Summary Abstract: The mechanism of nitrogen dissociation on Fe(111)

Strasser, G.; Grunze, M.; Golze, Manfred

doi:10.1116/1.573172

Cited by 15 publications

(7 citation statements)

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“…However, more than 100 years after its discovery, a full understanding of this catalytic process is still lacking. The Fe(111) crystal face is believed to be the most active, and as such it has been thoroughly investigated [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Ertl and coworkers [9,11] have measured the variation of the absorbed N 2 bond vibration frequency.…”

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confidence: 99%

Non-linear temperature dependence of nitrogen adsorption and decomposition on Fe(111) surface

Bonati

Polino

Pizzolitto

et al. 2023

Preprint

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The cleavage of the N2 triple bond on the Fe(111) surface is believed to be the rate limiting step of the famed Haber-Bosch ammonia catalysis. Using a combination of machine learning potentials and advanced simulation techniques, we study this important catalytic step as a function of temperature. We find that at low temperatures our results agree with the well-established picture. However, if we increase the temperature to reach operando conditions the surface undergoes a global dynamical change and the step structure of the Fe(111) surface is destroyed. The catalytic sites, traditionally associated with the Fe(111) surface appear and disappear continuously. Our simulations illuminate the danger of extrapolating low-temperature results to operando conditions and indicate that the catalytic activity can only be inferred from calculations that take dynamics fully into account. More than that, they show that it is the transition to this highly fluctuating interfacial environment that drives the catalytic process.

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mentioning

confidence: 99%

Non-linear temperature dependence of nitrogen adsorption and decomposition on Fe(111) surface

Bonati

Polino

Pizzolitto

et al. 2023

Preprint

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“…For Fe(l 11) a temperature programmed desorption peak is found at 84 K [22] or at 96 K [231]. Sequential adsorption of 14N and 15N shows that this peak is most likely a new N 2 * species; possibly this peak is physisorbed N 2 upon N 2 *…”

Section: Desorption Kineticsmentioning

confidence: 95%

“…The adsorption of N z * increases the work function on Fe [22,474]. The dipole moment of N z * is 0.4 D [467].…”

Section: Properties Of Chemisorbed N2mentioning

confidence: 97%

“…High resolution electron energy loss spectroscopy shows a N-N stretch in yN2 at 2100 cm -1 [231]. For N 2* the work function decreases linearly with the coverage up to saturation [22].…”

Section: Properties Of Physisorbed N2mentioning

confidence: 99%

“…For single crystal surfaces the heat of adsorption is 25-37 kllmole depending on the coverages by molecular and physisorbed N2 * [22,462].…”

Section: Thermodynamicsmentioning

confidence: 99%

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Structure and Surface Chemistry of Industrial Ammonia Synthesis Catalysts

Stoltze

1995

Ammonia

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4.2 Electron work function of metals and semiconductors

Jakobi¹

2002

Landolt-Börnstein - Group III Condensed Matter

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If an electron beam is directed towards a surface, it gets reflected if its potential is equal to -(E P /e + ∆Φ), the negative value of the primary energy divided by e and corrected for ∆Φ between the surface and the electron emitter (in the widest sense: cathode, electron gun, etc.). Since the surface serves here as the anode in a diode configuration, the name diode method has been chosen. This method was introduced early by P.A. Anderson [35A]. Many details of different experimental set-ups are discussed in [73K2, 79H3]. It was pointed out [85K8] that for carefully chosen conditions and for a patchy surface, i.e., a surface consisting of a composite of smaller areas of different work function, the diode method measures the same arithmetical average of Φ as the Kelvin method (see below). How to use a HREEL spectrometer for the diode method is reported in Ref.[85S3]. Vibrating capacitor method (Kelvin)The vibrating capacitor method is based on the work of Lord Kelvin [1898K] and of Zisman [32Z]. A condensor is formed of the surface to be studied and a reference electrode in front of it which are connected by a ammeter and a variable voltage source. If the capacitance between the plates (sample and reference electrode) is changed, e.g., by changing their distance, a current will flow. By compensating the Ref. p. 4.2-118] 4.2 Electron work function of metals and semiconductors Lando lt-Börnstein New Series III/42A2 4.2-7contact potential difference through the voltage source, the current can be brought to zero. Since Φ of the surface is part of the contact potential, its changes relative to the reference electrode can be measured. A more extended description can be found in Ref. [79H3]. A very versatile instrument of this kind was developed by Besocke [76B]. Data collectionData have been collected for metal as well as semiconductor substrates. In the case of metals only elemental, single-crystalline samples were considered. There are a few exceptions to this general rule. Some metallic alloys are listed in case of single-crystalline samples of well defined (stoichiometric) composition. Some data are also incorporated for evaporated, mostly polycrystalline films of materials for which no single-crystal data are available. For semiconductor substrates, adsorbate-induced workfunction changes consist of two contributions: band-bending and electron-affinity changes. Systems were discarded for which the overall change in work function was small (<0.2 eV) or for which the authors did not report a separation of the two contributions. With respect to the adsorbates, only single-component adsorption layers were considered, i.e., co-adsorbates were omitted. Furthermore, it should be noted that completeness -although intended -could not be achieved. It was learned that work-function data are very often not in the center of a publication. Work-function data even seemed to many authors too marginal to give explicitly reference to them in the title, abstract or key words. Therefore, also computer based research could not guarant...

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Summary Abstract: The mechanism of nitrogen dissociation on Fe(111)

Cited by 15 publications

References 0 publications

Non-linear temperature dependence of nitrogen adsorption and decomposition on Fe(111) surface

Non-linear temperature dependence of nitrogen adsorption and decomposition on Fe(111) surface

Structure and Surface Chemistry of Industrial Ammonia Synthesis Catalysts

4.2 Electron work function of metals and semiconductors

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