Advanced Powder Materials最新文献

Modulating electronic structures of single-atom metal cocatalysts is vital for highly active photoreduction of CO₂, and it's especially challenging to develop a facile method to modify the dispersion of atomical photocatalytic sites. We herein report an ion-loading pyrolysis route to in-situ anchor Pd single atoms as well as twinned Pd nanoparticles on ultra-thin graphitic carbon nitride nanosheets (Pd_TP/Pd_SA-CN) for high-efficiency photoreduction of CO₂. The anchored Pd twinned nanoparticles donate electrons to adjacent single Pd–N₄ sites through the carbon nitride networks, and the optimized Pd_TP/Pd_SA-CN photocatalyst exhibits a CO evolution rate up to 46.5 ​μmol ​g⁻¹ ​h⁻¹ with nearly 100% selectivity. As revealed by spectroscopic and theoretical analyses, the superior photocatalytic activity is attributed to the lowered desorption barrier of carbonyl species at electron-enriched Pd single atoms, together with the improved efficiencies of light-harvesting and charge separation/transport. This work has demonstrated the engineering of the electron density of single active sites with twinned metal nanoparticles assisted by strong electronic interaction with the support of the atomic metal, and unveiled the underlying mechanism for expedited photocatalytic efficiency.

Hf-based carbides are highly desirable candidate materials for oxidizing environments above 2000 ​°C. However, the static oxidation behavior at their potential service temperatures remains unclear. To fill this gap, the static oxidation behavior of (Hf, Ti)C and the effect of Ti substitutions were investigated in air at 2500 ​°C under an oxygen partial pressure of 4.2 ​kPa. After oxidation for 2000 ​s, the thickness of the oxide layer on the surface of (Hf, Ti)C bulk ceramic is reduced by 62.29 ​% compared with that on the HfC monocarbide surface. The dramatic improvement in oxidation resistance is attributed to the unique oxide layer structure consisting of various crystalline oxycarbides, HfO₂, and carbon. The Ti-rich oxycarbide ((Ti, Hf)C_xO_y) dispersed within HfO₂ formed the major structure of the oxide layer. A coherent boundary with lattice distortion existed at the HfO₂/(Ti, Hf)C_xO_y interface along the (111) crystal plane direction, which served as an effective oxygen diffusion barrier. The Hf-rich oxycarbide ((Hf, Ti)C_xO_y) together with (Ti, Hf)C_xO_y, HfO₂, and precipitated carbon constituted a dense transition layer, ensuring favorable bonding between the oxide layer and the matrix. The Ti content affects the oxidation resistance of (Hf, Ti)C by determining the oxide layer's phase distribution and integrity.

Layered transition metal dichalcogenides are promising candidates for sodium storage but suffering from low intrinsic electronic conductivity and limited interlayer spacing for fast electron/ion transport, which restricts their high-rate capability and cycling stability. In this work, rGO@MoSe₂/NAC hierarchical architectures, consisting of conductive reduced graphene oxide (rGO) supported by hollow nanospheres that are rolled from superlattices of alternatively overlapped MoSe₂ and N-doped amorphous carbon (NAC) monolayers, are synthesized as a high-performance sodium storage anode. Theoretical calculations reveal the intercalation of NAC monolayer between two adjacent MoSe₂ monolayers improving electronic conductivity of MoSe₂ in both surface and internal bulk to fully accelerate electron transport and enhance Na⁺ ​adsorption. The interoverlapped MoSe₂/NAC superlattice featuring a wide interlayer expansion (72.3 ​%) of MoSe₂ dramatically decreases Na⁺ ​diffusion barriers for fast insertion/extraction. Moreover, the hollow nanospheres and the rGO conductive network contribute to a robust hiberarchy that can well release internal stress and buffer the volume expansion, thereby enabling outstanding structural stability. Consequently, the rGO@MoSe₂/NAC anode exhibits excellent high-rate capability of 194 mAh g⁻¹ and ultralong cyclability of 12 ​000 cycles with a low capacity fading rate of 0.0038 ​% per cycle at an ultra-high current of 50 ​A ​g⁻¹, delivering the best high-rate cycling performance to date. Remarkably, the Na₃V₂(PO₄)₃‖rGO@MoSe₂/NAC full cells also present outstanding cycling stability (600 cycles) at 10C rate, which proves the great potential in fast-charging applications.

Layered materials with adjustable framework, as the most potential cathode materials for aqueous rechargeable zinc ion batterie, have high capacity, permit of rapid ion diffusion, and charge transfer channels. Previous studies have widely investigated their preparation and storage mechanism, but the intrinsic relationship between the structural design of layered cathode materials and electrochemical performance has not been well established. In this work, based on the first principles calculations and experiments, a crucial strategy of pre-intercalated metal-ions in vanadium oxide interlayer with administrable p-band center (ɛ_p) of O is explored to enhance Zn²⁺ storage. This regulation of the degree of covalent bond and the average charge of O atoms varies the binding energy between Zn²⁺ and O, thus affecting the intercalation/de-intercalation of Zn²⁺. The present study demonstrates that ɛ_p of O can be used as an important indicator to boost Zn²⁺ storage, which provides a new concept toward the controlled design and application of layered materials.

Mechanoluminescent (ML) materials, which have the ability to convert mechanical energy to optical energy, have found huge promising applications such as in stress imaging and anti-counterfeiting. However, the main reported ML phosphors are based on trap-related ones, thus hindering the practical applications due to the requirement of complex light pre-irradiation process. Here, a self-recoverable near infrared (NIR) ML material of LaAl_1-xO₃: xCr³⁺ (x=0.2 ​%, 0.4 ​%, 0.6 ​%, 0.8 ​%, 1.0 ​%, and 1.2 ​%) has been developed. Based on the preheating method and corresponding ML performance analysis, the influences of residual carriers are eliminated and the detailed dynamic luminescence process analysis is realized. Systematic experiments are conducted to reveal the origin of the ML emissions, demonstrating that ML is dictated more by the non-centrosymmetric piezoelectric crystal characteristic. In general, this work has provided significant references for exploring more efficient NIR ML materials, which may provide potential applications in anti-counterfeiting and bio-stress sensing.

Non-layered two-dimensional (2D) materials have sparked much interest recently due to their atomic thickness, large surface area, thickness- and facet-dependent properties. Currently, these materials are mainly grown from wet-chemistry methods but suffer from small size, low quality, and multi-facets, which is a major challenge hindering their facet-dependent property studies and applications. Here, we report the facet-engineered growth (FEG) of non-layered 2D manganese chalcogenides (MnX, X ​= ​S, Se, Te) based on the chemical vapor deposition method. The as-grown samples exhibit large-area surfaces of single facet, high-crystallinity, and ordered domain orientation. As a proof-of-concept, we show the facet-dependent electrocatalytic property of non-layered 2D MnSe, proving they are ideal candidates for fundamental research. Furthermore, we elucidate the underlying mechanism of FEG during the vapor growth process by the interfacial energy derived nucleation models. The method developed in this work provides new opportunities for regulating and designing the structure of 2D materials.

Laser powder bed fusion (LPBF) combined with reaction bonding (RB) of Al particles is an effective method for preparing high-performance 3D Al₂O₃ ceramic foams. However, the indistinct microstructure evolution hinders the regulation of pore features and the improvement of synthetic properties. Herein, the microstructure evolution of the Al₂O₃ ceramic foams during the LPBF/RB process is clarified by various characterization methods, and the corresponding mechanical property modulation is realized by optimizing LPBF parameters, organic binder (E12 epoxy resin) content, heating rate, sintering time, and coral-like Al₂O₃ content. The expansion from Al₂O₃ outward growth and Al granule precipitation counteracts the shrinkage from E12 decomposition and Al₂O₃ sintering, resulting in an ultra-low shrinkage of 0.94%–3.01%. The pore structures of particle packing pores, hollow spheres, and microporous structures allow a tunable porosity of 52.6%–73.7%. The in-situ formation of multi-scale features including hollow spheres, flaky grains, whiskers, nanofibers, and bond bridges brings about a remarkably high bending strength of 6.5–38.3 ​MPa. Our findings reveal the relationship between microstructure evolution and property optimization of high-performance ceramic foams, with potential significance for microstructure design and practical application.

Excessive emission of carbon dioxide (CO₂) has posed an imminent threat to human's environment and global prosperity. To achieve a sustainable future, solid oxide electrolysis cell (SOEC), which can efficiently combine CO₂ reduction reaction (CO₂RR) and renewable energy storage, has become increasingly attractive owing to its unique functionalities. Additionally, symmetrical SOEC (SSOEC) has been considered as one of the most versatile cell configurations due to its simplified process, high compatibility, and low cost. However, the electrode material requirements become very demanding since efficient catalytic-activities are required for both CO₂RR and oxygen evolution reaction (OER). Herein, we demonstrate a novel high-entropy perovskite type symmetrical electrode Pr_0.5Ba_0.5Mn_0.2Fe_0.2Co_0.2Ni_0.2Cu_0.2O_3-δ (HE-PBM) for SSOEC. B-site doping of transition metals such as Mn, Fe, Co, Ni, and Cu in HE-PBM anode has been found to strongly accelerate the OER in the anode. Moreover, the presence of in-situ formed Fe–Co–Ni–Cu quaternary alloy nanocatalysts from HE-PBM cathode under reducing atmosphere has resulted in superior catalytic-activity towards CO₂RR. The faster kinetics are also reflected by the significantly low polarization resistance of 0.289 ​Ω⋅cm² and high electrolysis current density of 1.21 ​A⋅cm⁻² for CO₂RR at 2.0 ​V and 800 ​°C. The excellent electrochemical performance and stability demonstrate that the high-entropy perovskite material is a promising electrode material in SSOEC for efficient and durable CO₂RR.

A new type of grain-interior planar defect in a ceramic phase in TiC doped cemented tungsten carbides was discovered. It is unique in that the monolayers of metal atoms exist stably in ceramic grains. The planar defects were induced by the ordered heteroatoms distributing on certain crystal planes of the matrix, which are distinct from the known planar defects such as phase-, grain-, and twin-boundaries, stacking faults, and complexions. Detailed characterization on the atomic scale was performed for the composition, structure, and crystallography of the planar defects, and their energy state and stability were evaluated by modeling. It was found that the Ti monolayer assists nucleation of the new WC crystal along the normal direction to its basal plane. Due to the disturbance of the heteroatom layer, the deposition of W and C atoms deviates from the regular sites occupied in the perfect crystal lattice, resulting in variations of the W–C arrangement in the grain structure. Experiments confirmed that tailoring the distribution density of the planar defects could give the best comprehensive mechanical performance with simultaneously outstanding strength and fracture toughness in the materials containing the grain-interior planar defects. This study provides a new strategy to greatly enhance the mechanical properties of materials by introducing and tailoring planar defects in the grain interiors.

Sulfide-based all-solid-state batteries (ASSBs) exhibit unparalleled application value due to the high ionic conductivity and good processability of sulfide solid electrolytes (SSEs). Carbon-based conductive agents (CAs) are often used in the construction of electronic conductive networks to achieve rapid electron transfer. However, CAs accelerate the formation of decomposition products of SSEs, and their effects on sulfide-based ASSBs are not fully understood. Herein, the effect of CAs (super P, vaper-grown carbon fibers, and carbon nanotubes) on the performance of sulfide-based ASSBs is investigated under different cathode active materials mass loading (8 and 25 ​mg·cm⁻²). The results show that under low mass loading, the side reaction between the CAs and the SSEs deteriorates the performance of the cell, while the charge transfer promotion caused by the addition of CAs is only manifested under high mass loading. Furthermore, the gradient design strategy (enrichment of CAs near the current collector side and depletion of CAs near the electrolyte side) is applied to maximize the benefits of CAs in electron transport and reduce the adverse effects of CAs. The charge carrier transport barrier inside the high mass loading electrode is significantly reduced through the regulation of electronic conductivity. Consequently, the optimized electrode achieves a high areal capacity of 5.6 ​mAh·cm⁻² at high current density (1.25 ​mA·cm⁻², 0.2 ​C) at 25 °C with a capacity retention of 87.85% after 100 cycles. This work provides a promising way for the design of high-mass loading electrodes with practical application value.