Search Results (39)

Defective graphene has emerged as a promising strategy to enhance electrochemical performance of pristine graphene (p-Gr) as anodes in lithium-ion batteries (LIBs). Herein, we perform a comprehensive first-principles study based on density functional theory (DFT) to systematically investigate the Li adsorption, charge transfer, and diffusion behaviors of p-Gr and defective graphene (d-Gr) with single vacancy (SV Gr) and double vacancy (DV5-8-5 Gr) defects, aiming to clarify the mechanism by which defects modulate Li storage performance. Structural optimization reveals that SV Gr undergoes notable out-of-plane distortion after Li adsorption, while DV5-8-5 Gr retains planar geometry but exhibits more significant C-C bond length variations compared to p-Gr. Binding energy results confirm that defects enhance Li adsorption stability, with DV5-8-5 Gr showing the strongest Li–graphene interaction, followed by SV Gr and p-Gr. Bader charge analysis and charge density difference plots further validate that defects enhance charge transfer from Li ions to graphene. Using the nudged elastic band (NEB) method, we find that defects reduce Li diffusion barriers: DV5-8-5 Gr exhibits a lower barrier than p-Gr. Our findings demonstrate that DV5-8-5 Gr exhibits the most favorable Li storage performance, providing a robust theoretical basis for designing high-performance graphene anodes for next-generation LIBs. Full article

Supercapacitors are limited by electrolyte cation desolvation, which directly impacts ion storage efficiency and capacitance. This study uses density functional tight-binding (DFTB+) first-principles calculations to investigate the desolvation of bispyrrolidinium cation complexes ([SBP(AN)]⁺, acetonitrile as solvent) in pristine (FP) and oxygen-functionalized (OFP: hydroxyl-HFP, carbonyl-CFP, aldehyde-AFP) bilayer graphene flat pores with AA/AB stacking. Critical desolvation diameters were determined: 5.0 Å (FP), 5.2 Å (HFP), 5.0 Å (AFP), and 4.6 Å (CFP). Hydroxyl functionalization expanded the critical diameter, reduced SBP⁺ intercalation energy, and increased relative capacitance by 1.02~1.03 times; carbonyl groups had the opposite effect, while aldehyde groups showed no significant impact. Density of States (DOS) analysis revealed enhanced conductivity for HFP and AFP after SBP⁺ embedding, but reduced conductivity for CFP. Charge density difference and Bader charge analysis confirmed electron transfer primarily between SBP⁺ (electron donor) and oxygen atoms in functional groups (electron acceptor), with SBP⁺ interacting mainly with functional groups rather than the carbon basal plane. This work provides theoretical guidance for optimizing graphene-based supercapacitor electrodes via pore structure and surface functionalization. Full article

Understanding the interactions between ionic liquid ions and lithium-metal surfaces is critical for designing safer and more efficient lithium metal batteries. In this work, we use density functional theory to investigate the electronic structure, binding energies, work-function shifts and interfacial charge redistribution of several ionic liquid ions, including FSI⁻, TFSI⁻, ${\mathrm{P}\mathrm{F}}_6^{-}$, ${\mathrm{B}\mathrm{F}}_4^{-}$, DFOB⁻, Pyr14⁺, and EMIM⁺, on a Li-metal anode (Li_m). Absorption orientation-dependent effects are examined for each molecule. Specifically, differences in charge density and electron localization function analyses revealed unique patterns of electron accumulation and delocalization that highlighted specific atomic roles in interfacial bonding. Interfacial charge transfer is analyzed through Bader charges, revealing a moderate charge redistribution for the cations (EMIM⁺, Pyr14⁺), and a more significant charge uptake for the reactive anions (FSI⁻, TFSI⁻, DFOB⁻). Among cations, EMIM⁺ was determined to have the most interfacial stability, while Pyr14⁺ displayed mid-level reactivity. For the anions, varying tendencies for bond formation with lithium metal and potential fragmentation could be determined. Overall, these discoveries detail an atomistic analysis of ionic liquid to Li_m interactions providing additional pathways for molecular design techniques to stabilize electrolytes performing not high-cost computational calculations. Full article

In this study, first-principles calculations were employed to systematically investigate the interaction mechanisms between (18-crown-6) potassium (18C6-K⁺) and six typical defect sites on the SnO₂ (110) surface, including Sn_i + Sn_O, O_i + O_Sn, V_O + Sn_i, V_Sn + Sn_O, V_Sn + Sn_i, and Sn_i. Six intrinsic or complex defects universally coexist on the SnO₂ surface, and the defect states they introduced allow for precise tuning of material performance. The results demonstrated that the 18C6-K⁺ molecule can stably adsorb on all six defect sites and significantly increase defect formation energies, indicating its thermodynamic capability to suppress defect generation. A subsequent density of states (DOS) analysis revealed that the 18C6-K⁺ molecule exhibits strong defect passivation effects at Sn_i + Sn_O, V_O + Sn_i, V_Sn + Sn_i, and Sn_i sites, and partially mitigated the electronic disturbances induced by O_i + O_Sn and V_Sn + Sn_O defects. Furthermore, the incorporation of 18C6-K⁺ has been shown to reduce the electronic effective mass of defective systems, thereby enhancing surface carrier transport. A subsequent charge density difference (CDD) analysis revealed that the 18C6-K⁺ molecule forms Sn-ether and O-ether interactions through its ether bonds (C-O-C) with surface Sn and O atoms, inducing interfacial electronic reconstruction and charge transfer. The Bader charge analysis revealed that the H, C, and O atoms in 18C6-K⁺ lose electrons, whereas the Sn or O atoms at the surface defect sites gain electrons. This outcome is consistent with the CDD analysis and quantitatively confirms the extent of electron transfer from 18C6-K⁺ to the SnO₂ defect regions. These interactions effectively passivate defect states, thereby enhancing interfacial stability. The present study offers theoretical guidance and design insights for the development of molecular passivation strategies in SnO₂-based optoelectronic devices. Full article

Climate change and the global energy crisis have led to an increasing need for greenhouse gas remediation and clean energy sources. The electrochemical CO₂ reduction reaction (CO₂RR) is a promising solution for both issues as it harvests waste CO₂ and chemically reduces it to more useful forms. However, the high overpotential required for the reaction makes it electrochemically unfavorable. Here, we fabricate a novel electrode composed of TiO₂ nanoparticles grown in situ on MXene charge acceptor 2D sheets with excellent CO₂RR characteristics. A straightforward solvothermal method was used to grow the nanoparticles on the Ti₃C₂T_x MXene flakes. The electrochemical performance of the TiO₂/MXene electrodes was analyzed. The Faradaic efficiencies of the TiO₂/MXene electrodes were determined, with a value of 99.41% at −1.9 V (vs. Ag/AgCl). Density functional theory mechanistic analysis was used to reveal the most likely mechanism resulting in the production of one CO molecule along with a carbonate anion through ∗CO, ∗O, and activated CO₂²⁻ intermediates. Bader charge analysis corroborated this pathway, showing that CO₂ gains a greater negative charge when TiO₂/MXene serves as a catalyst compared to MXene or TiO₂ alone. These results show that TiO₂/MXene nanocomposite electrodes may be very useful in the conversion of CO₂ while still being efficient in both time and cost. Full article

Co-electrolysis of CO₂ and H₂O offers a promising route for efficient and controllable syngas production from greenhouse gases and water. However, the atomic-scale reaction mechanism remains elusive, especially on complex oxide surfaces. In this study, we employ density functional theory (DFT) to investigate the adsorption and activation of CO₂ and H₂O on the FeMoO-terminated (001) surface of Sr₂Fe_1.5Mo_0.5O₆ (SFM), a double perovskite of growing interest for solid oxide electrolysis. Our results show that CO₂ strongly interacts with surface lattice oxygen, adopting a bent configuration with substantial charge transfer. In contrast, H₂O binds more weakly at Mo sites through predominantly electrostatic interactions. Co-adsorption analyses reveal a bidirectional interplay: pre-adsorbed H₂O enhances CO₂ binding by altering its adsorption geometry, whereas pre-adsorbed CO₂ weakens H₂O adsorption due to competitive site occupation. This balance suggests that moderate co-adsorption may facilitate proton–electron coupling, while excessive coverage of either species suppresses activation of the other. Bader charge analysis, charge density differences, and projected density of states highlight the key role of Fe/Mo–O hybridized states near the Fermi level in mediating surface reactivity. These results, obtained for a perfect defect-free surface, provide a theoretical benchmark for disentangling intrinsic molecule–surface and molecule–molecule interactions, and offer guidance for designing high-performance perovskite electrocatalysts for CO₂ + H₂O co-electrolysis. Full article

Addressing global energy and environmental issues calls for the development of effective photocatalysts capable of enabling solar-driven water splitting, a key route toward sustainable hydrogen generation. In this work, we conducted a detailed density functional theory (DFT) study on three bilayer van der Waals (vdW) heterojunctions, Ga₂SSe/GaP, Ga₂SSe/PtSSe, and Ga₂SSe/SnSSe, each explored in four distinct stacking configurations, with Ga₂SSe serving as the base monolayer. We assessed their structural stability, electronic properties, and optical responses to determine their suitability for photocatalytic water splitting. The analysis showed that Ga₂SSe/GaP and Ga₂SSe/SnSSe exhibit type-II band alignment, while Ga₂SSe/PtSSe displays a type-I alignment. Electrostatic potential profiles and Bader charge calculations identified SeGa₂S/SSnSe and SeGa₂S/SeSnS as direct Z-scheme systems, offering efficient charge carrier separation and robust redox potential. For effective water splitting, the band edges must straddle the water redox potentials. Our results indicate that configurations A and B in Ga₂SSe/GaP, along with C and D in Ga₂SSe/SnSSe, fulfill this requirement. These four configurations also exhibit strong absorption in both the visible and ultraviolet spectral ranges. Notably, configurations C and D of Ga₂SSe/SnSSe achieve high solar-to-hydrogen (STH) efficiencies, reaching 38.44% and 21.75%, respectively. Overall, our findings suggest that these direct Z-scheme heterostructures are promising candidates for water splitting photocatalysis. Full article

First-principles calculations were conducted to examine the impact of three sulfonamide-containing molecules (H₄N₂O₂S, CH₈N₄O₃S, and C₂H₂N₆O₄S) adsorbed on the FAPbI₃(001) perovskite surface, aiming to establish a significant positive correlation between the molecular structures and their regulatory effects on the perovskite surface. A systematic comparison was conducted to evaluate the adsorption stability of the three molecules on the two distinct surface terminations. The results show that all three molecules exhibit strong adsorption on the FAPbI₃(001) surface, with C₂H₁₂N₆O₄S demonstrating the most favorable binding stability due to its extended frameworks and multiple electron-donating/withdrawing groups. Simpler molecules lacking carbon skeletons exhibit weaker adsorption and less dependence on surface termination. Ab initio molecular dynamics simulations (AIMD) further corroborated the thermal stability of the stable adsorption configurations at elevated temperatures. Electronic structure analysis reveals that molecular adsorption significantly reconstructs the density of states (DOS) on the PbI₂-terminated surface, inducing shifts in band-edge states and enhancing energy-level coupling between molecular orbitals and surface states. In contrast, the FAI-terminated surface shows weaker interactions. Charge density difference (CDD) analysis indicates that the molecules form multiple coordination bonds (e.g., Pb–O, Pb–S, and Pb–N) with uncoordinated Pb atoms, facilitated by –SO₂–NH₂ groups. Bader charge and work function analyses indicate that the PbI₂-terminated surface exhibits more pronounced electronic coupling and interfacial charge transfer. The C₂H₁₂N₆O₄S adsorption system demonstrates the most substantial reduction in work function. Optical property calculations show a distinct red-shift in the absorption edge along both the XX and YY directions for all adsorption systems, accompanied by enhanced absorption intensity and broadened spectral range. These findings suggest that sulfonamide-containing molecules, particularly C₂H₁₂N₆O₄S with extended carbon skeletons, can effectively stabilize the perovskite interface, optimize charge transport pathways, and enhance light-harvesting performance. Full article

Transient liquid-phase bonding (TLPB) enables the low-temperature fabrication of encapsulated solder joints with high-temperature resistance and electromigration resilience; yet, Ni-Sn TLPB joints suffer from brittle fracture due to intermetallic compounds (IMCs). This study investigates the Co, Cu, and Pt alloying effects on Ni₃Sn via formation energy, molecular dynamics, and first-principles calculations. Occupancy models of Ni_6−xM_xSn₂ (M = Co, Cu, and Pt) were established, with the lattice parameters, B/G ratios, fracture toughness (K_IC), and stress–strain behaviors analyzed. The results reveal that Co enhances fracture toughness and reduces Ni₃Sn anisotropy, mitigating microcrack risks, while Cu/Pt introduce antibonding interactions (Cu–Sn and Pt–Sn), weakening the bonding strength. The classical B/G brittleness criterion proves inapplicable in Ni–M–Sn systems due to mixed bonding (metallic/covalent) and the hexagonal structure’s limited slip systems. The Ni_6−xCo_xSn₂ formation improves toughness with a low Co content, supported by an electronic structure analysis (density of states and Bader charges). The thermodynamic stability and reduced molar shrinkage (Ni + Sn → Ni₃Sn) confirm Co’s efficacy in optimizing Ni–Sn solder joints. Full article

This research aimed to explore the structural, electronic, mechanical, and vibrational properties of double half Heusler compounds with the generic formula Ti₂Pt₂ZSb (Z = Al, Ga, and In), using density functional theory calculations. The generalized gradient approximation within the PBE functional was employed for structural relaxation and for calculations of vibrational and mechanical properties and thermal conductivity, while the hybrid HSE06 functional was employed for calculations of the electronic properties. Our results demonstrate that these compounds are energetically favorable and dynamically and mechanically stable. Our electronic structure calculations revealed that the Ti₂Pt₂AlSb double half Heusler compound is a non-magnetic semiconductor with an indirect band gap of 1.49 eV, while Ti₂Pt₂GaSb and Ti₂Pt₂InSb are non-magnetic semiconductors with direct band gaps of 1.40 eV. Further analysis, including phonon dispersion curves, the electron localization function (ELF), and Bader charge analysis, provided insights into the bonding character and vibrational properties of these materials. These findings suggest that double half Heusler compounds are promising candidates for thermoelectric device applications and energy-conversion devices, due to their favorable properties. Full article

The single-atom catalysts (SACs) for the electrocatalytic nitrogen reduction reaction (NRR) have garnered significant attention in recent years. The NRR is regarded as a milder and greener approach to ammonia synthesis. The pursuit of highly efficient and selective electrocatalysts for the NRR continues to garner substantial interest, yet it poses a significant challenge. In this study, we employed density functional theory calculations to investigate the stability and catalytic activity of 29 transition metal atoms loaded on the two-dimensional (2D) AlN monolayer with Al monovacancy (TM@AlN) for the conversion of N₂ to NH₃. After screening the activity and selectivity of NRR, it was found that Os@AlN exhibited the highest activity for NRR with a very low limiting potential of −0.46 V along the distal pathway. The analysis of the related electronic structure, Bader charge, electron localization function, and PDOS revealed the origin of NRR activity from the perspective of energy and electronic properties. The high activity and selectivity towards the NRR of SACs are closely associated with the Os-3N coordination. Our findings have expanded the scope of designing innovative high-efficiency SACs for NRR. Full article

The segregation of solute atoms at grain boundary (GB) has an important effect on the GB characteristics and the properties of materials. The study of multielement co-segregation in GBs is still in progress and deserves further research at the atomic scale. In this work, first-principles calculations were carried out to investigate the effect of Mg and Cu co-segregation on the energetic and mechanical properties of the Al Σ5(210) GB. The segregation tendency of Mg at the GB in the presence of Cu is characterized, indicating a preference for substitutional segregation far away from Cu atoms. Cu segregation can facilitate the segregation of Mg due to their mutual attractive energy. The GB energy results show that Mg and Cu co-segregation significantly decreases GB energy and thus enhances the stability of the Al Σ5(210) GB. First-principles tensile test calculations indicate that Cu effectively counteracts the weakening effect of Mg segregation in the GB, particularly with the high concentration of Cu segregation. The phenomenon of Cu compensating the strength of the GB is attributed to an increase of charge density and the formation of newly formed Cu-Al bonds. Conversely, Mg segregation weakens the strengthening effect of Cu on the GB, but it can increase the strength of the GB when high concentrations of Cu atoms are present in the GB. The ICOHP and Bader charge analysis exhibits that the strengthening effect of Mg is attributed to charge transfer with surrounding Al and Cu, which enhances the Cu-Al and Al-Al bonds. The results provide a further understanding of the interplay between co-segregated elements and its influence on the energetic and mechanical properties of grain boundary. Full article

This study explores the potential of β-SnSe monolayers as a promising material for ozone (O₃) sensing using density functional theory (DFT) combined with the non-equilibrium Green’s function (NEGF) method. The adsorption characteristics of O₃ molecules on the β-SnSe monolayer surface were thoroughly investigated, including adsorption energy, band structure, density of states (DOSs), differential charge density, and Bader charge analysis. Post-adsorption, hybridization energy levels were introduced into the system, leading to a reduced band gap and increased electrical conductivity. A robust charge exchange between O₃ and the β-SnSe monolayer was observed, indicative of chemisorption. Recovery time calculations also revealed that the β-SnSe monolayer could be reused after O₃ adsorption. The sensitivity of the β-SnSe monolayer to O₃ was quantitatively evaluated through current-voltage characteristic simulations, revealing an extraordinary sensitivity of 1817.57% at a bias voltage of 1.2 V. This sensitivity surpasses that of other two-dimensional materials such as graphene oxide. This comprehensive investigation demonstrates the exceptional potential of β-SnSe monolayers as a highly sensitive, recoverable, and environmentally friendly O₃ sensing material. Full article

Density functional theory (DFT) and coupled cluster theory (CCSD(T)) calculations are performed to investigate the geometric and electronic structures and chemical bonding of a series of Cu-doped zinc oxide clusters: Cu_nZn₃O₃ (n = 1–4). The structural evolution of Cu_nZn₃O₃ (n = 1–4) clusters may reveal the aggregation behavior of Cu atoms on the Zn₃O₃ cluster. The planar seven-membered ring of the CuZn₃O₃ cluster plays an important role in the structural evolution; that is, the Cu atom, Cu dimer (Cu₂) and Cu trimer (Cu₃) anchor on the CuZn₃O₃ cluster. Additionally, it is found that Cu_nZn₃O₃ clusters become more stable as the Cu content (n) increases. Bader charge analysis points out that with the doping of Cu atoms, the reducibility of Cu aggregation (Cu_n−1) on the CuZn₃O₃ cluster increases. Combined with the d-band centers and the surface electrostatic potential (ESP), the reactivity and the possible reaction sites of Cu_nZn₃O₃ (n = 1–4) clusters are also illustrated. Full article

Oxyhydrides of rare-earth metals (REMOHs) exhibit notable photochromic behaviors. Among these, yttrium oxyhydride (YHO) stands out for its impressive transparency and swift UV-responsive color change, positioning it as an optimal material for self-cleaning window applications. Although semiconductor photocatalysis holds potential solutions for critical environmental issues, optimizing the photocatalytic efficacy of photochromic substances has not been adequately addressed. This research advances the study of REMOHs, focusing on the properties of gadolinium oxyhydride (GdHO) both theoretically and experimentally. The electronic and structural characteristics of GdHO, vital for ceramic technology, are thoroughly examined. Explicitly determined work functions for GdH₂, GdHO, and Gd₂O₃ stand at 3.4 eV, 3.0 eV, and 4.3 eV, respectively. Bader charge analysis showcases GdHO’s intricate bonding attributes, whereas its electron localization function majorly presents an ionic nature. The charge neutrality level is situated about 0.33 eV below the top valence band, highlighting these materials’ inclination for acceptor-dominant electrical conductivity. Remarkably, this research unveils GdHO films’ photocatalytic capabilities for the first time. Even with their restricted surface due to thinness, these films follow the Langmuir–Hinshelwood degradation kinetics, ensuring total degradation of methylene blue in a day. It was observed that GdHO’s work function diminishes with reduced deposition pressure, and UV exposure further decreases it by 0.2 eV—a change that reverts post-UV exposure. The persistent stability of GdHO films, hinting at feasible recyclability, enhances their potential efficiency, underlining their viability in practical applications. Overall, this study accentuates GdHO’s pivotal role in electronics and photocatalysis, representing a landmark advancement in the domain. Full article