Aug 2026· Journal of Materials Science: Materials in Engineering· 0 citations
Abstract
This study presents a comprehensive first-principles density functional theory (DFT) investigation into how single (Ni, N) and synergistic Ni–N co-doping modifies the structural, electronic, and electrochemical properties of V₂C/WS₂ an oxygen-terminated V₂CO₂/WS₂ heterostructure, with the aim of creating mechanically stabilized design principles for next-generation MXene-based devices. An oxygen-terminated (
–O
) surface chemistry was adopted in place of the bare-surface model used in past, since experimentally synthesised MXenes are typically surface-functionalised and
–O
termination leads to the
alkaline/mildly
acidic etching conditions. Calculations were performed using the
GGA-PBE
functional augmented with
DFT-D3(BJ)
van der Waals corrections
and Hubbard U corrections
(U
eff
= 3.5 eV for V-3d; 5.5 eV for Ni-3d) to treat long-range interlayer interactions and correlated
d-electron
physics, respectively. All doped heterostructure show negative formation energies, confirming thermodynamic feasibility; the Ni–N co-doped system exhibits the most favourable formation energy (− 1.48 eV) and the strongest interfacial adhesion (binding energy: − 2.32 eV), a 25.4% improvement over the pristine system (− 1.85 eV). Electronic structure analysis indicates that Ni–N co-doping raises the density of states at the Fermi level by 5.2-fold relative to the pristine heterostructure, driven by a fully synergistic three-way hybridisation of Ni-3d, N-2p, and V-3d orbitals that cannot be reproduced by either dopant independently. Bader charge analysis confirms a net interfacial charge transfer of + 0.47 e⁻ at the co-doped interface, substantially exceeding single-dopant configurations. Work function calculations identify a reduction of 0.72 eV (from 5.10 eV to 4.38 eV) in the Ni–N co-doped system, facilitating more effective charge injection at the electrode–electrolyte interface. CI-NEB calculations demonstrate that Li⁺ migration barriers decrease from 0.31 eV (pristine) to 0.18 eV (co-doped), a 41.9% reduction in diffusion resistance. The theoretical quantum capacitance of the Ni–N co-doped heterostructure reaches 133 μF cm⁻
2
(380 F g⁻
1
), a 5.3-fold enhancement over the pristine system (25 μF cm⁻
2
; 70 F g⁻
1
). Phonon dispersion calculations show no imaginary modes for any configuration, and ab initio
molecular dynamics
(
AIMD
) at 300 K over 5 ps confirms that the structural framework is kept without distortion, together developing dynamical and thermal stability of the
O-terminated
heterostructure. In-plane elastic-constant calculations further confirm mechanical (Born) stability, with Young's moduli of 136–151 GPa across the doping series. A combined mechanical framework is defined, where Ni–N synergy works through four interconnected pathways: complementary orbital hybridisation, Fermi level stabilisation at a DOS maximum, increased interfacial charge transfer, and higher ion adsorption active sites. These findings offer DFT-guided framework rules for systematic co-doping strategies in MXene-based heterostructure supercapacitor electrodes.
One of the most significant challenges for next-generation supercapacitors is developing high-performance electrode materials. This study presents the synthesis of N-TiO2@MXene in situ grown on conductive MXene sheets using a cost-effective, urea-assisted, scalable one-step hydrothermal method. Furthermore, structural and spectroscopic analyses show that crystalline N-doped TiO2 nanodomains adhere to the layered Ti3C2Tx MXene, forming a hierarchical composite. in situ growth effectively reduces MXene restacking, increases interlayer spacing, and creates continuous electron-transport pathways, while incorporating defect-rich heterointerfaces that accelerate charge transfer and ion diffusion. The N-TiO2@MXene electrode achieves a specific capacitance of 212.9 F g-1 at 1 A g-1, representing an approximately 55% increase compared to those of the pristine MXene (137 F g-1) and other externally mixed TiO2 and MXenes. Electrochemical impedance analysis shows that the hybrid system has significantly lower charge-transfer resistance and faster ion-transport kinetics. Long-term stability studies show 81.7% capacitance retention after 10 000 cycles at near-unity coulombic efficiency, indicating exceptional electrochemical durability. The (N-TiO2@MXene//N-TiO2@MXene) configuration produces a symmetric coin-cell device exhibiting a specific capacitance of 57.9 F g-1, an energy density of 11.58 Wh kg-1, and consistent cycling performance. A practical demonstration utilizing five series-connected coin cells effectively powers a digital clock, confirming the device's practical application. This study outlines a straightforward in situ interfacial engineering approach for fabricating defect-rich MXene-oxide heterostructures, thereby facilitating the development of high-rate, durable, and scalable energy storage systems.
Sheetal Sharma, A. P. Nagendra Babu, V. Kumar Singh et al.· Nanoscale· 0 citations
The Lithium- and Manganese-rich (LMR) layered oxides are being highlighted as the next-generation cathode materials due to the high energy density (≈ 300 mAh g-1) and low cost. However, their practical application is limited by oxygen release, structural instability, voltage decay, and limited cycle life. Cathodic doping is effective but limited by a fundamental misunderstanding of multi-dopant interactions, which prevents the systematic optimization of cathode compositions. Herein, we investigate the effects of five single dopants and four dual-dopant combinations on the electronic structure of LMR cathodes using first-principles density functional theory (DFT) calculations combined with ligand field theory. A Hamiltonian-based cluster expansion approach is employed to model the intricate delithiated configurations in doped systems. We compute phase stability, capacity, voltage, volume, oxygen stability, and cost depending on the type of doping. Based on this, we reveal the physical (e.g., atomic size) and chemical effects (e.g., charge transfer) of dopants on the electrochemical performance of LMR layered cathodes. Specifically, we identify a linear correlation between dopant-intrinsic electronic descriptors and the formation energy, demonstrating their direct influece on dopant-induced thermodynamic stability. In terms of electrochemical performance, we identify a clear synergy between d⁰ elements and redox-active dopants. In particular, combining d⁰ elements with redox active elements enhances the redox activity of the redox-active dopants themselves, which effectively stabilizes the anionic redox process. This dual dopant strategy also enables modulation of the operating voltage and suppresses lattice volume changes upon delithiation. We further uncover a pronounced trade-off between volume variation and oxygen vacancy formation. Based on this trade-off, the investigated dopant combinations can be classified into three distinct groups, allowing a systematic assessment of their cyclability. This study will provide predictive insights into dopant selection for designing novel LMR layered cathode materials.
Yongha Joo, K. Thekkepat, Yonjin Shin et al.· ECS Meeting Abstracts· 0 citations
This work reports a synergistic dual‑engineering strategy that integrates heterointerface construction with cationic modulation for developing high‑performance supercapacitor electrodes. Three‑dimensional V‑doped Ni
3
S
2
/MnS nanoflower heterostructures are successfully synthesized via a facile hydrothermal‑sulfidation method. The in situ‑formed heterojunctions create built‑in electric fields that accelerate charge transfer, while V
3+
doping optimizes the electronic structure and provides additional redox‑active sites. Benefiting from this rational design, the V‑Ni
3
S
2
/MnS electrode delivers a high specific capacity of 2725 F g
−1
at 1 A g
−1
, retains 1700 F g
−1
(62.4% retention) at 10 A g
−1
, and maintains 92.4% capacity retention after 5000 cycles. Theoretical calculations confirm the enhanced charge‑transfer kinetics in the heterostructure. When assembled into an asymmetric supercapacitor with activated carbon, the full cell achieves an energy density of 66.3 Wh kg
−1
at 1500 W kg
−1
. This study provides new insights into the design of heterostructured electrode materials for advanced energy storage applications.
Zhuoran Hou, Jian Cui, Gaosen Wang et al.· Batteries & Supercaps· 0 citations
In this study, the structural and electronic properties of hexagonal Li3P (space group P63/mmc, No. 194) and sulfur‐doped Li3P1‐xSx were investigated by the density functional theory (DFT) within the generalized gradient approximation (GGA‐PBE), as implemented in the Quantum ESPRESSO package. After full geometric optimization of the host material, sulfur incorporation was modeled by substituting P atoms within a supercell, corresponding to a 3.125% doping concentration. Cohesive energy analyses confirm the thermodynamic stability of both pristine and doped configurations, as indicated by their negative values. Electronic structure calculations reveal an indirect bandgap of 0.703 eV for pristine Li3P, obtained consistently with both ultrasoft pseudopotential (USPP) and projector augmented‐wave (PAW) PBE functionals. Remarkably, sulfur substitution at P sites induces pronounced reconstruction of the electronic band structure, giving rise to new energy states that cross the Fermi level (EF), which are attributed to the dopant‐induced electronic states. Through systematic structural relaxations and analysis of total (TDOS) and partial (PDOS) densities of states, the underlying modulation mechanism is elucidated. A detailed bonding‐character analysis further identifies the hybridization states of both doped and undoped systems.
Merve Özcan· physica status solidi (b)· 0 citations
Proton ceramic electrochemical cell (PCEC) is a promising technology for energy storage and conversion. However, the performance of its air electrode materials remains unsatisfactory. To improve the ORR/OER catalytic activity of air electrodes, most studies focus on doping elements at the A/B sites of perovskite materials, while O-site doping is rarely explored. We propose that O-site doping in air electrode materials could be a highly effective strategy. Using a triple-conductive perovskite, BaFeO
3−δ
, as the base material for the air electrode, we investigated the effects of F or Cl or Br doping at the O-site via first-principles density functional theory (DFT) calculations. First, we systematically analyzed the proton migration pathways in BaFeO
3−δ
with oxygen vacancies and determined key parameters governing proton migration. Subsequently, different concentrations of F/Cl/Br were doped at the O-site, and the proton migration pathways were recalculated. By comparing the average proton migration energy barriers before and after O-site doping, we evaluated the structural and property changes induced by F/Cl/Br doping. Additionally, we also calculated the ORR/OER catalytic pathways before and after anion doping, revealing the fundamental mechanisms by which anion doping enhances catalytic activity. This research offers powerful theoretical support for designing high-performance air electrodes for PCECs.
