Pt‐Ir‐Pd Trimetallic Nanocages as a Dual Catalyst for Efficient Oxygen Reduction and Evolution Reactions in Acidic Media

The development of dual catalysts with high efficiency toward oxygen reduction and evolution reactions (ORR and OER) in acidic media is a significant challenge. Here an active and durable dual catalyst based upon cubic Pt₃₉Ir₁₀Pd₁₁ nanocages with an average edge length of 12.3 nm, porous walls as thin as 1.0 nm, and well‐defined {100} facets is reported. The trimetallic nanocages perform better than all the reported dual catalysts in acidic media, with a low ORR‐OER overpotential gap of only 704 mV at a Pt‐Ir‐Pd loading of 16.8 µg_Pt+Ir+Pd cm^?2_geo. For ORR at 0.9 V, when benchmarked against the commercial Pt/C and Pt‐Pd nanocages, the trimetallic nanocages exhibit an enhanced mass activity of 0.52 A mg^?1_Pt+Ir+Pd (about four and two times as high as those of the Pt/C and Pt‐Pd nanocages) and much improved durability. For OER, the trimetallic nanocages show a remarkable mass activity of 0.20 A mg^?1_Pt+Ir at 1.53 V, which is 16.7 and 4.3 fold relative to those of the Pt/C and Pt‐Pd nanocages, respectively. These improvements can be ascribed to the highly open structure of the nanocages, and the possible electronic coupling between Ir and Pt atoms in the lattice.     

Balancing Light Absorption and Charge Transport in Vertical SnS2 Nanoflake Photoanodes with Stepped Layers and Large Intrinsic Mobility

Significant optical absorption in the blue–green spectral range, high intralayer carrier mobility, and band alignment suitable for water splitting suggest tin disulfide (SnS₂) as a candidate material for photo‐electrochemical applications. In this work, vertically aligned SnS₂ nanoflakes are synthesized directly on transparent conductive substrates using a scalable close space sublimation (CSS) method. Detailed characterization by time‐resolved terahertz and time‐resolved photoluminescence spectroscopies reveals a high intrinsic carrier mobility of 330 cm² V^?1 s^?1 and photoexcited carrier lifetimes of 1.3 ns in these nanoflakes, resulting in a long vertical diffusion length of ≈1 µm. The highest photo‐electrochemical performance is achieved by growing SnS₂ nanoflakes with heights that are between this diffusion length and the optical absorption depth of ≈2 µm, which balances the competing requirements of charge transport and light absorption. Moreover, the unique stepped morphology of these CSS‐grown nanoflakes improves photocurrent by exposing multiple edge sites in every nanoflake. The optimized vertical SnS₂ nanoflake photoanodes produce record photocurrents of 4.5 mA cm^?2 for oxidation of a sulfite hole scavenger and 2.6 mA cm^?2 for water oxidation without any hole scavenger, both at 1.23 V_RHE in neutral electrolyte under simulated AM1.5G sunlight, and stable photocurrents for iodide oxidation in acidic electrolyte.     

Biomass‐Derived 3D Carbon Aerogel with Carbon Shell‐Confined Binary Metallic Nanoparticles in CNTs as an Efficient Electrocatalyst for Microfluidic Direct Ethylene Glycol Fuel Cells

Flexible and 3D carbon aerogels (CAs) composed of carbon nanotubes (CNTs) with carbon shell‐confined binary palladium–nickel (Pd_x–Ni_y) nanocatalysts on carbon fibers (Pd_x–Ni_y/NSCNT/CA) have been developed through a facile chemical vapor deposition method. The 3D porous carbon network and the synergistic effect of carbon shell‐confined bimetal nanoparticles of rationally constructed aerogels facilitate enhanced electrocatalytic and antipoisoning activities toward ethylene glycol (EG) oxidation reaction compared to the commercial Pt/C catalyst. With the 3D morphological features and direct growth of Pd–Ni bimetallic nanoparticles encapsulated CNTs on carbon fibers, the Pd₅₂–Ni₄₈/NSCNT/CA delivers a maximum microfluidic direct ethylene glycol fuel cell (µDEGFC) power density and durability of, respectively, 62.8 mW cm^?2 and 60 h. The superior performance observed, with Pd₅₂–Ni₄₈/NSCNT/CA amongst the catalysts reported in the literature, opens an exciting research avenue towards powering next‐generation, portable electronics.     

Hydrogen Flux through Size Selected Pd Nanoparticles into Underlying Mg Nanofilms

The application of Mg for hydrogen storage is hindered due to the slow absorption of hydrogen in Mg films. Herein, the hydrogenation process is explored theoretically using density functional theory calculations, and energy barriers are compared for hydrogen diffusion through Pd nanoparticle/Mg film interfaces and their variations, i.e., Pd(H)/Mg(O). Decomposing the mechanism into basic steps, it is shown that Pd undergoes a strain‐induced crystallographic phase transformation near the interface, and indicated that hydrogen saturation of Pd nanoparticles enhances their efficiency as nanoportals. Using energetic arguments, it is explained why hydrogen diffusion is practically prohibited through native Mg oxide and seriously suppressed through existing hydride domains. Hydrogen flux is experimentally investigated through the nanoportals in Pd‐nanoparticle decorated Mg films by pressure‐composition isotherm measurements. An r ≈ t^1/3 relationship is theoretically calculated for the radial growth of hemispherical hydride domains, and this relationship is confirmed by atomic force microscopy. The diffusion constant of hydrogen in Mg films is estimated as D_H^film ≈ 8 × 10^?18 m² s^?1, based on transmission electron microscopy characterization. The unique nanoportal configuration allows direct measurement of hydride domain sizes, thus forming a model system for the experimental investigation of hydrogenation in any material.     

Enhancement of Thermoelectric Performance of n‐Type PbSe by Cr Doping with Optimized Carrier Concentration

Ti, V, Cr, Nb, and Mo are found to be effective at increasing the Seebeck coefficient and power factor of n‐type PbSe at temperatures below 600 K. It is found that the higher Seebeck coefficients and power factors are due to higher Hall mobility ≈1000 cm² V^?1s^?1 at lower carrier concentration. A larger average ZT value (relevant for applications) can be obtained by an optimization of carrier concentration to ≈10¹⁸–10¹⁹ cm^?3. Even though the highest room temperature power factor ≈3.3 × 10^?3 W m^?1 K^?2 is found in 1 at% Mo‐doped PbSe, the highest ZT is achieved in Cr‐doped PbSe. Combined with the lower thermal conductivity, ZT is improved to ≈0.4 at room temperature and peak ZTs of ≈1.0 are observed at ≈573 K for Pb_0.9925Cr_0.0075Se and ≈673 K for Pb_0.995Cr_0.005Se. The calculated device efficiency of Pb_0.995Cr_0.005Se is as high as ≈12.5% with cold side 300 K and hot side 873 K, higher than those of all the n‐type PbSe materials reported in the literature.     

Integrating Band Structure Engineering with All‐Scale Hierarchical Structuring for High Thermoelectric Performance in PbTe System

PbTe_1?x Se_x ‐2%Na‐y%SrTe system is investigated and a high maximum ZT of 2.3 at 923 K for PbTe_0.85Se_0.15‐2%Na‐4%SrTe is reported. This is achieved by performing electronic band structures modifications as well as all‐scale hierarchical structuring and combining the two effects. It is found that high ZTs in PbTe_0.85Se_0.15‐2%Na‐4%SrTe are possible at all temperature from 300 to 873 K with an average ZT_ave of 1.23. The high performance in PbTe_1?x Se_x ‐2%Na‐y%SrTe can be achieved by either choosing PbTe‐2Na‐4SrTe or PbTe_0.85Se_0.15‐2Na as a matrix. At room temperature the carrier mobility shows negligible variations as SrTe fraction is increased, however the lattice thermal conductivity is significantly reduced from ≈1.1 to ≈0.82 W m^?1 K^?1 when 5.0% SrTe is added, correspondingly, the lattice thermal conductivity at 923 K decreases from ≈0.59 to ≈0.43 W m?¹ K^?1. The power factor maxima of PbTe_1?x Se_x ‐2Na‐4SrTe shift systematically to higher temperature with rising Se fractions due to bands divergence. The maximum power factors reach ≈27, ≈30, ≈31 μW cm^?1 K^?2 for the x = 0, 0.05, and 0.15 samples peak at 473, 573, and 623 K, respectively. The results indicate that ZT can be increased by synergistic integration of band structure engineering and all‐scale hierarchical architectures.     

Co–B Nanoflakes as Multifunctional Bridges in ZnCo2O4 Micro‐/Nanospheres for Superior Lithium Storage with Boosted Kinetics and Stability

Transition metal oxides hold great promise as high‐energy anodes in next‐generation lithium‐ion batteries. However, owing to the inherent limitations of low electronic/ionic conductivities and dramatic volume change during charge/discharge, it is still challenging to fabricate practically viable compacted and thick TMO anodes with satisfactory electrochemical performance. Herein, with mesoporous cobalt–boride nanoflakes serving as multifunctional bridges in ZnCo₂O₄ micro‐/nanospheres, a compacted ZnCo₂O₄/Co–B hybrid structure is constructed. Co–B nanoflakes not only bridge ZnCo₂O₄ nanoparticles and function as anchors for ZnCo₂O₄ micro‐/nanospheres to suppress the severe volume fluctuation, they also work as effective electron conduction bridges to promote fast electron transportation. More importantly, they serve as Li⁺ transfer bridges to provide significantly boosted Li⁺ diffusivity, evidenced from both experimental kinetics analysis and density functional theory calculations. The mesopores within Co–B nanoflakes help overcome the large Li⁺ diffusion barriers across 2D interfaces. As a result, the ZnCo₂O₄/Co–B electrode delivers high gravimetric/volumetric/areal capacities of 995 mAh g^?1/1450 mAh cm^?3/5.10 mAh cm^?2, respectively, with robust rate capability and long‐term cyclability. The distinct interfacial design strategy provides a new direction for designing compacted conversion‐type anodes with superior lithium storage kinetics and stability for practical applications.     

Highly Active and Durable Pt72Ru28 Porous Nanoalloy Assembled with Sub‐4.0 nm Particles for Methanol Oxidation

The main challenges to the direct methanol fuel cells are the activity and durability of electrocatalysts. To alleviate such issues, a recently proposed strategy introduces an exotic element to form Pt‐based alloy nanostructures. This study reports a green route to prepare porous flowerlike Pt₇₂Ru₂₈ nanoalloys assembled with sub‐4.0 nm particles. The peak current density and mass activity on these as‐synthesized porous flowerlike Pt₇₂Ru₂₈ nanoalloys can be increased to 10.98 mA cm^?2 and 1.70 A mg^?1 Pt for methanol oxidation in acidic medium. They are respectively 4.19/3.54, 4.27/5.0, and 5.74/1.73 times those on the commercial Pt black, Pt₅₀Ru₅₀ black, and Ru₅₀Pt₅₀/C. These porous flowerlike Pt₇₂Ru₂₈ nanoalloys have a much higher long‐term durability than commercial Pt black, Pt₅₀Ru₅₀ black, and Ru₅₀Pt₅₀/C. More significantly, the porous Pt₇₂Ru₂₈ bimetallic nanoalloys have long‐term solvent durability after immersion in water for 16 months. The peak current density and mass activity on porous Pt₇₂Ru₂₈ nanoalloys are still 7.76 mA cm^?2 and 1.2 A mg^?1 Pt. These experimental results show an effective approach to the development of PtRu nanoalloys as electrocatalysts with substantially enhanced activity and durability for direct methanol fuel cells.     

Chemical Synthesis of 3D Graphene‐Like Cages for Sodium‐Ion Batteries Applications

Sodium (Na) super ion conductor structured Na₃V₂(PO₄)₃ (NVP) is extensively explored as cathode material for sodium‐ion batteries (SIBs) due to its large interstitial channels for Na⁺ migration. The synthesis of 3D graphene‐like structure coated on NVP nanoflakes arrays via a one‐pot, solid‐state reaction in molten hydrocarbon is reported. The NVP nanoflakes are uniformly coated by the in situ generated 3D graphene‐like layers with the thickness of 3 nm. As a cathode material, graphene covered NVP nanoflakes exhibit excellent electrochemical performances, including close to theoretical reversible capacity (115.2 mA h g^?1 at 1 C), superior rate capability (75.9 mA h g^?1 at 200 C), and excellent cyclic stability (62.5% of capacity retention over 30000 cycles at 50 C). Furthermore, the 3D graphene‐like cages after removing NVP also serve as a good anode material and deliver a specific capacity of 242.5 mA h g^?1 at 0.1 A g^?1. The full SIB using these two cathode and anode materials delivers a high specific capacity (109.2 mA h g^?1 at 0.1 A g^?1) and good cycling stability (77.1% capacity retention over 200 cycles at 0.1 A g^?1).     

Highly Efficient and Durable Pd Hydride Nanocubes Embedded in 2D Amorphous NiB Nanosheets for Oxygen Reduction Reaction

A highly efficient and durable electrocatalyst of Pd hydride nanocubes encapsulated within 2D amorphous Ni‐B nanosheets is reported. The PdH_0.43 nanocubes are first synthesized via a simple N ,N ‐dimethylformamide thermal treatment. The as‐synthesized PdH_0.43 nanocubes are then encapsulated in 2D amorphous NiB nanosheets by NaBH₄ reduction in the presence of nickel species. During the NaBH₄ treatment, the PdH_0.43 can be further transformed into PdH_0.706 due to the presence of endogenous H₂. Electrochemical studies demonstrate that the degree of hydride of Pd nanocubes (PdH_x ) plays an important role in the enhancement of their oxygen reduction reaction (ORR) activity. With increasing x value, both the activity and stability increase significantly. At 0.90 V versus reversible hydrogen electrode, the ORR activity of PdH_0.706 @Ni‐B reaches 1.05 A mg_Pd^?1, which is nearly five times higher than that of the state‐of‐the‐art Pt catalysts. Accelerated durability tests show that even after 10 000 potential cycles, there is negligible shift in their half‐wave potential and no shape and structure change occurs, indicating the incorporation of amorphous 2D Ni‐B nanosheets can greatly improve their stability without compromising their activity. The present study illustrates the importance of high degree of hydride and presence of amorphous Ni‐B nanosheets on the enhancement of ORR activity for Pd‐based electrocatalyst.     

Bimetallic Zeolitic Imidazolite Framework Derived Carbon Nanotubes Embedded with Co Nanoparticles for Efficient Bifunctional Oxygen Electrocatalyst

Bifunctional oxygen catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with high activities and low‐cost are of prime importance and challenging in the development of fuel cells and rechargeable metal–air batteries. This study reports a porous carbon nanomaterial loaded with cobalt nanoparticles (Co@NC‐x/y) derived from pyrolysis of a Co/Zn bimetallic zeolitic imidazolite framework, which exhibits incredibly high activity as bifunctional oxygen catalysts. For instance, the optimal catalyst of Co@NC‐3/1 has the interconnected framework structure between porous carbon and embedded carbon nanotubes, which shows the superb ORR activity with onset potential of ≈1.15 V and half‐wave potential of ≈0.93 V. Moreover, it presents high OER activity that can be further enhanced to over commercial RuO₂ by P‐doped with overpotentials of 1.57 V versus reversible hydrogen electrode at 10 mA cm^?2 and long‐term stability for 2000 circles and a Tafel slope of 85 mV dec^?1. Significantly, the nanomaterial demonstrates better catalytic performance and durability than Pt/C for ORR and commercial RuO₂ and IrO₂ for OER. These findings suggest the importance of a synergistic effect of graphitic carbon, nanotubes, exposed Co–N_x active sites, and interconnected framework structure of various carbons for bifunctional oxygen electrocatalysts.     

Lithium‐Pretreated Hard Carbon as High‐Performance Sodium‐Ion Battery Anodes

Hard carbon (HC) is the state‐of‐the‐art anode material for sodium‐ion batteries (SIBs). However, its performance has been plagued by the limited initial Coulombic efficiency (ICE) and mediocre rate performance. Here, experimental and theoretical studies are combined to demonstrate the application of lithium‐pretreated HC (LPHC) as high‐performance anode materials for SIBs by manipulating the solid electrolyte interphase in tetraglyme (TEGDME)‐based electrolyte. The LPHC in TEGDME can 1) deliver > 92% ICE and ≈220 mAh g^?1 specific capacity, twice of the capacity (≈100 mAh g^?1) in carbonate electrolyte; 2) achieve > 85% capacity retention over 1000 cycles at 1000 mA g^?1 current density (4 C rate, 1 C = 250 mA g^?1) with a specific capacity of ≈150 mAh g^?1, ≈15 times of the capacity (10 mAh g^?1) in carbonate. The full cell of Na₃V₂(PO₄)₃‐LPHC in TEGDME demonstrated close to theoretical specific capacity of ≈98 mAh g^?1 based on Na₃V₂(PO₄)₃ cathode, ≈2.5 times of the value (≈40 mAh g^?1) with nontreated HC. This work provides new perception on the anode development for SIBs.     

Mn‐Rich P′2‐Na0.67[Ni0.1Fe0.1Mn0.8]O2 as High‐Energy‐Density and Long‐Life Cathode Material for Sodium‐Ion Batteries

Herein, P′2‐type Na_0.67[Ni_0.1Fe_0.1Mn_0.8]O₂ is introduced as a promising new cathode material for sodium‐ion batteries (SIBs) that exhibits remarkable structural stability during repetitive Na⁺ de/intercalation. The O? Ni? O? Mn? O? Fe? O bond in the octahedra of transition‐metal layers is used to suppress the elongation of the Mn? O bond and to improve the electrochemical activity, leading to the highly reversible Na storage mechanism. A high discharge capacity of ≈220 mAh g^?1 (≈605 Wh kg^?1) is delivered at 0.05 C (13 mAg^?1) with a high reversible capacity of ≈140 mAh g^?1 at 3 C and excellent capacity retention of 80% over 200 cycles. This performance is associated with the reversible P′2–OP4 phase transition and small volume change upon charge and discharge (≈3%). The nature of the sodium storage mechanism in a full cell paired with a hard carbon anode reveals an unexpectedly high energy density of ≈542 Wh kg^?1 at 0.2 C and good capacity retention of ≈81% for 500 cycles at 1 C (260 mAg^?1).     

Rational Design of Core@shell Structured CoSx@Cu2MoS4 Hybridized MoS2/N,S‐Codoped Graphene as Advanced Electrocatalyst for Water Splitting and Zn‐Air Battery

A novel hybrid of small core@shell structured CoS_x@Cu₂MoS₄ uniformly hybridizing with a molybdenum dichalcogenide/N,S‐codoped graphene hetero‐network (CoS_x@Cu₂MoS₄‐MoS₂/NSG) is prepared by a facile route. It shows excellent performance toward the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in alkaline medium. The hybrid exhibits rapid kinetics for ORR with high electron transfer number of ≈3.97 and exciting durability superior to commercial Pt/C. It also demonstrates great potential with remarkable stability for HER and OER, requiring low overpotential of 118.1 and 351.4 mV, respectively, to reach a current density of 10 mA cm^?2. An electrolyzer based on CoS_x@Cu₂MoS₄‐MoS₂/NSG produces low cell voltage of 1.60 V and long‐term stability, surpassing a device of Pt/C + RuO₂/C. In addition, a Zn‐air battery using cathodic CoS_x@Cu₂MoS₄‐MoS₂/NSG catalyst delivers a high cell voltage of ≈1.44 V and a power density of 40 mW cm^?2 at 58 mA cm^?2, better than the state‐of‐the‐art Pt/C catalyst. These achievements are due to the rational combination of highly active core@shell CoS_x@Cu₂MoS₄ with large‐area and high‐porosity MoS₂/NSG to produce unique physicochemical properties with multi‐integrated active centers and synergistic effects. The outperformances of such catalyst suggest an advanced candidate for multielectrocatalysis applications in metal‐air batteries and hydrogen production.     

Hierarchical Fabric Decorated with Carbon Nanowire/Metal Oxide Nanocomposites for 1.6 V Wearable Aqueous Supercapacitors

Aqueous asymmetric supercapacitors (ASCs) may offer comparable or higher energy density than electric double‐layer capacitors (EDLCs) based on organic electrolytes. As such, ASCs may be more suitable for integration into smart textiles, where the use of flammable organic solvents is not acceptable. However, reported ASC devices typically suffer from poor rate capability and low areal loadings. This study demonstrates the development of nitrogen‐doped carbon (N‐C) nanowire/metal oxide (Fe₂O₃ and MnO₂) nanocomposite electrodes directly produced on the internal surface of a conductive fabric for use as high‐rate electrodes for solid‐state ASCs. The N‐C nanowires provide fast and efficient pathways for electrons, while short diffusion paths within nanosized metal oxides enable fast ion transport, leading to greatly enhanced performance at high rates. The porous structure of the fabric enables high areal capacitance loading in each electrode (≈150 mF cm^?2). Both electrodes show high specific capacitance of ≈180 F g^?1 (Fe₂O₃) and ≈250 F g^?1 (MnO₂) and excellent rate capability. Solid‐state ASCs assembled by using an aqueous gel electrolyte operate at 1.6 V and deliver over 60 mF cm^?2 during ≈50 s charging/discharging time and over 30 mF cm^?2 for ≈5 s discharge.     

Mo‐Based Ultrasmall Nanoparticles on Hierarchical Carbon Nanosheets for Superior Lithium Ion Storage and Hydrogen Generation Catalysis

Constructing 3D hierarchical architecture consisting of 2D hybrid nanosheets is very critical to achieve uppermost and stable electrochemical performance for both lithium‐ion batteries (LIBs) and hydrogen evolution reaction (HER). Herein, a simple synthesis of uniform 3D microspheres assembled from carbon nanosheets with the incorporated MoO₂ nanoclusters is demonstrated. The MoO₂ nanoclusters can be readily converted into the molybdenum carbide (Mo₂C) nanocrystals by using high temperature treatment. Such assembling architecture is highly particular for preventing Mo‐based ultrasmall nanoparticles from coalescing or oxidizing and endowing them with rapid electron transfer. Consequently, the MoO₂/C hybrids as LIB anode materials deliver a specific capacity of 625 mA h g^?1 at 1600 mA g^?1 even after 1000 cycles, which is among the best reported values for MoO₂‐based electrode materials. Moreover, the Mo₂C/C hybrids also exhibit excellent electrocatalytic activity for HER with small overpotential and robust durability in both acid and alkaline media. The present work highlights the importance of designing 3D structure and controlling ultrasmall Mo‐based nanoparticles for enhancing electrochemical energy conversion and storage applications.     

Amphoteric Indium Enables Carrier Engineering to Enhance the Power Factor and Thermoelectric Performance in n‐Type AgnPb100InnTe100+2n (LIST)

The Ag and In co‐doped PbTe, Ag_nPb₁₀₀In_nTe_100+2n (LIST), exhibits n‐type behavior and features unique inherent electronic levels that induce self‐tuning carrier density. Results show that In is amphoteric in the LIST, forming both In³⁺ and In¹⁺ centers. Through unique interplay of valence fluctuations in the In centers and conduction band filling, the electron carrier density can be increased from ≈3.1 × 10¹⁸ cm^?3 at 323 K to ≈2.4 × 10¹⁹ cm^?3 at 820 K, leading to large power factors peaking at ≈16.0 µWcm^?1 K^?2 at 873 K. The lone pair of electrons from In⁺ can be thermally continuously promoted into the conduction band forming In³⁺, consistent with the amphoteric character of In. Moreover, with rising temperature, the Fermi level shifts into the conduction band, which enlarges the optical band gap based on the Moss–Burstein effect, and reduces bipolar diffusion and thermal conductivity. Adding extra Ag in LIST improves the electrical transport properties and meanwhile lowers the lattice thermal conductivity to ≈0.40 Wm^?1 K^?1. The addition of Ag creates spindle‐shaped Ag₂Te nanoprecipitates and atomic‐scale interstitials that scatter a broader set of phonons. As a result, a maximum ZT value ≈1.5 at 873 K is achieved in Ag₆Pb₁₀₀InTe₁₀₂ (LIST).     

Engineering the Thermoelectric Transport in Half‐Heusler Materials through a Bottom‐Up Nanostructure Synthesis

Half‐Heusler (HH) alloys are among the best promising thermoelectric (TE) materials applicable for the middle‐to‐high temperature power generation. Despite of the large thermoelectric power factor and decent figure‐of‐merit ZT (≈1), their broad applications and enhancement on TE performance are limited by the high intrinsic lattice thermal conductivity (κ_L) due to insufficiencies of phonon scattering mechanisms, and the fewer powerful strategies associated with the microstructural engineering for HH materials. This study reports a bottom‐up nanostructure synthesis approach for these HH materials based on the displacement reaction between metal chlorides/bromides and magnesium (or lithium), followed by vacuum‐assisted spark plasma sintering process. The samples are featured with dense dislocation arrays at the grain boundaries, leading to a minimum κ_L of ≈1 W m^?1 K^?1 at 900 K and one of the highest ZT (≈1) and predicted η (≈11%) for n‐type Hf_0.25Zr_0.75NiSn_0.97Sb_0.03. Further manipulation on the dislocation defects at the grain boundaries of p‐type Nb_0.8Ti_0.2FeSb leads to enhanced maximum power factor of 47 × 10^?4 W m^?1 K^?2 and the predicted η of ≈7.5%. Moreover, vanadium substitution in FeNb_0.56V_0.24Ti_0.2Sb significantly promotes the η to ≈11%. This strategy can be extended to a broad range of advanced alloys and compounds for improved properties.     

Open‐Structured V2O5·nH2O Nanoflakes as Highly Reversible Cathode Material for Monovalent and Multivalent Intercalation Batteries

The high‐capacity cathode material V₂O₅·n H₂O has attracted considerable attention for metal ion batteries due to the multielectron redox reaction during electrochemical processes. It has an expanded layer structure, which can host large ions or multivalent ions. However, structural instability and poor electronic and ionic conductivities greatly handicap its application. Here, in cell tests, self‐assembly V₂O₅·n H₂O nanoflakes shows excellent electrochemical performance with either monovalent or multivalent cation intercalation. They are directly grown on a 3D conductive stainless steel mesh substrate via a simple and green hydrothermal method. Well‐layered nanoflakes are obtained after heat treatment at 300 °C (V₂O₅·0.3H₂O). Nanoflakes with ultrathin flower petals deliver a stable capacity of 250 mA h g^?1 in a Li‐ion cell, 110 mA h g^?1 in a Na‐ion cell, and 80 mA h g^?1 in an Al‐ion cell in their respective potential ranges (2.0–4.0 V for Li and Na‐ion batteries and 0.1–2.5 V for Al‐ion battery) after 100 cycles.     

Phase Transformation Induced Capacitance Activation for 3D Graphene‐CoO Nanorod Pseudocapacitor

Development of a pseudocapacitor over the integration of metal oxide on carbonaceous materials is a promising step towards energy storage devices with high energy and power densities. Here, a self‐assembled cobalt oxide (CoO) nanorod cluster on three‐dimensional graphene (CoO‐3DG) is synthesized through a facile hydrothermal method followed by heat treatment. As an additive‐free electrode, CoO‐3DG exhibits good electrochemical performance. Compared with CoO nanorod clusters grown on Ni foam (i.e., CoO‐Ni, ≈680 F g^?1 at 1 A g^?1 and ≈400 F g^?1 at 20 A g^?1), CoO‐3DG achieves much higher capacitance (i.e., ≈980 F g^?1 at 1 A g^?1 and ≈600 F g^?1 at 20 A g^?1) with excellent cycling stability of 103% retention of specific capacitance after 10 000 cycles. Furthermore, it shows an interesting activation process and instability with a redox reaction for CoO. In addition, the phase transformation from CoO nanorods to Co₃O₄ nanostructures was observed and investigated after charge and discharge process, which suggests the activation kinetics and the phase transformable nature of CoO based nanostructure. These observations demonstrate phase transformation with morphological change induced capacitance increasement in the emergent class of metal oxide materials for electrochemical energy storage device.