Anion Vacancies Research Articles

Visualization of Anion Vacancy Defect Annihilation in CZTSe Solar Cells by Hydrogen-Assisted Selenization with In Operando X-ray Nanoprobe Studies.

The traditional sulfur selenization process in Cu2ZnSn(S,Se)4 (CZTSSe) solar cell fabrication often results in the creation of localized anion vacancies (VS and VSe). These vacancies are considered harmful defects as they can trap carriers generated by light, leading to reduced solar cell efficiency. Moreover, concrete evidence has been lacking on the extent of the impact caused by these anion vacancies. Our research introduces a novel approach: the hydrogen-assisted selenization (HAS) process, specifically designed to minimize localized anion vacancies in Cu2ZnSnSe4 (CZTSe) solar cells. Our investigation, utilizing current-voltage (I-V) and admittance spectroscopy measurements, provides clear insights. We observed notable improvements in carrier collection efficiency and a discernible reduction in defect states. Furthermore, there was a significant decrease in the activation energy required within the solar cell device, dropping from 184 to 145 meV. To delve deeper into the structural and compositional aspects, we employed synchrotron-based X-ray nanoprobes. Through nanoscale X-ray fluorescence and hard X-ray beam-induced current measurements, we can directly observe and document the relationship between the local compositional distribution and photocurrent activity in operando. These comprehensive results furnish strong evidence that mitigating anion vacancies in the CZTSe layer can substantially improve the power conversion efficiency of the CZTSe solar cells. This advancement not only sheds light on the critical role of anion vacancies in solar cell performance but also underscores the effectiveness of the HAS process in enhancing overall device efficiency.

Thermal Quenching of Intrinsic Photoluminescence in Amorphous and Monoclinic HfO2 Nanotubes

Nanotubular hafnia arrays hold significant promise for advanced opto- and nanoelectronic applications. However, the known studies concern mostly the luminescent properties of doped HfO2-based nanostructures, while the optical properties of nominally pure hafnia with optically active centers of intrinsic origin are far from being sufficiently investigated. In this work, for the first time we have conducted research on the wide-range temperature effects in the photoluminescence processes of anion-defective hafnia nanotubes with an amorphous and monoclinic structure, synthesized by the electrochemical oxidation method. It is shown that the spectral parameters, such as the position of the maximum and half-width of the band, remain almost unchanged in the range of 7–296 K. The experimental data obtained for the photoluminescence temperature quenching are quantitatively analyzed under the assumption made for two independent channels of non-radiative relaxation of excitations with calculating the appropriate energies of activation barriers—9 and 39 meV for amorphous hafnia nanotubes, 15 and 141 meV for monoclinic ones. The similar temperature behavior of photoluminescence spectra indicates close values of short-range order parameters in the local atomic surrounding of the active emission centers in hafnium dioxide with amorphous and monoclinic structure. Anion vacancies VO− and VO2− appeared in the positions of three-coordinated oxygen and could be the main contributors to the spectral features of emission response and observed thermally stimulated processes. The recognized and clarified mechanisms occurring during thermal quenching of photoluminescence could be useful for the development of light-emitting devices and thermo-optical sensors with functional media based on oxygen-deficient hafnia nanotubes.

Entropy and Electronic Structure Modulation of a Prussian Blue Analogue Cathode with Suppressed Phase Evolution for Potassium-Ion Batteries.

Severe structural evolution and high content of [Fe(CN)6]4- defects drastically deteriorate K-ion storage performances of Prussian blue-based cathodes. Herein, a potassium manganese iron copper hexacyanoferrate (KFe2/3Mn1/6Cu1/6HCF), with suppressed anionic vacancies, eliminated band gap, and low K-ion diffusion barrier, is regarded as a cathode for potassium-ion batteries. The entropy stabilization effect and robust Cu-N bond induced by the inert Cu-ion with large electronegativity boost KFe2/3Mn1/6Cu1/6HCF to exhibit great phase state stability, thus inhibiting the structural transition of monoclinic ↔ cubic. Hence, KFe2/3Mn1/6Cu1/6HCF undergoes a zero-stress solid-solution reaction mechanism, where Fe and Mn serve as dual active sites for charge compensation. Consequently, KFe2/3Mn1/6Cu1/6HCF displays a high reversible capacity of 127.5 mAh·g-1 with an energy density of 469.2 Wh·kg-1 at 10 mA·g-1 and superior cyclic stability with a high retention of 90.7% over 100 cycles. A high-energy-density K-ion full battery is assembled, contributing an ultralong lifetime over 1000 cycles with a low-capacity fading rate of 0.038% per cycle.

Creating Cation Vacancies in BiOCl Nanosheets Toward Exceptional Visible-Light-Driven Photocatalytic CO2 Reduction.

BiOCl-based materials have emerged as promising photocatalysts for converting CO2 into valuable products and fuels. However, challenges such as low light absorption and inefficient charge carrier separation require effective solutions, with vacancy engineering offering a promising approach. Current research primarily focuses on anion vacancies, leaving cation vacancies less explored. In contrast, this study presents a novel method to enhance visible-light-driven photocatalysts by Bi cation vacancies in ultrathin BiOCl nanosheets through a straightforward hydrochloric acid etching process (HAE-BiOCl). These introduced Bi vacancies not only expand the light absorption range and enhance carrier separation, but also serve as active sites for CO2 adsorption. Additionally, Bi vacancies can effectively lower the activation energy of COOH- species and thereby enhance overall reaction activity. As a result, the HAE-BiOCl catalyst exhibits exceptional photocatalytic CO2 reduction performance without the need for co-catalysts or sacrificial agents. It achieves high CO generation rates of 68.39 and 17.43µmol g-1 h-1 under 300W Xe lamp and visible light irradiation, respectively. These rates are significantly higher compared to counterparts without vacancy creation and surpass those of most reported Bi-based photocatalysts. This study underscores the potential of inducing cation vacancies via acid etching as a valuable strategy for advancing photocatalysis.

Machine Learning Enabled High‐Throughput Screening of 2D Ultrawide Bandgap Semiconductors for Flexible Resistive Materials

AbstractThe 2D ultrawide bandgap (UWBG) semiconductors have attracted great attentions for the next generation of electronics and optoelectronics, owing to their superiority on material flexibility, device stability, and power consumption. However, few 2D UWBG semiconductors have been discovered, impeding their prosperous developments and widespread applications. Here, a high‐throughput workflow is constructed to screen 2D UWBG semiconductors assisted by machine learning, and 507 potential candidates are obtained. Moreover, by learning, predicting, and screening Young's modulus and Poisson's ratio, 31 flexible 2D UWBG semiconductors are identified. Then the generation and the diffusion of anion vacancies, as well as the corresponding electronic properties are investigated by using the first‐principles calculations, and 3 of them are demonstrated as the most promising candidates for the flexible resistive materials. The facile interface tunneling and the increased material conductance caused by the anion vacancies will contribute to the transition from high resistive state to low resistive state. This work provides an efficient high‐throughput screening protocol to enrich the family of 2D UWBG semiconductors and is expected to foster their practical applications.

Enhanced lithium-sulfur battery eilectrochemistry via Se-doped MoS2/rGO ultrathin sheets as sulfur hosts

In the pursuit of advancing lithium-sulfur (Li-S) battery technology, the intrinsic challenges of sulfur conductivity and the shuttle effect during charge-discharge cycles have posed significant barriers. Despite many efforts made through physical and chemical methodologies, the development of host materials with more active sites and good catalytic activities might still remain a challenging problem in Li-S batteries. This study presents a novel selenium-doped molybdenum disulfide (Se-MoS2) nanosheet, synthesized on reduced graphene oxide (rGO), which would address these issues. The Se-MoS2/rGO composite enhances conductivity and catalytic activity through the creation of anionic vacancies, facilitating lithium polysulfide adsorption. As a sulfur host, this material delivers an impressive initial capacity of 1008.1 mAh g−1 at 1C, maintaining 620.7 mAh g−1 after 500 cycles with a minimal capacity fade of 0.077 % per cycle, demonstrating superior coulombic efficiency and stability. The findings underscore the impact of heteroatom doping on the electrochemical performance of graphene-based materials for Li-S batteries.

Hierarchical hollow MnO/carbon fiber@WS2 composite material exhibits strong wideband electromagnetic wave attenuation

Constructing multi-layer heterogeneous interfaces has been studied as one of the important means to optimize electromagnetic wave absorption performance. WS2, as a special layered material with high specific surface area and multiple anionic vacancies, although its multi-layered interface structure cannot meet the requirements of all absorbing materials, composite absorbers designed through composition and structure are undoubtedly not one of the strategies to improve absorption bandwidth. In this study, we utilized the defect rich characteristics of WS2 Nano flowers and designed a multi-layer core–shell MnO/CF@WS2 (H-MCW) hybrid materials using carbon fiber (CF) as a carrier to provide a carbon source. The core cavity of H-MCW is conducive to multiple scattering of electromagnetic waves, with a large number of defects leading to an increase in electrochemical active sites in the material, and enhanced dipoles helping to improve impedance matching. This work provides a new method for designing lightweight thin film absorbing materials.

Zero-Strain Sodium Nickel Ferrocyanide as Cathode Material for Sodium-Ion Batteries with Ultra-Long Lifespan.

Prussian blue analogues are recognized as one of the most promising cathode materials for sodium-ion batteries (SIBs) owing to the open 3D framework structure with large interstitial sites and developed Na-ion diffusion channels. However, high content of anion vacancy and poor structural stability have hampered the prospect of their application. In this work, sodium nickel ferrocyanide (Na1.34Ni[Fe(CN)6]0.92, NNHCF) is proposed as cathode material for SIBs. N-coordinated Ni-ion can boost NNHCF to possess less Fe[(CN)6]4- defect, low Na-ion migration barrier, and more negative formation energy compared with Na0.91Cu[Fe(CN)6]0.77 (NCHCF), thus exhibiting more active sites, fast electrochemical kinetics behavior and great structure stability. It is confirmed that NNHCF undergoes a solid solution mechanism without phase evolution for reversible Na-ion intercalation/deintercalation, employing Fe associated with C atom as redox center for charge compensation. Therefore, NNHCF contributes a high initial energy density of 180.94 Wh·g-1 at 10 mA·g-1, excellent rate capability, superior cycling stability with ultra-long lifespan of 13000 cycles, and low fading rate of 0.0027% per cycle at 500 mA·g-1. This work sheds light on the construction of low-defect PBA cathodes with outstanding dynamics and stability.

Modifying the buried interface by a sulfamate enable efficient perovskite solar cells with high stability

The buried interface between the pivotal perovskite layer and the electron transfer layer (ETL) greatly affects the photoelectric property of perovskite layer and the final performance of a perovskite solar cell (PSC). Effectively modifying the buried interface is feasible to improve the photoelectric conversion efficiency (PCE) and stability of PSCs. Herein, we employ a sulfamate sodium 4-aminoazobenzene-4′-sulfonate (SABS) with zwitterion to modify the SnO2 film surface to improve the performance of PSCs. The post-treatment makes the surface of SnO2 film smoother and also passivate the anion and cation vacancies of SnO2, which are benefit to the growth of perovskite crystals and strengthen the interface contact between SnO2 layer and perovskite layer. Furthermore, SABS molecules can passivate defects of perovskite layer at the buried interface. By using this post-treating method, the PCE of the final PSC is increased from 21.76 % to 23.86 %, and the storage and operational stability are also significantly improved. This promotion the buried interface via post-treating the SnO2 film with a zwitterion passivator provides a convenient strategy to effectively improve the performance and stability of PSCs.

Hydrogen-Bonded Ionic Co-Crystals for Fast Solid-State Zinc Ion Storage.

The development of new ionic conductors meeting the requirements of current solid-state devices is imminent but still challenging. Hydrogen-bonded ionic co-crystals (HICs) are multi-component crystals based on hydrogen bonding and Coulombic interactions. Due to the hydrogen bond network and unique features of ionic crystals, HICs have flexible skeletons. More importantly, anion vacancies on their surface can potentially help dissociate and adsorb excess anions, forming cation transport channels at grain boundaries. Here, it is demonstrated that a HIC optimized by adjusting the ratio of zinc salt and imidazole can construct grain boundary-based fast Zn2+ transport channels. The as-obtained HIC solid electrolyte possesses an unprecedentedly high ionic conductivity at room and low temperatures (≈11.2 mScm-1 at 25°C and ≈2.78mScm-1 at -40°C) with ultra-low activation energy (≈0.12eV), while restraining dendrite growth and exhibiting low overpotential even at a high current density (<200mV at 5.0mAcm-2) during Zn symmetric cell cycling. This HIC also allows solid-state Zn||covalent organic framework full cells to work at low temperatures, providing superior stability. More importantly, the HIC can even support zinc-ion hybrid supercapacitors to work, achieving extraordinary rate capability and a power density comparable to aqueous solution-based supercapacitors. This work provides a path for designing facilely prepared, low-cost, and environmentally friendly ionic conductors with extremely high ionic conductivity and excellent interface compatibility.

Revealing the Synergistic Effect of Cation and Anion Vacancies on Enhanced Fenton-Like Reaction: The Electron Density Modulation of O 2p-Co 3d Bands.

Defect engineering is considered as a flexible and effective mean to improve the performance of Fenton-like reactions. Herein, a simple method is employed to synthesize Co3O4 catalysts with Co-O vacancy pairs (VP) for peroxymonosulfate (PMS) activation. Multi-scaled characterization, experimental, and simulation results jointly revealed that the cation vacancies-VCo contributed to enhanced conductivity and anion vacancies-VO provided a new active center for the 1O2 generation. Co3O4-VP can optimize the O 2p and Co 3d bands with the strong assistance of synergistic double vacancies to reduce the reaction energy barrier of the "PMS → Co(IV) = O → 1O2" pathway, ultimately triggering the stable transition of mechanism. Co3O4-VP catalysts with radical-nonradical collaborative mechanism achieve the synchronous improvement of activity and stability, and have good environmental robustness to favor water decontamination applications. This result highlights the possibility of utilizing anion and cation vacancy engineering strategies to rational design Co3O4-based materials widely used in catalytic reactions.

Optical characteristics and surface dendritic growth of Nd,Y:CaF2 crystals irradiated by high-energy He ions

This study aims to investigate the various responses of the optical characteristics to He-ion irradiation at different fluences and energies in Nd,Y:CaF2 crystals. Through optical absorption and photoluminescence spectra, we observe that electrons excited by He-ion irradiation are trapped by anionic vacancies, He ions and Nd3+ to form F-centers, He atoms and Nd2+, respectively. At an energy of 5 MeV, F-centers decrease with increasing fluence, whereas at a fluence of 1×1013 ions/cm2, increasing the energy promotes Nd2+ formation, and a further increase in the fluence based on an energy of 16 MeV can significantly promote Nd2+ production. After the irradiation, the electrons from F-centers are also captured by Nd3+, leading to the decay of F-centers and an increase in Nd2+ with time. In addition, the growth of CaF2 dendrites with multiple morphologies on the surface by high-energy irradiation was observed. It was explained by the surface recrystallization between the escape of F and surface metallization due to high-energy irradiation. This research provides significant insights into the conditions of irradiation modulating defect generation and evolution, as well as laying the groundwork for future applications of radiation-exposed crystals as radiation dosimeters and lasers.

Atomistic oxidation mechanism of Bi0.5Sb1.5Te3 (0001) surface

Surface oxidation can potentially influence transport properties of thermoelectric materials and service performance of thermoelectric devices. Here, the oxidation mechanism of the (0001) surface of a widely used p-type TE material, Bi0.5Sb1.5Te3 (BST), was investigated using spherical aberration corrected scanning transmission electron microscopy (STEM). Combining atomic resolution STEM and density function theory (DFT), it was revealed that oxidation occurs at room temperature in the dry air through O diffusion into the surface quintuple layer, facilitating formation of both cation and anion vacancies, weakening the Bi-Te and Sb-Te bonds, leading to oxidation product Sb2O3, amorphous Te, and Bi-rich Bi2Te3. Formation of a thin O-rich cation-deficient quintuple layer on the surface and the Bi-rich BST region can significantly reduce the interfacial reaction between BST and Ni electrode, as the reaction layer thickness is reduced by 75% after the surface oxidation. This work provides essential structural information on surface oxidation mechanism and its influence on properties and performance of TE materials and devices.

Enabling Sustainable Ammonia Synthesis: From Nitrogen Activation Strategies to Emerging Materials.

Ammonia (NH3) is one of the most important precursors of various chemicals and fertilizers. Given that ammonia synthesis via the traditional Haber-Bosch process requires high temperatures and pressures, it is critical to explore effective strategies and catalysts for ammonia synthesis under mild reaction conditions. Although electrocatalysis and photocatalysis can convert N2 to NH3 under mild conditions, their efficiencies and production scales are still far from the requirements for industrialization. Thermal catalysis has been proven to be the most direct and effective approach for ammonia synthesis. Over the past few decades, significant efforts have been made to develop novel catalysts capable of nitrogen fixation and ammonia generation via thermal catalytic processes. In parallel with catalyst exploration, new strategies such as self-electron donation, hydride fixation, hydridic hydrogen reduction, and anionic vacancy promotion have also been explored to moderate the operating conditions and improve the catalytic efficiency of ammonia synthesis. In this review, the emergence of new materials and strategies for promoting N2 activation and NH3 formation during thermal catalysis is briefly summarized. Moreover, challenges and prospects are proposed for the future development of thermal catalytic ammonia synthesis.

Zinc Tellurium with Anionic Vacancies Anchored on Ordered Macroporous Carbon Skeleton Enabling Accelerated Polysulfide Conversion for Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) showcase great promise for large-scale energy storage systems, however, their practical commercialization is seriously hindered by the sluggish redox reaction kinetics and detrimental shuttle effect of soluble polysulfides. Herein, small ZnTe1- x nanoparticles with anionic vacancies firmly anchored on 3D ordered macroporous N-doped carbon skeleton (3DOM-ZnTe1- x@NC) are elaborately constructed as a high-efficiency electrocatalyst for LSBs. The ordered macroporous carbon skeleton not only greatly increases the external surface area to expose sufficient active sites but also facilitates the electrolyte penetration. Additionally, the experimental studies combined with theoretical calculations confirm the presence of Te vacancies optimizes the electronic structure to enhance the intrinsic catalytic activity and chemical absorption. Consequently, LSBs assembled with the 3DOM-ZnTe1- x@NC modified separators exhibit high specific discharge capacity, as well as superior rate performance and good long-term cycling stability. Even under a high sulfur loading of 6.5 mg cm-2 and lean electrolyte, an impressive areal capacity of 5.28 mAh cm-2 is achieved at 0.1C after 100 cycles. More significantly, the 3DOM-ZnTe1- x@NC based pouch cells are also fabricated to demonstrate its potential for practical applications. This work highlights that the rational combination of 3DOM architecture and vacancy engineering is important for designing advanced Li-S electrocatalysts.

Boosting the electrocatalytic performance of CuCo2S4 via surface-state engineering for ampere current water electrolysis applications

For the efficient production of green H2 on an industrial scale, developing durable, cost-effective electrocatalysts using earth-abundant transition-metals is crucial. Herein, we report a robust, bifunctional sulfurized CuCo2O4 (CCS/Ov) catalyst with engineered oxygen-vacancies, in which the metal catalyst is tunes to high valence state, significantly altering the intrinsic reaction kinetics and generating better catalytic activity for efficient ion transport in various electrolytes (neutral, seawater, alkaline simulated-seawater (ASW), and KOH). The optimized dual-strategy synthesized CCS/Ov catalysts with hierarchical morphology exhibits modest overpotential of 383 and 355 mV at 1000 mA cm−2 for OER and HER, respectively, in 1 M KOH. Impressively, an electrolyzer cell (CCS/Ov||CCS/Ov) demonstrates low cell-voltage of 1.487 V (6 M KOH), with excellent robustness in an ASW (1 and 2 M) environment against corrosive chlorine. The bifunctional CCS/Ov||CCS/Ov catalyst outperforms a state-of-the-art paired Pt/C||RuO2 catalyst and maintains the lowest potential response at up to 2000 mA cm−2, while demonstrating remarkably stable simultaneous O2 and H2 generation over 10 days at various current rates. Additionally, DFT calculations confirmed that CCS/Ov catalysts demonstrate significantly enhanced HER and OER activities due to reduced H2O dissociation energy and strong intermediate binding energy, which is attributed to the anionic vacancy near Co3+. The excellent bifunctional performance of the hierarchical CCS/Ov highlights its potential as non-precious catalyst with facile fabrication approach.

High performance potassium/sodium-ion storage enabled by anchoring cobalt atoms on sulfur vacancies in WS2 nanosheets

Transition metal dichalcogenides (TMDs) as anodes have presented significant potential in alkali-ion batteries. Nevertheless, they are generally vulnerable to low conductivity and sluggish ion diffusion as well as severe volume variation. Here, a strategy of filling metal atoms into anion vacancies is proposed and applied to the example of WS2. More specifically, sulfur vacancies are produced and partially filled by Co atoms simultaneously in WS2 (denoted as Co@WS2-SV), creating a highly reactive micro-structure composed of Co-W-S, which can not only effectively provide more active sites, but also boost the charge transfer and reaction kinetics. Consequently, the as-prepared Co@WS2-SV exhibits superior K+ storage performance, which includes an ultrahigh reversible capacity of 382.9 mAh g−1 at 0.05 A g−1. Besides, Co@WS2-SV still maintain a capacity of 112.6 mAh g−1 after 1100 cycles at 2 A g−1 while the capacity fades to ∼0 mAh g−1 after only 800 cycles for WS2. Simultaneously, Co@WS2-SV also displays outstanding rate capability (338.7 mA h g−1 at 2 A g−1) and acceptable cycling performance (264.2 mA h g−1 at 1 A g−1 after 100 cycles) for sodium storage. The strategy in our study provides new way of precisely designing the other TMDs anodes for metal-ion batteries.

Structural, optical and magnetic characteristics of Mg2+- doped (Ba0.94Sr0.06)(Fe0.80Al0.20-xMgx)O3-ẟ (x = 0–0.20) oxides

Perovskite-type ABO3 oxides have attracted immense attention in recent technologies e.g., gas sensors, solar cells, fuel cells, oxygen-permeable membranes, etc. An attempt has been made here to synthesize (Ba0.94Sr0.06)(Fe0.80Al0.20-xMgx)O3-ẟ (x = 0–0.20) oxides using sol-gel method and characterized with regards to phase, Raman and magnetic properties. X-ray diffraction-cum-Rietveld refinement shows the structural transformation from cubic (Pm3m) to hexagonal (P63/mmc) via cubic (Pm3m) + rhombohedral (R3c) and increase of cubic lattice parameter ac = 4.0369–4.1296 Å with magnesium. FT-IR spectra exhibit different vibrational bands at 548, 555, 638, 667, and 692 cm−1, representing the metal-oxygen (M-O-M) bond vibrations (M - Fe, Mg, Al), deformation of MO6 octahedral, and internal changes in bond lengths. No Raman band was appeared for cubic phase with x=0–0.10. Bands between ∼ 250–450 cm−1 assign the tilting, rotation, and asymmetric bending vibrations of Fe – O, Mg – O and Al – O bonds and asymmetric bending mode of (Fe/Mg/Al)O6 octahedra. Oxygen bending vibration, anti-stretching mode and presence of oxygen vacancies lie in the bands of range ∼498–656 cm−1. Maximum coercivity (Hc ∼ 1081 Oe) and remanent magnetization (Mr ∼ 0.033 emu/g) have been observed for x = 0 and found similar variation with ‘x’. The saturation magnetization (Ms) and anisotropic constant (K1) values lie as Ms = ∼ 0.678 – 0.754 emu/g and K1 = ∼ 1.38× 104 – 1.53× 104 erg/cm3, respectively with magnesium (x). Presence of anion vacancies and high coercivity make the materials suitable for industrial applications.

Anionic vacancy filled-up mechanism in (Ti0.2V0.2Nb0.2Ta0.2W0.2)Cx high-entropy carbide

Carbothermic reduction for high-entropy carbide preparation has it’s promising potential for industrialization application and the relevant basic theory for formation process required to clarify urgently. This research reports the anionic vacancy filled-up (AVF) mechanism during the formation of (Ti0.2V0.2Nb0.2Ta0.2W0.2)Cx high-entropy carbide powder by predictions of first-principles calculations, thermodynamic phase diagram calculations and verification by experimental preparation and characterization. The mechanism demonstrated that the rock-salt carbide matrix with superfluous anionic vacancy was formed firstly and the residual carbon substance continuously occupied the vacancies to an equilibrium state. The origin of the equilibrium anionic vacancy concentration was revealed from the perspective of the energy variation.

Defect design and vacancy engineering of NiCo2Se4 spinel composite for excellent electromagnetic wave absorption

Vacancy engineering presents an appealing method for modifying the electronic structure of spinel architectures. However, based on well-defined vacancy concentrations, how to design anionic vacancies to modulate electromagnetic parameters as well as electromagnetic wave absorption (EMA) properties is less studied. Here, NiCo2Se4 spinel structures were prepared using different selenization methods, and the Se vacancy defect concentration was controlled by changing the annealing temperature, thus regulating the EMA properties. Among them, the design of the hollow structure effectively enhanced the EMA performance. Moreover, the increase of Se vacancy concentration increases the conductivity loss while regulating the electronic structure, and also acts as an unsaturated site to induce the formation of dipoles to optimize the polarization loss. The effective absorption bandwidth (EAB) of NiCo2Se4-130 reaches 8.48 GHz at 2.4 mm at the highest Se vacancy concentration. This work establishes a direct relationship between vacancy concentration and the electromagnetic wave dissipation capability, offering valuable insights for the development of advanced EMA materials.