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As a promising cathode material, Na3V2(PO4)2F3 (NVPF) has attracted wide attention for sodium-ion batteries (SIBs) because of its high operating voltage and high structural stability. However, the low intrinsic electronic conductivity and insufficient Na ion mobility of NVPF limit its development. Herein, K-doping NVPF is prepared through a facile ball-milling combined calcination method. The effects of K-doping on the crystal structure, kinetic properties and electrochemical performance are investigated. The results demonstrate that the Na2.90K0.10V2(PO4)3F3 (K0.10-NVPF) exhibits a high capacity (120.8 mAh g−1 at 0.1 C), high rate capability (66 mAh g−1 at 30 C) and excellent cycling performance (a capacity retention of 97.5% at 1 C over 500 cycles). Also, the occupation site of K ions in the lattice, electronic band structure and Na-ion transport kinetic property in K-doped NVPF are investigated by density functional theory (DFT) calculations, which reveals that the K-doped NVPF exhibits improved electronic and ionic conductivities, and located K+ ions in the lattice to contribute to high reversible capacity, rate capability and cycling stability. Therefore, the K-doped NVPF serves as a promising cathode material for high-energy and high-power SIBs.

Electrochemical CO2 reduction to higher-value hydrocarbons beyond C1 products has attracted much attention recently. Single-atom catalysts (SACs) are regarded as promising CO2 reduction electrocatalysts. However, most SACs only show activity to C1 products. In this work, we considered the activity and the synergetic effect of dual active sites for metal SACs supported on graphitic carbon nitride (g-C3N4) as CO2 reduction electrocatalysts. Density functional theory (DFT) calculations are employed. First, by using the adsorption energies of CO* on the metal site and that of H* on the nitrogen site as bi-descriptors, we predicted seven out of 14 metal centers have the propensity to generate beyond CO products. To further evaluate the catalyst activity on beyond CO product formation, we established reaction pathways towards ethylene through M/N or M/C. Ru has the best performance (the limiting potential is −0.90 V) by taking M/N as active sites. A dual volcano-shaped plot is built up based on the CO adsorption energies on metal sites, which can be used to indicate whether M/C or M/N shows better performance for a specific metal center. Our work shed light on developing criteria to guide the design of CO2 reduction electrocatalysts with dual active sites.

Electrochemical catalysts for the hydrogen evolution reaction (HER) have attracted increasing attentions. Noble metal-free cocatalysts play a vital role in HER applications. Herein, a novel strategy to prepare a Ni2P/MoS2 cocatalyst through a simple hydrothermal-phosphorization method was reported, and the prepared cocatalyst was then loaded on an N-doped carbon substrate with excellent conductive performance. The large surface area of the carbon substrate provided many active sites, and the interface between Ni2P and MoS2 improved the catalytic performance for the HER. Compared with pure Ni2P catalyst and MoS2 catalyst, the prepared Ni2P/MoS2 cocatalyst exhibited enhanced catalytic performance. In addition, the results indicate that the prepared cocatalyst has a wide pH range and low onset potential values of 280, 350 and 40 mV in acidic, phosphate-buffered saline and alkaline solutions, respectively, and the corresponding Tafel slopes are 75, 121 and 95 mV dec−1, respectively. Density functional theory (DFT) was adopted to calculate the hydrogen adsorption free energy (△GH∗). The results showed that the interface between Ni2P and MoS2 reduced △GH∗, which was beneficial to the adsorption of hydrogen. Present preparation of cocatalysts with unique interfaces provides a new strategy for improving the catalytic performance of HER.

Rely on the density functional theory (DFT) calculation, the catalytic performance of PdxCuy/GDY (x = 1, 2, 3, 4; x + y ≤ 4) for CO oxidative coupling reaction was obtained. The Pdx/GDY (x = 1, 2, 3, 4) are not ideal catalyst for dimethyl oxalate (DMO) formation because by-product dimethyl carbonate (DMC) is easily formed on Pd1/GDY and Pd2/GDY, and high activation energies are needed on Pd3/GDY and Pd4/GDY. Therefore the second metal Cu is doped to regulate the performance of Pdx/GDY (x = 1, 2, 3, 4). Doping Cu not only improve the activity of DMO formation, but more importantly, controlling the ratio of Cu:Pd can effectively regulate the selectivity of DMO. Thus taking into account the activity and selectivity of the reaction for the preparation of DMO by CO oxidative coupling, the Pd1Cu1/GDY and Pd1Cu2/GDY with the activation energies of 105.2 and 99.2 kJ/mol to generate DMO show excellent catalytic activity and high DMO selectivity, which are considered as good catalysts for CO oxidative coupling. The differential charge density analysis shows the decrease in the charge density of metal clusters is an important reason for improving the selectivity of the catalyst.

Tuning surface electron transfer process by sulfur (S)-vacancies engineering is an efficient strategy to develop high-efficient catalysts for electroreduction N2 reaction (NRR). Herein, the distinct Sb2S3 nanorods with S-vacancies (Sv-Sb2S3) have been synthesized by a simple two-step method including hydrothermal and hydrogenation in H2/Ar atmosphere, which shows improved performance for NRR with the NH3 yield rate of 10.85 μg h−1 mgcat−1 at −0.4 V vs. RHE, the faradaic efficiency (FE) of 3.75% at −0.3 V vs. RHE and excellent stability for 24 h, largely outperforming bulk Sb2S3. X-ray photoelectron spectroscopy (XPS) and density function theory (DFT) calculations demonstrate that the abundant S-vacancies can create an electron-deficient environment and modulate the electron delocalization in Sv-Sb2S3, which can not only facilitate the N2 molecule adsorption, but also activate the N[tbnd]N, resulting in the enhanced performance for NRR. © 2020 Institute of Process Engineering, Chinese Academy of Sciences

Whereas the proper choice of reaction solvent constitutes the cornerstone of the green solvent concept, solvent effects on chemical reactions are not mechanistically well understood due to the lack of feasible molecular models. Herein, by taking the case study of nucleophilic addition reaction in aqueous solution, we extend the proposed multiscale reaction density functional theory (RxDFT) method to investigate the intrinsic free energy profile and total free energy profile, and study the solvent effect on the activation and reaction free energy for the nucleophilic addition reactions of hydroxide anion with methanal and carbon dioxide in aqueous solution. The predictions of the free energy profile in aqueous solution for these two nucleophilic addition reactions from RxDFT have a satisfactory agreement with the results from the RISM and MD-FEP simulation. Meanwhile, the solvent effect is successfully addressed by examining the difference of the free energy profile between the gas phase and aqueous phase. In addition, we investigate the solvent effect on the reactions occurred near solid–liquid interfaces. It is shown that the activation free energy is significantly depressed when reaction takes place in the region within 10 A distance to the substrate surface owing to the decrease of hydration free energy at the solid–liquid interface.

International audience; The mechanisms of H 2 dissociation on three stoichiometric anatase TiO 2 terminations, (001), (100) and (101), have been studied by means of density functional theory (PBE+U) calculations. A two-step process was considered: first, H 2 dissociation into H + and H − pair, and second the H − species migrates to a neighboring O site, transferring the electrons to the substrate. On (001), it shows the lowest activation barriers for hydrogen dissociation, 0.37 eV, whereas the highest value was found on (101), 0.98 eV. For hydrogen transfer from Ti to near O, the activation barriers are higher (from 1.10 to 2.37 eV), which indicates the dissociation step is kinetically more favorable than the H transfer process, although the latter is thermodynamically more favorable. Electronic structure, vibrational frequency analysis as well as temperature effects are studied to characterize the reactivity. The relationship between electronic structure, geometry and reactivity is analyzed by means of reactivity descriptors, and the results are compared with ceria and rutile TiO 2 facets.

N-doped reduced graphene oxide quantum dots (N-rGQDs) have attracted more and more attention in efficient catalytic degradation of aqueous organic pollutants. However, the synthesis of N-rGQDs is generally a complex and high energy required process for the reduction and N-doping steps. In this study, a facile and green fabrication approach of N-rGQDs is established, based on a metal-free Fenton reaction without additional energy-input. The N structures of N-rGQDs play a significant role in the promotion of their catalytic performance. The N-rGQDs with relatively high percentage of aromatic nitrogen (NAr-rGQDs) perform excellent catalytic activities, with which the degradation efficiency of pollutant is enhanced by 25 times. Density functional theory (DFT) calculation also indicates aromatic nitrogen structures with electron-rich sites are prone to transfer electron, presenting a key role in the catalytic reaction. This metal-free Fenton process provides a green and cost-effective strategy for one-step fabrication of N-rGQDs with controllable features and potential environmental catalytic applications.

Two-dimensional (2D) materials have exhibited great potential for replacing costly Pt for oxygen reduction reaction (ORR) because of their distinctive structural features and high pre-site activity. However, their performance is generally hindered by the limited density of active sites (e.g., at the layer edges). Although they feature a high exposure of surface sites, these sites are typically inert for ORR. Herein, through density functional theory calculations, we propose a promising ORR catalyst candidate, a 2D TaTe2 nanosheet, which has an intrinsic high basal-plane activity. Both of the thermodynamic and kinetic processes are explored, which demonstrates that the basal-plane Te sites of the TaTe2 nanosheet have great potential for facilitating ORR. Specifically, we construct a microkinetic model of ORR proceeding on TaTe2, which unveils its dynamic intermediate coverage under different electrode potentials and identifies the dominating associative pathway. The theoretical half-wave potential of TaTe2 is predicted to be 0.87 V, which exceeds those of the well-established Pt (111) and Fe–N–C single-atom catalysts computed at the same level. This study not only presents the first 2D, non-Pt ORR catalyst candidate with an intrinsic basal-plane activity but also offers a rational methodology for unveiling the mechanism/activity of ORR and other electrochemical reactions.

Density functional theory (DFT) calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg (0001) surface with Ni incorporating at various locations. The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface. Further calculations reveal that Ni atom locating in/over the topmost Mg (0001) surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV. In these cases, the rate-limiting step has been converted from hydrogen dissociation to surface diffusion. In contrast, Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion. Therefore, it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg (0001) surface to maintain its catalytic effect. For all the case of Ni-incorporated Mg (0001) surfaces, the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk. It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.

Solid adsorbents that simultaneously have high selectivity and uptake capacity are highly promising as alternatives to conventional cryogenic distillation of propene/propane (C3H6/C3H8) separation. Coordinatively unsaturated metal sites (CUS) plays a vital role in selective adsorption of olefins over paraffins. Ultrathin poly (triazine imide) (PTI) nanosheets can reach rapid gas adsorption equilibrium, due to its large surface-to-volume ratio. In this work, combining the advantages of the CUS and the PTI nanosheets, Li CUSs were introduced into the PTI nanosheets for C3H6/C3H8 separation. Density functional theory (DFT) calculations demonstrated the thermodynamic feasibility of incorporating Li CUSs into the PTI nanosheets. These highly exposed Li CUSs were predicted to have a higher adsorption affinity toward C3H6 than C3H8. Using the DFT-derived force field parameters, we further performed grand canonical Monte Carlo (GCMC) simulations to investigate C3H6/C3H8 adsorption on the Li−PTI complexes slit pore model with different pore widths (H). We found that the Li−PTI complexes display considerable C3H6/C3H8 selectivity (4.2∼7.9) under relevant conditions. Moreover, the Li−PTI complexes slit pore have large C3H6 working capacities (1.5∼4.0 mmol g-1), superior to those calculated for the most of adsorbent materials that have been reported. The Li−PTI complexes with slit pore architecture show potential as C3H6/C3H8 separation materials.

The transformations of CO2 molecules into valuable products are of increasing interest due to the negative impact of anthropogenic CO2 emissions on global warming. The CO2-to-methanol hydrogenation is an economically profitable reaction of carbon fixation, but it still steps away from widespread industrialization because of the lack of efficient and selective catalysts. Recently, single-atom alloy (SAA) catalysts have been developed to work remarkably in CO2 hydrogenation reactions. Doping isolated single atoms into metallic catalyst can dramatically alter the catalytic performance of the host. We have performed a screening discovery on Ru and 6 RuX (X = Fe, Co, Ni, Cu, Ir and Pt) SAAs using density functional theory (DFT) computations. We considered 13 possible elementary reactions in 4 possible reaction pathways on Ru and all RuX surfaces. In the computed mechanisms, we found that the formation of *H2COOH and *HCOO intermediates plays a critical role in determining catalysts’ activities. Doping Co and Pt isolated single atoms into Ru surface can thermodynamically and kinetically facilitate these intermediates formation processes, eventually promoting the production of methanol. The combination of weak binding and enhanced charge redistribution on RuCo and RuPt surfaces give them improved catalytic activities over pure Ru. This work will ultimately facilitate the discovery and development of SAAs for CO2 to methanol, serving as guidance to experiments and theoreticians alike.

Transition metal dichalcogenides (TMDCs) are promising materials for applications in nanoelectronics and correlated fields, where their metallic edge states play a fundamental role in the electronic transport. In this work, we investigate the transport properties of MoS$_2$ zigzag nanoribbons under a butadiene (C$_4$H$_6$) atmosphere, as this compound has been used to obtain MoS$_2$ flakes by exfoliation. We use density functional theory combined with non-equilibrium Green's function techniques, in a methodology contemplating disorder and different coverages. Our results indicate a strong modulation of the TMDC electronic transport properties driven by butadiene molecules anchored at their edges, producing the suppression of currents due to a backscattering process. Our results indicate a high sensitivity of the TMDC edge states. Thus, the mechanisms used to reduce the dimensionality of MoS$_2$ considerably modify its transport properties.

The Dzyaloshinskii-Moriya interaction (DMI) manifesting in asymmetric layered ferromagnetic films gives rise to non-colinear spin structures stabilizing magnetization configurations with nontrivial topology. In this work magnetization reversal, magnetic domain alignment, and strength of DMI are related to the crystalline structure of W/Co/Pt multilayers grown by molecular beam epitaxy. The applied growth method enables the fabrication of layered systems with higher crystalline quality than commonly applied sputtering techniques. A relatively high value of the D coefficient was determined from the aligned magnetic domain stripe structure, substantially exceeding 2 mJ m-2. The highest value of DMI strength Deff = 2.64 mJ m-2 and surface DMI parameter DS = 1.83 pJ m-1 have been observed for a repetition number equal to 10. The experimental results correlate exactly with those obtained from the micromagnetic modelling and density functional theory calculations performed for the well-defined layered stacks. This high value of DMI strength originates from the additive contributions of the interfacial atomic Co layers at the two types of interfaces.

Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well understood. In the present contribution, the solid-solution (100-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-xBT), a prototypic lead-free relaxor is studied by the combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, dielectric measurements and ab-initio density functional theory (DFT). For the first time it is shown that the peculiar composition dependence of the EFG distribution width (ΔQISwidth) correlates strongly to the dispersion in dielectric permittivity, a fingerprint of the relaxor state. Significant disorder is found in the local structure of BNT-xBT, as indicated by the analysis of the electric field gradient (EFG) in 23Na 3QMAS NMR spectra. Aided by DFT calculations, this disorder is attributed to a continuous unimodal distribution of octahedral tilting. These results contrast strongly to the previously proposed coexistence of two octahedral tilt systems in BNT-xBT. Based on these results, we propose that considerable octahedral tilt disorder may be a general feature of these oxides and essential for their relaxor properties.

We present a study of the structure and differential capacitance of electric double layers of aqueous electrolytes. We consider electric double layer capacitors (EDLC) composed of spherical cations and anions in a dielectric continuum confined between a planar cathode and anode. The model system includes steric as well as Coulombic ion-ion and ion-electrode interactions. We compare results of computationally expensive, but “exact” , Brownian Dynamics (BD) simulations with approximate, but cheap, calculations based on classical Density Functional Theory (DFT). Excellent overall agreement is found for a large set of system parameters, including variations in concentration, ionic size- and valency-asymmetries, applied voltages and electrode separation, provided the differences between the canonical ensemble of the BD simulations and the grand-canonical ensemble of DFT are properly taken into account. In particular, a careful distinction is made between the differential capacitance $$C_N$$ C N at fixed number of ions and $$C_\mu $$ C μ at fixed ionic chemical potential. Furthermore, we derive and exploit their thermodynamic relations. In the future these relations will also be useful for comparing and contrasting experimental data with theories for supercapactitors and other systems. The quantitative agreement between simulation and theory indicates that the presented DFT is capable of accounting accurately for coupled Coulombic and packing effects. Hence it is a promising candidate to cheaply study room temperature ionic liquids at much lower dielectric constants than that of water.

A new metal-oxo-clusters-based inorganic framework [NaCo2Mo2O7(OH)3]n (NaCoMo), named as 3D platelike ternary-oxo-cluster, has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction structure analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) analyses, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). Structure analysis reveals that there are no classical building units in NaCoMo, and the asymmetric units of NaCoMo are directly extended into a new platelike 3D structure. Density functional theory calculations (DFT) indicates that the crystal formation process is exothermic and the structure is extremely stable. In addition, the compound presents excellent catalytic activity in the condensation and cyclization reaction of sulfonyl hydrazides and 1,3-diketones to synthesize pyrazoles, and the yield of the desired product is up to 99%. The successful synthesis of NaCoMo represents the discovery of a new kind of non-classical polyoxometalates.

CuPbBi5S9 compounds have been investigated as gladite for years. However, there have been no significant studies on their physical and chemical properties. This work demonstrates that upon alloying with moderate Cu, Pb, Bi, and S using an appropriate preparation method, quaternary CuPbBi5S9 compounds can exhibit excellent figure of merit ZT within the temperature range 298–723 K. A low average velocity, low Young’s modulus and Debye temperature, and large Gruneisen parameter, determined experimentally, indicate strong lattice anharmonicity in CuPbBi5S9 crystals. Furthermore, density functional theory calculations (local vibration of low-frequency acoustic phonons) justify the low lattice thermal conductivity of CuPbBi5S9 compounds. Because of the low thermal conductivity (0.514 W m−1K−1) and a relatively high power factor (293 μW m−1K−2), a maximum ZT of 0.42 was achieved at 723 K for CuPbBi5S9 prepared by mechanical alloying combined with solid-state melting. Thus, CuPbBi5S9 materials are promising candidates for use as high-performance thermoelectric materials in the intermediate-temperature range.

To understand the microscopic mechanism of the CO oxidation reaction at PtCu nanoparticles, which have unique geometric and electronic structures compared to their component metals, we present here a theoretical study, based on density functional theory calculations, of the main reaction steps of this reaction. We examine the O2 dissociation, the CO adsorption and the CO + O2 reaction at an atomic level and use the computed geometries, Bader charges, and vibrational frequencies to rationalize the role of the intermetallic nanoparticles surface structure on the experimentally observed much higher activity of these nanoparticles as catalysts of the preferential oxidation of CO. By comparing with clean Pt (111) surface and with different Cu-doped models of this same surface, our results show that, at the surface, the presence of Cu induces the segregation of CO molecules at Pt sites and of O2 molecules at Cu sites. Contrarily to Pt surfaces, the unassisted O2 dissociation has a high barrier at the intermetallic nanoparticle surface and proceeds through a CO-assisted mechanism in which the new CO bond is formed while the O O bond is broken with a kinetic barrier much lower than on either Pt (111) or in Pt-doped surfaces. The particular structure of the intermetallic surface is shown to have a significant role in the low kinetic barrier for the reaction, allowing for an easy approach of the CO to the adsorbed O2 molecule that permits an early transition state with a low energetic barrier.

The development of dual-function anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) is exceedingly essential. Herein, with rationally designed hierarchical metal-organic framework (MOF)@MXene as a precursor, a novel sandwich-like CoP-NC@Ti3C2Tx composite has been successfully fabricated by the following phosphorization reaction. As anode material for LIBs, the CoP-NC@Ti3C2Tx composite exhibits remarkable electrochemical performance with high-rate capability (147.8 mAh g−1 at 2000 mA g−1; 245.6 mAh g−1 at 100 mA g−1) and ultralong cycling life (2000 cycles with a capacity retention over 100%). For SIBs, it delivers a discharge capacity of 101.6 mAh g−1 at a current density of 500 mA g−1 after 500 cycles. The well-designed sandwich-like composite effectively supports the easy access to electrolyte, facilitate the Li/Na ion transportation, and protect the active material from pulverization upon long cycling. In addition, the electrochemical reaction kinetics and Li-migration kinetics of the CoP-NC@Ti3C2Tx composite have been pioneeringly illuminated by pseudocapacitive behavior calculation and density functional theory (DFT) computations, respectively. This work sheds light on the rational design and development of MOF/MXene-derived dual-function anode materials for Li/Na-storage.

Novel research avenues have been explored over the last decade on the use of transition metal carbides (TMCs) as catalytically active supports for metal nanoclusters, which display high catalytic activity despite the poor reactivity (or even inertness) of the bulk metal. It has been postulated that TMCs polarise the electron density of adsorbed metal particles in such a way that their catalytic activity ends up being superior to those dispersed on more traditional metal oxide supports. Herein, we investigate the structural and electronic properties of small clusters of precious metals (Rh, Pd, Pt and Au) and more affordable metals (Co, Ni and Cu) supported on TMCs with 1:1 stoichiometry (TiC, ZrC, HfC, VC, NbC, TaC, MoC and WC) by means of periodic Density Functional Theory calculations. Our high-throughput screening studies indicate that it is possible not only to have strongly bonded and stably dispersed metal nanoparticles on TMC surfaces, but also to manipulate their charge by carefully selecting elements with desired electronegativity for the host TMC and the metal cluster. By doing so, it is possible to tune the amount of charge density on the cluster hollow sites, which can facilitate the bonding of certain molecules. Moreover, we identify Pt, Pd and Rh clusters supported on hexagonal TMC (001) facets as the candidates with the highest potential catalytic activity -as estimated by the significant polarisation of the cluster electron density- and stability -as quantified by the strongly negative values of adsorption energy per atom and formation energy-.

Two–electron ( 2 e - ) oxygen reduction reaction (ORR) shows great promise for on–site electrochemical synthesis of hydrogen peroxide (H2O2). However, it is still a great challenge to design efficient electrocatalysts for H2O2 synthesis. To address this issue, the logical design of the active site by controlling the geometric and electronic structures is urgently desired. Therefore, using density functional theory (DFT) computations, two kinds of hybrid double–atom supported on C2N nanosheet (RuCu@C2N and PdCu@C2N) are screened out and their H2O2 performances are predicted. PdCu@C2N exhibits higher activity for H2O2 synthesis with a lower overpotential of 0.12 V than RuCu@C2N (0.59 V), Ru3Cu(110) facet (0.60 V), and PdCu(110) facet (0.54 V). In aqueous phase, the adsorbed O2 is further stabilized with bulk H2O and the thermodynamic rate–determining step of 2 e - ORR change. The activation barrier on PdCu@C2N is 0.43 eV lower than the one on RuCu@C2N with 0.68 eV. PdCu@C2N is near the top of 2 e - ORR volcano plot, and exhibits high selectivity of H2O2. This work provides guidelines for designing highly effective hybrid double–atom electrocatalysts (HDACs) for H2O2 synthesis.

Background and aim Epithelial ovarian cancer has the deadliest prognosis amongst gynaecological cancers, warranting an unmet need for newer drug targets. Based on its anticancer as well as abortifacient potential, Moringa oleifera Lam. root was hypothesized to have some implications in follicle stimulating hormone receptor (FSHR) dependent cancers like epithelial ovarian cancer. Experimental procedure Effect of Moringa oleifera Lam. root extract (MRE) was studied in epithelial ovarian cancer cell line through in vitro studies viz. MTT assay, clonogenic assay, cell cycle analysis, flow cytometry, western blot analysis, immunocytochemical analysis of FSHRand c-Myc expression and in vivo studies viz. effect of MRE in mice model of ovarian carcinoma. The structure of the active compound of MRE was elucidated following solvent extraction, purification through column chromatography, preparative TLC and bioactivity guided structural identification through 1H-NMR, 13C-NMR, DEPT-135, ESIMS,FT-IR spectrophotometry, UV–vis–NIR spectrophotometry and DFT study. Results and conclusion Crude MRE displayed cytotoxic activity, induced apoptosis, and attenuated expression of FSHR and c-Myc in ovarian cancer cell line OAW42. MRE also attenuated expression of CD31, FSHR, and c-Myc in tumour xenograft mouse model. Finally, the active compound purified from ethyl acetate-n-hexane subfraction ofMRE, that attenuated viability of ovarian carcinoma cell lines and reduced FSHR and c-Myc expression, was identified as a naturally hydrated-trifattyglyceride, showing aDFT-optimized folded amphipathic structure for easy transportation through hydrophilic and hydrophobic regions in a biological system, indicating its immense therapeutic relevance in epithelial ovarian carcinoma.

Marine biological fouling has always been a hot research topic. In this study, silver @ cuprous oxide (Ag@Cu2O) core-shell nanoparticles were synthesized via in-situ synthesis method and developed an outstanding antibacterial activity. The bacteriostasis efficiency of Ag@Cu2O reached to 99% and 98% against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. The minimum inhibitory concentration of Ag@Cu2O decreased from 113.6 μg/mL to 56.8 μg/mL compared with Cu2O. Ag@Cu2O had better antibacterial activity than Cu2O with lower content of Cu2O and was more environment friendly. The heterostructure formed at the interface between Ag and Cu2O promoted the separation and diffusion of photogenerated electron-hole pairs through the charge transfer channel and promoted the generation of reactive oxygen species. The outstanding antibacterial activity of Ag@Cu2O was strongly depended on the generation of the reactive oxygen species. Density functional theory and finite element method calculations demonstrated that the structure of core-shell improved photocatalytic efficiency. Additionally, synergetic effect of released Ag+ and Cu2+ also enhanced the bacteriostasis rate and the long-term antifouling performance in 60 days. Hence, the synthesized core-shell Ag@Cu2O can be applied as novel antifoulants in the marine field.

Bi2Te3-based thermoelectric (TE) materials have been demonstrated to be a potential candidate for mainly thermoelectric cooling/refrigeration applications. However, minority charge carriers excitation at high temperature reduces thermopower which restricts these materials for the use in power generation. In present work, substitution of Ni on Sb site in Bi0.5Sb1.5-xNixTe3 (x = 0, 0.01, 0.04 and 0.08) actuates the system to supress the intrinsic excitation leading to shift in highest ZT to higher temperature regime. The Density functional theory (DFT) calculations and experimental results reveal that Ni in Bi0.5Sb1.5Te3 provides the extra holes and slightly reduces the band gap Eg which enhances the σ of Ni-doped Bi0.5Sb1.5-xNixTe3 samples and α at elevated temperature. Moreover, Ni-doping in Bi0.5Sb1.5Te3 also reduces κL which is attributed to the phonon scattering due to mass fluctuations and microstructural features such as grain boundary and strain field domain observed from HRTEM investigation. These favourable condition leads to maximum ZT∼1.38 at 433K for Bi0.5Sb1.46Ni0.04Te3 and ZTavg ∼1.1 between 300K and 503K. Interestingly the calculated theoretical TE conversion device efficiency η of Bi0.5Sb1.46Ni0.04Te3 (η∼5.5%) was achieved to be nearly twice than the efficiency of matrix Bi0.5Sb1.5Te3 (η∼3%). Experimental electronic transport is well corroborated with theoretically estimated DFT results.

Various strategies for thermoelectric material optimization have been widely studied and used for promoting electrical transport and suppressing thermal transport. As a nontraditional method, pressure has shown great potential, as it has been applied to obtain a high thermoelectric figure of merit, but the microscopic mechanisms involved have yet to be fully explored. In this study, we focus on r-GeTe, a low-temperature phase of GeTe, and investigate the pressure effects on the electronic structure, electrical transport properties and anharmonic lattice dynamics based on density functional theory (DFT), the Boltzmann transport equations (BTEs) and perturbation theory. Electronic relaxation times are obtained based on the electron-phonon interaction and the constant relaxation time approximation. The corresponding electrical transport properties are compared with those obtained from previous experiments. Hydrostatic pressure is shown to increase valley degeneracy, decrease the band effective mass and enhance the electrical transport property. At the same time, the increase in the low-frequency phonon lifetime and phonon group velocity leads to an increase in lattice thermal conductivity under pressure. This study provides insight into r-GeTe under hydrostatic pressure and paves the way for a high-pressure strategy to optimize transport properties.

The rational design of the surface structure and morphology characteristics of the catalyst at atomic level are the key to improve the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in lithium-oxygen (Li-O2) battery. Here a series of cobalt phosphide (CoP) electrocatalysts with a variety of index facets are successfully prepared including concave polyhedrons CoP exposing with (2 1 1) crystal planes (CoP CPHs) spherical nanoparticles CoP exposed with (0 1 1) crystal planes and polyhedron particles CoP exposing with (0 1 1) and (1 1 1) crystal planes. The results show that CoP CPHs based Li-O2 battery presents a large discharge capacity of 33743 mA h g−1 at current density of 50 mA g−1 and a remarkable long cycle life of up to 950 h. The experimental results demonstrates that the CoP CPHs electrode exposing with high-index (2 1 1) facets based Li-O2 battery exhibits an extremely low overpotential (0.67 V) ultrahigh specific capacity (33743 mAh g−1) and remarkable long-term stability of up to 950 h. Most importantly density functional theory (DFT) calculations demonstrate the excellent electrocatalytic activity of high-index (2 1 1) facets as compared to the low-index (0 1 1) and (1 1 1) planes are because of the existence of large density of atomic steps edge ledge sites and kinks which supply a wide space for breaking chemical bonds and increasing the reaction activity for oxygen electrode.

Nitrogen-to-ammonia conversion under mild conditions offers a tremendous prospect as a sustainable technology for synthesizing ammonia (NH3) in the future. In this study, we elaborately designed Bi4O5Br2/Ti3C2 heterojunction combined with electrostatic adsorption with in-situ growth to form a photocatalyst with a 2D/2D structure. This unique structure substantially improved the exposure of active edge sites for photocatalytic dinitrogen reduction reaction. Notably, Ti3C2 MXene acted as an efficient cocatalyst for the conversion of N2 to NH3 of Bi4O5Br2/Ti3C2 with a yield of 277.74 μmol g−1h−1 without the use of a sacrificial agent; this yield was five times higher than that of Bi4O5Br2. Density functional theory calculations demonstrated that the ohmic contact was at the Bi4O5Br2/Ti3C2 interface. The ohmic heterojunction could expedite the separation of spatial carriers and extraction of photoexcited charge carriers, which had outstanding reducibility to cleavage the N≡N bond. This work provides a novel strategy for designing highly efficient Bi4O5Br2-based photocatalysts through the integration of multifunctional materials. This work also offers guidance for implementing high-performance nitrogen-to-ammonia conversion by introducing interfacial modifiers.

The protein adsorption has an immense influence on the biocompatibility of biodegradable Mg alloy. In this work, the effect of Zn content on the fibrinogen (Fg) adsorption behavior in Mg-Zn binary alloy was systematically investigated. Experimental results showed that the Fg adsorption amount increased at first and then decreased with the increase of Zn content. The adsorption mechanism was investigated by molecular dynamic and density functional theory simulations. The simulations results showed that Zn with low content existed in the inner layer of Mg alloys due to the lower system energy, which promoted Fg adsorption and the promotion effect was more obvious with the increase of Zn content. When Zn content increased to a higher concentration, parts of Zn atoms started to precipitate in the surface, and the Fg-surface interaction energy started to increase. Moreover, the Zn sites favored the formation of ordered water molecules layers, which inhibit the stable adsorptions of Fg. The inhibition effects of Fg adsorption was enhanced with the Zn content increase. In short, the simulation results explain the experimental phenomena and reveal the microscopic mechanism. This study would provide a significant guidance on the design of biodegradable Mg-Zn alloys.

Design and demonstration of cost-effective, robust, and earth-abundant electrocatalysts for efficient water splitting have attracted a great deal of interest. Herein, we have decorated NiFe2O4 nanoparticles on the emerging novel two-dimensional (2D) Ti3C2 (MXene) sheets in order to achieve better electrocatalytic performance for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The synthesized NiFe2O4/Ti3C2 composite showed extraordinary kinetic metrics for electrocatalytic OER, revealing a low overpotential of 266 mV at a current density of 10 mA/cm2, and a small Tafel slope of 73.6 mV/dec. For HER, the composite exhibited an overpotential of 173 mV at 10 mA/cm2 with a small Tafel slope of 112.2 mV/dec. The high electrocatalytic performance of NiFe2O4/Ti3C2 composite is believed to be originated from a well-constructed nanoparticle-sheet interface, synergistic effect, and the high metallic conductivity of Ti3C2 MXene sheets. These experimental results are further supported by the state-of-the-art density functional theory (DFT) simulations. The study providing information about the structure, electronic properties, bonding, and interaction mechanism between Ti3C2 (MXene) and NiFe2O4. Moreover, offering the values of the theoretical overpotential of Ti3C2 (MXene), NiFe2O4, and the NiFe2O4/Ti3C2 composite for both OER and HER activities. Interestingly, the theoretical overpotential follows the qualitative trend of NiFe2O4/Ti3C2

The exciton dynamics of violanthrone-79 are investigated in solution and in the solidstate. In solution, the photo-prepared singlet is found to exhibit a strong ground-state bleachand stimulated emission feature, but when sensitized in its triplet state, exhibits only a narrowand weak ground-state bleach. As supported by density functional theory calculations,this is explained by the triplet state having absorptions in the same region, with a similaroscillator strength, as the ground state molecule. In solid films, the excited singlet isfound to survive only 100 ps, giving way to a long-lived transient absorption spectrum withcharacteristics reminiscent of the triplet in solution. This is interpreted in terms of singletfission in the solid film.

Most of the properties of epoxy resins are tied to their degree of cross-linking, making understanding the reactivity of different epoxy systems a crucial aspect of their utilization. Here, epoxy-amine reactivity is studied with density functional theory (DFT) at various cut-off levels to explore the suitability of the method for estimating the reactivity of specific epoxy systems. Although it is common to use minimal structures in DFT to reduce computational cost, the results of this study highlight the important role of hydrogen bonding and other noncovalent interactions in the reactivity. This is a promising result for differentiating the most probable reactive paths for different resin systems. The significance of amine groups as a potential source of catalyzing H-bonds was also explored and, while not quite as effective as a catalyst as a hydroxyl group, a clear catalyzing effect was observed in the transition state energies. Unfortunately, the added complexity of a more representative reactive system also results in increased computational cost, highlighting the need for proper selection of structural cutoffs. publishedVersion

The central moiety of porphyrins is shown to control the charge state of the inner complex and links it by covalent interaction to the peripheral substituents. This link, which enables the versatile functions of porphyrins, is not picked up in the established, reduced four orbital picture [Gouterman, J. Mol. Spectrosc., 1961, 6, 138]. X-ray absorption spectroscopy at the N K-edge with density functional theory approaches gives access to the full electronic structure, in particular the π* manifold beyond the Gouterman orbitals. Systematic variation of the central moiety highlights two linked, governing trends: The ionicity of the porphyrin center increases from the aminic N–H to N–Cu to N–Zn to N–Mg to the iminic N:. At the same time covalency with peripheral substituents increases and compensates the buildup of high charge density at the coordinated nitrogen sites., The porphyrin center is shown to control both the covalency of the central complex and π hybridization with peripheral substituents.

Photoanode is the key issue for photoelectrocatalytic (PEC) water splitting and organics degradation. However, it always faces several restrictions including severe photocorrosion, low charge separation and transfer efficiencies, poor visible light harvesting, and sluggish interfacial reaction kinetics, which often required a variety of modifications with only low improvements achieved. Herein, a high performance CQDs/TiO2/WO3 photoanode was designed on the basis of density function theory (DFT) alignment of lattice parameters and energy band, and charge distribution. The TiO2/WO3 heterojunction can abate photocorrosion through the hetero-epitaxial growth of TiO2 (0 0 1) on WO3 (0 0 2) for the lattice mismatch

High-entropy alloys (HEA) are of high current interest due to their unique and attractive combination of structural, physical, chemical or magnetic properties. HEA comprise multiple principal elements, unlike conventional alloys. The composition space of HEA is enormous and only a minuscule fraction has been studied. Magnetic HEA are a promising alternative to conventional soft magnetic metallic materials, which typically exhibit poor mechanical properties. We review the progress in the development of magnetic HEA. The influence of alloy composition, crystal structure, phase fraction and processing parameters on the magnetic properties are discussed. Magnetic HEA processed by advanced experimental high throughput techniques such as additive manufacturing, co-sputtering, diffusion multiples, rapid prototyping, and designed via combinatorial computational techniques, such as thermodynamic and phase diagram calculations, density functional theory, machine learning etc. are reviewed. Conventional processing techniques are also discussed. Future trends in magnetic HEA are outlined.

Das Sammeln von Informationen über die atomare Natur von reaktiven Zentren und Fallenzuständen ist der Schlüssel zur Feinabstimmung der Katalyse und zur Unterdrückung schädlicher Oberflächenpotentialverluste in photoelektrochemischen Technologien. Hier wurden spektroelektrochemische und rechnerische Methoden kombiniert, um eine Modellphotokathode aus der vielversprechenden Chalkopyrit-Familie zu untersuchen: CuIn0.3Ga0.7S2. Es wurde festgestellt, dass Potentialverluste mit Fallen verbunden sind, die durch Oberflächen-Ga- und In-Leerstellen induziert werden, wohingegen Operando-Raman-Spektroskopie zeigte, dass Katalyse an Ga-, In- und S-Stellen stattfand. Diese Studie ermöglicht es, eine Brücke zwischen der Leistung des Chalkopyrits und seiner Oberflächenchemie zu schlagen, wobei die Vermeidung der Bildung von Ga- und In-Leerstellen entscheidend ist, um eine hohe Aktivität zu erzielen. Diese Arbeit wurde vom Schweizerischen Nationalfonds (SNF) im Rahmen des Ambizione Energy Grant (PZENP2_166871) und vom Gaznat-EPFL Forschungsprogramm unterstützt. M.B. und U.A. wurden durch die Förderungsprofessuren PP00P2_157615 und PP00P2_187185 des Schweizerischen Nationalfonds unterstützt. Die Berechnungen wurden auf UBELIX, dem HPC-Cluster der Universität Bern, durchgeführt. M.X. dankt dem China Scholarship Council (Nr. CSC201806160172) und dem Strategic Japanese–Swiss Science and Technology-Programm (514259) für die Unterstützung. Open access funding provided by Ecole Polytechnique Federale de Lausanne.

Modification of MoS2-based catalysts is effective in solving the overdependence of hydrogen evolution reactions (HERs) on noble metal catalysts. In this work, a Zn-doped molybdenum disulfide-reduced graphene oxide (Zn–MoS2–RGO) hybrid was synthesized in one step employing a hydrothermal method. By substituting the position of Mo, uniform doping with Zn improved the catalytic activity of MoS2 for HER. The interlayer spacing of MoS2 increased from 0.65 to 0.75 nm, demonstrating RGO effectively interpolate into MoS2 nanosheets. This prevented aggregation and exposed more edge active sites of MoS2. According to density functional theory (DFT) calculations, the layered structure of the MoS2 nanosheets doped with Zn and intercalated with RGO promoted charge transfer and resulted in outstanding hydrogen evolution activity. Compared with MoS2 (6.86 eV), the Zn–MoS2–RGO hybrid (5.47 eV) with a considerably lower energy level value exhibited excellent electrocatalytic performance. Under optimal conditions, at a potential of −0.3 V vs. RHE, the current density reached −169 mA cm−2 in a 0.5 M H2SO4 solution, 4.78 μmol of H2 was produced in 6 h, and the Faraday efficiency reached 92%. The results obtained herein indicated that Zn–MoS2–RGO was a promising candidate for application in electrocatalytic HER.

Ketene, a versatile reagent in production of fine and specialty chemicals, is produced from acetic acid. We investigate the synthesis of ketene from acetic acid over the (3,0;1,1) surface of Cu2O(1 0 0) through analysis of the adsorption and desorption characteristics of formic and acetic acids. The results allow us to establish a reaction mechanism for ketene formation. Observations from x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy, and temperature programmed desorption (TPD), supported by a comparison with formic acid results, suggest that acetic acid reacts with Cu2O through deprotonation to form acetate species coordinated to copper sites and hydroxylation of nearby surface oxygen sites. For formic acid the decomposition of adsorbed formate species results in desorption of CO2 and CO while, for acetic acid, high yields of ketene are observed at temperature >500 K. Modeling by density functional theory (DFT) confirms the strong interaction of acetic acid with the (3,0;1,1) surface and the spontaneous dissociation into adsorbed acetate and hydrogen atom species, the latter forming an OH-group. In an identified reaction intermediate ketene binds via all C and O atoms to Cu surface sites, in agreement with interpretations from XPS. In the vicinity of the adsorbate the surface experiences a local reorganization into a c(2 × 2) reconstruction. The total computed energy barrier for ketene formation is 1.81 eV in good agreement with the 1.74 eV obtained from TPD analysis. Our experimental observations and mechanistic DFT studies suggests that Cu2O can operate as an efficient catalyst for the green generation of ketene from acetic acid., Swedish Research Council (VR); VR Starting Grant; Knut och Alice Wallenbergs stiftelse; STINT Joint China-Sweden Mobility Program; Ragnar Holm Foundation; Trygger’s Foundation; Chalmers Areas of Advance-Materials Science

The electrochemical synthesis of hydrogen peroxide (H2O2) provides a greener and more efficient method compared with classic catalysts containing toxic metals. Herein, we used first-principles density functional theory (DFT) calculations to investigate 174 different single-atom catalysts with graphyne substrates, and conducted a three-step screening strategy to identify the optimal noble metal-free single atom catalyst. It is found that a single Ni atom loaded on γ-graphyne with carbon vacancies (Ni@V-γ-GY) displayed remarkable thermodynamic stability, excellent selectivity, and high activity with an ultralow overpotential of 0.03 V. Furthermore, based on ab-initio molecular dynamic and DFT calculations under the H2O solvent, it was revealed that the catalytic performance for H2O2 synthesis in aqueous phase was much better than that in gas phase condition, shedding light on the hydrogen bond network being beneficial to accelerate the transfer of protons for H2O2 synthesis.

We present the electrical properties of zinc phthalocyanine covalently conjugated to cellulose nanocrystals (CNC@ZnPc). Thin films of CNC@ZnPc sandwiched between two gold electrodes showed pronounced hysteresis in their current–voltage characteristics. The layered metal–organic–metal sandwich devices exhibit distinct high and low conductive states when bias is applied, which can be used to store information. Density functional theory results confirmed wave function overlap between CNC and ZnPc in CNC@ZnPc, and helped visualize the lowest (lowest unoccupied molecular orbital) and highest molecular orbitals (highest occupied molecular orbital) in CNC@ZnPc. These results pave the way forward for all-organic electronic devices based on low cost, earth abundant CNCs and metallophthalocyanines.

Molecular electronic spins are good candidates as qubits since they are characterized by a large tunability of their electronic and magnetic properties through a rational chemical design. Coordination compounds of light transition metals are promising systems for spin-based quantum information technologies, thanks to their long spin coherence times up to room temperature. Our work aims at presenting an in-depth study on how the spin-phonon coupling in vanadyl-acetylacetonate, [VO(acac)2], can change as a function of temperature using terahertz time-domain spectroscopy and density functional theory (DFT) calculations. Powder THz spectra were recorded between 10 and 300 K. The temperature dependence of vibrational frequencies was then accounted for in the periodic DFT calculations using unit-cell parameters measured at two different temperatures and the optimized ones, as usually reported in the literature. In this way, it was possible to calculate the observed THz anharmonic frequency shift with high accuracy. The overall differences in the spin-phonon coupling magnitudes as a function of temperature were also highlighted showing that the computed trends have to be ascribed to the anisotropic variation of cell parameters.

We present vibrational properties of Franckeite, which is a naturally occurring van der Waals heterostructure consisting of two different semiconducting layers. Franckeite is a complex layered crystal composed of alternating SnS$_2$ like pseudohexagonal and PbS-like pseudotetragonal layers stacked on top of each other, providing a unique platform to study vibrational properties and thermal transport across layers with mass density and phonon mismatches. By using micro-Raman spectroscopy and first-principles Raman simulations, we found that the PbS-like pseudotetragonal structure is mostly composed of Pb$_3$SbS$_4$. We also discovered several low-frequency Raman modes that originate from the intralayer vibrations of the pseudotetragonal layer. Using density functional theory, we determined all vibrational patterns of Franckeite, whose signatures are observed in the Raman spectrum. By studying temperature dependent Raman spectroscopy (300 K - 500 K), we have found different temperature coefficients for both pseudotetragonal and pseudohexagonal layers. We believe that our study will help understand the vibration modes of its complex heterostructure and the thermal properties at the nanoscale., Comment: 15 pages, 10 figures

Geometric structures of carbon networks are key in designing their material properties. In particular, optimization of curved structures through the introduction of topological defects and doping of heteroatoms in the lattice is crucial to the design of carbon-based, non-noble-metal-free catalysts. A simple and practical mathematical model based on discrete geometric analysis is proposed to describe the geometric features of carbon networks and their relationships to their material properties. This model can pre-screen candidates for novel material design, and these candidates can be further examined by the density functional theory (DFT). Inspired by observations regarding the preferential doping of heteroatoms at local curved sites, the important characteristics of the candidate material were experimentally realized, and its enhanced catalytic activity facilitated by chemical dopants was confirmed in the designed carbon network.

In recent years, graphene-like boron carbide and carbon nitride nanosheets have attracted remarkable attentions, owing to their semiconducting electronic nature and outstanding mechanical and heat transport properties. Graphene-like BC6N is an experimentally realized layered material and most recently has been the focus of numerous theoretical studies. Interestingly, the most stable form of BC6N monolayer remains unexplored and limited information are known concerning its intrinsic physical properties. Herein, on the basis of density functional theory (DFT) calculations we confirm that the most stable form of BC6N nanosheet shows a rectangular unitcell, in accordance with an overlooked experimental finding. We found that BC6N monolayer is a semiconductor with 1.19 eV HSE06-based direct gap and yields anisotropic and excellent absorption of visible light. First-principles results highlight that BC6N nanosheet exhibits anisotropic and ultrahigh tensile strength and lattice thermal conductivity, outperforming all other fabricated 2D semiconductors. We moreover develop classical molecular dynamic models for the evaluation of heat transport and mechanical properties of BC6N nanomembranes. The presented results in this work not only shed light on the most stable configuration of BC6N nanosheet, but also confirm its outstandingly appealing electronic, optical, heat conduction and mechanical properties, extremely motivating for further theoretical and experimental endeavors.

Ag3PO4 as a novel photoanode material, despite its arguably highest photoactivity, suffers for its poor light absorption and stability for photoelectrochemical (PEC) water oxidation. In this work, 4.5 × 4.5 cm2 Ag3PO4 microcrystalline films are grown via a room-temperature solution process, and vacuum annealing is proposed to solve the stability and light absorption issues. It is found that the major process below 400 °C of vacuum annealing is the |Recovery| process for Ag3PO4 microcrystals, when lattice defects and Ag0 surface species get reduced. Next, |Recrystallization| stage occurs at >400 °C. The recovery of native defects of silver vacancies, with both density functional theory calculation and experimental results, could simultaneously improve the light absorption and catalytic activity of Ag3PO4. The 400 °C-annealed Ag3PO4 photoanode, with enhanced light harvesting and crystal quality, exhibits 88% increase in (Jlight − Jdark) value (1.94 mA cm−2) than non-annealed photoanode (1.03 mA cm−2). Moreover, it retains >99% current density after a 4000-s stability test. These results suggest that vacuum annealing can substantially improve the PEC performance of Ag3PO4 microcrystalline film photoanodes due to mitigated effects of native defects, improved light harvesting, and inhibited Ag3PO4 decomposition during water oxidation reaction.

The physicochemical properties of small metal clusters strongly depend on their precise geometry. Determining such geometries, however, is challenging, particularly for clusters formed by multiple elements. In this work, we combine infrared multiple photon dissociation spectroscopy and density functional theory calculations to investigate the lowest-energy structures of Pd doped gold clusters, PdAun−1+ (n ≤ 10). The high-quality experimental spectra allow for an unambiguous determination of the structures adopted by the clusters. Our results show that the Pd–Au interaction is so large that the structures of PdAun−1+ and Aun+ are very different. Pd doping induces a 2D to 3D transition at much smaller cluster sizes than for pure Aun+ clusters. PdAun−1+ clusters are three-dimensional from n = 4, whereas for Aun+ this transition only takes place at n = 7. Despite the strong Au–Pd interaction, the Aun−1+ cluster geometries remain recognizable in PdAun−1+ up to n = 7. This is particularly clear for PdAu6+. In PdAu8+ and PdAu9+, Pd triggers major rearrangements of the Au clusters, which adopt pyramidal shapes. For PdAu4+ we find a geometry that was not considered in previous studies, and the geometry found for PdAu8+ does not correspond to the lowest-energy structure predicted by DFT, suggesting kinetic trapping during formation. This work demonstrates that even with the continuous improvement of computational methods, unambiguous assignment of cluster geometries still requires a synergistic approach, combining experiment and computational modelling., The physicochemical properties of small metal clusters strongly depend on their precise geometry.

Density functional theory calculations are employed to investigate the electronic, adsorption, and catalytic properties of Bi-, Sb-, and As-nanoclusters. The stability of these clusters are confirmed by the obtained positive binding energies, the change in the free energy, and frequencies, also they can be grown on different substrates such as graphene and hexagonal boron nitride. They have energy gaps ranging from 2.1 to 3 eV that can be controlled by adsorption of different gases or molecules, for instance, adsorption of C2 decreases the gap in Sb-18-a cluster from 2.7 eV to 0.8 eV. These clusters show also interesting adsorption properties where some gases are physically adsorbed (like, N2 and CH4) while others are chemically adsorbed (O2 and SO2). In the first case, the linear N2 molecule has a strong triple bond, from the sp-hybridization, that can’t be broken through the interaction with the clusters, the same occurs also for the sp3-hybridized CH4 with the strong sigma bonds. For the sp2-hybridized O2 molecule, one of the relatively weaker double bond can be broken through the interaction to form another with the cluster. The oxygen evolution reaction (OER) on the edges of these clusters requires lower overpotential than their surfaces due to the moderate adsorption of O by one edge atom with respect to the strong adsorption by two surface atoms. Nanoclusters and quantum dots of Sb provide the best values for the overpotential due to moderate bonding that Sb atoms form with all intermediates not only O, namely overpotentials equal 0.31 and 0.39 V for the nanocluster and the quantum dots, respectively. This significant enhancement of the OER activity makes such clusters strong applicants for water oxidation catalysts.

Single photocatalysts usually exhibit unsatisfactory performance due to the serious recombination of photogenerated electron‒hole pairs. Combining two photocatalysts to construct S-scheme heterojunction could solve this problem. In S-scheme mechanism, the interfacial built-in electric field (IEF) provides a vital driving force for efficient charge separation. Modifying the IEF is a feasible strategy to further improve the photocatalytic activity. Herein, a novel idea of tuning the strength of IEF in 2D/2D graphitic carbon nitride (g-C3N4)/MS2 (M = Sn, Zr) S-scheme heterojunctions by nonmetal doping was developed by employing density functional theory calculation. Three nonmetal elements (O, P, and S) were severally introduced into g-C3N4/MS2 composites. Charge density difference suggested that O and S doping led to increased interfacial electron transfer, while P doping had minimal influence. As expected, the calculated field strength of O- and S-doped g-C3N4/MS2 composites was significantly larger than that of pristine and P-doped g-C3N4/MS2 composites. Therefore, O and S doping endowed g-C3N4/MS2 S-scheme heterojunctions with enhanced IEF and more thorough charge transfer. Correspondingly, the experimentally synthesized O-C3N4/SnS2 composite exhibited better photocatalytic H2-production activity than g-C3N4/SnS2 composite. This work proposed an original idea of employing proper nonmetal doping to magnify the advantage of S-scheme heterojunction in accelerating charge separation.

Alkali metal potassium is conducive to structure promotion and electronic modulation in metal oxides. Here, K species was successfully introduced into α-MnO2 via in situ synthesis (Pre-K/MnO2) and hydrothermal impregnation method (Post-K/MnO2) with target to boost the low-temperature reactivity and deep destruction efficiency for toluene oxidation. Results reveal that Post-K/MnO2 possesses the highest catalytic activity with toluene (1000 ppm) totally mineralized at just 258 °C, achieving over 70 °C of temperature reduction than that of Pre-K/MnO2. K specie shows obvious charge transfer balance ability in MnO2, forming MnO6-K-MnO6 bridging bond and leading to more uniform energy of Mn-O bonds. High electron density of K+ can promote the activation of oxygen molecules, resulting in a better catalytic performance of toluene. Abundant Bronsted acid sites are beneficial for toluene adsorption and regeneration of hydroxyl on the surface, which promote the degradation of intermediates during toluene oxidation. Moreover, Post-K/MnO2 shows satisfied catalytic performance under different space velocities and initial concentrations and humid condition. Density functional theory (DFT) calculation revealed the situation of oxygen vacancy and toluene/oxygen adsorption energy in catalysts with different K doping locations. Results showed that the adsorption energy is stronger when K located in large tunnel (0.46 × 0.46 nm), and it is easier to form oxygen vacancy while K entered the small tunnel (0.33 × 0.33 nm). The present work paves new insights into the designing of efficient transition metal oxide catalyst for VOC deep purification.

Silicon carbide surface modification is still a challenging task. Its modification mechanism is also still unclear. This paper provides a study of the surface modification mechanism of KH5X0 (X = 5, 6, 7, 8, 9) on the silicon carbide (111) using density functional theory. The electronic structures and densities of states of KH5X0 (X = 5, 6, 7, 8, 9) on SiC surfaces indicates that the surface modification mechanism is attributed to the electronic effects of the functional groups of KH5X0 (X = 5, 6, 7, 8, 9). From the results the easier it is for a functional group to obtain electrons, the better the modifying performance of silane coupling agent will be. Furthermore, the interface energy results showed that silicon carbide (111) modification performance by KH580 silane and KH590 silane is better than KH550, KH560, and KH570. The present work provides theoretical guidance for the fabrication of SiC heat sink products.