Abundant Defects Research Articles

Optical Centers in Cr-, Mn-, and O-Doped AlN and Their Thermodynamic Stability Designed by a Multiscale Computational Approach.

The optical centers in AlN can frequently exist in various charge states and can be accompanied by many coexisting defect species, creating a complex environment where mutual interactions are inevitable. Therefore, it is an immediate quest to design AlN crystal growth protocols that can target a specific optical center of interest and tune its concentration while preventing the formation of other unwanted point defects. Here, we provide a powerful workflow for point defect engineering in wide band gap, binary semiconductors that can be readily used to design optimal crystal growth protocols through combining CALPHAD-based phase analysis, and ab initio defect calculations. We investigate technologically relevant chromium- and manganese-induced optical centers in AlN, followed by studying the impact of oxygen that can be unintentionally incorporated during crystal growth. We present the dominant defects in all three cases as a function of process parameters along with the optical signatures. In the case of both Cr and Mn doping, the CrAl and MnAl defects are most likely, and increasing nitrogen partial pressure tends to enhance their concentration. We show that it is possible to use nitrogen fugacity as a tool for tuning the intensity of optical signatures. We calculate the CrAl charge transition levels with respect to the valence-band maximum at 2.60 eV (E+/-), 3.83 eV (E0/-), and 5.41 eV (E-/2-) and electron and hole capture transitions with luminescence bands centered at 2.82, 1.91, and 3.15 eV. Unlike the Cr doping, Mn aggregation is unlikely, and the MnAl-VN is the most abundant defect after MnAl under most synthesis conditions. Oxygen tends to form complexes with VAl, and ON-VAl is a prominent defect following ON, with near-UV emission bands at 3.17, 3.26, and 3.81 eV. Our results agree with the available experimental optical signatures of Cr-, Mn-, and O-related centers and provide pathways on how to tune the luminous intensity of these centers through changes in growth conditions.

Collaborative Hollow Porous Structure Design and N Doping to Achieve a Win–Win Situation of “Stable” and “Fast” Lithium Battery

ABSTRACTPolymer‐derived SiOC materials are widely regarded as a new generation of anodes owing to their high specific capacity, low discharge platform, tunable chemical/structural composition, and good structural stability. However, tailoring the structure of SiOC to improve its electrochemical performance while simultaneously achieving elemental doping remains a challenge. Besides, the lithium storage mechanism and the structural evolution process of SiOC are still not fully understood due to its complex structure. In this study, a hollow porous SiOCN (Hp‐SiOCN) featuring abundant oxygen defects is successfully prepared, achieving both the creation of a hollow porous structure and nitrogen element doping in one step, finally enhancing the structural stability and improving the lithium storage kinetics of Hp‐SiOCN. In addition, the formation of a fully reversible structural unit, SiO3C─N, through the chemical interaction between N and Si/C, showcases a strong lithium adsorption capacity. Taking advantage of these combined benefits, the as‐prepared Hp‐SiOCN electrode delivers a reversible specific capacity of 412 mAh g−1 (93% capacity retention) after 500 cycles at 1.0 A g−1 and exhibited only 4% electrode expansion. This work offers valuable mechanistic insights into the synergistic optimization of elemental doping and structural design in SiOC, paving the way for advanced developments in battery technology.

Evolutionary trends and photothermal catalytic reduction performance of carbon dioxide by MOF-derived MnOx

Metal oxide catalysts derived from MOFs can inherit the excellent performance from their parent MOFs, possess abundant surface defects and high stability, and have attracted widespread interest in multiphase catalysis. In this study, we used Mn-MOF as a precursor and systematically investigated the evolution of MnOx catalysts by setting different calcination temperatures and times. XRD, SEM, TEM, Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption analysis, XPS, H2-TPR, CO2-TPD, electrochemical characterization, and other methods were used to investigate the structural characteristics, microstructure, surface properties, and photoelectric properties of the catalysts. The catalytic performance of the catalysts was also investigated through photocatalytic carbon dioxide hydrogenation reduction tests. Research has shown that calcination temperature and time have a significant impact on the phase structure and surface properties of MnOx, and the physicochemical properties of derived MnOx can be controlled by controlling calcination temperature and time. Among them, MnOx-500 has a wider light absorption range, better electron transfer performance, richer oxygen vacancies, and excellent separation performance of photo generated charge carriers, resulting in higher photocatalytic CO2 hydrogenation and reduction performance. Its CO yield and selectivity reached 7420 μmol/g/h and above 99 %, respectively. This study provides valuable references for the preparation, optimization, and utilization in CO2 photothermal catalytic conversion of MnOx catalysts derived from MOFs.

Minimizing vacancy defects with Eu passivation strategy to enable highly efficient perovskite photovoltaics

The intrinsic ionic nature of metal halide perovskites facilitates the formation of abundant defects at grain boundaries (GBs) and surfaces, consequently diminishing the stability and photovoltaic performance of perovskite solar cells (PSCs). Due to the low formation energies and instability of Pb-I bonds, iodine (I) and lead (Pb) vacancies are prevalent high-density point defects. In this study, we explore the use of europium (Eu) as a novel passivator to concurrently address I and Pb vacancies through first-principles calculations. Our results demonstrate that Eu significantly lowers the defect formation energies and adjusts the bandgap, enlarged by vacancy defects, to align with the ideal Shockley-Queisser limit, indicating a strong potential for achieving high power conversion efficiency (PCE). Furthermore, Eu passivation markedly increases the activation energy barriers for ion migration, resulting in substantially reduced migration rates. This suggests a minimal likelihood of I and Pb ion migration on defected surfaces, underscoring Eu’s potential to mitigate hysteresis effects and enhance stability. This work advances our understanding of the passivation effects of rare earth elements and establishes a foundation for designing highly effective passivation strategies to achieve stable and efficient PSCs.

Selective hydrogenolysis of furfural-derived tetrahydrofurfuryl alcohol to 1,5-Pentanediol over Ni-Co/La(OH)x bimetallic catalysts

The selective activation of targeted bonds within renewable biomass-derived furanic compounds for the production of high-value alkyl diols holds significant importance for biomass upgrading, necessitating well-defined catalysts and clearly defined catalytically active sites. Herein, 1,5-pentanediol is synthesized through the selective hydrogenolysis of furfural-derived tetrahydrofurfuryl alcohol utilizing Ni-Co/La(OH)x bimetallic catalysts. The La(OH)x with abundant defect sites polarizes Ni-Co alloy for heterocracking of H2, as well as leads to expose more interfacial NiCo-OV-La3+ sites. By harnessing the synergistic interplay between the alloy sites and the interfacial sites, the optimized Ni4Co1/La(OH)x bimetallic catalyst markedly enhances the adsorption of –OH groups in tetrahydrofurfuryl alcohol and facilitates the selective assault of active H species on the C-O-C bonds within tetrahydrofuran rings. This approach markedly elevates the selective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol, attaining an exceptional selectivity of 88.6 % with a conversion of 98.1 % for tetrahydrofurfuryl alcohol. Furthermore, the Ni4Co1/La(OH)x bimetallic catalyst demonstrates exceptional performance in the one-pot hydrogenation-hydrogenolysis of furfural to 1,5-pentanediol, exhibiting a low activation energy of 17.77 kJ/mol and a high turnover frequency of 192.1 h−1. Notably, the Ni4Co1/La(OH)x bimetallic catalyst showcases remarkable stability. This outcome provides invaluable insights for the advancement of a sustainable process to produce diol monomers from renewable resources with a low carbon footprint.

Deep P‐C Interface Reconstruction for High‐Performance Potassium Storage

AbstractPotassium‐ion batteries (PIBs) capable of achieving full charge in minutes, or even in seconds, while maintaining high energy densities, are highly desirable for practical applications. However, significant challenges exist in developing electrodes that can sustain both high capacity and rapid charging rates. Conventional phosphorus‐carbon composites, limited by the intrinsic common carbon materials structure, often fail to prevent the edges reconstruction of black phosphorus (BP), thereby limiting its potential advantages as a high‐capacity, high‐rate anode. This study addresses these challenges by grafting BP onto a super‐porous carbon (SPC) framework to serve as an anode for potassium storage. The large number of open pores in SPC ensures the uniform distribution of BP nanoparticles in this carbon matrix, realizing the complete potassiation reactions and uniform volumetric strain dispersion. The abundant defects significantly promote the phosphorus‐carbon reconstruction between edge carbon atoms and edge phosphorus atoms, effectively inhibiting the P‐P edge reconstruction of BP to ensure open edges for rapid K+ diffusion. As a result, the composite exhibits excellent performance in potassium storage, demonstrating superior capacity, charging rates, and cycling durability. This research provides a new insight into enhancing BP‐base anodes, offering favorable guidance for the development of high‐performance materials.

Microwave Shock Synthesis of Porous 2D Non‐Layered Transition Metal Carbides for Efficient Hydrogen Evolution

ABSTRACTTransition metal carbides (TMCs) serve as efficient catalysts for electrocatalytic hydrogen evolution reactions (HERs), holding significant importance in promoting hydrogen production for carbon neutrality. To optimize interfacial catalytic activity, structurally designing TMCs into two‐dimensional (2D) and porous structures to expose more practical surface areas and enhance electronic configurations is a common and effective strategy. Particularly, porous 2D non‐layered TMCs (2D NL‐TMCs) demonstrate richer active sites distinct from layered interfacial inertness. However, mainstream selective etching and chemical deposition growth mechanisms struggle to prepare highly active porous 2D NL‐TMCs due to constraints posed by their high structural strength and formation temperature. Herein, we successfully synthesized porous 2D W2C (2D p‐W2C) rapidly using a microwave shock method. Mechanistic verification reveals that leveraging transient high temperature and rapid on‐off properties of microwave effectively combines with an oxidation‐induced porosity mechanism, facilitating the evolution of porous 2D structures. These low‐dimensional nanostructures with abundant edge defect sites aid in efficient adsorption reactions of intermediate species in HER. Moreover, the successful preparation of a series of porous 2D NL‐TMCs (Mo2C, NbC, TaC) confirms the universality of this method, with the synthesized 2D p‐W2C exhibiting optimal HER performance. This strategy offers new insights into the topological synthesis of porous 2D NL crystals.

High surface density of Mn-N sites in atomically dispersed Mn catalyst for effective CO2 electroreduction

Electrocatalytic CO2 reduction to chemical fuels driven by renewable energy provides a highly promising route to fabricate the circular economy. However, the high overpotential and competitive side reactions severely hinder the industrial application of this process. Here we prepare the atomically dispersed Mn catalyst with high surface density of Mn-N sites via carbon protection and pyrolysis strategies, which exhibits a maximum of 90 % CO faradaic efficiency and the low overpotential of 80 mV to produce CO. The enhanced catalytic performance is mainly attributed to the high surface density of Mn-N4 sites, abundant defects, and high electrochemical active surface area. This work provides the possibility to improve the CO2 electroreduction performance of inert catalysts through surface structure design.

Enhanced electrochemical nitrate reduction with a novel (Mn,Fe)2O3/Co3S4 electrocatalyst for sustainable ammonia production

This study presents a novel (Mn,Fe)2O3/Co3S4 composite catalyst designed for electrochemical nitrate reduction reaction (NO3-RR) to overcome challenges in sustainable ammonia production and potentially replace the energy-intensive Haber-Bosch process. The ternary (Mn,Fe)2O3/Co3S4 composite catalyst exhibited outstanding performance, achieving a high ammonia (NH3) yield rate of 17.54 mg.h−1 cm−2 and an impressive Faradaic efficiency of 95.5 % at −0.3 V vs. RHE, with stable durability in alkaline condition. This performance surpasses the NH3 yield rate of the S-free MnFeCo(3:1:1) ternary catalyst and the binary MnFe(31:1) catalyst by 1.6 and 5.3 times, respectively. This enhanced performance was accredited to the abundant cation and anion defects with multiple valence charges of (Mn, Fe)2O3/Co3S4 catalyst, which were introduced by inserting a third metal of Co and the nonmetal of S into a binary MnFe system. The proposed mechanism for NO3-RR indicates that oxygen vacancies, combined with the multiple valance charges of the (Mn,Fe)2O3/Co3S4 phase, enable effective nitrate adsorption and H2O dissociation. This interaction boosts NO3-RR performance, resulting in a notable NH3 yield rate and Faradaic efficiency. This research opens a promising new opportunity for the rational strategy and future research for introducing third metal and nonmetal-oxide/sulfide electrocatalysts to realize the critical need for alternative NH3 production.

Self-Etching Synthesis of Superhydrophilic Iron-Rich Defect Heterostructure-Integrated Catalyst with Fast Oxygen Evolution Kinetics for Large-Current Water Splitting.

Developing catalysts with rich metal defects, strong hydrophilicit, and extensive grain boundaries is crucial for enhancing the kinetics of electrocatalytic water oxidation and facilitating large-current water splitting. In this study, we utilized pH-controlled etching and gas-phase phosphating to synthesize a flower-like Ni2P-FeP4-Cu3P modified nickel foam heterostructure catalyst. This catalyst features pronounced hydrophilicity and a high concentration of Fe defects. It exhibits low overpotentials of 156 mV and 210 mV at current densities of 10 and 100 mA cm-2 respectively, and maintains stability for up to 200 h at 100 mA cm-2 with only 7.3% degradation, showcasing outstanding electrocatalytic water oxidation performance. Furthermore, when integrated into a Ni2P-FeP4-Cu3P/NF||Pt-C/NF electrolyzer, it achieves excellent overall water splitting performance, reaching current densities of 10 and 400 mA cm-2 at just 1.47 V and 1.73 V, respectively, and operates stably for 60 h at 500 mA cm-2 with minimal degradation. Analysis indicates that high-valence oxyhydroxides/phosphides of Ni, Fe, and Cu act as the primary active species. The presence of abundant Fe defects enhances electron transfer, strong hydrophilicity improves electrolyte contact, and numerous grain boundaries synergistically modulate the activation energy between active sites and oxygen-containing intermediates, significantly improving the kinetics of water oxidation.

Thermally-Stable Single-Site Pd on CeO2 Catalyst for Selective Amination of Phenols to Aromatic Amines without External Hydrogen.

Developing a new route to produce aromatic amines as key chemicals from renewable phenols is a benign alternative to current fossil-based routes like nitroaromatic hydrogenation, but is challenging because of the high dissociation energy of the Ar-OH bond and difficulty in controlling side reactions. Herein, an aerosolizing-pyrolysis strategy was developed to prepare high-density single-site cationic Pd species immobilized on CeO2 (Pd1/CeO2) with excellent sintering resistance. The obtained Pd1/CeO2 catalysts achieved remarkable selectivity of important aromatic amines (yield up to 76.2 %) in the phenols amination with amines without external hydrogen sources, while Pd nano-catalysts mainly afforded phenyl-ring-saturation products. The excellent catalytic properties of the Pd1/CeO2 are closely related to high-loading Pd single-site catalysts with abundant surface defect sites and suitable acid-base properties. This report provides a sustainable route for producing aromatic amines from renewable feedstocks.

Thermally‐Stable Single‐Site Pd on CeO2 Catalyst for Selective Amination of Phenols to Aromatic Amines without External Hydrogen

AbstractDeveloping a new route to produce aromatic amines as key chemicals from renewable phenols is a benign alternative to current fossil‐based routes like nitroaromatic hydrogenation, but is challenging because of the high dissociation energy of the Ar−OH bond and difficulty in controlling side reactions. Herein, an aerosolizing‐pyrolysis strategy was developed to prepare high‐density single‐site cationic Pd species immobilized on CeO2 (Pd1/CeO2) with excellent sintering resistance. The obtained Pd1/CeO2 catalysts achieved remarkable selectivity of important aromatic amines (yield up to 76.2 %) in the phenols amination with amines without external hydrogen sources, while Pd nano‐catalysts mainly afforded phenyl‐ring‐saturation products. The excellent catalytic properties of the Pd1/CeO2 are closely related to high‐loading Pd single‐site catalysts with abundant surface defect sites and suitable acid‐base properties. This report provides a sustainable route for producing aromatic amines from renewable feedstocks.

Supercapacitive behavior of two-dimensional carbon nanosheets with oxygen-induced interfacial modification

Biomass-derived carbon typically contains abundant heteroatomic defects and interfacial functional groups, which can contribute to additional pseudocapacitance. However, the type of interfacial functional groups in biomass-derived carbon is uncontrollable and variable, reducing their homogeneity. In this work, recyclable boric acid was employed as an activator to convert bioaerogels into carbon nanosheets. Subsequently, low-temperature air oxidation was utilized to modulate their thickness and microstructure. Notably, the multiple and uncontrollable functional groups at the carbon interface were uniformly transformed into oxygen-containing functional groups under oxygen induction, resulting in 2D carbon nanosheet materials with enhanced stability properties. Meanwhile, the introduction of more oxygen-containing functional groups, such as carbonyl (C=O) and carboxyl (-COOH) groups, improves material wettability and capacitive properties. In addition, the boron and nitrogen elements doping introduced by activators and precursors enhances its pseudocapacitive properties and electrical conductivity from the carbon lattice perspective. Moreover, the rich electron/deficient effect of BN valence bond can effectively boost their conductivity and rate performance. In fact, the materials present good capacitive properties (high specific capacitance of 298.5 F g−1 in KOH three-electrode system) and CDI (capacitive deionization) performance (good desalting capacity of 35.2 mg g−1 in CDI system).

Acid washing-assisted synthesis of porous Co3O4 nanosheet catalyst featuring efficient benzene oxidation performance

Co-based catalysts exhibit considerable catalytic activity in oxidative reactions, yet challenges remain in synthesizing Co3O4 materials featuring both large surface area and high activity. Here, ultrathin La0.029CoOx nanosheets were post-treated with various concentrations of dilute nitric acid to obtain the two-dimensionally geometric Co3O4-H nanosheets catalysts. Among them, the resultant Co3O4-0.1H catalyst disclosed significantly enhanced catalytic activity, enabling to achieve 100 % conversion of benzene at 230 °C under an ultrahigh weight hourly space velocity (WHSV) of 60,000 mL·g−1·h−1. Additionally, the catalyst also displayed excellent catalytic durability and well catalytic stability over 5 cyclic tests and 45 h of long-period operation. A thorough characterization results revealed that the superior catalytic performance of Co3O4-0.1H was attributed to its distinct nanosheet morphology, high specific surface area and abundant surface defect sites. This work highlights the effectiveness and simplicity of acid washing treatment strategy in improving the catalytic oxidation activity of transition metal oxide catalysts.

Inorganic-Derived 0D Perovskite Induced Surface Lattice Arrangement for Efficient and Stable All-Inorganic Perovskite Solar Cells.

The inverted inorganic CsPbI3 perovskite solar cells (PSCs) are prospective candidates for next-generation photovoltaics owing to inherent robust thermal/photo-stability and compatibility for tandems. However, the performance and stability of the inverted CsPbI3 PSCs fall behind the n-i-p counterparts due to poor energetic alignment and abundant interfacial defect states. Here, an inorganic 0D Cs4PbBr6 with a good lattice strain arrangement is implemented as the surface anchoring capping layer on CsPbI3. The Cs4PbBr6 perovskite induces enhanced electron-selective junction and thus facilitates efficient charge extraction and effectively inhibits non-radiative recombination. Consequently, the CsPbI3 PSCs with Cs4PbBr6 demonstrate the highest power conversion efficiency (PCE) of CsPbI3-based inverted PSCs, reaching 21.03% PCE from a unit cell and 17.39% PCE from a module with a 64 cm2 aperture area. Furthermore, the resulting devices retain 92.48% after 1000h under simultaneous 1-sun and damp heat (85°C / 85% relative humidity) environment.

Defect-rich In2S3/CoS2 heterostructure for rapid storage of sodium ions

Aiming to accelerate sodium-ion transport kinetics and improve electrochemical cyclability of batteries, an In2S3/CoS2 bimetallic sulfide heterostructure was synthesized as anodes of sodium-ion batteries (SIBs) in this paper by a feasible ion exchange and subsequent hydrothermal vulcanization technique based on a cobalt metal-organic skeleton (ZIF-67) precursor. As-prepared In2S3/CoS2 composite exhibited an excellent rate capability of 453.8 mAh g-1 at 10 A g-1 and outstanding cyclability of 464.06 mAh g-1 after 600 cycles at 2 A g-1. The built-in electric filed between heterogeneous interface of In2S3 and CoS2 plays a dominant contribution on improvement of electronic conductivity and charge transfer kinetics. Beyond that abundant defects derived from ion exchange and nanocrystallization of composite particles also have a positive synergistic effect on inducing additional active centers for adsorption of Na+ and shortening ion transport distance for further accelerating reaction kinetics. Based on exploring conversion and alloying mechanism of In2S3/CoS2 composite via ex situ XRD and TEM, high-performance SIBs with heterostructure bimetallic sulfide anodes may be a prospective strategy.

Cobalt nanoclusters Deposit on Nitrogen-Doped graphene Sheets as bifunctional electrocatalysts for high performance lithium – Oxygen batteries

Rechargeable lithium-oxygen (Li-O2) batteries are being considered as the next-generation energy storage systems due to their higher theoretical energy density. However, the practical application of Li-O2 batteries is hindered by slow kinetics and the formation of side products during the oxygen reduction and evolution reactions on the cathode. These reactions lead to high overpotentials during charging and discharging. To address these challenges, we propose a simple ultrasonic method for synthesizing cobalt nanoclusters embedded in nitrogen-doped graphene nanosheets (GrZnCo) derived from metal-organic frameworks (MOFs). The resulting material, due to the retention of metallic cobalt structure, exhibits better electronic conductivity. Additionally, the GrZnCo catalyst shows vigorous catalytic activity, which can improve reaction kinetics and suppress side reactions, thus lowering the charging overpotential. We have investigated the impact of different catalyst compositions (GrZnCox; x = 1, 3, 5) by varying the amounts of cobalt and zinc. The optimum catalyst, GrZnCo3, contains high cobalt-N active components, graphitic-N, pyridinic-N, pyrrolic-N, and abundant defect structures, which enhance the electrochemical performance. The defect-rich GrZnCo3 catalyst enables Li-O2 batteries to achieve a high discharge capacity of 13500 mAh·g−1 at 50 mA·g−1 and a remarkable long-term cycling performance of over 400 cycles at 100 mA·g−1 with a limited capacity of 500 mAh·g−1. This work demonstrates an effective approach to fabricate cost-effective electrocatalysts for various energy storage systems.

In-situ formation of La2O2CO3 uniformly immobilized on biomass-derived carbon aerogel for enhanced phosphate removal

In the face of the dual pressures of eutrophication and phosphorus shortages, it is of utmost importance to efficiently remove and recover phosphate from wastewater. In this study, waste-biomass-derived carbon aerogel (CA) was utilized as a dispersing carrier for lanthanum (La), resulting in the successful in-situ generation of an La2O2CO3 (La3.5-CA-450) phosphate adsorbent on the CA matrix. The results demonstrated that the introduction of CA as an adsorbent led to abundant carbon defects and pore structures, which significantly enhanced its performance. Moreover, through the coordinated pyrolysis of CA and La3+, CO32−, capable of exchanging with PO43−, was generated, thereby contributing to the exceptional phosphate adsorption capacity exhibited by the adsorbent. Specifically, La3.5-CA-450 displayed a high phosphate adsorption capacity of 155.8 mg P/g (272.4 mg P/g La), with the molar ratio of P to La being 1.22:1, indicating a high utilization efficiency for La. The adsorbent exhibited exceptional performances in terms of selectivity, renewability, efficient use in natural water environments, and robust application in a broad range of synthetic availability. This research adheres to the green concept “using waste to treat waste” while providing a novel approach for preparing efficient La-based phosphate adsorbents.

Nickel-Nitrogen Doped MnO2 as Oxygen Reduction Reaction Catalyst for Aluminum Air Batteries.

Aluminum-air battery has the advantages of high energy density, low cost and environmental protection, and is considered as an ideal next-generation energy storage conversion system. However, the slow oxygen reduction reaction (ORR) in air cathode leads to its unsatisfactory performance. Here, we report an electrode made of N and Ni co-doped MnO2 nanotubes. In alkaline solution, Ni/N-MnO2 has higher oxygen reduction activity than undoped MnO2, with an initial potential of 1.00 V and a half-wave potential of 0.75 V. This is because it has abundant defects, high specific surface area and sufficient Mn3+ active sites, which promote the transfer of electrons and oxygen-containing intermediates. Density functional theory (DFT) calculations show that MnO2 doped with N and Ni atoms reduces the reaction overpotential and improves the ORR kinetics. The peak power density and energy density of the Ni/N-MnO2 air electrode increased by 34.03 mW cm-2 and 316.41 mWh g-1, respectively. The results show that N and Ni co-doped MnO2 nanotubes are a promising air electrode, which can provide some ideas for the research of aluminum-air batteries.

Electronic synergy between NiCo2O4 and adjacent carbon defects to enhance styrene cracking activity for styrene-saturated activated carbon regeneration

The design and construction of catalysts featuring abundant electron transfer and defect structures for the regeneration of styrene-saturated activated carbon (AC) pose a significant challenge. This paper presents successful preparation of a regenerated adsorbent with synergistic catalytic active sites of NiCo2O4 spinel and carbon defects using a simple impregnation method. Enhanced catalytic activity is attributed to the electronic synergy between NiCo2O4 and carbon defects in 2.5Ni-2.5Co-900, involving substantial electron transfers, abundant acidic sites, and strong reducibility. Reactive oxygen species and the robust oxygen transfer facilitate the deep oxidation of intermediates and carbon elimination. The optimized regenerated adsorbent achieved a styrene adsorption capacity of 446.4 mg/g with a recovery of 92.4 % of the fresh sample, which is 1.5 times higher than 5Ni-900 and about 1.8 times higher than the unmodified regenerated activated carbon sample, RAC-900. The mechanism of styrene cracking and the evolution of intermediates were investigated using thermogravimetric-infrared coupling, and the effects of catalytic temperature and active sites on styrene cracking, deep oxidation of intermediates, and elimination of carbon deposits were explored. Kinetic analysis demonstrated that the adsorption of styrene on regenerated samples entailed a multifaceted process integrating both physical and chemical adsorption. The significance of chemical adsorption became increasingly evident as the concentration of defective sites grew. Intra-pore diffusion is the main determining step of the adsorption process. After five cycles, the adsorption capacity of 2.5Ni-2.5Co-900 decreased to below 25 %, suggesting promising strategies to overcome challenges of regenerating styrene-saturated AC.