Search

Molybdenum disulfide (MoS 2) has been considered a promising high-efficiency, low-cost hydrogen evolution reaction (HER) catalyst in acidic and alkaline media. However, the lack of active sites in the basal plane become the most significant obstacle hindering the widespread application of MoS 2. Here, we systematically studied the HER performance of MoS 2 plane or edge by co-doping Co atom and other 3 d transition metals (TM = Ti–Fe, Ni) by density functional theory calculation methods. Interestingly, the dual atoms doping in both the basal plane and edges of MoS 2 is a feasible fabrication with small or negative formation energies. Compared with the pristine MoS 2 electrocatalyst, the HER performance in these doped systems is largely enhanced in both basal plane and edges due to the effective charge regulation on the S site by dual atom doping. Remarkably, close to zero H adsorption free energy (ΔG H = −0.161–0.119 eV) is identified for the TM-Co co-doped MoS 2 basal, indicating that they are potential alternate HER electrocatalysts of Pt. Our study provides a new strategy to design highly efficient non-noble metal electrocatalysts accessibility for energy-related applications. • Effect of dual TM atoms doping for HER on MoS 2 basal plane and edge. • Ti–Co-, Mn–Co-, and Cr–Co-doped MoS 2 plane yield near-zero Δ G H. • Ti–Co-doped MoS 2 edge yields near-zero Δ G H. • The dual atom doping leads to the effective charge regulation on the S site. [ABSTRACT FROM AUTHOR]

[Display omitted] Morphology engineering and element doping are two effective strategies to boost the capacitive performance of electroactive materials. The morphology control through doping process is conducive to simplifying the preparation process. Herein, an aluminum-doped (Al-doped) strategy was used to prepare Al-doped NiCo 2 O 4 nanosheet-wire structure (Al-NiCo 2 O 4 NSW) by hydrothermal method and subsequent calcination. The nanosheet-wire structure was composed of one-dimensional (1D) nanowires and two-dimensional (2D) ultrathin nanosheets. 1D nanowires can provide efficient pathways for the electrons/ions transport. 2D nanosheets can enlarge the specific surface area and expose more active sites. The Al doping can change the electronic structure of NiCo 2 O 4 with enhanced electrical conductivity as revealed by density functional theory (DFT) calculations. Meanwhile, a strong adsorption capacity of OH– was obtained on Al-NiCo 2 O 4 NSW for redox reactions. The Al-NiCo 2 O 4 NSW electrode demonstrated a high specific capacity of 1441C g−1 (2446F g−1) at 1 A g−1 and excellent cycling stability (87.6% capacity retention at 10 A g−1 for 5000 charge-discharge cycles). The assembled asymmetric supercapacitor manifested a superior energy density of 46.2 Wh Kg−1 at a power density of 800 W kg−1. [ABSTRACT FROM AUTHOR]

Alkylamines are ubiquitous in pharmaceuticals, materials and agrochemicals. The Mannich reaction is a well-known three-component reaction for preparing alkylamines and has been widely used in academic research and industry. However, the nucleophilic components in this process rely on C(sp2)−H and activated C(sp3)−H bonds while the unactivated C(sp3)−H bonds involved Mannich alkylamination is a long-standing challenge. Here, we report an unprecedented multicomponent double Mannich alkylamination for both C(sp2)−H and unactivated benzylic C(sp3)−H bonds. In this process, various 3-alkylbenzofurans, formaldehyde and alkylamine hydrochlorides assemble efficiently to furnish benzofuran-fused piperidines. Mechanistic studies and density functional theory (DFT) calculations revealed a distinctive pathway that a multiple Mannich reaction and retro-Mannich reaction of benzofuran and dehydrogenation of benzylic C(sp3)−H bonds were key steps to constitute the alkylamination. This protocol furnishes a Mannich alkylamine synthesis from unusual C–H inputs to access benzofuran-fused piperidines with exceptional structural diversity, molecular complexity and drug-likeness. Therefore, this work opens a distinctive vision for the alkylamination of unactivated C(sp3)−H bonds, and provides a powerful tool in diversity-oriented synthesis (DOS) and drug discovery. The Mannich reaction is a three-component reaction for preparing alkylamines, but the nucleophilic components rely on C(sp2)−H and activated C(sp3)−H bonds. Here, the authors report an unprecedented multicomponent double Mannich alkylamination for both C(sp2)−H and unactivated benzylic C(sp3)−H bonds. [ABSTRACT FROM AUTHOR]

The elastic and photocatalytic properties of multiferroic material InFeO3 under strain are calculated through density functional theory. The calculated results indicate that the intrinsic InFeO3 and the strained InFeO3 meet the mechanical stability conditions and hold a relatively larger elastic coefficient than popular multiferroic material BiFeO3. The calculated bandgap and band edge of InFeO3 under tensile strain show that InFeO3 could be a high-efficiency photocatalytic hydrogen production material. InFeO3 under tensile strain holds the ability of photocatalytic water splitting to produce hydrogen with excellent ferroelectric, mechanical properties and absorption of visible light. [ABSTRACT FROM AUTHOR]

The search for new two-dimensional monolayers with diverse electronic properties has attracted growing interest in recent years. Here, we present an approach to construct MA2Z4 monolayers with a septuple-atomic-layer structure, that is, intercalating a MoS2-type monolayer MZ2 into an InSe-type monolayer A2Z2. We illustrate this unique strategy by means of first-principles calculations, which not only reproduce the structures of MoSi2N4 and MnBi2Te4 that were already experimentally synthesized, but also predict 72 compounds that are thermodynamically and dynamically stable. Such an intercalated architecture significantly reconstructs the band structures of the constituents MZ2 and A2Z2, leading to diverse electronic properties for MA2Z4, which can be classified according to the total number of valence electrons. The systems with 32 and 34 valence electrons are mostly semiconductors. Whereas, those with 33 valence electrons can be nonmagnetic metals or ferromagnetic semiconductors. In particular, we find that, among the predicted compounds, (Ca,Sr)Ga2Te4 are topologically nontrivial by both the standard density functional theory and hybrid functional calculations. While VSi2P4 is a ferromagnetic semiconductor and TaSi2N4 is a type-I Ising superconductor. Moreover, WSi2P4 is a direct gap semiconductor with peculiar spin-valley properties, which are robust against interlayer interactions. Our study thus provides an effective way of designing septuple-atomic-layer MA2Z4 with unusual electronic properties to draw immediate experimental interest. The discovery of a new two-dimensional van der Waals layered MoSi2N4 material inspires many attentions. Here, the authors report intercalation strategies to explore a much wider range of MA2Z4 family and predict amount of materials accessible to experimental verifications with emergent topological, magnetic or Ising superconductivity properties. [ABSTRACT FROM AUTHOR]

Photodetectors based on high-performance, two-dimensional (2D) layered transition metal dichalcogenides (TMDCs) are limited by the synthesis of larger-area 2D TMDCs with high quality and optimized device structure. Herein, we report, for the first time, a uniform and stacked–layered MoSe2 film of high quality was deposited onto Si substrate by using the pulsed laser deposition technique, and then in situ constructed layered MoSe2/Si 2D–3D vertical heterojunction. The resultant heterojunction showed a wide near-infrared response up to 1550 nm, with both ultra-high detectivity up to 1.4 × 1014 Jones and a response speed approaching 120 ns at zero bias, which are much better than most previous 2D TMDC-based photodetectors and are comparable to that of commercial Si photodiodes. The high performance of the layered MoSe2/Si heterojunction can be attributed to be the high-quality stacked–layered MoSe2 film, the excellent rectifying behavior of the device and the n-n heterojunction structure. Moreover, the defect-enhanced near-infrared response was determined to be Se vacancies from the density functional theory (DFT) simulations. These results suggest great potential of the layered MoSe2/Si 2D–3D heterojunctions in the field of communication light detection. More importantly, the in situ grown heterojunctions are expected to boost the development of other 2D TMDCs heterojunction-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Based on density functional theory combined with non-equilibrium Green's function method, we investigate the thermoelectric transport properties of zigzag-edged graphene nanoribbons (ZGNRs) co-doped by two BN pairs at one edge. By applying the co-doping scheme of BN pairs instead of single B and N atoms as reported in literature, the energy of the quasi-bound states gets very close to the Fermi level. Due to the back scattering from the quasi-bound states, transmission valleys appear around the Fermi level, which results in a large transmission slope and Seebeck thermopower for both spin channels. Interestingly, the signs of the Seebeck thermopower of the two spin channels are opposite and the magnitudes are nearly equal, which can be utilized for generating pure spin current with a thermal gradient. More importantly, the thermal spin current is robust against the change of the distance between the two BN pairs and the doping configuration. These findings suggest a fascinating strategy for thermal spin current generation using BN pair co-doping and will be significant for the design of spintronic devices based on graphene nanoribbons. [ABSTRACT FROM AUTHOR]

By means of variable-compositional evolutionary algorithms, in combination with first-principles calculations, the compositions, structures and mechanical properties of the W-B system have been theoretically investigated. As well as confirming the experimental observations (including their crystal structures) for the four known compounds W2B, WB, WB2 and WB3, the new stable compound W8B7 and two nearly stable compounds, W2B3 and WB4, have also been predicted in the ground state. The elastic properties and estimated Vickers hardnesses of all these borides have been systematically derived. The results show that, among these borides, hP6-WB2 exhibits the largest ultra-incompressibility along the c axis, with the highest C33 value (953 GPa, comparable with that of the most incompressible diamond). hP16-WB3 exhibits the highest hardness of 36.9 GPa, in good agreement with the experimentally measured data from 28.1 to 43.3 GPa, close to the superhard threshold, and oC8-WB shows the highest bulk modulus of about 350 GPa. The new stable compound W8B7 crystallizes in the monoclinic mP15 phase, with infinite zigzag B chains running parallel to the W-atom layers, resulting in a relatively high estimated hardness of 19.6 GPa. The anisotropic Young's modulus E and torsion shear modulus Gt have been derived for both oC8-WB and hP16-WB3. The current state of research and the historic inconsistency of the W-B system are briefly summarized, in particular clarifying the fact that the previous experimentally attributed hP20-WB4 is in fact the defect-containing hP16-WB3. [ABSTRACT FROM AUTHOR]

Abstract: The vibronically resolved spectra of an intermediate and a product involved in the photoreaction of α-santonin have been explored by the density functional theory and the post-SCF methodologies, and a detailed comparison of theory with experiment was conducted to obtain reliable assignments to the observed spectra. The predicted emission energies of photosantonic acid and a topochemical product are found to match with the experimental values reasonably. The further calculations manifest that the absorption spectrum of photosantonic acid exhibits vibrationally resolved features, while the absorption band of topochemical product without vibrational resolution is opposite to the experimental observation. These new computational findings lead to a revised assignment to the observed bands and provide a basis for experimentalists to draw a convinced reaction mechanism for the α-santonin photorearrangement. [Copyright &y& Elsevier]

The development of effective and non-precious electrocatalyts for hydrogen evolution reaction (HER) has attracted massive research interests. Herein, we report a density functional theory (DFT) investigation on the activation and optimization of Molybdenum disulfide (MoS 2) monolayer as efficient HER electrocatalysts by cobalt-nonmetal atom (X = B, C, N, P, Se) codoping. Our results show that three CoX-MoS 2 (X = C, N, and Se) catalysts display enhanced HER performance with |Δ G H |s in the range of 0.12–0.23 eV. Careful electronic structure analysis manifests that the favorable H adsorption process on the MoS 2 basal plane is induced by suitable in-gap states upon codoping. Furthermore, appropriate biaxial strain can help optimize the HER performance of these co-doped systems, e.g, the Δ G H s of CoC@MoS 2 , CoN@MoS 2 , and CoSe@MoS 2 reaches 0.0 eV, −0.04 eV, and −0.01 eV at 1.86% tensile strain, 5% compressive strain, and 4% compressive strain, respectively. Our work offers a highly promising catalyst for HER and guides the atomic design of more efficient non-noble electrocatalysts. • Designed MoS 2 based catalysts by co-doping metallic and nonmetallic elements in the basal plane. • Co-X (X = C, N, and Se) co-doped MoS 2 display enhanced HER performance than that of the pristine one. • Co-C, Co-N, and Co-Se co-doping yield near-zero Gibbs free energy at moderate extensile or compressive strain. • The synergistic effect of double elements doping promotes the catalytic activity of MoS 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1. The ball-flower hierarchical structure composites Co 0.85 Se-NC/C is synthesis. • 2. The introduction NC decreased the free energy and protected the nanoparticles. • 3. Co 0.85 Se-NC/C-750 exhibits a small Tafel slope of 47.2 mV dec-1 in 1.0 M KOH. • 4. DFT analysis showed superior intermediates adsorption property of Co 0.85 Se-NC. In this work, with the assistance of polymeric nonionic surfactant Pluronic F127, 2D nanosheets glycerol cobalt self-assembled into the ball-flower structure composites (CoG@F127). Then, CoG@F127 is coated by polydopamine (PDA) to form CoG@F127@PDA. After the calcination with Se powder, CoG@F127@PDA is transformed into the ball-flower hierarchical structure Co 0.85 Se-NC/C, in which Co 0.85 Se nanoparticles are coated with nitrogen doped carbon (NC). The Co 0.85 Se nanoparticles anchored on the NC can avoid the aggregation, maintain structure stability and expose more electrocatalytic active sites for oxygen evolution reaction (OER). Specially, Co 0.85 Se-NC/C-750 shows a small Tafel slope of 47.2 mV dec-1 in 1.0 M KOH that is even lower than IrO 2 and most of the reported Co-based catalysts. Besides, the theoretical calculations by density functional theory (DFT) suggest that NC could tailor the electronic structure of Co 0.85 Se, leading to optimized free energy change (Δ G) of the speed-controlled step and density of states (DOS). [ABSTRACT FROM AUTHOR]

A density functional theory (DFT) concept is utilized for a selected class of compounds to propose phase transitions for which the coupling of magnetic ordering and vibrational properties is manifested. The total electronic energies and the phonon spectra are calculated with the same level of accuracy. The total free energy becomes temperature dependent because of the phonon free energy. In particular, the Laves phase compounds ZrMn2 and HfMn2 are studied because they reveal a close competition of phases with different structural properties and different magnetic orderings as a function of temperature. The temperature dependence of the free energy is driven by the entropy of the lattice vibrations, which therefore is responsible for the predicted phase transitions. These ab initio predictions of phase transitions (or indications of peculiar magnetic ground states) are awaiting experimental verification. [ABSTRACT FROM AUTHOR]

To keep excellent redox ability and facilitate the separation of charge carriers, step-scheme (S-scheme) photocatalytic systems have been used in the photocatalytic H 2 production. Recently, all kinds of photocatalysts with excellent performance and stability have been formed. Especially, 2D/2D heterojunction materials have attracted tremendous attention for the faster interfacial charge separation and transfer between them and much active centers. In this work, we designed a series of heterostructure photocatalysts of 2D/2D porous graphitic C 3 N 4 (Pg-C 3 N 4)/CdS-diethylenetriamine (DETA) nanocomposites and explored the S-scheme mechanism via density functional theory (DFT) calculations and XPS analysis. Under visible light irradiation, the experimental results indicated that the designed nanocomposites of water splitting photocatalytic activity for hydrogen evolution was 9738 μmol h−1 g−1, which is 1.7 and 12.2 times higher than that of CdS-DETA and Pg-C 3 N 4. The performance improvement is mainly due to the following reasons: 1) Pg-C 3 N 4 with large specific surface area could provide more active sites; 2) 2D/2D heterojunction have the faster interfacial charge separation and transfer rate; 3) DETA could synergistically promote the improvement of performance. This work not only introduces a novel Pg-C 3 N 4 /CdS-DETA heterojunction but also provides an approach on designing 2D/2D heterojunction for application in photocatalysis. ga1 • Pg-C 3 N 4 /CdS-DETA system was prepared. • Pg-C 3 N 4 /CdS-DETA system exhibited excellent photocatalytic H 2 production. • Pg-C 3 N 4 /CdS-DETA system is stable during the photocatalytic reaction. • S-scheme photocatalytic mechanism is proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] Water dissociation is of fundamental importance in scientific fields and has drawn considerable interest in diverse technological applications. However, the high activation barrier of breaking the O H bond within the water molecule has been identified as the bottleneck, even for the water adsorbed on the graphene oxide (GO). Herein, using the density functional theory calculations, we demonstrate that the water molecule can be spontaneously dissociated on GO supported by the (1 1 1) surface of the copper substrate (Copper-GO). This process involves a proton transferring from water to the interfacial oxygen group, and a hydroxide covalently bonding to GO. Compared to that on GO, the water dissociation barrier on Copper-GO is significantly decreased to be less than or comparable to thermal fluctuations. This is ascribed to the orbital-hybridizing interaction between copper substrate and GO, which enhances the reaction activity of interfacial oxygen groups along the basal plane of GO for water dissociation. Our work provides a novel strategy to access water dissociation via the substrate-enhanced reaction activity of interfacial oxygen groups on GO and indicates that the substrate can serve as an essential key to tuning the catalytic performance of various two-dimensional material devices. [ABSTRACT FROM AUTHOR]

• Ni(OH) 2 nanoflowers were prepared on Ti mesh using rapid electrodeposition. • Ni(OH) 2 /Ti exhibited excellent OER catalytic activity (η 100 = 290 mV). • Flowerlike Ni 2 P/Ti showed outstanding HER performance over the full pH range. • DFT calculation confirm that Ni and P as active sites have the best |Δ G H* |. • The Ni 2 P/Ti (−) || Ni(OH) 2 /Ti (+) displayed a low voltage of 1.493 V at 10 mA cm−2. The exploration of efficient, robust and nonprecious transition metal electrocatalysts for electrochemical hydrolysis is urgently needed. Herein, we developed Ni(OH) 2 with 3D nanoflower structure on the titanium mesh by a simple electrodeposition method. The Ni(OH) 2 /Ti exhibited excellent oxygen evolution reaction performance and achieved 10 mA cm−2 at 190 mV with fast kinetics in alkaline conditions. Ni 2 P, NiS 2 and NiSe 2 were prepared by solid-phase reaction, and the 3D nanoflower increased the open structure and greatly enhanced catalytic activity. The Ni 2 P/Ti electrode required an overpotential of 52, 88 and 109 mV to reach 10 mA cm−2 for hydrogen evolution reaction in acidic, alkaline and neutral media, respectively. The results of electrochemical measurements and mechanistic studies showed that the catalytic activity of HER: Ni 2 P > NiS 2 > NiSe 2 > Ni(OH) 2. The Ni 2 P/Ti and Ni(OH) 2 /Ti electrodes were assembled into an integrated water splitting electrolytic cell. The water electrolysis device assembled with the Ni 2 P/Ti and Ni(OH) 2 /Ti electrodes only needed a low potential of 1.608 V to achieve 50 mA cm−2 in alkaline environment and was operated stably for 50 h. [ABSTRACT FROM AUTHOR]

Hexafluoropropylene oxide dimer acid (HFPO-DA), an alternative of perfluorooctanoic acid (PFOA), has been detected frequently in environmental media worldwide. It has been reported that HFPO-DA is equal to or more toxic than PFOA, as well as more recalcitrant to degradation. In this study, the efficient degradation of HFPO-DA was achieved by the thermally activated persulfate (TAP) system, but the influence of co-contaminants in the field can be significant. The degradation pathways of HFPO-DA were proposed through an integrated approach of experiment and density functional theory (DFT) calculations. CF 3 CF 2 COO− and CF 3 COO−, were the stable intermediates identified by ultra-performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry (UPLC-Q-TOF-MS). Electron transfer, decarboxylation, H abstraction, HF elimination using H 2 O as a catalyst and hydrolysis occurred in different steps of HFPO-DA degradation process, with –COO− as the initial oxidative site attacked by SO 4 −. In addition, the acute toxicity assessment for HFPO-DA degradation in the TAP system performed by Escherichia coli suggested that HFPO-DA was degraded to a level having no adverse effect on the growth of E. coli , and no more toxic intermediates were formed. Overall, this work provides insights for the degradation of HFPO-DA contamination by the TAP system. [Display omitted] • Effective degradation of HFPO-DA could be achieved in the TAP system. • The –COO− group, rather than the etheric bond, was the initial reactive site. • C 2 F 5 COO− and CF 3 COO− were the stable intermediates identified by UPLC-Q-TOF-MS. • DFT was employed to determine the degradation mechanism of HFPO-DA. • No more toxic intermediate byproducts than HFPO-DA were formed. [ABSTRACT FROM AUTHOR]

• Carbon fragments incorporated carbon nitride was obtained by a one-step process. • The carbon sites on DCN facilitates the charge loss process of HSO 5 −. • DCN has excellent non-photocatalytic capability on PMS conversion into 1O 2. • DCN/PMS system exhibited stable and efficient degradation on 4-chlorophenol. The metal-free nature of carbon nitride endows it the advantages of low cost and less secondary pollution when uses in peroxymonosulfate (PMS)-based advanced oxidation processes. However, practical applications call for continued efforts on developing modification protocols to achieve higher catalytic efficiency while breaking its dependence on visible light. Herein, a one-step carbon fragments doping method was developed to synthesis a series modified carbon nitride. The obtained catalyst DCNs showed high efficiency on non-photocatalytic activation of PMS for organic pollutant removal. Characterization results proved that carbon fragments were incorporated into the skeleton of carbon nitride during the thermal treatment process. Along with the rise of doping amount, the system efficiency on pollutant removal increased first then decreased. The dominant reactive species was identified as singlet oxygen, which was deduced to originate from the electron loss process of HSO 5 − at the carbon sites on DCN. Density functional theory calculations suggest that appropriate doping of carbon fragments on carbon nitride improves the adsorption energy and charge transfer efficiency of PMS on the catalyst surface, thereby elevating the catalytic efficiency on pollutant removal. In addition, as a non-radical species dominated process, the DCN catalyst well resisted the interference from water matrices to degrade pollutants in high efficiency. At the same time, DCN had good reusability, exhibiting considerable prospects for practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simulations show that there exist two growth modes of channel induced by oxygen. • Quantitative conditions of channel initiation are found by a series of simulations. • Oxygen content model to initiate channel is built and widely extended. • Critical oxygen of 0.0008 wt% to eliminate channel is first found and validated. Macrosegregation is the key issue in the solidification field. Oxygen and its inclusions play the important role in driving the melt flow and the resulting macrosegregation in steel. Here, to reveal the inducing mechanism and quantitative model of oxygen content in real industrial steel ingots, we demonstrate for the first time that there exists the critical oxygen content in triggering the formation of channel-type segregation, the most undesirable macrosegregation type in steel. Our multiscale simulations from density functional theory calculations to multiphase/multicomponent macromodel, clarify the quantitative conditions initializing channel-type segregation and reveal two typical growth modes via oxide flotation. The oxygen content model and criterion to induce the channel onset is built accordingly, which are validated by the numerous full ingot dissections and experimental characterizations including the in situ electrolysis of inclusions, X-ray microtomography, scanning electron microscope, large-scale measurement system of inclusions and chemical analysis. With oxygen controlled below this critical value of 0.0008 wt%, channel disappears. This study quantitatively uncovers the novel role of oxygen in steel, changes the traditional sole concept of cleanliness, and highlights an innovative and controlling-effective route to fabricate homogenized steel. [ABSTRACT FROM AUTHOR]

• θ- to α-Al 2 O 3 phase transformation followed a "synchro-shear" model. • The details of transformation were mapped out through first-principles calculations. • There was a critical size of ~22.88 nm for θ-Al 2 O 3 before it transformed to the α-Al 2 O 3. ga1 The mechanism of θ- to α-Al 2 O 3 phase transformation is proved by the "synchro-shear" model through the first-principles calculations. The proposed model is based on a reorganization of oxygen anions sublattice from f.c.c. to h.c.p. which is achieved by series of shears of the oxygen closed-stacking plane (20 1 ̅) along the direction of [102] and a migration of Al-cations to the near octahedral interstices to form a "honey comb" lattice. On this basis, it is concluded that there is a critical size of ~22.88 nm at which θ-Al 2 O 3 is thermodynamically able to transform to an α form. The obtained data is in a good agreement with the experimental observations. [ABSTRACT FROM AUTHOR]

• There is an inhibition efficiency limitation of BTA towards 20SiMn steel in 3.5 wt% NaCl with the increasing concentration. • The chemisorption of BTA through N-Fe bond on the surface of 20SiMn steel is responsible for the inhibition effect of BTA. • The limitation of inhibition efficiency is the result of the unchanged DOS of Fe atom and Fe(1 1 0) surface. The inhibition effect of benzotriazole (BTA) with the increase of concentration for 20SiMn steel in 3.5 wt% NaCl solutions was investigated by electrochemical methods, Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS) and Density Functional Theories(DFT). Results indicate that BTA could suppress the corrosion of 20SiMn steel through chemisorption but with a limited inhibition efficiency (around 60%). DFT calculated results show that the chemisorption of BTA has noticeable effects on the charge distribution of the whole BTA molecule, as well as that of N atom which bonds with Fe atom, but has little influence on those of Fe atom in N-Fe bond and Fe(1 1 0) surface where BTA molecules adsorb. The DFT calculated Density of States (DOS) peaks of N atom in N-Fe and those of BTA molecule become lower after the adsorption, and the location of DOS peaks move far away from the Femi surface, implying a more stable structure. As to Fe atom in N-Fe bond and Fe(1 1 0) surface, neither height nor locations of the DOS peaks change,which is crucial for losing electrons of metallic matrix and thus responsible for the limitation of BTA inhibition effect. [ABSTRACT FROM AUTHOR]

• The band structure and density of states indicates a high electron transfer. • The structure integrates macroporous structure and stable interconnection. • The supercapacitor gains a good rate retention and long-term cycling stability. The sandwich‐like nano-micro LDH-MXene-LDH is synthesized by the coprecipitation method. The design of MXene@Ni-Mn LDH is estimated by the band structure and partial density of states using density functional theory. MXene as a carrier can promote the electron conductivity of Ni-Mn LDH to improve the rate retention. LDH can uniformly cover MXene surface to provide more available active sites for the capacitance enhancement. The electronic coupling between Ni-Mn LDH and MXene can improve the electron transfer and ensure the structure stability for the long-term cycling. As a three-electrode cell, MXene@Ni-Mn LDH exhibits the enhanced capacitance and rate retention by the synergistic effect. The asymmetric supercapacitor gains the energy density of 44.7 Wh kg−1 at the power density of 800 W kg−1 and maintained the 90.3% of the initial capacitance after 5000 cycles. [ABSTRACT FROM AUTHOR]

We fabricated a novel adsorbent to remove glyphosate (PMG) in solution by in situ growing of NH 2 -MIL-101 metal-organic framework on biochar derived by the calcination of waste rice husk (hereafter NMBC 61 formulated as NH 2 -MIL-101: BC = 6:1 ratio). The new adsorbent was systematically characterized by atomic, molecular spectroscopic and conventional experimental methods. The PMG adsorption efficiency on NMBC 61 was examined as a function of contact time, solution pH, temperature, matrix solutes, and substrate concentration. The modification of amino group significantly improved the adsorption performance of the material. The PMG adsorption data were modeled using Langmuir isotherm and pseudo-second-order kinetics formulations. The maximum adsorption capacities of NMBC 61 at 323 K for PMG is 186.71 mg g−1. The PMG adsorption did not significantly interfere with NO 3 −, Cl−, HCOO−, and citric acid in the solution matrix; SO 4 2− show an intermediate interfering behavior. However, PMG adsorption interferes significantly in the presence of H 2 PO 4 2− and citric acid. The contrasting interfering patterns show the nature of surface bonding in PMG adsorption on NBMC 61. The subtilties arisen between surface –NH 2 and –OH sites on PMG adsorption were resolved by IR and XPS spectral data. The PMG adsorbed on NBMC 61 via ligand exchange by inner-sphere surface complex formation. When foreign solutes show similar surface complexing, they interfere with PMG adsorption. Based on the adsorption experiments and density functional theory (DFT) calculations, the van der Waals (vdW) interactions and hydrogen bonding were assumed to be involved in the adsorption. NBMC 61 shows over 83% PMG removal efficiency at the end of three cycles. The NMBC 61 show optimal PMG adsorption between pH 2 and 6 with minimal interference from the solution matrix. Therefore, NBMC 61 has the potential in treating organic pollutants found in natural and wastewaters efficiently with minimal pre-treatment steps. [Display omitted] • NMBC 61 was synthesized by in situ growing of NH 2 -MIL-101 metal-organic framework on biochar through solvothermal method. • PMG could be efficiently removed by NMBC 61. • The PMG adsorbed on NBMC 61 via ligand exchange, electrostatic interactions and hydrogen bonding. • No by-products were produced during the adsorption of PMG by NMBC 61. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual-/tri-metal active centers are constructed to study electrocatalytic mechanisms. • Charge transfer on the catalyst surface is exhibited by differential charge density. • N -doped graphene configurations with excellent bifunctional activities are screened. • Homonuclear FeFeN 6 -G and CoCoCoN 9 -G exhibit superior bifunctional activities. • Heteronuclear NiNiCoN 9 -G and CoCoNiN 9 -G exhibit superior bifunctional activities. The development of high activity bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of great significance in renewable energy conversion and storage. In our study, density functional theory (DFT) is used to explore electrocatalytic mechanisms of dual-metal and tri-metal atoms anchored on graphene monolayer coordinated with pyridine nitrogen atoms. The stability of dual-metal and tri-metal sites is evaluated, and the charge redistribution of doped structures is quantitatively studied through Bader charge analysis. Furthermore, several N -doped graphene configurations with excellent bifunctional activities are screened based on the overpotentials in ORR and OER processes. More importantly, the volcano plots are constructed using appropriate ORR and OER descriptors to analyze and predict catalytic activities of metal/nitrogen co-doped graphene with different configurations. Among them, NiNiCoN 9 -G has superior bifunctional activities, and the most suitable metal and nitrogen doping association can be predicted. These findings will provide insights into the structure–activity relationship and catalytic mechanisms of doped graphene and offer guidelines for future designs of OER/ORR bifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

As an emerging peroxymonosulfate (PMS) activation catalyst, graphitic carbon nitride (g-C 3 N 4) is non-toxic and eco-friendly, while its poor catalytic performance hinders the application of pristine g-C 3 N 4. Herein, a simple LiCl/KCl molten salts-assisted thermal polymerization method was adopted to promote the photocatalytic performance of g-C 3 N 4. With the insertion of Li/K dopants and the introduction of surface cyano defects, the modified catalyst exhibited greatly enhanced ability on PMS activation towards acetaminophen removal, observing a 13 times higher rate constant than pristine g-C 3 N 4 (k = 0.0435 min−1 vs. 0.0033 min−1). The main reactive oxygen species for pollutant degradation were identified as sulfate radicals and singlet oxygen. The wavefunction analysis at excited states based on density functional theory suggests that the introduction of cyano defects greatly promotes the separation of photo-generated electron-hole pairs, thereby achieving higher photocatalytic efficiency. In addition, the doping of Li/K significantly enhances the interaction between PMS and the catalyst surface, and orients the electron transfer from PMS to catalyst to generate non-radical species singlet oxygen, which improves the catalyst resistance to anions-containing water matrices. [Display omitted] • Li/K dopants and cyano defects were simultaneously introduced into LiK–CN. • The main reactive oxygen species from PMS activation were SO 4 · - and 1O 2. • DFT calculations were performed for analysis of electron-hole distribution. • Cyano defects significantly promote photocatalytic performance. • Li/K dopants enhanced the interaction between PMS and LiK–CN. [ABSTRACT FROM AUTHOR]

The stability, ferroelectricity, and electronic structure of R3c-MgSnO 3 and R3c-MgSnO 3 under compressive strain were investigated by density functional theory. The calculated phonon frequencies and elastic coefficient indicated that MgSnO 3 and MgSnO 3 under compressive strain could meet dynamic and mechanical stability. The phonon frequencies, elastic coefficient, and mechanical property have been increased in MgSnO 3 under compressive strain, which is explained by the bond length, Bader charge, and electronic structure. The bandgap of R3c-MgSnO 3 under compressive strain has been increased to 3.8 eV with an indirect bandgap to enhance optical transparency, which agrees with the experiment. The ferroelectric stability and polarization strength could also be promoted by the compressive strain in MgSnO 3. The stability, ferroelectric, mechanical, and photoelectric properties of R3c-MgSnO 3 could be controlled by compressive strain. • The calculated phonon frequencies and elastic coefficient indicated MgSnO 3 under compressive strain could meet stability. • The calculated band gap of R3c-MgSnO 3 under compressive strain by MBJ functional is agreement with the recent experiment. • The compressive strain can effectively regulate the stability, ferroelectricity and photoelectric properties of MgSnO 3. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mpg-CN was prepared and used with PDS for photodegradation of ATN. • DFT calculations reveal ATN has chemical adsorption states on active sites. • Experimental and theoretical results confirmed the electron acceptor role of PDS. • Primary degradation mechanisms of ATN were investigated by DFT calculations. • Possible degradation pathways were proposed with mass spectrometry analysis. The visible light sensitive metal-free mesoporous graphitic carbon nitride (mpg-CN) was fabricated for photodegradation of atenolol (ATN), a widely used drug for cardiovascular diseases. Peroxydisulfate (PDS) as an electron acceptor as well as a radical origin was introduced to enhance the catalytic performance, and retaining the nature of metal-free and mesoporous of mpg-CN. The photo-induced holes, SO 4 − and O 2 − were identified as the active species. Integrated with density functional theory (DFT) calculations and photoelectrochemical experiments, the interaction among PDS, catalyst, and ATN is unveiled. PDS can obtain an electron from the catalyst, hence to improve the separation of electron-hole pairs and activates itself. ATN has stable chemical adsorption states on catalyst surface. Then the electron-deficient catalysts can acquire electrons from ATN. In addition, primary degradation sites of ATN and following possible degradation pathways were explored with DFT calculations and mass spectrometry analysis. [ABSTRACT FROM AUTHOR]