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Understanding the nature of H-bonding interactions is essential to modern sciences, such as biology, chemistry, and physics. Using density functional theory calculations, herein, we have identified two unique H-bonding types existing in a single sheet of a mixed water–hydroxyl phase on close-packed metal surfaces, in sharp contrast to conventional H-bonds in liquid water and water ices. Interestingly, the shallow H-bonds show reduced electrostatic and Pauli repulsion interactions, with an electrostatic polar character resulted from complete σ resonances, whereas the deep H-bonds exhibit enhanced electrostatic and Pauli repulsion interactions, with an electrostatic dipolar feature originated from hybrid orbital interactions. A trade-off-like cooperativity law of the two types of H-bonds was discovered, that is, strengthening in the internal bonds (dO–H) leads to weakening in the external bonds (dO:H) or vice versa. However, the shallow H-bonds exhibit a non-linear cooperativity, whereas the deep H-bonds show a linear cooperativity. We also identified an oxygen backbone cooperativity rule that strengthening the adsorbate–metal interactions has a net effect in analogy to reducing the O–O repulsion within the adlayer. Furthermore, we have discovered several universality classes in geometrical, vibrational, and electronic spaces for the two H-bonding types. Although shared by electronic universality classes, the two contrasting H-bonding types are featured by divergent trends with significant overlapping, where competitive variations in the electrostatic and Pauli repulsion strengths are basic rules for the cooperative H-bonding types. The knowledge of the unconventional H-bonding types expands our current understanding of H-bonding interactions in liquid water and water ices and points to the importance of H-bonding manipulation at electronic levels. These findings not only shed new light on probing the fundamental nature of H-bonds in general but also have insightful implications for resolving the cooperative H-bonding nature of interfacial water, liquid water, water ices, and aqueous solutions. Published version This work was supported by Na- tional Natural Science Foundation of China under Contract No. 21875024.

Photocatalysis activated by visible light remains highly challenging. Here, we report novel MoSe2/ZnO/ZnSe (ZM) hybrids fabricated via a simple hydrothermal method for photocatalytic reduction of Cr(VI) under visible light irradiation. ZM hybrids show improved photocatalytic reduction ability under visible light irradiation compared to pure ZnO owing to good visible light absorption and rapid electron transfer and separation. The ZM hybrid shows the highest Cr(VI) reduction rate of 100%. Moreover, the photocatalytic Cr(VI) reduction process is mainly controlled by photoinduced electrons.

Bond relaxation from one equilibrium to another under perturbation matters uniquely the performance of a substance and thus it has enormous impact to materials science and engineering. However, the basic rules for the perturbation-bond-property correlation and efficient probing strategies for high-resolution detection stay yet great challenge. This treatise features recent progress in this regard with focus on the multifield bond oscillation notion and the theory-enabled phonon spectrometrics. From the perspective of Fourier transformation and the Taylor series of the potentials, we correlate the phonon spectral signatures directly to the transition of the characteristic bonds in terms of stiffness (frequency shift), number fraction (integral of the differential spectral peak), structure fluctuation (linewidth), and the macroscopic properties of the substance. A systematic examination of the spectral feature evolution for group IV, III-V, II-VI crystals, layered graphene nanoribbons, black phosphor, (W, Mo)(S2, Se2) flakes, typical nanocrystals, and liquid water and aqueous solutions under perturbation has enabled the ever-unexpected information on the perturbation-bond-property regulations. Consistency between predictions and measurements of the crystal size-resolved phonon frequency shift clarifies that atomic dimer oscillation dictates the vibration modes showing blueshift while the collective vibration of oscillators formed between a certain atom and its nearest neighbors governs the modes of redshift when the sample size is reduced. Theoretical matching to the phonon frequency shift due to atomic undercoordination, mechanical and thermal activation, and aqueous charge injection by solvation has been realized. The reproduction of experimental measurements has turned out quantitative information of bond length, bond energy, single bond force constant, binding energy density, vibration mode activation energy, Debye temperature, elastic modulus, and the number and stiffness transition of bonds from the mode of references to the conditioned upon perturbation. Findings prove not only the essentiality of the multifield lattice oscillating dynamics but also the immense power of the phonon spectrometrics in revealing the bond-phonon-property correlation of solid and liquid substance.

Exploiting efficient visible light active photocatalyst is a great challenge with potential applications such as environmental pollution and solar energy conversion. Herein, a series of CaIn 2 S 4 /WS 2 hybrids was fabricated via a simple hydrothermal method. WS 2 as cocatalyst increases the visible light absorption and separation efficient of charge carrier at the interface, leading to the enhanced photocatalytic activity of CaIn 2 S 4 /WS 2 . CaIn 2 S 4 /20 wt% WS 2 hybrid shows the highest Cr(VI) reduction rate of 98% and methyl orange degradation rate of 96%. This work could offer some thought for designing and fabricating hybrid photocatalyst with high efficient and stable activity. Financial support from the province Natural Science Foundation of Zhejiang Province (No. LY18E060005, LY18E020007, LY19E020006 and LQ18E030005) is gratefully acknowledged.

The theoretical prediction of the catalytic activity is very beneficial for the design of highly efficient catalysts. At present, most theoretical descriptors focus on estimating the catalytic activity and understanding the enhancement mechanism of catalysts, while it is also quite important to find a factor to correlate the descriptors with preparation methods. In this work, a correlation factor, the d electron density of transition metal ions, was developed to correlate the d band center values of transition metal ions with the preparation methods of amorphization and Al introduction. According to the results of theoretical simulations, the correlation factor not only exhibited favorable linear relationships with the theoretical overpotentials of (CoFeAlx)3O4 and (CoFeAlx)3O4 + (CoFeAlx)OOH systems but also correlated with two preparation methods by altering the volume of systems. Based on theoretical guidance, the electrocatalytic activities of the prepared (CoFeAlx)3O4 specimens were gradually improved by the preparation methods of amorphization and Al introduction, and the Am-CoFeAl-2-10h specimen exhibited a low kinetic barrier of 268 mV, fast charge transfer rate, and stable electrocatalytic activity. This strategy could be applied to design highly efficient catalysts by adjusting the correlation factor of the active site with suitable preparation methods.

Summary The long-standing performance-stability contradiction issue of high energy density materials (HEDMs) is of extremely complex and multi-parameter nature. Herein, machine learning was employed to handle 28 feature descriptors and 5 properties of detonation and stability of 153 HEDMs, wherein all 21,648 data used were obtained through high-throughput crystal-level quantum mechanics calculations on supercomputers. Among five models, namely, extreme gradient boosting regression tree (XGBoost), adaptive boosting, random forest, multi-layer perceptron, and kernel ridge regression, were respectively trained and evaluated by stratified sampling and 5-fold cross-validation method. Among them, XGBoost model produced the best scoring metrics in predicting the detonation velocity, detonation pressure, heat of explosion, decomposition temperature, and lattice energy of HEDMs, and XGBoost predictions agreed best with the 1,383 experimental data collected from massive literatures. Feature importance analysis was conducted to obtain data-driven insight into the causality of the performance-stability contradiction and delivered the optimal range of key features for more efficient rational design of advanced HEDMs., Graphical abstract, Highlights • Crystal-level quantum mechanics calculations of 21,648 physicochemical data of 153 HEDMs • Machine learning of detonation and stability of HEDMs and experimental validation • Data-driven insight into the causality of performance-stability contradiction • Optimal range of key features for rational design of advanced HEDMs, Computational Materials Science; Computational Method in Materials Science; Energy Materials; Materials Design

We systematically examined the effect of (H, Li)Cl and LiOH solvation on the O:H[sbnd]O bond network deformation, surface tension (contact angle), solution electrical conductivity, thermomics, and viscosity evolution aiming to clarifying the functionalities for ions, lone pairs, and protons acting in these solutions. Results confirmed that H + and electron lone pair ‘:’ introduction turns out the (H 3 O + , OH − )·4H 2 O motifs and that the Li + and Cl − form each a hydration volume through the screened electrostatic polarization. The (H 3 O + , OH − )·4H 2 O turns an O:H[sbnd]O bond into the H ↔ H anti–HB that disrupts the HCl solution network and its surface tension and into the O:⇔:O super–HB compressor that raises the LiOH solution surface tension and viscosity, as well as the solution temperature during solvation. The Li + /Cl − ion reserves/reduces its hydration volume because of the complete/incomplete screen shielding by the ordered hydrating H 2 O dipoles and the Cl − ↔ Cl − repulsion at higher concentrations. The invariant/variant Li + /Cl − hydration volume dictates, respectively, the linear/nonlinear concentration dependence of the Jones–Dole viscosity. Except for the HCl/H 2 O surface tension and LiOH/H 2 O viscosity, the conductivity, surface tension, and viscosity of these solutions follow the Jones–Dole notion that underscores the faction of bond transition from the mode of water to hydration. Accepted version

Pentazole anion, the best candidate for full-nitrogen energetic materials, can be isolated only from acidic solution for unclear reasons, which hinders the high-yield realization of a full-nitrogen substance with higher energy density. Herein, we report for the first time the discovery of the dual aromaticity (π and σ) of cyclo-N5–, which makes the anion unstable in nature but confers additional stability in acidic surroundings. In addition to the usual π-aromaticity, similar to that of the prototypical benzene, five lone pairs are delocalized in the equatorial plane of cyclo-N5–, forming additional σ-aromaticity. It is the compatible coexistence of the inter-lone-pair repulsion and inter-lone-pair attraction within the σ-aromatic system that makes the naked cyclo-N5– highly reactive to electrophiles and easily broken. Only in sufficiently acid solution can the cyclo-N5– become unsusceptible to the electrophilic attack and gain extra stability through the formation of hydrogen-bonded complex from surrounding electrophiles; otherwise, the cyclo-N5– cannot be productively isolated. The dual aromaticity discovered in cyclo-N5– is expected to be universal for pnictogen five-membered ring systems. Accepted version Financial support from the National Natural Science Foundation of China (Nos. 11604017, 11572053, and U1730244), the Science Challenging Program of China (No. TZ2016001), and the National Supercomputing Center (Shenzhen) and helpful discussions with B.C. Hu, M. Gozin, M. Š ob, E. Hayward, C.Y. Zhang, J.G. Zhang and H.H. Zong are gratefully acknowledged.

It has been a long pursuit to discriminate the ionic roles of mono- and di-valent salt solutions in modulating the hydrogen bonding network and solution properties. We attended this issue by examining the effect of concentrated YX 2 (Y[dbnd]Mg, Ca, Sr; X[dbnd]Cl, Br) solvation on O:H–O bonds transition from the mode of ordinary water to hydration in terms of the number fraction f YX2 (C) and the segmental O:H–O bond phonon stiffness shift Δω(C) with C being the solute concentration. The invariant df Y (C) / dC at C ≤

We investigated the bond, electronic and magnetic behavior of adsorption Yttrium atoms on Lithium (110) surface using a combination of Bond-order-length-strength(BOLS) correlation and density-functional theory(DFT). We found that adsorption Y atoms on Li(110) surfaces form two-dimensional (2D) geometric structures of hexagon, nonagon, solid hexagonal, quadrangle and triangle. The consistent with the magnetic moment are 6.66{\mu}B, 5.54{\mu}B, 0.28{\mu}B, 1.04{\mu}B, 2.81{\mu}B, respectively. In addition, this work could pave the way for design new 2D metals electronic and magnetic properties. Financial support was provided by the NSF (Grant No. 11747005), the Science and Technology Research Program of Chongqing Municipal Education Commission (Grant No. KJ1712299) and Yangtze Normal University (Grant No. 2016XJQN28 and 2016KYQD11).

Understanding the performance of individual ions in salt solutions and the consequence of ionic hydration on hydrogen bonding network distortion, surface stress, and solution viscosity remains great challenge. We show herein findings pertained to alkali halide YX solutions using differential phonon spectroscopy (X = Cl, Br, I; Y = Li, Na, K, Rb, Cs): (i) an ion occupies eccentrically the tetrahedrally-coordinated interstitial of water to form a (±:4H2O:6H2O) hydration cell without bonding to H2O molecules; (ii) ionic polarization shortens and stiffens the H-O bond while does the O:H nonbond contrastingly; (iii) the screening of the hydrating water dipoles limits the cation hydration cell to be size invariant while the inter-anion repulsion reduces its hydration volume by weakening the anionic long-range electric field when the ionic separation shrinks; and (iv) the polarization of cation and anion dictates respectively the linear and the nonlinear part of Jones-Dale’s viscosity and surface stress. Findings would provide profound impact to the understanding and deep engineering of water, ice, and aqueous solutions.

Intermetallic alloy has become a hot topic in heterogeneous catalysis due to improved activity and stability. We report here the results of Pd monolayer supported on face-centered tetragonal (fct) Pd-M (M = Ni or Fe) intermetallic alloy as cathode materials by first principle calculations. Adsorbed O2 is found to undergo hydrogenation process into OOH instead of direct dissociative mechanism. The oxygen reduction reaction (ORR) proceeds via four-electron transfer pathway on both surfaces. The enhanced activities are ascribed to moderate adsorption strength for ORR intermediates due to compression strain and substrate electron transfer. The dissolution potential analysis indicates that both Pd/PdNi(111) and Pd/PdFe(111) are stable under operating condition. Gibbs free energy analysis and barrier calculations suggest that the proposed Pd monolayer structures are promising for cathode material. These results can be useful in designing intermetallic Pd-M alloy as ORR electrocatalysts.

Freezing-thawing cycling of salt solutions is ubiquitously important to fields varying from biochemistry to agriculture, climate, and geological engineering. However, understanding the dynamics of energy exchange and freezing-temperature TN shift during phase transition of the concentrated solutions remains elusive despite intensive investigations since the discovery of Homeister series in 1888. Here we address this issue by focusing on the performance of the hydrogen bond (O:H O) in the fraction fS molecules of the hydrating supersolid phase and in the remaining fraction fO molecules of the pristine phase during NaCl solution ice formation. The supersolid formation is related to the effect of ionic polarization that shortens and stiffens the H O bond, while lengthening and weakening the O:H non-bonding interactions in the hydration cells. The supersolid phase is gel-like, less dense, viscoelastic, and mechanically and thermally stable. We demonstrate that the polarization-weakening of the O:H non-bonding interactions of the supersolid phase reduces the TN of the solution and that the H O cooling contraction in the quasisolid (QS) phase of the pristine water absorbs energy during the Liquid-QS-Ice transition of solution. At fS = 1, neither TN nor energy absorption is resolved within the range of 273 ± 20 K. The least saturation number of molecules is 10 per pair of Na+ and Cl− ions. These findings shall help to develop solutions with tunable TN for practical applications and to understand the mechanism of energy exchange during phase transition in the temperature and time domains.

Deep engineering of liquid water by charge and impurity injection, charged support, current flow, hydrophobic confinement, or applying a directional field has becoming increasingly important to the mankind toward overcoming energy and environment crisis. One can mediate the processes or temperatures of molecular evaporation for clean water harvesting, H O bond dissociation for H2 fuel generation, solidification for living-organism cryopreservation, structure stiffening for bioengineering, etc., with mechanisms being still puzzling. We show that the framework of “hydrogen bonding and electronic dynamics” has substantiated the progress in the fundamental issues and the aimed engineering. The segmental disparity of the coupled hydrogen bond (O:H O or HB with “:” being lone pair of oxygen) resolves their specific-heat curves and turns out a quasisolid phase (QS, bound at −15 and 4 °C). Electrification shows dual functionality that not only aligns, orders, polarizes water molecules but also stretches the O:H O bond. The O:H O segmental cooperative relaxation and polarization shift the QS boundary through Einstein's relation, ΔΘDx ∝ Δωx, resulting in a gel-like, viscoelastic, and stable supersolid phase with raised melting point Tm and lowered temperatures for vaporization TV and ice nucleation TN. The supersolidity and electro structure ordering provide additional forces to reinforce Armstrong's water bridge. QS dispersion and the secondary effect of electrification such as compression define the TN for Dufour's electro-freezing. The TV depression, surface stress disruption, and electrostatic attraction raise Asakawa's molecular evaporability. Composition of opposite, compatible fields eases the H O dissociation and soil wetting. Progress evidences not only the essentiality of the coupled O:H O bond theory but also the feasibility of engineering water and solutions by programmed electrification.

Atoms with even fewer neighbors perform both atomic like and bulk like associated with shorter and stronger interatomic bonds. The bond contraction raises the local charge and energy density and the bond strength gain deepens the local potential well and entraps the core electrons. The locally and densely entrapped core electrons in turn polarize the valence electrons. The subjective valence electron polarization occurs to those atoms with unpaired lone electrons in the s orbitals such as Rh, Au, Ag, Cu and the unpaired 4f145d46s2 (5d56s1 seems to be stable) electrons of the W adatoms and Mo(4d55s1) as well. However, the Co(3d74s2) with fully-occupied s electrons and the Re(5d56s2) with semi-occupied d electrons exhibit entrapment dominance. The undercoordination resolved valence electron entrapment or polarization laid foundations for the extraordinary catalytic ability of the excessively undercoordinated atoms and the dispersed single atom.

Physical perturbation mediates material’s properties by relaxing the interatomic bonding and electron configuration in various bands. Phonon spectroscopy probes bond relaxation or bond tranformation from one equilibrium to another under perturbation and electron spectroscopy fingerprints bond-relaxation induced electronic configuration, which have important impact to chemistry, physics, and material engineer and science. However, extracting information from the phonon spectroscopic measurements and gaining consistent insight into the physics behind observations are still infancy compared to crystallography and surface morphology because of lacking basic regulations. Conventional decomposition of spectral peaks or empirical simulation of spectral evolution under perturbation provide limited information with freely adjustable parameters and debating mechanisms. The featured multifield phonon spectrometrics aims to extracting atomistic, local, and quantitative information on the bonding and nonbonding dynamics and their correlation to performance of a variety of substances under external perturbations.

Electron binding energy shift directly features the change of bond energy with coordination environments and chemical conditions, from which one can evaluate the local and quantitative information on the local bond length, bond energy, core charge entrapment and valence electron polarization. Bonds and electrons associated with undercoordinated adams, point defects, skins, and nanostructures follows the BOLS-NEP notion but bonds associated with the hetero-coordinated and the tetrahedrally-coordinated impurities and interfaces may subject to bond nature alteration and the local electrons may subject to entrapment or polarization.

Decomposition of the XPS profiles into components of sublayers derives information on the local bond length, bond energy, atomic cohesive energy, binding energy density, and the energy levels Eν(0) of an isolated atom and its shift with the coordination environment. The Eν(0) and Eν(12) remain constant and the atomic CN varies only with the layer order and surface registry, regardless of the skin chemical constituent. Atomic undercoordination induced bond contraction drives relaxation and reconstruction of the surface of a crystal.

A physical perturbation mediates intrinsically the performance of a substance through relaxing the length and energy of the chemical bonds and associated electrons in various energy bands. From the perspective of Fourier transformation, one can formulate the bond oscillation frequency ∆ω (z, d, E, μ) for a variety of materials by perturbing the Hamiltonian. Reproduction of the excited ∆ω by a perturbation xi such as bond-order-imperfection, electric polarization, compression, tension, and thermal activation turns out information on the bond length d(xi), bond energy E(xi), single-bond force-constant, binding energy density, mode cohesive energy, Debye temperature, elastic modulus, etc., complementing the electron spectrometrics. Exercises proved the immense power of the phonon spectrometrics in revealing the nature behind the lattice vibration in terms of multifield single-bond oscillation dynamics in liquid and solid phases.

Like adatoms, monoatomic chain ends, and atomic clusters with even less-coordinated atoms demonstrate extraordinary properties due to dominance of stronger quantum entrapment and polarization. Consistency between quantum calculations and XPS/STS observations resolves the origin of the unusual performance of such even undercoordinated atoms. A combination of the XPS and AES, called APECS, refines the energy shifts of both the core band and the valence band with derived information of the screening effect and charge transport during reaction.

A set of analytical strategies has enabled atomistic, local, dynamic, and quantitative information on the bonding and electronic energetics induced by atomic under- and hetero-coordination. With the aids of the ZPS, one can purify the energy states with high precision without needing decomposition of the spectral peaks. APECS and NEXAS probe simultaneously the shifts of a core and the valence energy bands with provision of the screening and recharging information. Quantitative information includes the bond length, bond energy, core level shift, core charge entrapment and valence electron polarization, atomic cohesive energy, and binding energy density. Such a collection of information is fundamentally crucial to designing and synthesizing functional materials.

A combination of the hetero- and under-coordination forms a promising means of mediating the bonding and electronic dynamics and properties of a substance as the hetero- and under-coordination enhance each other on the charge entrapment and polarization. However, at a critical size, polarization may compensate or override quantum entrapment because of the polarization screens and splits the interatomic potentials.

VLLED has enabled quantification of the four-stage Cu3O2 pairing-tetrahedra formation in the Cu(001) surface transiting from O− to O2− with production of the missing rows, Cu-O-Cu chains, oppositely paired Cup crossing the missing rows. The surface stress turns from tensile in the O− derived first phase to the O2− derived second phase. The phase transition dynamics is beyond the scope of computations from the perspective of total energy minimization or structural optimization. Annealing relaxes the Cu3O2 bond geometry, the SPB, and the valence states accordingly while heating at a dull-red color de-hybridizes the sp orbits of oxygen, desorption will occur at higher temperatures.

Phonon spectrometrics examination of the effect of pressure, temperature, molecular undercoordination, and charge injection by acid, base, and salt solvation establishes the regulations for the hydrogen bonding and electronic dynamics and the properties of the deionized water and aqueous solutions. Consistency between theory and measurements confirms the essentiality of the quasisolid phase of negative thermal expansion due to O:H–O segmental specific heat disparity, and the supersolid phase due to electrostatic polarization by ions injection or molecular undercoordination. Lewis acid and base solvation creates the H↔H anti–HB due to the excessive protons and the O:⇔:O super–HB because of the excessive lone pairs, respectively. The multifield mediation of the HB network results in anomalies of water ice and aqueous solutions such as ice friction, ice floating, regelation, superheating and supercooling, warm water speedy cooling, and critical conditions for phase transition. Extending the knowledge towards the deep engineering of liquid water would be promising.

The presence of the nonbonding XH tension constrains and the presence of the anti or super hydrogen bond fosters the explosion in aqueous alkali and molten alkali halides; the combination of the coupled hydrogen bond and the repulsive anti or super hydrogen bond not only stabilzes the structure but also stores energy of the energetic molecular assemblies by shortening all covalent bonds., Comment: 4 figure, 3500 works

Hetero-coordinated bond formation changes the local bond strength and charge distribution. Polarization dominance reduces the CL and makes the alloy a donor-like catalyst with weakened interface mechanical strength; entrapment dominance does it contrastingly. The ZPS offers such a unique yet straightforward means that diagnosis the interface bonding and electronic dynamics in alloys, compounds, impurities, and interfaces for devising functional substance.

Oxide tetrahedral bond formation with orbital occupation by the shared bonding and nonbonding electron pairs determine uniquely the bond geometry, valence density of states, and the surface potential barrier. Parameterization of all involved parameters as a function of the bond angle and length and the origin of the SPB not only simplified the calculations but also importantly ensured the solution approaching true situations.

O-Cu(001) chemisorption derives the Cu3O2 pairing-tetrahedronand the Cup:O2−:CuP chains lined along the missing-raw edges, which roughen the SPB and the surface morphology. At the dipole site, The origin of the SPB moves \(\sqrt {2}z_{0}\) outwardly with \(\sqrt {2}\lambda_{0}\) saturation degree, at the atomic vacancy site, the SPB is characterized by \(z_{0} /\sqrt 2\) and \(\lambda_{0} /\sqrt 2\), with z0 and λ0 being the references for clean Cu(001) surface. Connecting the Bragg diffraction peaks results in the first and the second two-dimensional Brillouin zones with the 〈11〉 direction deformation corresponding to a 0.22 A dislocation of the Cup towards the MR. Matching the theoretical Brillouin zones derived the electronic effective mass of \(m_{1}^{*}\) = 1.10, and \(m_{2}^{*}\) = 1.14 at the boundaries.

VLEED offers such a unique tool that collects information of bond geometry, valence density-of states (DOS), and SPB outside the second atomic layer with high sensitivity and reliability. Based on the principle of Fourier transformation, VLEED calculation derives consistent information obtained with electron spectroscopy, crystallography, and morphology on an atomic scale.

The inter oxygen repulsion opposes compression minimizing the compressibility. Polarization enlarges the bandgap and the dielectric permittivity of water ice by raising the nonbonding states above the Fermi energy. Progress evidences the efficiency and essentiality of the coupled hydrogen bonding and electronic dynamics in revealing the core physics and chemistry of water ice, which could extend to other molecular crystals such as energetic materials., Comment: 15 k words, 118 refs, 17 figures

Density functional computation revealed that in YOH solvation (Y = Li, Na, and K), the Y+ cation locates eccentrically at the interstitial hollow site to form the Y+·4H2O unit, and the hydroxyl adds an excessive electron lone pair ":" to form a OH-·H2O unit where the hydroxide stays in the the center. The surrounding four oriented H2O neighbors interact with the Y+ through Y+ ↔ H+ repulsion and Y+:O2- attraction, causing the Y+ eccentric dislocation by some 0.80 A. The ":" turns one O:H-O bond into the O: ⇔ :O super hydrogen bond by altering H2O·4H2O into HO-·4H2O. The repulsive Y+ ↔ H+ enlarges its separation and the attractive Y+:O shortens itself, showing the anisotropic polarization of the Y+ cation. The anisotropic Y+ polarizability, O: ⇔ :O compressibility, and the H-O bond contraction of the solute OH- distorts the solute bonding network and disperses the O:H-O segmental phonon frequencies, as confirmed spectroscopically.

To design a catalyst for the dissociation of H2 with better CO-tolerance performance is very important for proton exchange membrane fuel cells (PEMFCs) towards high efficiency. With slab model, the catalytic properties of overlayer Pt on Cu substrate (Pt/Cu) are analyzed by first-principle calculations. The CO saturation coverage (40%) on Pt2/Cu is found to be lower than that of pure Pt (about 75%). The dissociation barrier from H2 to H is less than 0.4 eV under the saturation coverage of CO. On the basis of kinetics of proton formation, the CO-tolerance ability on double-layer Pt with Cu is found to be greatly improved compared with that on pure Pt. It is expected that Pt overlayer on Cu(1 1 1) is a potential anode material with lower cost for PEMFCs.

A novel system combining photocatalysis and capacitive deionization (CDI) was proposed and used to efficiently remove the total Cr from the aqueous solution for the first time. MIL-53(Fe) with wide visible-light absorption was successfully prepared by a simple solvothermal method, and applied as positive photoelectrode material of the photocatalysis-CDI system (PCS) to convert Cr(VI) to Cr(III). Active carbon was used as negative electrode material to absorb Cr(III). An enhanced removal of Cr(VI) can be obtained by applying visible light irradiation and 1.3 V direct current (DC) voltage simultaneously and the Cr(VI) removal can reach a maximum value of 81.6%, much higher than those under individual 1.3 V DC voltage (39.4%) or visible light irradiation (54.2%), demonstrating the synergistic effect from CDI and photocatalysis. More importantly, effective removal of the total Cr with high removal ratio (72.2%) can be achieved, which is difficult to be realized using current other technologies. The strategy in this work provides a promising method for the complete removal of high-valence heavy metal ions.

Heteroatom doping is known as an effective strategy to improve the electrochemical performance of carbon materials. In this work, phosphorus (P)-doped carbon nanofiber aerogels (P-CNFA) were prepared from bacterial cellulose via freeze-drying and thermal treatment. The structure and electrochemical characterizations show that P-CNFA exhibit a porous, interconnected, well-organized 3D network structure and P doping can enhance the specific surface area, facilitate the charge transfer, and thus improve the specific capacitance and electrosorption capacity of CNFA. Especially, the electrosorption capacity of P-CNFA can reach up to a high value of 16.20 mg g−1 in 1000 mg L−1 NaCl solution, much higher than that of undoped CNFA (12.81 mg g−1). These results indicate that P-CNFA should be a promising candidate for capacitive deionization application.