Volcano plots in hydrogen electrocatalysis – uses and abuses

• Paola Quaino,
• Fernanda Juarez,
• Elizabeth Santos and
• Wolfgang Schmickler

Beilstein J. Nanotechnol. 2014, 5, 846–854, doi:10.3762/bjnano.5.96

• , Córdoba, Argentina 10.3762/bjnano.5.96 Abstract Sabatier’s principle suggests, that for hydrogen evolution a plot of the rate constant versus the hydrogen adsorption energy should result in a volcano, and several such plots have been presented in the literature. A thorough examination of the data shows

• adsorption energy should be neither too high nor too low. If it is is too high (endothermic), adsorption is slow and limits the overall rate; if it is too low (exothermic), desorption is slow. In terms of hydrogen electrocatalysis it can be stated more precisely: at the equilibrium potential the free energy

• explained by Sabatier’s principle. In both cases, the rate is somewhat faster on the (111) than on the (100) surfaces [15][18][19], and the adsorption energy is also lower on the more compact surfaces [20]. Theses differences are so small that we could not show them in our plot, but they are well

Neutral and charged boron-doped fullerenes for CO₂ adsorption

• Suchitra W. de Silva,
• Aijun Du,
• Wijitha Senadeera and
• Yuantong Gu

Beilstein J. Nanotechnol. 2014, 5, 413–418, doi:10.3762/bjnano.5.49

• population analysis method [25]. The adsorption energies were calculated using the following equation. where Eads is the adsorption energy, is the total energy of the BC59 cage with a CO2 molecule adsorbed and and are the energies of the isolated BC59 cage and CO2 molecule, respectively. For a favourable

• adsorption the calculated adsorption energy should have a negative value. To provide more accurate results for the chemisorption energy the counterpoise corrected energy [26][27] was also calculated. The transition state was located by using the synchronous transit-guided quasi-Newton (STQN) method [28][29

• has occurred from the BC59 fullerene to the CO2 molecule. Comparison of the charge distribution on BC59− before (Figure 4b) and after (Figure 5c) CO2 adsorption, confirms that the injected electron is occupied by the CO2 molecule. The higher adsorption energy and the significant distortions in the

The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production

• Jakob G. Howalt and
• Tejs Vegge

Beilstein J. Nanotechnol. 2014, 5, 111–120, doi:10.3762/bjnano.5.11

• over nitrogen and hydrogen at neutral bias, but under electrochemical reaction conditions needed for nitrogen reduction, oxygen adsorption is severely weakened and the adsorption energy is comparable to hydrogen and nitrogen adsorption. The potentials required to reduce oxygen off the surface are −0.72

• H2 H+ + e−. Hereby, a description of the effects of an external applied potential U on the electrons and the concentration of protons in the electrolyte [20][21][22][23][24] are implemented. The adsorption energy of O* under electrochemical reaction conditions under an applied potential U are

Some reflections on the understanding of the oxygen reduction reaction at Pt(111)

• Ana M. Gómez-Marín,
• Ruben Rizo and
• Juan M. Feliu

Beilstein J. Nanotechnol. 2013, 4, 956–967, doi:10.3762/bjnano.4.108

• completed, the potential is close to 1.2 V and this is a strict upper potential limit (Eup) that ensures the surface order of the Pt(111) electrode. In this respect, a good Pt(111) blank voltammogram would have no contributions at 0.12 V nor at 0.27 V, the hydrogen adsorption energy on {110} and {100} step

• adsorption energy of ORR intermediates, and thus also have a negative energetic effect on the reaction [26][47]. However, OHads is also considered an intermediate reactive species in the H2O2 reduction (HPRR) on Pt [48][49][50][51], a mass-controlled reaction at potentials of up to approximately 0.95 V [25

Adsorption of the ionic liquid [BMP][TFSA] on Au(111) and Ag(111): substrate effects on the structure formation investigated by STM

• Benedikt Uhl,
• Florian Buchner,
• Dorothea Alwast,
• Nadja Wagner and
• R. Jürgen Behm

Beilstein J. Nanotechnol. 2013, 4, 903–918, doi:10.3762/bjnano.4.102

• ) reconstruction act as nucleation sites for 2D island formation. A few examples are visible in Figure 1b. More clearly, this is observed in STM images recorded at low coverages, where only the steps and the elbows are covered with adsorbates, as illustrated in Figure 1c. This points to a higher adsorption energy

Influence of the solvent on the stability of bis(terpyridine) structures on graphite

• Daniela Künzel and
• Axel Groß

Beilstein J. Nanotechnol. 2013, 4, 269–277, doi:10.3762/bjnano.4.29

• scheme, such as the recently developed enveloping distribution sampling (EDS) method [30]. However, using one of these schemes often requires a series of molecular dynamics simulations. In order to derive the adsorption energy of the BTP molecules from solution at finite temperatures, we rather take

• . In the CVFF calculation, the difference is only about 3 eV and the solvation in water is not decidedly unfavorable from an energetic point of view. Adsorption of a dissolved BTP molecule Finally, we consider the adsorption energy of 3,3′-BTP on graphite under different conditions, namely for the BTP

• adsorption under vacuum conditions, at the solid/liquid interface with TCB as a solvent, as in the experiment, and additionally the case of adsorption of a BTP molecule from water. These numbers are listed in Table 1. Furthermore, in Figure 7 they are compared to the adsorption energy under vacuum conditions

Electronic and transport properties of kinked graphene

• Jesper Toft Rasmussen,
• Tue Gunst,
• Peter Bøggild,
• Antti-Pekka Jauho and
• Mads Brandbyge

Beilstein J. Nanotechnol. 2013, 4, 103–110, doi:10.3762/bjnano.4.12

• minimum kinetic energy for the first hydrogen to react [32][33] is required, in an out-of-equilibrium situation such as in an atomic beam [34]. Casolo et al. [35] calculated the reaction barrier and adsorption energy for multiple hydrogen atoms on flat graphene. In agreement with other studies they found

Spontaneous dissociation of Co₂(CO)₈ and autocatalytic growth of Co on SiO₂: A combined experimental and theoretical investigation

• Kaliappan Muthukumar,
• Harald O. Jeschke,
• Roser Valentí,
• Evgeniya Begun,
• Johannes Schwenk,
• Fabrizio Porrati and
• Michael Huth

Beilstein J. Nanotechnol. 2012, 3, 546–555, doi:10.3762/bjnano.3.63

• stable configuration. The difference in adsorption energy between the C4 configuration and the rest of the configurations ranges between 0.3–0.5 eV. These differences may be small under typical FEBID conditions, in particular if local beam heating has to be taken into account. In this case the molecule

• surfaces. The least stable configuration is C2, in which one of the terminal ligands is bonded to the surface Si atoms. The most stable case, with an adsorption energy of −3.54 eV, is obtained when relaxations are started with C4, in which one bridging and one terminal ligand are involved in bonding to the

Dipole-driven self-organization of zwitterionic molecules on alkali halide surfaces

• Laurent Nony,
• Franck Bocquet,
• Franck Para,
• Frédéric Chérioux,
• Eric Duverger,
• Frank Palmino,
• Vincent Luzet and
• Christian Loppacher

Beilstein J. Nanotechnol. 2012, 3, 285–293, doi:10.3762/bjnano.3.32

• are much stronger than the molecule–substrate interactions)? Second, is the orientation of the molecular layers along the directions of the substrate due to a registry between the lattices of the substrate and the molecule (i.e., the gain in adsorption energy for a point-on-line coincidence as

• following one-dimensional model for the cases of KBr (i.e., 10 cmsps for 11 substrate distances) and NaCl (i.e., 9 cmsps for 11 substrate distances) along both molecular axis directions as depicted in Figure 4. First, we assume that the adsorption energy Eads varies laterally following the Madelung surface

An NC-AFM and KPFM study of the adsorption of a triphenylene derivative on KBr(001)

• Antoine Hinaut,
• Adeline Pujol,
• Florian Chaumeton,
• David Martrou,
• André Gourdon and
• Sébastien Gauthier

Beilstein J. Nanotechnol. 2012, 3, 221–229, doi:10.3762/bjnano.3.25

• molecule is strongly adsorbed in the MLh structure with an adsorption energy of 1.8 eV. In the MLv layer, the molecules form π-stacked rows aligned along the polar directions of the KBr surface. In these rows, the molecules are less strongly bound to the substrate, but the structure is stabilized by the

• that bind the molecule are at a mean distance of 0.28 nm while the central aromatic core lies flat at a distance of 0.4 nm from the surface plane. The calculated adsorption energy of 1.8 eV is quite large. It includes not only the contribution of the five CN groups but also the interaction energy of

• the negatively charged oxygen atoms and the aromatic core with the surface, which can be roughly evaluated by calculating the adsorption energy of hexamethoxytriphenylene on KBr(001) under the same conditions. We obtain 0.8 eV, meaning that each CN group contributes approximately (1.8 − 0.8)/5 = 0.2

Terthiophene on Au(111): A scanning tunneling microscopy and spectroscopy study

• Berndt Koslowski,
• Anna Tschetschetkin,
• Norbert Maurer,
• Elena Mena-Osteritz,
• Peter Bäuerle and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 561–568, doi:10.3762/bjnano.2.60

• molecules exhibited almost identical interparticle distances pointing to repulsive intermolecular interactions, probably due to electrical dipoles formed by the adsorption. The lateral variation of the adsorption energy appeared to be relatively small allowing for tip-induced rotations and displacements of

Influence of water on the properties of an Au/Mpy/Pd metal/molecule/metal junction

• Jan Kučera and
• Axel Groß

Beilstein J. Nanotechnol. 2011, 2, 384–393, doi:10.3762/bjnano.2.44

• structure with every second water molecule bound to the metal surface via the oxygen atom. The other water molecules have one hydrogen atom either pointing away from the surface (Hup) or towards the surface (Hdown). In such an arrangement the adsorption energy related to one H2O in the gas phase is higher

• compared to the adsorption energy of a single water molecule, e.g., for the Hdown structure on Pd(111) it is −0.56 eV per molecule. However, the dominating contribution is coming from intermolecular hydrogen bonds rather then from water–molecule interactions [16][18]. Consequently, because of the rather

• interaction of an isolated H2O molecule with the bare monolayer (Pdmonolayer/H2O), i.e., without any attached Mpy molecule. Interestingly enough, we obtained an adsorption energy of −0.34 eV with an O–Pd bond distance of 2.28 Å, which is similar to the situation for H2O/Pdbulk (111) [18], and this means that

Intermolecular vs molecule–substrate interactions: A combined STM and theoretical study of supramolecular phases on graphene/Ru(0001)

• Michael Roos,
• Benedikt Uhl,
• Daniela Künzel,
• Harry E. Hoster,
• Axel Groß and
• R. Jürgen Behm

Beilstein J. Nanotechnol. 2011, 2, 365–373, doi:10.3762/bjnano.2.42

• corrugated surface without any disturbance due to the different adsorption sites [37]. Calculations To determine the corrugation of the adsorption potential, we summed up the different contributions to the adsorption energy (molecule–graphene and molecule–Ru interaction) and subtracted the adsorption energy

• adsorption energy can be compared with the intermolecular interactions. For the adsorption of 3,3'-BTP molecules, the STM images shown above reveal that very similar hexagonal local units are formed upon adsorption on HOPG and on graphene/Ru(0001). On both surfaces, these units consist of six molecules in a

• calculated adsorption energy for both the hill and the valley position and the resulting corrugation of the adsorption potential ΔE for PTCDA molecules on graphene/Ru(0001) for different force fields. Dependent on the applied force field, the resulting ΔE ranges from −0.435 to −0.690 eV. To rationalize the