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Recently, deuterium-labeled drugs, such as deutetrabenazine, have attracted considerable attention. Consequently, understanding the reaction mechanisms of deuterium-labeled drugs is crucial, both fundamentally and for real applications. To understand the mechanisms of H- and D-transfer reactions, in this study, we used deuterated anisole as a deutetrabenazine model and computationally considered the nuclear quantum effects of protons, deuterons, and electrons. We demonstrated that geometrical differences exist in the partially and fully deuterated methoxy groups and hydrogen-bonded structures of intermediates and transition states due to the H/D isotope effect. The observed geometrical features and electronic structures are ascribable to the different nuclear quantum effects of protons and deuterons. Primary and secondary kinetic isotope effects (KIEs) were calculated for H- and D-transfer reactions from deuterated and undeuterated anisole, with the calculated primary KIEs in good agreement with the corresponding experimental data. These results reveal that the nuclear quantum effects of protons and deuterons need to be considered when analyzing the reaction mechanisms of H- and D-transfer reactions and that a theoretical approach that directly includes nuclear quantum effects is a powerful tool for the analysis of H/D isotope effects in H- and D-transfer reactions.

The ambipolar triclinic C60/Fc nanosheet FETs were converted to n-type face-centered cubic C60 nanosheet FETs due to the loss of ferrocene with void formation upon heating at 150 °C.

We demonstrate thermo-electrochemical (TEC) conversion using a biocompatible redox couple of lactic acid and pyruvic acid on earth-abundant TiO2. The TEC cell exhibited a positive Seebeck coefficient of 1.40 mV K−1. DFT calculations figured out that the adsorption of intermediate species and protons on TiO2 controls both the redox reaction and current polarity.

We analysed the H/D isotope effect of CH4/CD4 adsorption on a Rh(111) surface using our combined plane wave and localized basis sets method, that we proposed for the consideration of delocalized electrons on a surface and the quantum effect of protons (deuterons) in metal–molecule interactions. We observed that the adsorption distance and energy of CD4 were larger and lower than those of CH4, respectively. This is in reasonable agreement with the corresponding experimental results of cyclohexane adsorption. We clearly found that the trend of the H/D isotope effect in the geometrical and energetic difference was similar to that of the hydrogen-bonded systems.

Polysilanes are important materials for photoresist masks used in semiconductor chipmaking processes. As the oxidation of a polyalkylsilane can lead to the failure of the chipmaking process, it is ...

Although hydrogen plays a crucial role in ammonia synthesis, very little is known about its poisoning of Ru catalysts. In this study, density functional theory calculations of H2 and N2 dissociations, and H atom binding on Ru153 were performed to provide a fundamental understanding of hydrogen poisoning. Because of the kinetic dominance of the H2 dissociation over N2 (vertically or horizontally adsorbed) splitting, the dissociated H atoms block the active sites required for horizontal (less energetically demanding dissociation) N2 adsorption to occur either from the gas phase or after its geometrical transformation from being adsorbed vertically. Additionally, the dissociated H atoms withdraw electrons from the surface, which reduces the ability of the neighboring Ru atoms to donate electrons for N2 activation, hindering its dissociation and suppressing ammonia synthesis.

The adsorption states of N2 and H2 on MgO-supported Ru nanoparticles under conditions close to those of ammonia synthesis (AS; 1 atm, 250 °C) were uncovered by modulation-excitation infrared spectroscopy and density functional theory calculations using a nanoscale Ru particle model. The two most intense N2 adsorption peaks corresponded to the vertical chemisorption of N2 on the nanoparticle's top and bridge sites, while the remaining peaks were assigned to horizontally adsorbed N2 in view of the site heterogeneity of Ru nanoparticles. Long-term observations showed that vertically adsorbed N2 molecules gradually migrated from the top sites to the bridge sites. Compared to those adsorbed vertically, N2 molecules adsorbed horizontally exhibited a lower dipole moment, an increased N─N bond distance, and a decreased N─N bond order (i.e., were activated), which was ascribed to enhanced Ru-to-N charge transfer. H2 molecules were preferentially adsorbed horizontally on top sites and then rapidly dissociated to afford strongly surface-bound H atoms and thus block the active sites of Ru nanoparticles. Our results clarify the controversial adsorption/desorption behavior of N2 and H2 on AS catalysts and facilitate their further development.

The adsorption states of N

The electronic and vibrational structures of 1,2-benzanthracene- h12 ( aBA- h12) and 1,2-benzanthracene- d12 ( aBA- d12) were elucidated by analyzing fluorescence excitation spectra and dispersed fluorescence spectra in a supersonic jet on the basis of DFT calculation. We also observed the high-resolution and high-precision fluorescence excitation spectrum of the [Formula: see text] band, and determined the accurate rotational constants in the zero-vibrational levels of the S0 and S1 states. In this high-resolution measurement, we used a single-mode UV laser whose frequencies were controlled with reference to an optical frequency comb. The inertial defect is negligibly small, the molecule is considered to be planar, and the obtained rotational constants were well reproduced by the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) calculation. Both a-type and b-type transitions are found to be included in the rotationally resolved spectrum, and the a-type contribution is dominant, that is, the transition moment is nearly parallel to the long axis of the aBA molecule. We concluded that the S1 state is mainly composed of the Φ(B) configuration. The observed fluorescence lifetime (106 ns) is considerably longer than that of the Φ(A) system, such as anthracene (18 ns). The transition moment for the lower state of mixed states becomes small, reflecting a near-cancelation of the contributions from the parts of the wavefunction corresponding to the two electronic configurations. The bandwidth of the S2 ← S0 transition is large, and the structure is complicated. It is attributed to vibronic coupling with the high vibrational levels of the S1 state.

CH $_3$ internal rotation is one of the typical large amplitude motions in polyatomic molecules, the spectral analysis and theoretical calculations of which, were developed by Li-Hong Xu and Jon Hougen. We observed a Doppler-free high-resolution and high-precision spectrum of 9-methylanthracene (9MA) by using the collimated supersonic jet and optical frequency comb techniques. The potential energy curve of CH $_3$ internal rotation is expressed by a six-fold symmetric sinusoidal function. It was previously shown that the barrier height ( $V_6$ ) of 9MA- $d_{12}$ was considerably smaller than that of 9MA- $h_{12}$ [M. Baba, et al., J. Phys. Chem. A 113, 2366 (2009)]. We performed ab initio theoretical calculations of the multi-component molecular orbital method. The barrier reduction by deuterium substitution was partly attributed to the difference between the wave functions of H and D atomic nuclei.

In this work, we investigated the mechanisms for the high activity and durability of Rh single nanosized catalysts for the CO–NO reaction in three-way catalysis. For this, we analyzed the relations...

Toward the design and manipulation of innovative materials, we propose a new concept called “model-based research (MBR)”. In MBR, measurable physical and chemical properties of materials are mathematically modelled by explanatory parameters obtained by computer simulation from an atomistic point of view. To demonstrate the potential of MBR, we modelled the molecular weights of a series of polysilsesquioxanes with respect to the H2O/silane molar ratio employed for the polymerization of monomers bis(triethoxysilyl)methane, ethane, ethylene, and acetylene (BTES-M, -E1, -E2, and -E3), as an example. The equation y = axn well reproduced the behaviour of the molecular weights of the BTES series, in which a and n were obtained using the calculated molecular parameters for monomers as the explanatory parameters. Detailed understanding and discussion were theoretically possible on the basis of the mathematical model. We predicted the molecular weights of polymers that would be obtained from monomers BTES-P and BTES-Ph with C3H6 and C6H4 as the spacer, respectively, using the mathematical model. Experimental validation of these polymers clearly showed the possibility of qualitative categorization. Our proposed concept, MBR, is a powerful tool to analyse materials science toward innovative materials design.

Testing the stretching frequency shift of adsorbed CO has been a popular tool to evaluate the chemical property change of catalysts. We demonstrated first-principles models to reveal the mechanism of oxides effect on the frequency shift of CO on the Ni catalysts. Our calculations show that higher coverage of CO molecules leads to blue frequency shift, and there is negligible frequency shift when co-adsorbed with Al2O3 species and red frequency shift when co-adsorbed with ZrO2 or CeO2 species, which are consistent with the experimental literatures. The frequency shift is conformed to be proportional to the charge transfer amount of the π back-donation from Ni to the π⁎ orbital of CO molecule. The frequency shift direction is not determined by whether the oxide species is an electron acceptor or donor when adsorbed on Ni surface, but by how the oxide species affects the electrons on t2g and eg orbitals of the Ni atom under the CO molecule. The redistribution between t2g and eg orbitals induces the decreasing or increasing back-donation when a CO molecule co-adsorbed with the CO molecules or CeO2 species.

[Ir(tpy)2](PF6)3 (tpy = 2,2′:6′,2′′-terpyridine) dissolved in CH3CN was found to exhibit dual color luminescent emission depending on the excitation wavelength. Specifically, blue and green emissions were obtained with excitation at 350 and 410 nm, respectively. Because the associated emission spectra were consistent with those of [Ir(tpy)2]Cl3 in water and [Ir(tpy)2](PF6)3 in the crystalline state, respectively, this dual emission is attributed to emissions from the [Ir(tpy)2]3+ cation and its ion pair [Ir(tpy)2]3+·PF6−. The emission is assigned to the 3π–π* transition of the ligands based on time-dependent density functional theory (TD-DFT) calculations. Conversely, [Ir(tpy)2]I3 in CH3CN shows emission due to [Ir(tpy)2]3+ but not [Ir(tpy)2]3+·I−, while crystalline [Ir(tpy)2]I3 emits red luminescence at 77 K that is inconsistent with that from [Ir(tpy)2]3+. Since the emission energies of crystalline [Ir(tpy)2]X3 (X− = Cl−, Br− or I−) show a good correlation with the electron affinity of X, the emissions are assigned to a counter anion to complex ion charge-transfer transition. This hypothesis is supported by TD-DFT calculations regarding [Ir(tpy)2]3+·X−.

We analysed the H/D isotope effect of CH

We demonstrate thermo-electrochemical (TEC) conversion using a biocompatible redox couple of lactic acid and pyruvic acid on earth-abundant TiO2. The TEC cell exhibited a positive Seebeck coefficient of 1.40 mV K−1. DFT calculations figured out that the adsorption of intermediate species and protons on TiO2 controls both the redox reaction and current polarity.

Detailed information on the H/D isotope effects for adsorption on the surface and absorption in the bulk is important for understanding the nuclear quantum effect. To achieve this purpose, we developed a new theoretical approach, namely, the combined plane wave and localized basis set (CPLB) method. By using the multi-component quantum chemical method, which takes into account the quantum effect of proton or deuteron, with localized part in CPLB method, direct analysis of H/D isotope effect about adsorption and absorption is achieved. In this study, we performed a theoretical investigation of the H/D isotope effects for adsorption on a Pd(111) surface and absorption in bulk Pd. We clearly showed H/D isotope effect on geometry during adsorption and absorption. Our developed CPLB approach is a powerful tool for analyzing the quantum nature of H/D in surface, bulk, and inhomogeneous systems.

The oxidation of carbon monoxide (CO) over PdRu solid solution nanoparticles was studied by the combined theoretical and experimental approaches. In this work, CO and O adsorptions on PdRu alloy surface models were theoretically investigated to understand the kinetics of CO oxidation reaction. It was found that CO adsorption on Pd atom in the PdRu alloy surfaces is weaker than on monometallic surfaces. From the experiment, reaction order of CO on the PdRu surface was observed to be smaller than that on Pd surface. While, the positive first order with respect to O2 obtained for both Pd and PdRu alloy surfaces. Catalytic reaction mechanism is discussed on the basis of both theoretical and experimental observations.

The palladium-hydrogen system is one of the most famous hydrogen-storage systems. Although there has been much research on β-phase PdH(D)x , we comprehensively investigated the nature of the interaction between Pd and H(D) in α-phase PdH(D)x (x

The performance of a solid oxide fuel cell based on BaTiO3 anode improves when H2 and CH4 containing H2S are employed as fuels. In this work, density functional theory calculations were conducted to reveal the origin behind this boost in performance. Our calculations predicted that the sulfidation of the BaTiO3(001) surfaces is possible via different reaction pathways. For the hydrogen oxidation reaction, the presence of sulfur led to the formation of different molecular entities; thus alternative sequences of elementary steps for the reaction to proceed came to light, and no significant detrimental effect was noticed on the adsorption of the species involved. On the other hand, for the methane sequential dissociation, no detrimental effect on the methane activation and the promoted scission of some C–H bonds may be responsible for the mentioned boost in performance.

To understand detailed geometrical changes and electronic structures of the adsorbed water molecules (H2O, D2O, and HDO) and H2O- and D2O-ice Ih(0 0 0 1) basal surfaces induced by the H/D isotope effect, nuclear quantum effects of the proton and deuteron in the first-principles calculations should be considered. We applied our developed combined plane wave and localized basis set (CPLB) method, which can directly treat the electronic structures of the surface and the localized adsorbed region with the nuclear quantum effect, to analyze the H/D isotope effect of adsorbed water molecules on ice. We demonstrated the geometrical change in the adsorbed water and H2O-ice surface due to the H/D isotope effect because the hydrogen bonds involving D (D2O and HDO) were longer than those involving H. Hence, the adsorption energies of D2O and HDO molecules were smaller than those of H2O because of the geometrical changes induced by the H/D isotope effect. The H/D isotope effect led to weaker adsorption energy and longer hydrogen bonds on the D2O-ice surface than those on the H2O-ice surface. We successfully described the H/D isotope effect of water adsorption on the ice Ih(0 0 0 1) surface by directly considering the quantum effect of the proton and deuteron.

We have analyzed the crucial factors that stabilize face-centered cubic (fcc) ruthenium nanoparticles (Ru-NPs) using the density functional theory method. We calculated the cohesive energy of the decahedral fcc, icosahedral fcc, truncated octahedral fcc, and hexagonal close-packed (hcp) Ru-NPs with between 55 and 1557 atoms. The cohesive energy of the icosahedral fcc Ru-NPs became closer to that of the hcp Ru-NPs with decreasing number of atoms, i.e., particle size. This characteristic is mainly caused by the high coordination number of the icosahedral fcc Ru-NP and the negative twin boundary energy for fcc {111}. On the other hand, the d-band center of Ru atoms in the surface layer of icosahedral fcc Ru-NPs is less negative than those of the other structures. This characteristic is caused by the longer interatomic distance between Ru atoms in the surface layer of the icosahedral fcc Ru-NP. Together with the structural stability, the icosahedral fcc structure shows a unique electronic structure compared w...

A one-dimensional microkinetic model combining H and O migration mechanisms is used to simulate the surface diffusion, chemical and charge-transfer reactions near the triple phase boundary of the Ni/YSZ patterned anode. A number of parameter sets are exhaustively examined in the microkinetic schemes to obtain a proper set for the explanation of experimental observations. We find a set of parameters free from unphysical fitting parameters, and can explain a large activity gap of patterned anodes reported in literature. From our simulation, we found that the lower activity patterned anode is kinetically governed by both H and O migration across the triple phase boundary, while the higher activity patterned anodes are governed by the O migration.

We analyzed theoretically the hydrogen absorption properties and kinetics into Pd nanocubes coated with copper(II) 1,3,5-benzenetricarboxylate (HKUST-1), which is a type of metal–organic framework, using density functional theory. We prepared an interface model consisting of the Pd(100) surface and Cu-edged HKUST-1 structure and calculated the hydrogen adsorption and absorption energies in a Pd nanocube model. To discuss the kinetics of the hydrogen absorption, we also evaluated the hydrogen diffusion barrier near the interface. Compared with bare Pd, the hydrogen diffusion barrier from the surface to the subsurface decreased. We found that the adsorption of HKUST-1 on the Pd nanocube leads to chemical and steric effects for the diffusion rate increase of hydrogen. As a chemical effect, hydrogen adsorption was destabilized by the change of electronic structure of the Pd surface because of the atomic charge displacement between the Pd and Cu atoms in HKUST-1. As a steric effect, a new hydrogen diffusion pa...

Introduction Doped lanthanum cobaltite and its derivatives are used as cathode materials in solid oxide fuel cell (SOFC). For a high catalytic activity, the improvement of properties governing the cathode performance is important. It is generally regarded that one of the important factors is the electronic structure of cathode material. Recently, the influence of the lattice strain on the kinetics of the oxygen reduction reaction (ORR) was reported [1]. In addition, the heterostructured oxide interface ((La,Sr)2CoO4±δ/La1-xSrxCoO3-δ (LSC)) and thin-film heterostructure interface (La0.6Sr0.4Co0.2Fe0.8O3-δ/gadolinium-doped CeO2 (GDC)) enhanced the surface oxygen exchange kinetics and ORR activity [2,3]. These results indicate the possibility that the structural change near interface changes the electronic structure of cathode materials. Detailed understandings of electronic structure of doped lanthanum cobaltite near the interface is important to design the high catalytic cathode materials. In this study, we analyzed the stability of oxygen vacancy in LSC of LSC/GDC interface by using the density functional theory (DFT) calculation. Computational Details We used LaO-terminated (001) surface of cubic LaCoO3 crystal structure. Half of La atoms were substituted by Sr atoms in LaO layers in LSC slab model (La6Sr6Co8O28). As a surface of CeO2, we used (111) surface model (Ce14O28) from the surface stability. GDC surface model was prepared based on the previous DFT calculation [4]. The interface of LSC and GDC was modeled from CoO2-terminated LSC(001) and GDC(110) surfaces. The initial spin configuration of Co3+ ion was set as intermediate spin state. GGA-PAW potentials were applied with cutoff energy of 600 eV and 1×1×1 k-points. We employed GGA+U to improve the description of Co 3d and Ce 4f electrons. All DFT calculations were performed by using VASP. Results and Discussion We first analyzed the charge distribution near LSC/GDC interface. In case of LSC/CeO2 interface, the electron transferred from CeO2 to LSC. We clearly observed the larger electron transfer from GDC to LSC. These results indicate that the LSC region near CeO2 or GDC interface shows the negatively charged structure. We analyzed the oxygen vacancy formation energy in LSC. The oxygen vacancy formation energy from surface at LSC/GDC interface was more stable than that of LSC model. Although the oxygen vacancy formation energy from 2ndlayer in LSC model was stable, unstable oxygen vacancy formation energy was obtained in the LSC/GDC interface model. One of the reasons of oxygen vacancy formation energy difference between LSC and LSC/GDC interface is an effect of electron transfer from GDC to LSC. The atomic position change at interface is also influenced the oxygen vacancy formation energy. To see the relation between oxygen vacancy formation energy and distance from interface, we prepared larger LSC/GDC interface models. Details are discussed in the presentation. Acknowledgement This work was supported by CREST, Japan Science and Technology Agency. All calculations were performed on the HA8000 computer systems in Research Institute for Information Technology, Kyushu University. The activities of Advanced Automotive Research Collaborative Laboratory in Hiroshima University are supported by Mazda Corporation. The activities of INAMORI Frontier Research Center in Kyushu University are supported by Kyocera Corporation. References [1] N. Tsvetkov, Q. Li, and B. Yildiz, ACS Nano, 9, 1613 (2015). [2] D. Lee, Y. Lee, W. T. Hong, M. D. Biegalski, D. Morgan, and Y. Shao-Horn, J. Mater. Chem. A, 27, 7910 (2015). [3] E. M. Hopper, E. Perret, B. J. Ingram, H. You, K. Chang, P. M. Baldo, P. H. Fuoss, and J. A. Eastman, J. Phys. Chem. C, 119, 19915 (2015). [4] X. Aparicio-Anglès, A. Roldan, and N. H. de Leeuw, Chem. Mater., 27, 7910 (2015).

The electrode performance in solid oxide fuel cell depends both on electrode materials and microstructure. Therefore, it is important to breakdown the complexity of multi-physics in the porous electrode into processes in different scales. To clarify the multi-physics toward better electrode design, the use of both the advanced measurement and the simulation techniques is inevitable. For this purpose, we have taken the combined top-down and bottom-up approaches. In this manuscript, we discuss the practical issues in multi-scale, multi-physics simulation, focusing on the local activity of Ni-YSZ anode.

Understanding the electrode kinetics in solid oxide fuel cells is important to realize the highly efficient system. Doped lanthanum cobaltite and its derivatives are used as cathode materials in solid oxide fuel cell. As results of considerable number of studies, it is generally accepted that the dissociative adsorption of oxygen at the cathode surface is one of the rate-determining steps. Toward the rational design of cathode materials, we discuss how the electronic structure affects the surface kinetics of doped cobaltite in this study. We focus on La0.5Sr0.5CoO3-δ (LSC) as cathode material and discuss the properties (001) surface with LaO termination based on density functional theory method. We investigated the oxygen adsorption energy and vacancy formation energy by changing the spin states of Co in LSC. The calculated properties are discussed in the context of the kinetic process of oxygen reduction at LSC surface together with future perspectives.

Recently, organic donor-acceptor (D-A) cocrystals have attracted special interest as functional materials because of their unique chemical and physical properties that are not exhibited by simple mixtures of their components. Herein, we report the preparation of one-dimensional novel D-A cocrystals from C60 and 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrin (3,5-TPP); these cocrystals have near-infrared (NIR) light-sensing abilities, despite each of their component molecule individually having no NIR light-sensing properties. Micrometer-sized rectangular columnar C60-3,5-TPP cocrystals were produced by a simple liquid-liquid interfacial precipitation method. The cocrystals exhibit a new strong transition in the NIR region indicative of the existence of charge-transfer interactions between C60 and 3,5-TPP in the cocrystals. The C60-3,5-TPP cocrystals showed n-type transport characteristics with NIR light-sensing properties when the cocrystals were incorporated in bottom-gate/bottom-contact organic phototransistors, revealing that organic cocrystals with suitable charge-transfer interaction are useful as functional materials for the creation of novel NIR-light-sensing devices.

Abstract While Pt-nanoparticles supported on SnO2 exhibit improved durability, a substantial detriment is observed on the Pt-nanoparticles’ activity toward the oxygen reduction reaction. A density functional theory method is used to calculate isolated, SnO2- and graphene-supported Pt-nanoparticles. Work function difference between the Pt-nanoparticles and SnO2 leads to electron donation from the nanoparticles to the support, making the outer-shell atoms of the supported nanoparticles more positively charged compared to unsupported nanoparticles. From an electrostatic point of view, nucleophilic species tend to interact more stably with less negatively charged Pt atoms blocking the active sites for the reaction to occur, which can explain the low activity of Pt-nanoparticles supported on SnO2. Introducing oxygen vacancies and Nb dopants on SnO2 decreases the support work function, which not only reduces the charge transferred from the Pt-nanoparticles to the support but also reverses the direction of the electrons flow making the surface Pt atoms more negatively charged. A similar effect is observed when using graphene, which has a lower work function than Pt. Thus, the blocking of the active sites by nucleophilic species decreases, hence increasing the activity. These results provide a clue to improve the activity by modifying the support work function and by selecting a support material with an appropriate work function to control the charge of the nanoparticle’s surface atoms. Graphic abstract

The triple phase boundary (TPB) of metal, oxide, and gas phases in the anode of solid oxide fuel cells plays an important role in determining their performance. Here we explore the TPB structures from two aspects: atomic-resolution microscopy observation and reaction dynamics simulation. Experimentally, two distinct structures are found with different contact angles of metal/oxide interfaces, metal surfaces, and pore opening sizes, which have not previously been adopted in simulations. Reaction dynamics simulations are performed using realistic models for the hydrogen oxidation reaction (HOR) at the TPB, based on extensive development of reactive force field parameters. As a result, the activity of different structures towards HOR is clarified, and a higher activity is obtained on the TPB with smaller pore opening size. Three HOR pathways are identified: two types of hydrogen diffusion processes, and one type of oxygen migration process which is a new pathway. The triple phase boundary structure in solid-oxide fuel cells largely determines the thermodynamics and kinetics of electrochemical processes therein. Here the authors use atomic-resolution microscopy and reaction dynamics simulation to reveal three discrete hydrogen oxidation reaction pathways.

We investigated H-spillover mechanisms on Pt atoms decorating defective carbon nanocones (Pt/dCNC) using the multicomponent B3LYP (MC_B3LYP) method, which can take account of the nuclear quantum effect (NQE) of light nuclei. MC_B3LYP shows reduced relative energies for all stationary-point structures and lower energy barriers to H-spillover reactions. Interestingly, MC_B3LYP calculations reveal that the activation energy for H2 dissociation completely vanishes indicating that H2 molecules dissociate readily on Pt/dCNC. Our crucial finding is that the different metal (Pt and Pd) on dCNC surface has affected the thermodynamic favorability of the hydrogen dissociation process, on Pt/dCNC is facile and highly exothermic, while on Pd/dCNC is dramatically endothermic. Furthermore, comparison of combined dissociation-spillover mechanism on Pt decorated on carbon nanocone (Pt/dCNC) and Pt decorated on graphene (Pt/dG) catalysts have been focused to explain the curvature effect which can facilitate the hydrogen spillover process and provide a highly exothermic reaction, which is more thermodynamically favorable than that of a metal-graphene surface. Our new understanding of this reaction mechanism and the influence of NQEs on electronic properties will be useful for the future development of the spillover mechanism as well as the synthesis of high-performance Pt/dCNC for H2 energy applications.

Understanding the sintering mechanism of Ni in a solid oxide fuel cell (SOFC) anode is one of the important issues to discuss the long-term durability of SOFC performance. The sintering behavior of Ni is affected not only by the operating temperature but also by the gas composition in the anode chamber. We analyzed the surface diffusion of a Ni adatom and Ni complexes on the Ni(111) surface under the operating temperature and gas compositions in the anode by using density functional theory. The Ni adatom, Ni-H and Ni-S complexes, which can be formed by H2 and H2S in anode gas, were considered as diffusion species on the Ni surface. It is theoretically confirmed that the formation of a NiS complex influences the sintering behavior of Ni depending on the temperature and the impurity H2S concentration in the fuel. Our calculated results are compared with the experimental observation on Ni sintering under various temperatures and H2S concentrations to find a good agreement. We clearly showed the important eff...

The density of states and the H absorption energy of Ag x Rh 1- x alloys were theoretically investigated by the first-principles method. The electronic structure of the alloys near the Fermi edge was similar to that of Pd, which is known as hydrogen-storage metal, and this indicated the electronic state at the part plays important role to determine the H absorption property. The results showed that the H absorption into the Ag x Rh 1- x alloys was thermodynamically stable and the trend of composition dependence agreed well with the experimental observation. Considering the atomic configuration of alloys, homogeneous structure is found to be a key in the emergence of H absorption nature in this alloy system.

We analyzed the X-ray absorption spectra (XAS) of Co 2 p orbital in LaCoO 3 by using density functional theory method to understand the temperature effect on the electronic structures, especially low-spin (LS), intermediate-spin (IS), and high-spin (HS) states of Co 3 + ion. We considered the lattice change, thermal excitation of electrons, and displacement of atoms from equilibrium position in LaCoO 3 as a temperature effect in this study. We observed negligible change in the shape of Co 2 p XAS of LaCoO 3 for each LS, IS, and HS state associated with the lattice expansion due to temperature increase, while different spectral features for LS, IS, and HS states were observed. The change of spectra observed by in situ XAS measurement of LaCoO 3 at Co L II - and L III -edges would be due to the increase in HS and decrease in LS and IS at higher temperature. In addition, the geometry change by thermal displacement of atomic position was analyzed by using first-principles molecular dynamics calculation. Our results indicated that the electronic structure is sensitively changed by the change of Co-O bond distance due to the displacement of atoms from the equilibrium position at studied temperature when the spin state was IS.

A model of Ni-yttria stabilized zirconia (YSZ)-gas triple phase boundary (TPB) is built to simulate the oxygen transfer and hydrogen oxidation processes in solid oxide fuel cell anodes by using density functional theory. The highest barrier in the anodic processes is found in the step of oxygen transfer from the YSZ surface to the TPB site, where the oxygen is connected with nickel and yttrium/zirconium atoms. Three TPB sites and associated reaction paths, near Y or Zr atoms, and one nickel site on the Ni terrace are compared for the hydrogen oxidation reaction. Depending on the local structures of TPB sites, the reaction barrier of the (O + H)* → OH* reaction varies from 0.46 to 0.57 eV, and the reaction barrier of (OH + H)* → H2O* varies from 0.83 to 1.05 eV. When O or OH is on the Ni site, which is only 3 A from the Y at TPB site, the reaction barriers of the above reactions are 1.15 and 1.02 eV, respectively.