate structures formed in aqueous solutions under potential control and their influence on electrocatalytic processes, in situ SPM methodologies under electrochemical conditions are required.…”

Section: Adsorbate Structures At Catalytic Surfacesmentioning

confidence: 99%

Electrochemical Scanning Probe Microscopies in Electrocatalysis

et al. 2018

View full text Add to dashboard Cite

surface coordination, strain effects, [6][7][8][9] ligand effects, [10,11] ensemble effects, [12] and the electrolyte composition. [13] A detailed understanding of these effects requires experimental and computational procedures to investigate the working mechanisms of the electrocatalysis. Ideally, atomically resolved topographic and chemical information of the catalyst surface under reaction conditions is required. Transmission electron microscopy (TEM) has been reported to be capable of in operando investigation of catalyst structures while catalytic reactions are taking place. [14] However, the instrumentation utilized for such purpose has very strong restrictions and realistic operating conditions cannot be easily applied so far. Alternatively, scanning probe microscopies (SPMs) and electrochemical scanning probe microscopies (EC-SPMs) are able to perform structural measurements of catalytic systems under reaction conditions with resolution down to atomic scales. Normally, EC-SPMs, for instance electrochemical scanning tunneling microscopy (EC-STM), electrochemical atomic force microscopy (EC-AFM), and scanning electrochemical potential microscopy (SECPM), can provide structural information on the solid side of the electrode/electrolyte interface at the atomic level for conductive samples (EC-STM is limited in the case of semi/nonconductive samples). However, these techniques usually lack the capability of chemical sensitivity, ultrahigh resolution reactivity monitoring, and probing the property of the electrolyte side of the interface. One well-developed exception is the scanning electrochemical microscopy (SECM), which will also be discussed in detail within this review. Additionally, SECM and related methods permit gleaning information about the electrolyte side of the electrochemical interface. However, the resolution of SECM and related methods is limited by the size of the SECM-probe and the working principle of SECM.In this review, first a very brief overview on electrocatalysis and on the importance of model substrates for understanding the fundamental underlying principles is given. Thereafter, the operational principle of different SPM techniques is summarized. The main focus of the work lies then on the application of the techniques to study phenomena important for electrocatalysis, including surface topography and adsorption processes. Within that context, also the application of room Improvements toward highly efficient electrochemical energy conversion require a detailed understanding of the underlying electrochemical processes at electrified solid-liquid interfaces. In situ and in operando studies by means of electrochemical scanning probe microscopy (EC-SPM) have become indispensable experimental tools due to their capability of resolving surface topography down to the atomic level even within the harsh environment of electrolytes. EC-SPM methodologies have thus contributed tremendously to the current understanding of electrocatalysis. In this review article, recent achievements in complement...

show abstract

NH3 adsorption on anatase-TiO2(101)

Cited by 15 publications

References 34 publications

Elasticity of Cross-Linked Titania Nanocrystal Assemblies Probed by AFM-Bulge Tests

Elasticity of Cross-Linked Titania Nanocrystal Assemblies Probed by AFM-Bulge Tests

Multidentate Interaction of Methylamine with Rutile TiO₂ (110)

Electrochemical Scanning Probe Microscopies in Electrocatalysis

Contact Info

Product

Resources

About

NH3 adsorption on anatase-TiO2(101)

Cited by 15 publications

References 34 publications

Elasticity of Cross-Linked Titania Nanocrystal Assemblies Probed by AFM-Bulge Tests

Elasticity of Cross-Linked Titania Nanocrystal Assemblies Probed by AFM-Bulge Tests

Multidentate Interaction of Methylamine with Rutile TiO2 (110)

Electrochemical Scanning Probe Microscopies in Electrocatalysis

Contact Info

Product

Resources

About

Multidentate Interaction of Methylamine with Rutile TiO₂ (110)