Lower Adsorption Energy Research Articles

High-Quality Epitaxial N Doped Graphene on SiC with Tunable Interfacial Interactions via Electron/Ion Bridges for Stable Lithium-Ion Storage.

Tailoring the interfacial interaction in SiC-based anode materials is crucial to the accomplishment of higher energy capacities and longer cycle lives for lithium-ion storage. In this paper, atomic-scale tunable interfacial interaction is achieved by epitaxial growth of high-quality N doped graphene (NG) on SiC (NG@SiC). This well-designed NG@SiC heterojunction demonstrates an intrinsic electric field with intensive interfacial interaction, making it an ideal prototype to thoroughly understand the configurations of electron/ion bridges and the mechanisms of interatomic electron migration. Both density functional theory (DFT) analysis and electrochemical kinetic analysis reveal that these intriguing electron/ion bridges can control and tailor the interfacial interaction via the interfacial coupled chemical bonds, enhancing the interfacial charge transfer kinetics and preventing pulverization/aggregation. As a proof-of-concept study, this well-designed NG@SiC anode shows good reversible capacity (1197.5mAhg-1 after 200 cycles at 0.1Ag-1) and cycling durability with 76.6% capacity retention at 447.8mAhg-1 after 1000 cycles at 10.0Ag-1. As expected, the lithium-ion full cell (LiFePO4/C//NG@SiC) shows superior rate capability and cycling stability. This interfacial interaction tailoring strategy via epitaxial growth method provides new opportunities for traditional SiC-based anodes to achieve high-performance lithium-ion storage and beyond.

Rapid and effective treatment of chronic osteomyelitis by conductive network-like MoS2/CNTs through multiple reflection and scattering enhanced synergistic therapy

Staphylococcus aureus (S. aureus)-infected chronic osteomyelitis (COM) is one of the most devastating infectious diseases with a high recurrence rate, often leading to amputation and even death. It is incurable by all the current strategies involving the clinical use of radical debridement and systemic intravenous antibiotics. Here, we reported on a microwave (MW)-assisted therapy for COM by constructing a heterojunction formed by flake nanoflower-shaped molybdenum disulfide (MoS2) and tubular carbon nanotubes (CNTs). This composite could achieve a combination of MW thermal therapy (MTT) and MW dynamic therapy (MDT) to accurately and rapidly treat COM with deep tissue infection. In vitro and in vivo experiments showed that MoS2/CNTs were effective in non-invasively treating S. aureus-induced COM due to the heat and reactive oxygen species (ROS) produced under MW irradiation. The mechanism of heat and ROS generation was explained by MW network vector analysis, density of states (DOS), oxygen adsorption energy, differential charge and finite element (FEM) under MW irradiation. Since the Fermi layer was mainly contributed by the Mo-4d and C–2P orbitals, MoS2/CNTs could store a large amount of charge and easily release more electrons. In addition, charge accumulation and dissipation motion were strong on the surface of and inside MoS2/CNTs because of electromagnetic hot spots, resulting in the spilling out of a great deal of high-energy electrons. Due to the low oxygen adsorption energy of MoS2/CNTs-O2, these high-energy electrons combined further with the adsorbed oxygen to produce ROS.

Theoretical study of 2D PbSe/Bi2Se3 heterojunctions as gas sensors for the detection of SO2 and Cl2

In this paper, we construct a two-dimensional PbSe/Bi2Se3 van der Waals heterojunction to study the adsorption of Cl2 and SO2 by this heterojunction. Based on the help of Bader charge, charge density difference diagram, and electron localization function, we find the following conclusions. Among the six configurations, three meet the requirements for semiconductor gas sensor detection materials, namely α-PbSe-Bi2Se3, β-PbSe-Bi2Se3, and Bi2Se3-γ-PbSe. The Bi surface of the configuration α-PbSe-Bi2Se3 does not break the Cl-Cl bond in the Cl2 molecule after the adsorption of Cl2, and the band gap of the adsorbed material is reduced by 73.1%. The band gap of the Pb surface of the α-PbSe-Bi2Se3, β-PbSe-Bi2Se3 and Bi2Se3-γ-PbSe configurations change significantly after the adsorption of SO2, directly changing from a narrow band gap to a metallic material with a low adsorption energy and easy desorption of SO2 from the adsorbed material. Therefore, the two-dimensional PbSe/Bi2Se3 van der Waals heterojunction has the potential to become a core detection material for Cl2 and SO2 gas sensors.

A first principles study on the catalytic performance of methylcyclohexane dehydrogenation on a monoatomic catalyst

SummaryThis research explores how methylcyclohexane (MCH) interacts with individual metal atoms M (M= Pt, Pd, and Cu) based on density functional theory (DFT) total energy calculations. We analyzed the adsorption energies of MCH on these metal atoms to understand their stability and reactivity. The results show that MCH prefers to attach to single Pt atoms, which exhibited the strongest adsorption energy. Compared with Pt(111) surfaces, the adsorption energies on Pt atoms were slightly higher, indicating enhanced stability at the nanoscale. Adsorption on Pd and Cu atoms resulted in lower adsorption energies than on Pt. We also focused on the initial step of dehydrogenation, where we studied the removal of one hydrogen atom (H1) from MCH. The presence of a single metal atom significantly lowered the energy required for breaking the C1–H1 bond, with Pt showing the lowest energy barrier compared with Pd and Cu due to the excessive of charge transfer. We analyzed the electronic properties and charge transfer during dehydrogenation, revealing the influence of the metal atom's electronic structure on catalytic behavior. Overall, this research provides valuable insights into how MCH interacts with monoatomic metal catalysts, emphasizing the role of the metal atom's electronic configuration in determining reactivity.

Configurations, electronic and magnetic properties of small-sized iron clusters on the graphdiyne surface

Using first-principles calculations, we have investigated the growth mode, magnetic and electronic properties of Fen clusters (n=1–10,13) on graphdiyne (GDY) surface. The small-size Fen with n≤3 clusters adsorbed on the surface of GDY favor a planar configuration and other clusters with n>3 have three-dimensional structures. The original morphology was maintained upon adsorption on the GDY surface. The Fen clusters with n=3–6,13 tend to bind with the surface with the lower adsorption energy. The relative stability of Fen clusters was not changed upon the adsorption. The remarkable charge transfers from the neighboring Fe atoms to the GDY surface account for the strong interactions of Fen with GDY. The magnetic moments of the adsorbed clusters were significantly reduced compared with free clusters. The adsorption of Fen clusters improves the conductivity of GDY.

Adsorption of Sc on the Surface of Kaolinite (001): A Density Functional Theory Study.

The adsorption behavior of Sc on the surface of kaolinite (001) was investigated using the density functional theory via the generalized gradient approximation plane-wave pseudopotential method. The highest coordination numbers of hydrated Sc3+, ScOH2+, and ScOH2 + species are eight, six, and five, respectively. The adsorption model was based on ScOH2H2O5+, which has the most stable ionic configuration in the liquid phase. According to the adsorption energy and bonding mechanism, the adsorption of Sc ionic species can be categorized into outer layer and inner layer adsorptions. We found that the hydrated Sc ions were mainly adsorbed on the outer layer of the kaolinite (001)Al-OH and (00-1)Si-O surfaces through hydrogen bonding while also being adsorbed on the inner layer of the deprotonated kaolinite (001)Al-OH surface through coordination bonding. The inner layer adsorption has three adsorption configurations, with the lying hydroxyl group (Ol) position having the lowest adsorption energy (-653.32 KJ/mol). The adsorption energy for the inner layer is lower compared to the outer layer, while the extent of deprotonation is limited. This is because the deprotonation of the inner adsorption layer is energetically unfavorable. We speculate that Sc ions species predominantly adsorb onto the surface of kaolinite (001) in an outer layer configuration.

New insight into the visible-light-driven photoinduced electron transfer mechanism for ozone activation over defective sites of ceria for organic compounds destruction

Herein, we prepared CeO2 with varying concentrations of oxygen vacancies (Ov) and investigated the effects of the Ov concentration and photoinduced electron transfer (PET) on O3 activation under visible-light-driven (VLD) photocatalytic-ozonation (PO) for removal of oxalic acid (OA). Density functional theory calculations showed the formation of Ov reduced the bandgap of CeO2, leading to region around the Ce atom with a low adsorption energy barrier toward O3. Notably, no distinct linear correlation was found between the Ov concentration and VLD-PO activity. This implies that CeO2 with a lower amount of Ov (14.64%) exhibits better PET and higher photoexcited electron density than CeO2 with a relatively higher Ov (17.62%), suggesting that the PET properties of CeO2 are crucial for the Ov regeneration and O3 activation and conversion for OA removal. Electric energy per order (EEO) for VLD-PO using CeOx(700) was 6.94 kWh m−3 order−1. Additionally, bioassay experiments with Daphnia Magna showed toxicity reduction in the PO-treated effluent and continuous-flow experiments (CFEs) proved that VLD-PO could effectively remediate the toxic and refractory micropollutants containing water. The study findings can promote the application of PO systems in water treatment for treating organic pollutants.

Probing the influence of defects and Si-doping in graphene sheet as an efficacious carrier for drug delivery system in gas and aqua phases - Combined DFT and classical MD simulation

In this study, for the bioavailability and distribution of the drug on the tumor cells we have chosen targeted drug delivery system and for the delivery system, pristine, defected, and doped graphene sheets are chosen with the anticancer drugs as lapachol and β – lapachone which are studied using density functional theory (DFT) for efficacious drug delivery. The defect formation and doping are shown to alter the properties of pristine sheets, which results in the enhanced adsorption of anticancer drugs. The cohesive energy found for all the sheets are in the 7 eV range which shows their high stability. This study revealed that the adsorption of lapachol and β – lapachone in pristine graphene sheet is poor with low adsorption energy of about −1.49 (−1.39) eV and −1.52 (−1.43) eV in gas (water) medium respectively and the adsorption energy is enhanced about 30–70% by introducing defects and about 55% by doping of silicon in the pristine graphene sheet. The highest adsorption energy for both lapachol and β – lapachone are found to be about −2.69 (−2.59) eV and −2.55 (−2.41) eV in mono vacant graphene sheet in gas (water) medium respectively. The major interaction within the complexes is studied using quantum theory of atoms in molecule (QTAIM) analysis and it is further studied via non-covalent interaction (NCI) analysis with the help of reduced density gradient (RDG) map. The ρ values at bond critical points (BCP) lie between 0.007 and 0.01 a. u. With ∇2ρ and H(r) > 0, −G/V > 1 for all the complexes showing that non-covalent interaction plays a major role in the adsorption of active drugs. Furthermore, NCI analysis shows that the van der Waals interaction and hydrogen bonding play a major influence on the interaction between the anticancer drug and the carrier sheets. The molecular dynamic (MD) study shows that all the drug-loaded complexes are stable with minimal variation in the van der Waals energy during the production run. Thus, the results obtained from DFT and MD shows that the defected and Si-doped graphene sheets are much more suitable as a carrier for drug delivery than the pristine sheet. This study paves the way for the future research on the defected and doped graphene sheets as a suitable drug carrier for numerous drugs in the targeted drug delivery system.

Construction of novel photocatalysts for efficient hydrogen evolution: The key role of natural halloysite nanotubes

Hydrogen (H2) evolution by photocatalytic water splitting is a potential strategy to solve worldwide energy shortage. Sulfide nanocatalysts showed great potential for H2 evolution, but suffered from low charge separation efficiency and easy agglomeration. In this work, ZnIn2S4 (ZIS) nanoflowers were anchored onto the surface of halloysite nanotubes (HNTs) modified by ethylenediaminetetraacetic acid (EDTA). Photocatalyst 3ZnIn2S4-HNTs/EDTA3 (3ZIS-HNTs/E3) displayed the optimum H2 evolution rate of 10.4 mmol·g−1·h−1, being 3.4 times as that of the original ZIS. Moreover, 3ZIS-HNTs/E3 presented satisfied property in the photocatalytic hydrogenation reaction of 4-nitrophenol to produce 4-aminophenol. HNTs as substrates not only hindered the growth and agglomeration of ZIS, but also induced more S vacancies in ZIS. The production of Schottky junctions between ZIS and Pt, the high utilization of light energy in tubular HNTs, and the trapping effect of EDTA for photogenerated h+ were all favorable for enhancing the catalytic property. The density functional theory (DFT) calculations showed that 3ZIS-HNTs/E3 with more S vacancies had the lowest adsorption energy and the most appropriate ΔGH* for H* to enhance the H2 evolution efficiency, which was consistent with the experimental catalytic results. This study contributes a novel thought for synthesizing composites on the basis of natural minerals for taking part in and enhancing the catalytic performance.

Synergetic effects of Cu cluster-doped g-C3N4 with multiple active sites for CO2 reduction to C2 products: A DFT study

The photocatalytic reduction of CO2 is a promising strategy for converting this greenhouse gas into valuable products. However, developing highly efficient photocatalysts remains a challenging task. In this study, we investigated the properties of Cu4 and Cu5-doped g-C3N4 photocatalysts using density functional theory. Our findings revealed that Cu clusters can form an Ohmic contact with C3N4, promoting the separation and transfer of photo-generated electrons and holes, and reducing the reaction barrier. We optimized the adsorption models of gas-phase intermediate molecules and identified the most stable configuration with the lowest adsorption energy. The results indicated that Cu clusters and C3N4 can work synergistically to provide active sites for the adsorption of gas-phase molecules, revealing the mechanism for lowering the activation energy. Cu4-doped C3N4 was identified as the most promising photocatalyst through the comparison of the Gibbs free energy change in CO2 reduction and the HER energy barrier. Further research found that the co-adsorption of *CO on the Cu clusters effectively suppressed the hydrogen evolution reaction, providing insights into the potential mechanism underlying the high selectivity of Cu clusters for the production of C2 products through CO2 reduction.

A Multifunctional Additive Strategy Enables Efficient Pure-Blue Perovskite Light-Emitting Diodes.

Lead halide perovskites have shown exceptional performance in light-emitting devices (PeLEDs), particularly in producing significant electroluminescence in sky-blue to near-infrared wavelengths. However, PeLEDs emitting pure-blue light at 465-475 nm are still not satisfactory. Herein, efficient and stable pure-blue PeLEDs are reported by controlling phase distribution, passivation of defects, as well as surface modifications using multifunctional phenylethylammonium trifluoroacetate (PEATFA) in reduced-dimensional p-F-PEA2 Csn-1 Pbn (Br0.55 Cl0.45 )3n+1 polycrystalline perovskite films. Compared with 4-fluorophenylethylammonium (p-F-PEA+ ) in the pristine films, phenylethylammonium (PEA+ ) has lower adsorption energy while interacting with perovskites, resulting in large-n low-dimensional perovskites, which can greatly facilitate charge transport within the low-dimensional perovskite films. The interaction between the CO group in trifluoroacetate (TFA- ) and perovskites significantly reduces defects in the perovskite films. Additionally, the electron-giving CF3 group in TFA- uplifts surface potential in the films, resulting in smooth electronic injection in devices. The multifunctional additive strategy leads to elevated radiative recombination and efficient carrier transport in the films and devices. As a result, the devices exhibit a maximum external quantum efficiency (EQE) of 11.87% at 468 nm with stable spectral output, the highest reported to date for pure-blue PeLEDs. Thus, this study extends the way for high-efficiency pure-blue LED with perovskite polycrystal films.

Realizing efficient electrochemical overall water electrolysis through hierarchical CoP@NiCo-LDH nanohybrids

It is very important to design the catalysts with special spatial architectures and excellent electrochemical performance. It is well known that non-noble metal catalysts are inferior to Pt-like ones in electro-activity. However, their catalytic ability can be improved by the synergistic effect of different components. Herein, we synthesize several dendritic-like CoP@NiCo-LDH hetero-catalysts by a multi-step growth route. The CoP@NiCo LDH-100 samples present an overpotential of 225 mV @ 46.6 mV dec−1 for OER and 68.7 mV @ 74.03 mV dec−1 for HER, which is superior to the commercial IrO2 (OER) and Pt/C (HER) in alkaline electrolyte. The density functional theory (DFT) calculation demonstrates that the composites possess low adsorption energy (1.11 eV) and tunable charge redistribution at the interface. An increased Fermi-level PDOS value proves the enhanced conductivity of the catalyst. The upward shift of the D-band center optimizes the desorption of the intermediates and accelerates the hydrolysis dissociation process. This increases the HER activity and thus reduces the overall electrolysis voltage.

First-principles study on two-dimensional Mo2B for its potential application in gas sensing

Through first principles, we first demonstrated the structural and thermal stability of monolayer Mo2B by analyzing the results of phonon spectrum and ab initio molecular dynamics simulations. In addition, the adsorption energies for four kinds common noxious molecules NO, NO2, CO, CO2 are calculated with values of −2.978 eV, −2.838 eV, −1.914 eV and −0.586 eV, respectively. The relatively low adsorption energy for NO, NO2 means that Mo2B has a high selectivity for these molecules. The charge transfer number of NO, NO2, CO, and CO2 on monolayer Mo2B are 0.855 e, 1.189 e, 0.658 e, and 0.926 e. The CO2/Mo2B system has smallest adsorption energy and a relatively large charge transfer value, which suggests Mo2B may be used as a highly reversible and sensitive detector for CO2. More importantly, the recovery time for CO2/Mo2B system is only 10−4 s. The recovery time for the other three molecules is calculated to exceed 1010 s at room temperature which indicates irreversible detection of these molecules. These results could provide guidance for the achievement of high-performance gas sensitive materials.

Reshaping the coordination and electronic structure of single atom sites on the right branch of ORR volcano plot

The coordination environment of atomic metal sites in single atom catalysts is of vital significance in tailoring the d-orbital states and thus the catalytic behavior towards oxygen reduction reaction (ORR), thereby offering great promise to boost activity via regulating the local chelation structure. Herein we designed a carbon coordination environment for the atomic M sites reside on the right leg of the volcano plot, to effectively counter balance the low adsorption energy of the metal center to oxygen species. Combining time-of-flight secondary ion mass spectrometry and density functional theory calculations, we unveiled the M-C coordination structure and the thus induced changes in electronic structure and ORR catalytic behavior. The reshape in coordination structure, i.e., the replacement of typical nitrogen coordination by low electronegativity carbon coordination, gives rise to exceptional intrinsic activity towards ORR. This work brings a new perspective to boost the activity of single atom catalysts on the weak bonding leg, with exceptional ORR activity being further expected through advancing the chelation structure.

Unravelling the pathway for the dehydrogenation of n-butane to 1,3-butadiene using thermodynamics and DFT studies

Dehydrogenation of n-butane is one of the main on-purpose method for producing 1,3- butadiene. Thermodynamics studies revealed that reasonable yields of 1,3-butadiene can only be achieved at higher temperatures, while the formation of butene isomers are favored at lower temperatures, confirming that 1,3-butadiene is a secondary product. In the present study, NiO/Al2O3 and Ni-BiOx/Al2O3 catalysts, having 10 and 20 wt% Ni and 10 and 30 wt% Bi loading were synthesized. Experimental testing using fixed bed reactor validated that the addition of BiOx improved 1,3-butadiene selectivity from 20 % to 43 % with similar n-butane conversion, at 500 °C. Also, density functional theory (DFT) studies for n-butane adsorption on Ni (111) and Bi-Ni (111) surfaces confirmed that, the addition of Bi promoters to the Ni surface modifies the n-butane adsorption strength resulting in lower adsorption energies of −0.02 eV weaker than −0.36 eV on Ni (111) surfaces. The reaction pathways investigation for the successive dehydrogenation route of n-butane on the most stable structures of Ni (111) and Bi-Ni (111) surfaces revealed that 1-butene pathway via the formation of 1-butyl, is most favorable relative to the 2-butene pathway via 2-butyl formation. This is due to the higher activation barrier for the formation of 2-butene intermediate on both Ni (111) and Bi-Ni (111) surfaces.

Rational construction of S-scheme Pt-MnO2/TiO2@Ti3C2Tx via Ti-O-Mn bond for distinguished charge transfer in photocatalytic wastewater environmental governance and hydrogen production

Exploring and adjusting the migration pathway of photogenerated electron-hole pairs in novel semiconductor composites is vital to enhance the charge separation efficiency and transferability in photocatalytic environmental governance and hydrogen generation performance. Herein, an electrostatic self-assembly combining with a low-temperature hydrothermal strategy for forming the Ti-O-Mn bond was designed to rationally construct the S-scheme Pt-MnO2/TiO2@Ti3C2Tx composite. Through the systematic characterization and density functional theory calculations, the metastable marginal Ti atoms and the electrostatic adsorbed Mn2+ ions on Ti3C2Tx surface are oxidized and in situ form TiO2/MnO2 nanoparticles (NPs) due to its fitted lattice energy and low adsorption energy, which are intercalated on the conductive Ti3C2Tx multilayer surfaces and construct a new-fashioned S-scheme TiO2/MnO2 heterojunction via the Ti-O-Mn bond, for affecting the density of charge states, promoting the charge separation and shortening migration carrier distance. Also, Pt NPs as the cocatalyst is selectively decorated on MnO2/TiO2@Ti3C2Tx surface for further improving the charge carrier transfer and visible light absorption. Benefiting from the extraordinary composition and structure, the obtained Pt-MnO2/TiO2@Ti3C2Tx composite exhibits high photocatalytic degradation of organic pollutants (more than 90%), hydrogen generation activity (3610 μmol g−1 h−1) and wonderful cycle stability.

Boosting the CO2 adsorption performance by defect-rich hierarchical porous Mg-MOF-74

Adsorbents with high adsorption capacity and high selectivity are crucial for carbon capture, utilization and storage (CCUS) technology applied to industrial flue gas to reduce carbon emissions. In this paper, a defect-rich hierarchical porous Mg-MOF-74 was synthesized successfully with MgCl2·6H2O used as a metal source considering that the weak coordination of Cl− may interfere with the normal coordination process of metal centers and organic ligands, which causes the formation of crystal defects. Through the analysis of a series of characterizations, ligand deletion of Mg-MOF-74 prepared with MgCl2·6H2O was confirmed, and the deleted ligand was estimated to be approximately 20% compared with the traditional Mg-MOF-74 prepared with Mg(NO3)2·6H2O, which led to mesopores accounting for 36.9%, and the width of mesopores reached 13.1 nm. Compared with traditional Mg-MOF-74, the adsorption heat of CO2 at zero load of the defect-rich hierarchical porous Mg-MOF-74 increased from 36 kJ·mol−1 to 46 kJ·mol−1, and the saturated adsorption capacity of CO2 under ambient pressure was improved by 15%. Interestingly, the IAST selective adsorption performance of CO2/N2 was increased by 20 times. Compared with the saturated adsorption capacity for traditional Mg-MOF-74, the equivalent adsorption capacity of hierarchical porous Mg-MOF-74 only needs 17 kPa, indicating that it is suitable for carbon capture operation in a real flue environment. Calculations of density functional theory (DFT) confirmed that the active site of the hierarchical porous Mg-MOF-74 has a lower adsorption energy with CO2 due to the presence of defects, which is regarded to play a key role in improving the CO2 capture performance.

Metallic Particles‐Induced Surface Reconstruction Enabling Highly Durable Zinc Metal Anode

AbstractAqueous zinc batteries usher in a renaissance due to their intrinsic security and cost effectiveness, bespeaking vast application foreground for large‐scale energy storage system. However, uncontrolled dendrite growth along with hydrogen evolution severely restricts its reversibility and stability for practical application. Herein, the surface of Zn metal is reconstructed with metallic particles (In, Sn, In0.2Sn0.8) to diminish surface defects and regulate Zn deposition behavior. The alloyed In–Sn greatly activates the Zn surface for lower Zn adsorption energy barrier to expedite plating kinetics and confine Zn aggregation. Dense and uniform deposition of Zn on the reconstructed surface significantly prevents the Zn substrate from dendrites growth for catastrophic damage. Meanwhile, alloy layer embodies high hydrogen evolution overpotential, ensuring high plating and stripping efficiency for Zn anode. Consequently, In0.2Sn0.8 reconstructed surface realizes long‐term lifespan up to 1800 h with low polarization (12 mV) at the condition of 1 mA cm−2 and 1 mAh cm−2. When paired with sodium vanadate (NVO) cathode, the full cell steady operates for a high‐capacity retention of 94.0% after 5000 cycles at 5 A g−1. This study provides new insights into the surface‐defects dependent Zn deposition process and offers a guide for constructing stable surface for dendrite‐free Zn growth.

Homo-interface and gradient N-doping cooperation to boost the rate capability of porous NaV8O20·nH2O nanoflake cathode in Zn-ion batteries

Vanadium-based materials are expected to achieve high-rate capability with high energy density in Zn-ion batteries (ZIBs) due to the layered-structure and multi-electron redox mechanism. However, the high-rate charge/discharge capacity is usually restricted by limited charge storage active sites on material surface and poor electrode kinetics. Herein, homo-interfaces and built-in electric fields were constructed to boost the Zn2+ diffusion and electron transmission kinetics of NaV8O20·xH2O (NaVO) nanoflake cathodes, respectively, which cooperated to achieve high-rate charge/discharge capacity in ZIBs. Specifically, firstly, homo-interfacial NaVO nanoflakes were prepared, and then gradient N-doping was introduced from homo-interface to surface of NaVO due to the lower N-doping formation energies of interface than that of surface, which improved electrical conductivity and formed a build-in field to accelerate electron transmission; Moreover, there is a large difference between Zn2+ concentration in homo-interfaces and surfaces of the N-doped NaVO as the homo-interfaces with lower zinc adsorption energy are more conducive to the adsorption and aggregation of Zn2+ than that of the surface, which boost Zn2+ diffusion; Furthermore, numerous micropores were created to shorten ion transport pathways. These structural advantages enabled ultra-fast Zn-storage kinetics and excellent cycling performance of NaV8O20·xH2O in ZIBs, the reversible capacity can reach 417 mA h g−1 at 0.1 A g−1, and as high as ∼110 mA h g−1 at 100 A g−1 with capacity retention of 68.4% after 50,000 cycles. Dynamic analysis verifie that high capacitive capacity contributes most to the excellent performance, which can be ascribed to the structural advantages described above. The findings of this study provide new insights for designing Zn-ion storage materials with high-rate capability and long life.

Insight into the role of SO2 on selenium conversion during adsorption by CaO: Theoretical calculation and experimental study

SO2 can noticeably impact the control of high toxic selenium emissions from flue gas by CaO. Surprisingly, our experiments showed that under certain conditions, SO2 can promote selenium capture by CaO, rather than hinder it. To elucidate the underlying mechanism, a combination of theoretical calculations and experiments was conducted. Thermodynamic equilibrium analysis revealed that gaseous SO2 and solid Ca-S reaction products can promote SeO2 converting to SeO/Se0. The Ca-S products facilitated greater SeO2 conversion compared to SO2. Experimental results demonstrated that selenium adsorption capacity of incompletely sulfurized CaO (CaO with pre-adsorbed SO2) was higher than that of completely sulfurized CaO (Ca-S products), highlighting the importance of adsorption sites of CaO. Density functional theory calculations showed that the pre-adsorbed SO2 hardly affected selenium adsorption energy on the SO2/CaO surface, while completely sulfurized CaO had low selenium adsorption energy, explaining the experimental phenomenon and proving necessary of CaO. Additionally, SeO/Se0 had higher adsorption energy on CaO than SeO2. Overall, the promotion of SO2 on selenium adsorption was primarily affected by two factors: 1) sulfur facilitating SeO2 conversion to SeO/Se0 which can be adsorbed more easily by CaO; 2) sufficient adsorption sites on CaO surface existing for SeO/Se0 adsorption, despite co-adsorption with sulfur.