Dissociative adsorption

Last updated October 28, 2024

Dissociative adsorption is a process in which a molecule adsorbs onto a surface and simultaneously dissociates into two or more fragments. This process is the basis of many applications, particularly in heterogeneous catalysis reactions. The dissociation involves cleaving of the molecular bonds in the adsorbate, and formation of new bonds with the substrate.

Breaking the atomic bonds of the dissociating molecule requires a large amount of energy, thus dissociative adsorption is an example of chemisorption, where strong adsorbate-substrate bonds are created.^[1] These bonds can be atomic, ionic or metallic in nature. In contrast to dissociative adsorption, in molecular adsorption the adsorbate stays intact as it bonds with the surface. Often, a molecular adsorption state can act as a precursor in the adsorption process, after which the molecule can dissociate only after sufficient additional energy is available.^[2]

A dissociative adsorption process may be homolytic or heterolytic , depending on how the electrons participating in the molecular bond are divided in the dissociation process. In homolytic dissociative adsorption, electrons are divided evenly between the fragments, while in heterolytic dissociation, both electrons of a bond are transferred to one fragment.^[1]

Kinetic theory

In the Langmuir model

The Langmuir model of adsorption ^[2] assumes

The maximum coverage is one adsorbate molecule per substrate site.
Independent and equivalent adsorption sites.

This model is the simplest useful approximation that still retains the dependence of the adsorption rate on the coverage, and in the simplest case, precursor states are not considered. For dissociative adsorption to be possible, each incident molecule requires n available adsorption sites, where n is the number of dissociated fragments. The probability of an incident molecule impacting a site with a valid configuration has the form

$f(\theta )=(1-\theta )^{n}$ ,

when the existing coverage is $θ$ and the dissociative products are mobile on the surface. The order of the kinetics for the process is n. The order of kinetics has implications for the sticking coefficient

$s=s_{0}(1-\theta )^{n}$ ,

where $s_{0}$ denotes the initial sticking coefficient or the sticking coefficient at 0 coverage. The adsorption kinetics are given by

$\theta ={\frac {s_{0}It}{1+s_{0}It}}$ for (n=2),

where $I$ is the impinging flux of molecules on the surface. The shape of the coverage function over time is different for each kinetic order, so assuming desorption is negligible, dissociative adsorption for a system following the Langmuir model can be determined by monitoring the adsorption rate as a function of time under a constant impinging flux.

Precursor states

Often the adsorbing molecule does not dissociate directly upon contact with the surface, but is instead first bound to an intermediate precursor state. The molecule can then attempt to dissociate to the final state through fluctuations. The precursor molecules can be intrinsic, meaning they occupy an empty site, or extrinsic, meaning they are bound on top of an already occupied site. The energies of these states can also be different, resulting in different forms of the overall sticking coefficient $f(\theta )$ . If extrinsic and intrinsic sites are assumed energetically equivalent and the adsorption rate to the precursor state is assumed to follow the Langmuir model, the following expression for the coverage dependence of the overall sticking coefficient is obtained:

$f(\theta )={\frac {(1+K)(1-\theta )^{n}}{1+K(1-\theta )^{n}}}$ ,

where $K$ is the ratio between the rate constants of dissociation and desorption reactions of the precursor.^[2]

Temperature dependence

The behaviour of the sticking coefficient as a function of temperature is governed by the shape of the potential energy surface of adsorption. For the direct mechanism, the sticking coefficient is almost temperature independent, because for most systems $E_{ads}\gg k_{B}T$ . When a precursor state is involved, thermal fluctuations determine the probability of the weakly bound precursor either dissociating into the final state or escaping the surface. The initial sticking coefficient is related to the energy barrier for dissociation $\epsilon _{a}$ and desorption $\epsilon _{d}$ , and their rate constants $\nu _{a}$ and $\nu _{a}$ as

$s_{0}=\left(1+{\frac {\nu _{d}}{\nu _{a}}}exp\left(-{\frac {\epsilon _{d}-\epsilon _{a}}{k_{B}T}}\right)\right)^{-1}$ .

From this arises two distinct cases for the temperature dependence:

When $\epsilon _{d}<\epsilon _{a}$ , the sticking coefficient increases with substrate temperature. This is the case of activated adsorption
When $\epsilon _{d}>\epsilon _{a}$ , the sticking coefficient decreases as substrate temperature increases. This is the behaviour of non-activated adsorption.

By measuring the sticking coefficient at different temperatures, it is then possible to extract the value of $\epsilon _{d}-\epsilon _{a}$ .^[2]

Experimental techniques

The measurement of adsorption properties relies on controlling and measuring the surface coverage and conditions, including the substrate temperature, impinging molecular flux or partial pressure.^[2] To detect dissociation on the surface, additional techniques that can distinguish surface ordering due to the interaction of dissociated fragments, identify desorbed particles,^[3]^[4] determine the order of kinetics^[5] or measure the chemical bond energies of the adsorbed species are required^[6]^[7]. In many experiments, a combination of multiple methods that probe different surface properties is used to form a complete picture of the adsorbed species. Comparisons between the experimental adsorption energy and simulated energies for dissociative and molecular adsorption can also indicate the type of adsorption for a system^[8]

For measurement of adsorption isotherms, a controlled gas pressure and temperature determine the coverage when adsorption and desorption rates are in balance.^[2]^[9] The coverage can then be measured with various surface sensitive methods like AES or XPS. Often, the coverage can also be related to a change in the surface work function,^[9] which can enable faster measurements in otherwise challenging conditions.^[4] The shape of the isotherms is sensitive to the order of kinetics of the adsorption and desorption processes,^[2] and though the exact forms can be difficult to find, simulations have been used to find general functional forms for isotherms of dissociative adsorption for specific systems.^[10]

XPS is a surface sensitive method that allows the direct probing of the chemical bonds of the surface atoms, thus being capable of differentiating bond energies corresponding to intact molecules or dissociated fragments. A challenge with this method is that the incident photons can induce surface modifications that are difficult to separate from the effects to be measured.^[7]^[11] LEED patterns are often combined with other measurements to verify surface structure and recognize ordering of the adsorbates.^[4]^[6]^[7]

Temperature programmed desorption (TPD or TDS) can be used to measure the properties of desorption, namely the desorption energy, order of desorption kinetics and the initial surface coverage.^[2] The desorption order contains information about the mechanisms like recombination required for the desorption process. As TPD also measures the masses of the desorbed particles, it can be used to detect individually desorbed dissociated fragments or their different combinations.^[5] Presence of masses different from the original molecules, or the detection of additional desorption peaks with higher order kinetics can indicate that the adsorption is dissociative.

Modeling

Density functional theory (DFT) can be used to calculate the change in energy caused by the adsorption and dissociation of molecules.^[12]^[13] The activation energy is calculated as the highest energy point on the optimal molecular paths of the fragments as they transform from the initial molecular state to the dissociated state.^[13] This is the saddle point of the potential energy surface of the process.^[9]

Properties for dissociative adsorption of example gases from DFT^[13]^[14]
Reaction	number of sites	sites	$E_{ads}\;{\textrm {[kcal/mol]}}$
NO + Ni(100) → N/Ni(100) + O/Ni(100)	2	hl	-33.7
H₂O + Pd(111) → OH/Pd(111) + H/Pd(111)	2	top + fcc	7.15
H₂ + Ni(111) → 2H/Ni(111)	2	hl	-23.9
H₂ + Pd(111) → 2H/Pd(111)	2	fcc	-23.3

Another approach for considering the stretching and dissociation of adsorbates is through the charge-transfer between the electron bands near the Fermi surface using molecular orbital (MO) theory. A strong charge transfer caused by overlap of unoccupied and occupied orbitals weakens the molecular bonds, which lowers or eliminates the barrier for dissociation. The charge transfer can be local or delocalized in terms of the substrate electrons, depending on which orbitals participate in the interaction. The simplest method used for approximating the electronic structure of systems using MO theory is Hartree-Fock self-consistent field, which can be extended to include electron correlations through various approximations.^[12]

Applications and examples

Water and transition metals

In atmospheric conditions, the adsorption of water and oxygen on transition metal surfaces is a well studied phenomenon. It has also been found that dissociated oxygen content on a surface lowers the activation energy for the dissociation of water, which on a clean metal surface can have a high barrier for dissociation. This is explained by the oxygen atoms binding with one hydrogen of the adsorbing water molecule to form an energetically favourable hydroxyl group.^[13] Likewise, molecular pre-adsorbed water can be used to lower the barrier for dissociation of oxygen that is needed in metal-catalyzed oxidation reactions. The relevant effects for this promoting role are hydrogen bonding between the water molecule and oxygen, and the electronic modification of the surface by the adsorbed water.^[15]

On clean close-packed surfaces of Ag, Au, Pt, Rh and Ni, dissociated oxygen prefers adsorption to hollow sites. Hydroxyl and molecular water prefers to adsorb on low coordination top sites, while the dissociated hydrogen atoms prefer hollow sites for most transition metals. A typical dissociation pathway on these metals is that as a top-site adsorbed molecule dissociates, at least one fragment migrates to a bridge or hollow site.^[13]

The formation and dissociation of water on transition metals like palladium has important applications in reactions for obtaining hydrogen and for the operation of proton-exchange membrane fuel cells, and much research has been conducted to understand the phenomenon. The rate-determining reaction for water formation is the creation of adsorbed OH. However, details of the specific adsorption sites and preferred reaction pathways for water formation have been difficult to determine. From kinetic Monte Carlo simulations combined with DFT calculations of the reaction energetics, it has been found that water formation on Pd(111) is dominated by step-edges through a combination of reactions:

O + H → OH

OO + H → OOH

OOH → OH + H

OH + OH → H₂O + O

OH + H → H₂O

At low temperatures and low relative pressure of H₂, the dominant reaction path for hydroxyl group formation is the direct association of O and H, and the ratios of each reaction path vary significantly in different conditions.^[16]

Metal-catalyzed oxidation

The oxidation of carbon monoxide in catalytic converters utilizes a transition metal surface as a catalyst in the reaction

2CO + O₂ → 2CO₂.

This system has been extensively studied to minimize the emissions of toxic CO from internal combustion engines, and there is a trade-off in the preparation of the Pt catalyst surface between the dissociative adsorption of oxygen and the sticking of CO to the metal surface. A larger step density increases the dissociation of oxygen, but at the same time decreases the probability of CO oxidation. The optimal configuration for the reaction is with a CO on a flat terrace and a dissociated O at a step edge.^[12]

Hydrogen economy

The most prevalent method for hydrogen production, steam reforming, relies on transition metal catalysts which dissociatively adsorb the initial molecules of the reaction to form intermediates, which then can recombine to form gaseous hydrogen. Kinetic models of the possible dissociative adsorption paths have been used to simulate the properties of the reaction.^[17]

A method for hydrogen purification involves passing the gas through a thin film of Pd-Ag alloy between two gas vessels. The hydrogen gas dissociates on the surface of the film, after which the individual atoms are able to diffuse through the metal, and recombine to form a higher hydrogen content atmosphere inside the low-pressure receiving vessel.^[18]

A challenge with hydrogen storage and transport through conventional steel vessels is hydrogen-induced-cracking, where a hydrogen atoms enter the container walls through dissociative adsorption. If enough partial pressure builds up inside the material, this can cause cracks, blistering or embrittlement of the walls.^[19]

Related Research Articles

<span class="mw-page-title-main">Haber process</span> Industrial process for ammonia production

The Haber process, also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia. It converts atmospheric nitrogen (N₂) to ammonia (NH₃) by a reaction with hydrogen (H₂) using a finely divided iron metal catalyst:

Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface. Examples include macroscopic phenomena that can be very obvious, like corrosion, and subtler effects associated with heterogeneous catalysis, where the catalyst and reactants are in different phases. The strong interaction between the adsorbate and the substrate surface creates new types of electronic bonds.

Physisorption, also called physical adsorption, is a process in which the electronic structure of the atom or molecule is barely perturbed upon adsorption.

Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid is dissolved by or permeates a liquid or solid. While adsorption does often precede absorption, which involves the transfer of the absorbate into the volume of the absorbent material, alternatively, adsorption is distinctly a surface phenomenon, wherein the adsorbate does not penetrate through the material surface and into the bulk of the adsorbent. The term sorption encompasses both adsorption and absorption, and desorption is the reverse of sorption.

Palladium hydride is palladium metal with hydrogen within its crystal lattice. Despite its name, it is not an ionic hydride but rather an alloy of palladium with metallic hydrogen that can be written PdH_x. At room temperature, palladium hydrides may contain two crystalline phases, α and β. Pure α-phase exists at x < 0.017 while pure β-phase exists at x > 0.58; intermediate values of x correspond to α–β mixtures.

A thin film is a layer of materials ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films is a fundamental step in many applications. A familiar example is the household mirror, which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once commonly used to produce mirrors, while more recently the metal layer is deposited using techniques such as sputtering. Advances in thin film deposition techniques during the 20th century have enabled a wide range of technological breakthroughs in areas such as magnetic recording media, electronic semiconductor devices, integrated passive devices, light-emitting diodes, optical coatings, hard coatings on cutting tools, and for both energy generation and storage. It is also being applied to pharmaceuticals, via thin-film drug delivery. A stack of thin films is called a multilayer.

Temperature programmed desorption (TPD) is the method of observing desorbed molecules from a surface when the surface temperature is increased. When experiments are performed using well-defined surfaces of single-crystalline samples in a continuously pumped ultra-high vacuum (UHV) chamber, then this experimental technique is often also referred to as thermal desorption spectroscopy or thermal desorption spectrometry (TDS).

Heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reagents or products. The process contrasts with homogeneous catalysis where the reagents, products and catalyst exist in the same phase. Phase distinguishes between not only solid, liquid, and gas components, but also immiscible mixtures, or anywhere an interface is present.

Desorption is the physical process where adsorbed atoms or molecules are released from a surface into the surrounding vacuum or fluid. This occurs when a molecule gains enough energy to overcome the activation barrier and the binding energy that keep it attached to the surface.

In chemistry, molecularity is the number of molecules that come together to react in an elementary (single-step) reaction and is equal to the sum of stoichiometric coefficients of reactants in the elementary reaction with effective collision and correct orientation. Depending on how many molecules come together, a reaction can be unimolecular, bimolecular or even trimolecular.

Brunauer–Emmett–Teller (BET) theory aims to explain the physical adsorption of gas molecules on a solid surface and serves as the basis for an important analysis technique for the measurement of the specific surface area of materials. The observations are very often referred to as physical adsorption or physisorption. In 1938, Stephen Brunauer, Paul Hugh Emmett, and Edward Teller presented their theory in the Journal of the American Chemical Society. BET theory applies to systems of multilayer adsorption that usually utilizes a probing gas (called the adsorbate) that does not react chemically with the adsorptive (the material upon which the gas attaches to) to quantify specific surface area. Nitrogen is the most commonly employed gaseous adsorbate for probing surface(s). For this reason, standard BET analysis is most often conducted at the boiling temperature of N₂ (77 K). Other probing adsorbates are also utilized, albeit less often, allowing the measurement of surface area at different temperatures and measurement scales. These include argon, carbon dioxide, and water. Specific surface area is a scale-dependent property, with no single true value of specific surface area definable, and thus quantities of specific surface area determined through BET theory may depend on the adsorbate molecule utilized and its adsorption cross section.

The sticking probability is the probability that molecules are trapped on surfaces and adsorb chemically. From Langmuir's adsorption isotherm, molecules cannot adsorb on surfaces when the adsorption sites are already occupied by other molecules, so the sticking probability can be expressed as follows:

Reactions on surfaces are reactions in which at least one of the steps of the reaction mechanism is the adsorption of one or more reactants. The mechanisms for these reactions, and the rate equations are of extreme importance for heterogeneous catalysis. Via scanning tunneling microscopy, it is possible to observe reactions at the solid gas interface in real space, if the time scale of the reaction is in the correct range. Reactions at the solid–gas interface are in some cases related to catalysis.

Sticking coefficient is the term used in surface physics to describe the ratio of the number of adsorbate atoms that adsorb, or "stick", to a surface to the total number of atoms that impinge upon that surface during the same period of time. Sometimes the symbol S_c is used to denote this coefficient, and its value is between 1 and 0. The coefficient is a function of surface temperature, surface coverage (θ) and structural details as well as the kinetic energy of the impinging particles. The original formulation was for molecules adsorbing from the gas phase and the equation was later extended to adsorption from the liquid phase by comparison with molecular dynamics simulations. For use in adsorption from liquids the equation is expressed based on solute density rather than the pressure.

The Langmuir adsorption model explains adsorption by assuming an adsorbate behaves as an ideal gas at isothermal conditions. According to the model, adsorption and desorption are reversible processes. This model even explains the effect of pressure; i.e., at these conditions the adsorbate's partial pressure $is related to its volume V adsorbed onto a solid adsorbent. The adsorbent, as indicated in the figure, is assumed to be an ideal solid surface composed of a series of distinct sites capable of binding the adsorbate. The adsorbate binding is treated as a chemical reaction between the adsorbate gaseous molecule and an empty sorption site S . This reaction yields an adsorbed species with an associated equilibrium constant :$

Adsorption is the adhesion of ions or molecules onto the surface of another phase. Adsorption may occur via physisorption and chemisorption. Ions and molecules can adsorb to many types of surfaces including polymer surfaces. A polymer is a large molecule composed of repeating subunits bound together by covalent bonds. In dilute solution, polymers form globule structures. When a polymer adsorbs to a surface that it interacts favorably with, the globule is essentially squashed, and the polymer has a pancake structure.

Transition metal oxides are compounds composed of oxygen atoms bound to transition metals. They are commonly utilized for their catalytic activity and semiconducting properties. Transition metal oxides are also frequently used as pigments in paints and plastics, most notably titanium dioxide. Transition metal oxides have a wide variety of surface structures which affect the surface energy of these compounds and influence their chemical properties. The relative acidity and basicity of the atoms present on the surface of metal oxides are also affected by the coordination of the metal cation and oxygen anion, which alter the catalytic properties of these compounds. For this reason, structural defects in transition metal oxides greatly influence their catalytic properties. The acidic and basic sites on the surface of metal oxides are commonly characterized via infrared spectroscopy, calorimetry among other techniques. Transition metal oxides can also undergo photo-assisted adsorption and desorption that alter their electrical conductivity. One of the more researched properties of these compounds is their response to electromagnetic radiation, which makes them useful catalysts for redox reactions, isotope exchange and specialized surfaces.

The strength of metal oxide adhesion effectively determines the wetting of the metal-oxide interface. The strength of this adhesion is important, for instance, in production of light bulbs and fiber-matrix composites that depend on the optimization of wetting to create metal-ceramic interfaces. The strength of adhesion also determines the extent of dispersion on catalytically active metal. Metal oxide adhesion is important for applications such as complementary metal oxide semiconductor devices. These devices make possible the high packing densities of modern integrated circuits.

The potential theory of Polanyi, also called Polanyi adsorption potential theory, is a model of adsorption proposed by Michael Polanyi where adsorption can be measured through the equilibrium between the chemical potential of a gas near the surface and the chemical potential of the gas from a large distance away. In this model, he assumed that the attraction largely due to Van Der Waals forces of the gas to the surface is determined by the position of the gas particle from the surface, and that the gas behaves as an ideal gas until condensation where the gas exceeds its equilibrium vapor pressure. While the adsorption theory of Henry is more applicable in low pressure and BET adsorption isotherm equation is more useful at from 0.05 to 0.35 P/Po, the Polanyi potential theory has much more application at higher P/Po (~0.1–0.8).

Heterogeneous gold catalysis refers to the use of elemental gold as a heterogeneous catalyst. As in most heterogeneous catalysis, the metal is typically supported on metal oxide. Furthermore, as seen in other heterogeneous catalysts, activity increases with a decreasing diameter of supported gold clusters. Several industrially relevant processes are also observed such as H₂ activation, Water-gas shift reaction, and hydrogenation. One or two gold-catalyzed reactions may have been commercialized.

References

1 2 Burwell, Robert L (1976). "Manual of Symbols and Terminology for Physicochemical Quantities and Units - Appendix II. Definitions, Terminology and Symbols in Colloid and Surface Chemistry. Part II: Heterogeneous Catalysis". Pure and Applied Chemistry. 46: 76. doi: 10.1351/pac197646010071 .
1 2 3 4 5 6 7 8 Oura, Kenjiro; Katayama, Mitsuhiro; Zotov, Andrey V.; Lifshits, Victor G.; Saranin, Alexander A. (2003). Surface Science – An Introduction. Berlin, Heidelberg: Springer. pp. 295–323. ISBN 978-3-662-05179-5.
↑ Mukerji, R. J.; Bolina, A. S.; Brown, W. A. (2003-11-22). "The influence of steps on the dissociation of NO on Pt surfaces: Temperature-programmed desorption studies of NO adsorption on Pt{211}". The Journal of Chemical Physics. 119 (20): 10844–10852. doi:10.1063/1.1619940. ISSN 0021-9606.
1 2 3 Caglar, Basar; Kizilkaya, Ali Can; Niemantsverdriet, J. W. (Hans); Weststrate, C. J. (Kees-Jan) (2018-01-02). "Application of work function measurements in the study of surface catalyzed reactions on Rh(1 0 0)". Catalysis, Structure & Reactivity. 4 (1): 1–11. doi:10.1080/2055074X.2018.1434986. hdl: 11147/9290 . ISSN 2055-074X.
1 2 Christmann, Klaus (2012). "Thermodynamics and Kinetics of Adsorption" (PDF). IMPRS-Lecture Series 2012: 'Experimental and Theoretical Methods in Surface Science'. Retrieved 29 May 2024.
1 2 Kong, Dandan; Zhu, Junfa; Ernst, Karl-Heinz (2016-03-24). "Low-Temperature Dissociation of CO 2 on a Ni/CeO 2 (111)/Ru(0001) Model Catalyst". The Journal of Physical Chemistry C. 120 (11): 5980–5987. doi:10.1021/acs.jpcc.5b10338. ISSN 1932-7447.
1 2 3 Gladys, M.J.; El Zein, A.A.; Mikkelsen, A.; Andersen, J.N.; Held, G. (2008). "Chemical composition and reactivity of water on clean and oxygen-covered Pd{111}". Surface Science. 602 (22): 3540–3549. doi:10.1016/j.susc.2008.09.031. ISSN 0039-6028.
↑ Zhu, Ling; Liu, Chunli; Wen, Xiaodong; Li, Yong-Wang; Jiao, Haijun (2019). "Molecular or dissociative adsorption of water on clean and oxygen pre-covered Ni(111) surfaces". Catal. Sci. Technol. 9 (1): 199–212. doi:10.1039/C8CY02198H.
1 2 3 Christmann, Klaus (2018). "Some Basic Processes at Surfaces—Exemplified by Means of Hydrogen Interaction With Transition Metals". Encyclopedia of Interfacial Chemistry. Elsevier. pp. 213–220. ISBN 9780128098943 . Retrieved 29 May 2024.
↑ Danielson, Thomas; Hin, Celine; Savara, Aditya (2016-08-10). "Generalized adsorption isotherms for molecular and dissociative adsorption of a polar molecular species on two polar surface geometries: Perovskite (100) (Pm-3m) and fluorite (111) (Fm-3m)". The Journal of Chemical Physics. 145 (6). Bibcode:2016JChPh.145f4705D. doi:10.1063/1.4960508. ISSN 0021-9606. OSTI 1311241.
↑ Pachecka, M.; Sturm, J. M.; Lee, C. J.; Bijkerk, F. (2017-03-30). "Adsorption and Dissociation of CO 2 on Ru(0001)". The Journal of Physical Chemistry C. 121 (12): 6729–6735. doi:10.1021/acs.jpcc.7b00021. ISSN 1932-7447. PMC 5388902 . PMID 28413569.
1 2 3 Taft, C.A.; Guimaraes, T.C.; Pavao, A. C.; Lester, W. A. (1999). "Adsorption and dissociation of diatomic molecules on transition-metal surfaces". International Reviews in Physical Chemistry. 18 (2): 163–233. Bibcode:1999IRPC...18..163T. doi:10.1080/014423599229947. ISSN 0144-235X.
1 2 3 4 5 Mäkinen, Mario; Laasonen, Kari (2023). "Density functional theory study of trends in water dissociation on oxygen-preadsorbed and pure transition metal surfaces". Surface Science. 734: 122305. Bibcode:2023SurSc.73422305M. doi: 10.1016/j.susc.2023.122305 . ISSN 0039-6028.
↑ Araujo, Rafael B; Rodrigues, Gabriel L. S.; dos Santos, Egon Campos; Pettersson, Lars G. M. (2022). "Adsorption energies on transition metal surfaces: towards an accurate and balanced description". Nature Communications. 13 (1): 6853. Bibcode:2022NatCo..13.6853A. doi:10.1038/s41467-022-34507-y. PMC 9652424 . PMID 36369277.
↑ Yan, Ming; Huang, Zheng-Qing; Zhang, Yu; Chang, Chun-Ran (2017). "Trends in water-promoted oxygen dissociation on the transition metal surfaces from first principles". Physical Chemistry Chemical Physics. 19 (3): 2364–2371. Bibcode:2017PCCP...19.2364Y. doi:10.1039/C6CP06974F. ISSN 1463-9076. PMID 28054681.
↑ Dietze, Elisabeth M.; Chen, Lin; Grönbeck, Henrik (2022-02-08). "Surface steps dominate the water formation on Pd(111) surfaces". The Journal of Chemical Physics. 156 (6). Bibcode:2022JChPh.156f4701D. doi: 10.1063/5.0078918 . ISSN 0021-9606. PMID 35168342.
↑ Hou, Kaihu; Hughes, Ronald (2001). "The kinetics of methane steam reforming over a Ni/α-Al2O catalyst". Chemical Engineering Journal. 82 (1): 311–328. doi:10.1016/S1385-8947(00)00367-3. ISSN 1385-8947.
↑ Häussinger, Peter; Lohmüller, Reiner; Watson, Allan M. (2011). "Hydrogen, 3. Purification". Ullmann's Encyclopedia of Industrial Chemistry. John Wiley & Sons, Ltd. doi:10.1002/14356007.o13_o04. ISBN 9783527306732.
↑ Sun, Yinghao; Cheng, Y. Frank (2021). "Thermodynamics of spontaneous dissociation and dissociative adsorption of hydrogen molecules and hydrogen atom adsorption and absorption on steel under pipelining conditions". International Journal of Hydrogen Energy. 46 (69): 34469–34486. Bibcode:2021IJHE...4634469S. doi:10.1016/j.ijhydene.2021.07.217. ISSN 0360-3199 – via Elsevier Science Direct.

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[iupac-1] 1 2 Burwell, Robert L (1976). "Manual of Symbols and Terminology for Physicochemical Quantities and Units - Appendix II. Definitions, Terminology and Symbols in Colloid and Surface Chemistry. Part II: Heterogeneous Catalysis". Pure and Applied Chemistry. 46: 76. doi: 10.1351/pac197646010071 .

[oura-2] 1 2 3 4 5 6 7 8 Oura, Kenjiro; Katayama, Mitsuhiro; Zotov, Andrey V.; Lifshits, Victor G.; Saranin, Alexander A. (2003). Surface Science – An Introduction. Berlin, Heidelberg: Springer. pp. 295–323. ISBN 978-3-662-05179-5.

[3] Mukerji, R. J.; Bolina, A. S.; Brown, W. A. (2003-11-22). "The influence of steps on the dissociation of NO on Pt surfaces: Temperature-programmed desorption studies of NO adsorption on Pt{211}". The Journal of Chemical Physics. 119 (20): 10844–10852. doi:10.1063/1.1619940. ISSN 0021-9606.

[:2-4] 1 2 3 Caglar, Basar; Kizilkaya, Ali Can; Niemantsverdriet, J. W. (Hans); Weststrate, C. J. (Kees-Jan) (2018-01-02). "Application of work function measurements in the study of surface catalyzed reactions on Rh(1 0 0)". Catalysis, Structure & Reactivity. 4 (1): 1–11. doi:10.1080/2055074X.2018.1434986. hdl: 11147/9290 . ISSN 2055-074X.

[:3-5] 1 2 Christmann, Klaus (2012). "Thermodynamics and Kinetics of Adsorption" (PDF). IMPRS-Lecture Series 2012: 'Experimental and Theoretical Methods in Surface Science'. Retrieved 29 May 2024.

[:5-6] 1 2 Kong, Dandan; Zhu, Junfa; Ernst, Karl-Heinz (2016-03-24). "Low-Temperature Dissociation of CO 2 on a Ni/CeO 2 (111)/Ru(0001) Model Catalyst". The Journal of Physical Chemistry C. 120 (11): 5980–5987. doi:10.1021/acs.jpcc.5b10338. ISSN 1932-7447.

[:4-7] 1 2 3 Gladys, M.J.; El Zein, A.A.; Mikkelsen, A.; Andersen, J.N.; Held, G. (2008). "Chemical composition and reactivity of water on clean and oxygen-covered Pd{111}". Surface Science. 602 (22): 3540–3549. doi:10.1016/j.susc.2008.09.031. ISSN 0039-6028.

[8] Zhu, Ling; Liu, Chunli; Wen, Xiaodong; Li, Yong-Wang; Jiao, Haijun (2019). "Molecular or dissociative adsorption of water on clean and oxygen pre-covered Ni(111) surfaces". Catal. Sci. Technol. 9 (1): 199–212. doi:10.1039/C8CY02198H.

[h2_encyclo-9] 1 2 3 Christmann, Klaus (2018). "Some Basic Processes at Surfaces—Exemplified by Means of Hydrogen Interaction With Transition Metals". Encyclopedia of Interfacial Chemistry. Elsevier. pp. 213–220. ISBN 9780128098943 . Retrieved 29 May 2024.

[10] Danielson, Thomas; Hin, Celine; Savara, Aditya (2016-08-10). "Generalized adsorption isotherms for molecular and dissociative adsorption of a polar molecular species on two polar surface geometries: Perovskite (100) (Pm-3m) and fluorite (111) (Fm-3m)". The Journal of Chemical Physics. 145 (6). Bibcode:2016JChPh.145f4705D. doi:10.1063/1.4960508. ISSN 0021-9606. OSTI 1311241.

[11] Pachecka, M.; Sturm, J. M.; Lee, C. J.; Bijkerk, F. (2017-03-30). "Adsorption and Dissociation of CO 2 on Ru(0001)". The Journal of Physical Chemistry C. 121 (12): 6729–6735. doi:10.1021/acs.jpcc.7b00021. ISSN 1932-7447. PMC 5388902 . PMID 28413569.

[:1-12] 1 2 3 Taft, C.A.; Guimaraes, T.C.; Pavao, A. C.; Lester, W. A. (1999). "Adsorption and dissociation of diatomic molecules on transition-metal surfaces". International Reviews in Physical Chemistry. 18 (2): 163–233. Bibcode:1999IRPC...18..163T. doi:10.1080/014423599229947. ISSN 0144-235X.

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