3.4.1 Adsorbate properties of hydrogen on solid surfaces

Christmann, K.

doi:10.1007/11364856_1

Cited by 5 publications

(9 citation statements)

References 857 publications

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“…In this simple model, an adsorbate that (in vacuum) causes the metal work function to decrease would form a dipole (consisting of the metal and the adsorbed species) with the positive end away from the metal, which would be stabilized by the change in the double layer field that arises from increasing pH. Hydrogen adatoms on metal surfaces such as platinum form a dipole with the positive end at the hydrogen, , and so, changes in the double layer could influence its binding energy via dipole–dipole interactions (as attractions at higher pH, making it bind more strongly).…”

Section: Discussionmentioning

confidence: 99%

Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

et al. 2018

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In aqueous phase, the rates of hydrogenation of aromatic substrates such as phenol on Pt/C and Rh/C are influenced by varying activity of hydronium ions. Decreasing the pH from 8 to 1 increases the rate of hydrogenation of phenol on Pt at 20 bar H 2 and 80 °C by 15-fold. This increase is attributed to weakening of the hydrogen binding energy (HBE) on the metal surface with decreasing pH. A weaker HBE at lower pH is also predicted by ab initio molecular dynamics simulations, providing atomistic insight into the impact of electrolyte ion distribution and interfacial solvent reorganization on HBE. The lower HBE results in a decrease in the activation energy for addition of adsorbed H from the metal to the adsorbed organic (with a Brønsted−Evans− Polanyi slope of ∼1). The kinetic model derived accounts also for the lack of pH dependence at low hydrogen coverages (at 1 bar H 2 on Pt or up to 70 bar H 2 on Rh), when the weakening of the HBE decreases the hydrogen coverage.

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Section: Discussionmentioning

confidence: 99%

Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

et al. 2018

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“…where w equals the difference between the refractive index of the adsorbate n a and the refractive index of the environment n e , normalized with the maximum possible Figure 2 shows the time evolution of the number of adsorbed molecules in case of single-component adsorption for five different situations occurring in practice (hexane and oxygen adsorption on gold, hydrogen adsorption on nickel and adsorption of carbon dioxide on iron and palladium). Numerical data for desorption energies were adopted from (Christmann, 2006;Fichthorn & Miron, 2002;Wetterer et al, 1998). All calculations were done for room temperature, a volume of 3 lit, a pressure of 0.05 Pa and a surface area of 1 cm 2 .…”

Section: Methodsmentioning

confidence: 99%

“…Literature data for desorption energies is relatively scarce and usually defined for very specific gas-surface material pairs. Among the few sources of numerical data that can be used in the models described here are (Christmann, 2006;Wetterer et al, 1998 Molecules with their projected area smaller than the area of a binding site cannot be packed denser than allowed by the binding sites, which is determined by the (Leung, 2005), where it is said: "A flat metal surface typically has a surface binding site density 10 -5 moles/m 2 or 6 . 10 18 sites/m 2 ".…”

Section: Physical Parameters For Adsorption Kineticsmentioning

confidence: 99%

Plasmonic sensors in multi-analyte environment: Rate constants and transient analysis

Jakšić

Randjelović

Jakšić

et al. 2014

Chemical Engineering Research and Design

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This paper investigates multicomponent gas adsorption at the active surface of plasmonic chemical sensors and shows that there are situations where transients in a single sensor element can be used for simultaneous detection of different gases in multicomponent mixtures. A general master equation set is provided, describing multicomponent adsorption. Analytical expressions for sorption rates are derived and high-accuracy simplified models are proposed. Expressions for adsorption rate constants and rates and for number of binding sites are proposed. The derived analytical model takes into account the adsorbate molecule size, distribution of binding sites as determined by the crystallographic structure of the sensor surface and multi-site adsorption. The model allows for the calculation and optimization of deterministic behavior of the system. It is shown that trace amounts of target gas species can be made detectable by adding controlled amounts of known carrier gas. Besides being applicable in plasmonic sensor design and optimization, the obtained results may be of importance in situations where fast and low-cost detection of trace amounts of gases is needed, including natural gas leakage in residential heating, radon outgassing in dwellings, environmental protection, homeland defense and hazardous materials management, greenhouse footprint investigations, etc. HIGHLIGHTS  general equation set for multicomponent monolayer gas adsorption is derived  analytical model of adsorption takes into account adsorbate molecule size  adsorption rate constants are modeled using chemical software and data mining  simultaneous plasmonic sensing of several gas species in mixture is considered

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“…The interaction of hydrogen with metal surfaces has been subject of innumerous studies [36]. Hydrogen recombinatively desorbs from Pt films in several features located at about 200, 320 and 430 K in thermal desorption spectroscopy (TDS) [37,38].…”

Section: Introductionmentioning

confidence: 99%

“…The last one is believed to arise from imperfect sites [39,40]. Recombinative desorption from Cu, Ag and Au surfaces is observed at temperatures between 170 and 300 K, whereby the higher end belongs to Cu [36]. For Au an activation energy for desorption decreasing with coverage from 57 to 34 kJ/mol was reported [41].…”

Section: Introductionmentioning

confidence: 99%

Electronic Excitations in the Course of the Reaction of H with Coinage and Noble Metal Surfaces: A Comparison

Schindler

Diesing

Hasselbrink

2013

Zeitschrift für Physikalische Chemie

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The creation of electronic excitations during the reaction of atomic hydrogen on and with coinage and noble metals has been studied using metal-insulator-metal heterostructures. A characteristic current trace is observed when the outer metal surface of the structure is exposed to a 20 s pulse of H atoms. Comparison to the chemical kinetics allows to disentangle the contributions from the different chemical processes to this current. In the case of the coinage metals studied the observation is interpreted to suggest that predominantly electrons excited in connection with the hydrogen recombination reaction are the source of the current. For Pt such phenomenon is not observed. This difference allows insights into the role of the transition state for the non-adiabaticity in this simple chemical reaction.

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3.4.1 Adsorbate properties of hydrogen on solid surfaces

Cited by 5 publications

References 857 publications

Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

Plasmonic sensors in multi-analyte environment: Rate constants and transient analysis

Electronic Excitations in the Course of the Reaction of H with Coinage and Noble Metal Surfaces: A Comparison

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