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The perovskite-type hydride compounds are potential candidate materials in the field of hydrogen storage. This paper presents a systematical study of XTiH 3 (X = K, Rb, Cs) using density functional theory. The analysis of formation energy, elastic properties and phonon dispersion curves indicate that all the studied materials are thermodynamically, mechanically and dynamically stable. By analyzing the B/G ratio, it is determined that these compounds are brittle materials. The electronic properties reveal that the XTiH 3 compounds exhibit semi-metallic characteristics. The charge transfer characteristics of these compounds were analyzed using Bader partial charges. Moreover, the thermodynamic characteristics of these compounds were investigated and the dependence of their free energy, entropy and heat capacity on the temperature were analyzed. Finally, the gravimetric hydrogen storage capacities of KTiH 3 , RbTiH 3 and CsTiH 3 were calculated to be 3.36, 2.22 and 1.65 wt%, respectively. The hydrogen desorption temperatures of KTiH 3 , RbTiH 3 and CsTiH 3 were found to be 209 K, 161 K and 107 K, respectively. To our knowledge, this study represents the very first investigation of XTiH 3 compounds and offers valuable references to this hydrogen storage material. [Display omitted] • XTiH 3 (X = K, Rb, Cs) perovskite have been investigated using first-principles. • XTiH 3 perovskite exhibit thermodynamic, mechanical and dynamical stability. • The gravimetric hydrogen storage capacity is found to be 3.36 wt% for KTiH 3. [ABSTRACT FROM AUTHOR]

The effects of pressure on the mechanical, electrical structure, and optical characteristics of cubic fluoroperovskite XMgF 3 (X = Al, Ga, In, Tl) are investigated based on the first principles methods. The calculated lattice constants are in good agreement with those in the literature. According to the mechanical properties, all the compounds exhibit ductility and anisotropy, and the inter-atomic binding bonds of these materials are ionic. According to Kleinman's parameter, bond stretching is dominant in XMgF 3 (X = Al, Ga, In, Tl). Among all studied compounds, AlMgF 3 carries the highest machinable index, indicating that it is the most machinable and suitable material for industrial applications. The electronic structures show that AlMgF 3 and InMgF 3 are indirect bandgap semiconductors, while GaMgF 3 and TlMgF 3 are direct bandgap insulators at 0 GPa. The values of band gap for all the compounds decrease with the increasing pressure. X-s and F-p orbital states contribute primarily to the top of the valence band, whereas X-p orbital states dominate the bottom of the conduction band. The overall shape of electron state density under pressure does not change significantly, but its peak widens. The optical properties of XMgF 3 (X = Al, Ga, In, Tl) crystal at zero pressure and high pressures are further investigated. The results indicate that XMgF 3 compounds have outstanding ultraviolet (UV) absorption properties and could be used in UV optical devices. Moreover, the low reflectivity values of XMgF 3 crystals make the compounds potential anti-reflective coating materials. [ABSTRACT FROM AUTHOR]

Theoretical studies demonstrated that P350 is a promising extractant for separation of neptunium and plutonium. [Display omitted] • The complexation behaviors of Np(IV,V,VI) and Pu(IV) with three neutral phosphate ligands were explored by DFT. • These phosphate ligands have the ability to Pu(IV)/Np(IV) and Np(VI)/Np(V) separation. • The complexing ability of P350 is stronger than TBP and TiAP. • P350 is the more promising extractant for separation of Np and Pu in nitric acid solution. Effective treatment of the transuranic neptunium and plutonium from nuclear waste is of great importance and remains a challenge for developing advanced nuclear fuel cycles. Currently, novel ligands for efficient separation of actinides need to be designed urgently. Neutral extractants containing phosphorus have shown great potential for actinides separation. In this paper, we systematically explored the extraction and separation performances of neptunium(IV,V,VI) and plutonium(IV) by three phosphorus derivatives, di(1-methyl-heptyl) methyl phosphonate (P350), tri- iso -amyl phosphate (TiAP), and tributyl phosphate (TBP) by density functional theory (DFT). The outcomes showed that these neutral phosphorus reagents act as monodentate ligands through the P O group for all the extraction complexes. According to bonding nature analysis, the P350 ligand has the strongest complexing ability to the studied actinide cations. In addition, these ligands show a preference to coordination with Pu4+ and NpO 2 2+ over Np4+ and NpO 2 +, respectively. As expected, the thermodynamic analysis demonstrated the potential application of these neutral extractants in Np and Pu separation, among which the P350 ligand is more promising than TBP and TiAP in acid solution system. This work can help to further understand the separation mechanism of Np/Pu with neutral phosphorus reagents and provide insight into the development of highly efficient extractants in recovery of Np and Pu. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) surfaces with rich and diverse oxygen-containing functional groups might endow GOs with unique chemical adsorption activity. Exploring the adsorption behavior of gas molecules on GOs with different degrees of oxidation can help design highly efficient adsorbents and catalysts. Herein, the interaction energies between two kinds of gas molecules, CH 4 and CO 2 , and the GO surfaces with varied oxidization degrees were simulated by density functional theory. It is numerically demonstrated that CO 2 has a stronger interaction strength than CH 4. More specifically, the interaction energies for the gases on GO surfaces do not show monotonous variation with the degree of oxidization. The results suggest that there exists an appropriate range of oxidized degrees on GOs, which can impose higher adsorption interaction. The AIM (atom in molecule) and NOCV (natural orbital for chemical valence) analyses were applied to reveal the interaction mechanisms between the gas molecules and GO surfaces. The adsorption free energy and adsorption coverage of CH 4 and CO 2 on GO surfaces were calculated. Generally, the gas adsorption on GO is thermodynamically unfavorable under standard conditions. The computational results provide an improved understanding of the adsorption mechanism, which might be valuable for the application of high-performance GO-based adsorbents and catalysts. • Interaction mechanism of CH 4 /CO 2 on GO surfaces was simulated by DFT. • Interaction energy shows nonmonotonic variation with surface oxygen concentration. • CO 2 has a stronger interaction strength on GOs than CH 4 due to distinctive binding modes. • Thermodynamic free energies of CH 4 /CO 2 on GOs were estimated for varied conditions. [ABSTRACT FROM AUTHOR]

• Carbazole and triphenylamine substituted zinc porphyrins are synthesized. • Electronic property of porphyrins is calculated by density functional theory. • Dye structure impacts interfacial charge separation and transport efficiencies. • Triphenylamine- superiors carbazole-zinc porphyrin in AB1 photodegradation. • Superoxide radicals and holes are the main reactive species in photocatalysis. Porphyrin-sensitized semiconductor particles can intensely absorb light in the visible wavelength range. Modification on molecular structure by either tuning the substituent species or elongating the distance between the second chromophore and porphyrin core may reduce interfacial electron-hole recombination and thus improving photocatalytic activity. Two zinc porphyrins are synthesized and doped on TiO 2 for photodegrading an organic pollutant AB1. Electronic structure of the molecules is studied by density functional theory calculations, showing more delocalized electron density on TPA-BiPh-ZnP than Cb-Ph-ZnP. Photo-electrochemical impedance measurements suggest greater electron-hole separation and interfacial charge transport efficiencies of TPA-BiPh-ZnP/TiO 2 than Cb-Ph-ZnP/TiO 2. Both composites perform promising photodegradation activity of AB1, with superoxide radicals (•O2−) and holes (h+) as the major reactive species at the reaction interfaces. Importantly, TPA-BiPh-ZnP/TiO 2 exhibits faster degradation kinetics than Cb-Ph-ZnP/TiO 2 , reaching a C/C 0 value of 10% within 60 min. [Display omitted] [ABSTRACT FROM AUTHOR]

• Density functional theoretical calculations were used to predict the complex structures of benzyl radical and chloride as well thermodynamic properties for electroreduction reaction of benzyl chloride on silver cathodes. • Surface-enhanced Raman feature of chemisorbed intermediates has a very strong Raman band from the wagging vibration of benzyl radical adsorbed on silver cathodes. • The high electrocatalytic activity of silver cathode arises from the synergetic effect of the thermodynamics and kinetics of the first electron transfer reaction. The reductive cleavage of carbon-halogen bonds is one of the classical model systems of concerted versus non-concerted bond breaking electron transfer in molecular electrochemistry, but most studies did not consider the influence of adsorption of reaction intermediates on this phenomenon. We performed density functional theory (DFT) calculations to understand the electrochemical reduction of benzyl chloride at silver electrodes through predicting the surface adsorption effect of the reactant and of follow-up intermediates and analyzing the energetics of the overall dissociative electron transfer. The ensuing DFT calculations of surface-enhanced Raman spectroscopic (SERS) signals provided some key information for characterizing different surface species at different potentials at the molecular level. The most intense and broad spectral peak observed near 800 cm−1 in the electrochemical SERS was thus assigned to the CH 2 wagging vibration closely associated with the co-adsorption of benzyl radical and chlorine. After the dissociation of the C-Cl benzyl chloride bond, the chloride anion adsorbs at the three-fold hollow site on silver electrodes, as indicated by a low vibrational frequency and a weak Raman signal. Conversely, the formed benzyl radical intermediate is found to adsorb at the top site with the characteristic vibrational frequency and strong Raman intensity. DFT calculations further confirmed that the kinetic effect underlying the electrocatalytic activity of silver electrodes is closely associated with the intrinsic energy barrier and the dissociative adsorption state of benzyl radical and chlorine on silver electrodes. Finally, we discuss the fundamental meaning of the kinetic rate constant of the first-step dissociative electron transfer for benzyl chloride on silver electrodes based on the different electron transfer models, indicating the synergistic roles of thermodynamics and kinetics. [ABSTRACT FROM AUTHOR]

Donor-π bridge-acceptor (D-π-A) design principle has been widely employed to build functionalized materials with excellent optical properties, whereas its feasibility in electrocatalytic reactions is seldom investigated. We demonstrate the primary study of D-π-A rule in constructing electrocatalysts for oxygen reduction reaction (ORR) purpose by rationally designing three cobalt porphyrins EGZ1–3 with 9H-carbazole, triphenylamine and N,N-diphenyl-[1,1′-biphenyl]-4-amine as the donor substituents, respectively, cobalt porphyrin as the π bridge, and cyanoacrylic acid as the acceptor unit. The electronic properties of the molecules are calculated using the density functional theory and the composite catalysts EGZs/C are characterized by a series of spectroscopic approaches. The electrochemical measurements show that EGZ3/C attains a more positive reduction potential and a greater response current density than EGZ1/C and EGZ2/C, which is possibly due to the optimized electronic structure and the substituent effect. The electron transfer number as well as hydrogen peroxide generation yield values suggest slightly better selectivity of EGZ3/C and EGZ2/C than those of EGZ1/C (i.e., ~ 2.9, ~ 2.9 vs. ~ 2.7 and ~ 54%, ~ 53% vs. ~ 62%, respectively) towards full oxygen reduction. Our result reveals the feasibility of the D-π-A design rule and the importance of molecular electronic state and the substituent feature in constructing ORR electrocatalysts. [Display omitted] • Three donor-π-acceptor cobalt porphyrins are synthesized. • The electronic structure of porphyrins is calculated by density functional theory. • Porphyrin-carbon black composites are studied in oxygen reduction reaction. • The electrocatalyst EGZ3/C attains the best ORR performance. • Both electronic structure and substituents affect the electrocatalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • • EA, VDE and frequencies of RhO n −(n = 1–––2) were determined by experiment and calculations. • • Based on the DFT calculations, the theoretical ADEs, VDEs and simulated PES of anionic RhO n − (n = 1–––4) clusters were obtained. • • The associated molecular orbitals (MOs), natural population analysis (NPA) and bond order analysis have been utilized. The photoelectron spectroscopies of RhO n – (n = 1–2) were obtained via using the photoelectron velocity-map imaging (PE-VMI) approach. The experimental values of the adiabatic detachment energy (ADE) and vertical detachment energy (VDE) for RhO– were reported to be 1.58 ± 0.02 eV. The experimental AED and VDE values of RhO 2 – were reported to be 2.70 ± 0.02 eV and 2.79 ± 0.02 eV, respectively. The vibrational frequencies of RhO– and RhO 2 – measured from photoelectron spectra (PES) were 817(76) cm−1 and 932(55) cm−1, respectively. Based on the density functional theory (DFT), the RhO n –1/0 (n = 1–4) clusters were investigated. The optimized configurations of corresponding ground states and low-lying clusters were discovered. Meanwhile, the simulated photoelectron spectroscopy (PES) of RhO n – (n = 1–4) and the theoretical ADE and VDE values of RhO n – (n = 1–4) clusters were unveiled to assist future experimental studies of Rhodium oxide clusters. Moreover, the associated molecular orbitals (MOs), natural population analysis (NPA) and bond order analysis have been utilized to investigate the chemical bonding in these groups. [ABSTRACT FROM AUTHOR]

Arundina graminifolia (D. Don) Hochr. is an ethnic medicine that has been used as an antidote for food poisoning and urinary tract infection by Dai minorities for centuries. However, its pharmacological mechanism of antibacterial activity and efficacy components are not clearly defined. Thirteen compounds were isolated from the whole plant of A. graminifolia and their structures were identified by spectroscopic analysis, and their antibacterial effects against Escherichia coli and Staphylococcus aureus were tested by micro-broth dilution method. Four compounds (6, 11, 12 and 13) possessed excellent antibacterial activities. Among them, blestiarene A (11) and densiflorol B (13) triggered significant bacteriostatic efficacy with the minimum inhibitory concentration between 25-50 μg/mL (positive drug amoxicillin 0.3-0.6 μg/mL). Mechanism research showed that compound 11 and 13 increased the level of reactive oxygen species and altered the bacterial membrane structure, leading to leakage of alkaline phosphatase and DNA, which consequently caused the death of bacteria. In addition, density functional theory calculation showed that the electron affinity of the antibacterial agent was positively correlated with antibacterial activity. Our work highlighted the antibacterial potential of natural phenanthrenes with membrane disrupt mechanism, and the tested phenanthrene derivatives could serve as lead compounds for the novel bactericides. [Display omitted] • Phenanthrenes from Arundina gramnifolia exhibited prominent antibacterial activity • Blestriarene A and densiflorol B disrupted cell membrane, inducing production of ROS • The structure-activity relationship helped to understand the antibacterial mechanism [ABSTRACT FROM AUTHOR]

Chemical methods for preparing SERS substrates have the advantages of low cost and high productivity, but the strong background signals from the substrate greatly limit their applications in characterization and identification of organic compounds. Herein, we developed a one-step synthesis method to prepare silver nanoparticle substrates with ultralow SERS background using anionic ligands as stabilizing agents and applied the SERS substrate for the reliable and reproducible identification of typical organic pollutants and corresponding degradation intermediates. The synthesis method shows excellent universality to different reducing agents cooperating with different anionic ligands (Cl−, Br−, I−, SCN−). As model applications, the machine learning algorithm can realize the precise prediction of six organophosphorus pesticides and eight sulfonamide antibiotics with 100% accuracy based on SERS training data. More importantly, the ultralow-background SERS substrate enables one to detect and identify the time-dependent degradation intermediates of organophosphorus pesticides by combining them with density functional theory (DFT) calculations. All the results indicate that the ultralow-background SERS substrate will greatly push the development of SERS characterization applications. [Display omitted] • A one-pot method to prepare low SERS background silver nanoparticle is developed. • The anionic ligands act as the stabilizers to decrease the SERS background signal. • This method exhibits universality to various anionic ligands and reducing agents. • Low-background substrates allow for accurate discrimination of organic pollutants. • Low-background substrates investigate the degradation intermediates of pesticides. [ABSTRACT FROM AUTHOR]

Achieving large current density is crucial to the practical application of large-scale hydrogen production by water splitting, but it is hindered by sluggish and unstable catalysts. Herein, a Pt-induced NiFe layered double hydroxide (Pt-NiFe LDH) nanosheet is synthesized for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It affords 10 mA cm–2 at overpotentials of only 198 mV and 36 mV for OER and HER, respectively. Impressively, an alkali-electrolyzer (Pt-NiFe LDH || Pt-NiFe LDH) exhibits a stable cell voltage of 1.887 V to deliver a current density of 1000 mA cm–2 over 3000 h. The introduction of Pt modulates the electronic structure on the surface of NiFe LDH by charging redistribution at the interface and decreasing the Gibbs free energy change (ΔG) for the potential determining step (from *O to *OOH) during OER. This work provides a facile strategy for developing catalysts for large current density water splitting. [Display omitted] • The Pt-NiFe LDH obtains excellent HER/OER activity in alkaline medium. • The homemade alkaline electrolyzer operated at 1000 mA cm−2 for over 3000 h. • The density functional theory (DFT) reveals that the introduction of Pt clusters on NiFe LDH reduces the energy barrier of OER. [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomic layer deposition was adapted to deposit Co 9 S 8 on the Ni(OH) 2 nanosheets, which were then in-situ activated to form Ni@Co hetero-structured electrodes. • The Ni@Co heterostructure exhibited strongly promoted glucose detection performance. • The changes in the local electronic structure and the promoted deprotonation process near the heterointerface contributed to the high detection performance. Developing noble-metal free electrocatalysts with high sensitivity is critical for the large-scale application of electrochemical glucose sensors. This work reports an atomic-scale interfacial engineering strategy to construct highly-active electrocatalyst for glucose detection. Ni(OH) 2 nanosheets are decorated with an ultra-thin layer of Co 9 S 8 using the atomic layer deposition (ALD) technique. After in-situ reconstruction, we obtain Ni@Co heterostructure composed of Ni hydroxide nanosheets and CoO x clusters, which exhibits outstanding electrochemical glucose sensing performance. Combining synchrotron-based X-ray adsorption spectroscopy, in situ Raman Spectroscopy, intermittent electrochemical measurements and density functional theory (DFT) calculations, we find that the presence of surface CoO x not only lowers the valence state of Ni, but also facilitates the deprotonation of Ni(OH) 2 to form NiOOH active species for glucose oxidation. The approach used in this work can be adapted to synthesizing high-performance electrocatalysts for other energy and environmental devices. [ABSTRACT FROM AUTHOR]

It has been a hot research topic to look for inexpensive alternative oxygen evolution reaction (OER) catalysts to replace noble metal-based materials due to their scarcity. Transition metals are ideal candidates because of their high abundance, impressive activities, and easy accessibility. However, a facile method leading to improved performance and stability is still needed. Herein, a highly efficient carbon-encapsulated bimetal catalyst derived from Ni-based metal-organic-frameworks (MOF) was successfully prepared through the low-temperature (350 ℃) pyrolysis of Prussian blue analogue (PBA) precursors under H 2 /Ar atmosphere. Cube-structured PBA as template and precursor，parameters during the pyrolysis process including temperature and calcination atmosphere can be tuned to control the structure and properties of the catalysts. Benefiting from the porous three-dimensional (3D) cubic structure and abundant defect-rich amorphous N-doped carbon shell, Ni 3 Fe@NC-350 exhibits excellent OER activity. The as-prepared catalysts exhibited excellent catalytic performance for OER in 1.0 M KOH with an overpotential of 237 mV to achieve 10 mA cm−2. More importantly, the presented catalyst has an extremely good durability. • A simple low-temperature annealing method was developed to produce alloy encapsulated with N-doping carbon. • The NiFe PBA was employed as nitrogen and carbon source. • The increased activity of OER is due to the synergy of Ni 3 Fe alloy and N-doped carbon layer. • Theoretical calculations revealed that the synergistic effect of NiFe alloy nanoparticles and N-doped carbon layer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defective MoS 2 enhanced PCA removal of Fe3+/PS system compared with pristine MoS 2. • S defects in MoS 2 facilitated the cycle of Fe3+/Fe2+ to enhance PCA degradation. • S defects in MoS 2 increased the electron density around Mo. • S defects in MoS 2 enhanced the adsorption of Fe3+. Advanced oxidation processes (AOPs) based on persulfate (PS) has attracted great attention because of its outstanding performance for decomposing chlorinated aromatic hydrocarbons in wastewater. While Fe-based materials can effectively activate PS and are environment-friendly, the low stability of Fe2+ and little activation capability of Fe3+ limit the broad applications of Fe2+ (or Fe3+) activated PS system in practical applications. In this work, taking molybdenum disulfide (MoS 2) as the co-catalyst in Fe3+/PS system, we report a strongly enhanced persulfate activation efficiency of Fe3+/PS system by engineering S defects in MoS 2. The combination of experiments and density functional theory (DFT) calculation demonstrate that S defects in MoS 2 modify the surface charge distribution, leading to the formation of an electron deficient center near S defect and increasing the electron density near Mo site. As a result, more Fe3+ in Fe3+/PS system is reduced into Fe2+ by MoS 2 with S defects, resulting in more reactive oxygen species generated. Furthermore, S defects promote the adsorption of Fe3+ on the MoS 2 surface, which further enhance the activating performance for PS through promoting to form cycle of Fe3+/Fe2+. This work provides a new strategy for improving co-catalytic properties of MoS 2 and expands the application of Fe3+/PS system for contaminants remediation. [ABSTRACT FROM AUTHOR]