Ultrafine Nanocrystals Research Articles

Insight into the polysulfides conversion kinetics and its activation energy relationship on ultrafine V8C7 in Li-S batteries

Catalytic conversion of lithium polysulfides (LiPSs) is regarded as an effective approach to boosting kinetics and suppressing shuttling effect in lithium-sulfur (Li-S) batteries, but developing efficient catalysts and understanding of its catalytic mechanism still remain challenges. Herein, the ultrafine V8C7 nanocrystals embedded into the porous N-doped carbon frameworks (V8C7/NC) was designed for accelerating the LiPSs catalytic-conversion kinetics toward high-performance Li-S batteries. We propose that the ultrafine V8C7 nanocrystals with abundant unsaturated coordination atoms increase the active sites for catalytic-conversion of LiPSs and also accelerate the corresponding kinetics by reducing its reaction activation energy, meanwhile the interlinked nano-channels of V8C7/NC can effectively confine LiPSs and also promote electron/ion transfer. These attributes enable the Li-S cell equipped with V8C7/NC to deliver a large discharge capacity of 1393.3 mAh g−1 at 0.2 C, excellent rate capability (496.0 mAh g−1 at 10 C), and robust cycling stability (1000 cycles with a negligible capacity decay rate of 0.019 % per cycle even at 5 C). The innovative concept of ultrafine V8C7 nanocrystals embedded into the porous carbon toward improved LiPSs catalytic-conversion kinetics could be extended to develop other electrocatalytic hosts for high-performance Li-S batteries.

Mesoporous Hollow Carbon Sphere-Embedded MXene Architectures Decorated with Ultrafine Rh Nanocrystals toward Methanol Electrooxidation.

The development of advanced Pt-alternative anode electrocatalysts with high activity and reliable stability is critical to overcoming the technical challenges of direct methanol fuel cells. Here, we propose a robust bottom-up strategy for the spatial construction of mesoporous hollow carbon sphere (HCS)-embedded MXene architectures decorated with ultrafine Rh nanocrystals (Rh/HCS-MX) via stereoscopic coassembly reactions. The rational intercalation of HCS effectively separates the MXene nanowalls to achieve a rapid mass-transfer efficiency, while the intimate coupling of the hybrid carrier with Rh nanocrystals enables their electronic structure optimization, thus contributing to strong synergistic catalytic effects. Accordingly, the resulting Rh/HCS-MX architectures exhibit outstanding methanol electrooxidation properties in terms of large electrochemical active surface areas, high mass/specific activities, and good long-term stability, all of which are significantly superior to the traditional Rh/carbon black, Rh/HCS, and Rh/MXene as well as commercial Pt/carbon balck and Pd/carbon balck electrocatalysts.

High-voltage electrosynthesis of organic-inorganic hybrid with ultrahigh fluorine content toward fast Li-ion transport.

Hybrid materials with a rational organic-inorganic configuration can offer multifunctionality and superior properties. This principle is crucial but challenging to be applied in designing the solid electrolyte interphase (SEI) on lithium metal anodes (LMAs), as it substantially affects Li+ transport from the electrolyte to the anode. Here, an artificial SEI with an ultrahigh fluorine content (as high as 70.12 wt %) can be successfully constructed on the LMA using a high-voltage electrosynthesis strategy. This SEI consists of ultrafine lithium fluoride nanocrystals embedded in a fluorinated organic matrix, exhibiting excellent passivation and mechanical strength. Notably, the organic-inorganic interface demonstrates a high dielectric constant that enables fast Li+ transport throughout the SEI. Consequently, LMA coated with this SEI substantially enhances the cyclability of both half-cells and full cells, even under rigorous conditions. This work demonstrates the potential of rationally designed hybrid materials via a unique electrosynthetic approach for advanced electrochemical systems.

Defect engineering in seaweed-like TiO2@carbon nitride strengthening hydroxyl production for thorough elimination of antibiotics

The highly selective production of ·OH to strengthen the mineralization of antibiotics remains a significant scientific challenge. In this work, the seaweed-like fibrous membrane containing oxygen-vacancies in TiO2 ultrafine nanocrystals and nitrogen-vacancies in g-C3N4 nanosheets, was rationally designed through a HCl-mediated polycondensation strategy. The photocatalytic test confirmed that the dual-defects membrane containing dual defects exhibited highly efficient capacities in removing a variety of antibiotics under visible light and natural light irradiation, which was much stronger than that of single- or none-defective samples. The mechanism analysis displayed that the dual defects were beneficial to migration of photogenerated charges, expansion of Fermi level gap, and capture of oxygen. The strengthened ·OH production was derived from the decomposition of H2O2, bypassing the high barrier of direct oxidation of H2O. This work focuses the key roles of defects in photocatalytic reaction and attempts to present a promising stride towards advancing defect engineering.

The Facile and Controllable Synthesis of Ultrafine Sn Nanocrystals Loaded on Carbon Black for High-Performance Lithium Storage.

Sn and C nanocomposites are ideal anode materials for high-energy and high-power density lithium ion batteries. However, their facile and controllable synthesis for practical applications is still a critical challenge. In this work, a facile one-step method is developed to controllably synthesize ultrafine Sn nanocrystals (< 5 nm) loaded on carbon black (Sn@C) through Na reducing SnCl4 by mechanical milling. Different from traditional up-down mechanical milling method, this method utilizes mechanical milling to trigger bottom-up reduction reaction of SnCl4. The in-situ formed Sn nanocrystals directly grow on carbon black, which results in the homogeneous composite and the size control of Sn nanocrystals. The obtained Sn@C electrode is revealed to possesses large lithium diffusion coefficient, low lithiation energy barrier and stable electrochemical property during cycle, thus showing excellent lithium storage performance with a high reversible capacity (942 mAh g-1 at a current density of 100 mA g-1), distinguished rate ability (480 mAh g-1 at 8000 mA g-1) and superb cycling performance (730 mAh g-1 at 1000 mA g-1 even after 1000 cycles).

Well-Dispersed CoNiO2 Nanosheet/CoNi Nanocrystal Arrays Anchored onto Monolayer MXene for Superior Electromagnetic Absorption at Low Frequencies

Developing microwave absorbers with superior low-frequency electromagnetic wave absorption properties is one of the foremost important factors driving the boom in 5G technology development. In this study, via a simple hydrothermal and pyrolysis strategy, randomly interleaved CoNiO2 nanosheets and uniformly ultrafine CoNi nanocrystals are anchored onto both sides of a single-layered MXene. The absorption mechanism demonstrated that the hierarchical heterostructure prevents the aggregation of MXene nanoflakes and magnetic crystallites. In addition, the introduction of the double-magnetic phase of CoNiO2/CoNi arrays can not only enhance the magnetic loss capacity but also generate larger void spaces and abundant heterogeneous interfaces, collectively promoting impedance-matching and furthering microwave attenuation capabilities at a low frequency. Hence, the reflection loss of the optimal absorber (M–MCNO) is −45.33 dB at 3.24 GHz, which corresponds to a matching thickness of 5.0 mm. Moreover, its EAB can entirely cover the S-band and C-band by tailoring the matching thickness from 2 to 7 mm. Satellite radar cross-section (RCS) simulations demonstrated that the M–MCNO can reduce the RCS value to below −10 dB m2 over a multi-angle range. Thus, the proposed hybrid absorber is of great significance for the development of magnetized MXene composites with superior low-frequency microwave absorption properties.

Constructing Zn-based MOF-MXene nanoarchitectures to stabilize ultrafine Pt nanocrystals with enhanced methanol oxidation performance

Although the development of direct methanol fuel cell technology is regarded as one rational option to against severe energy crises and environmental pollution, the low efficiency and considerable costs of current Pt-based anode catalysts largely impede the broad-scale commercialization. Herein, a convenient bottom-up approach is developed to the spatial construction of ultrafine Pt nanocrystals stabilized on a porous heterojunction matrix built from Zn-based metal organic frameworks and Ti3C2Tx MXene nanolamellas (Pt/ZIF-Ti3C2Tx) through the stepwise solvothermal reactions. The intercalation of metal organic frameworks produces plentiful cavities and channels for the dispersion and immobilization of small-sized Pt nanoparticles, while the incorporation of Ti3C2Tx nanosheets optimizes the Pt electronic structure and ensures a high electron conductivity. As a consequence, the as-acquired Pt/ZIF-Ti3C2Tx nanoarchitectures manifest exceptional electrocatalytic methanol oxidation abilities in terms of a large electrochemically active surface area of 110.5 m2 g−1, a high mass activity of 1900.1 mA mg−1, and preferable long-term stability, all of which are significantly superior to those of conventional Pt/carbon and Pt/unmodified Ti3C2Tx catalysts.

A new method for preparing Mg-Al-layered double hydroxides coating using supercritical CO2 fluid

A new method for preparing Mg-Al-layered double hydroxides (Mg-Al-LDHs) coating using supercritical CO2 fluid was developed. The morphologies, structures, compositions, and corrosion resistances of the surface coatings were investigated. Unlike traditional methods, the method using supercritical CO2 fluid generated ultrafine nanocrystal coatings with an average size of 30 nm, and a thickness of ca. ∼ 11 μm. The Mg-Al-LDHs coating was mainly composed of C, O, Mg, and Al. Corrosion resistance measurements show that the amount of hydrogen evolution for the nanocrystal LDHs coating was only 0.133 mL·cm−2, the polarisation resistance was 3174.9 Ω·cm2, and the immersion test corrosion grade of 7G. Finally, the formation mechanism of the Mg-Al-LDHs coating under supercritical CO2 fluid was proposed.

Constructing a mesoporous carbon nanobowls embedded with ultrafine CoSe2 Nanocrystals for High-Performance potassium ion battery electrode

In the quest for advanced electrode materials for potassium ion batteries (KIBs), an innovative anode featuring ultrafine CoSe2 nanocrystals embedded within mesoporous carbon nanobowls (CoSe2@MCNBs) is presented herein. Diverging from conventional hollow carbon nanospheres, the distinctive bowl structure is crafted to enhance the structural integrity and volumetric energy density of the electrodes. CoSe2@MCNBs synthesized using an iterative drop and dry method followed by selenization exhibit well-preserved morphology with a shell thickness of 20 nm. The successful integration of ultrafine CoSe2 nanocrystals into MCNBs imparts the nanobowls with the benefits of conventional hollow carbon-based composites, including abundant ion storage sites and high electrical conductivity. Simultaneously, the bowl structure boasts a higher packing density than the conventional hollow mesoporous carbon sphere (HMCS) structure, significantly augmenting the volumetric energy density of the fabricated electrode. Capitalizing on these advantages, the CoSe2@MCNB electrode displays exceptional cycling stability, achieving a reversible capacity of 523 mA h g−1 after 500 cycles at 0.5 A/g and an impressive rate capacity of 247 mA h g−1 at 2.0 A/g. This study demonstrates the strong potential of CoSe2@MCNB as an electrode material for the next generation of KIBs.

Monodispersed hollow ceramic microspheres fabricated based on preceramic polymers and pulse‐controlled coaxial injection

AbstractHollow ceramic microspheres (HCMs) have widespread applications in aerospace and electronic areas owing to their multiple merits such as low density, low thermal conductivity, oxidation, and high‐temperature resistance. In this work, monodispersed HCMs were fabricated based on preceramic polymers and the pulse‐controlled coaxial injection approach. The size and shell morphology of hollow ceramic spheres can be flexibly tailored by adjusting the diameters of coaxial needles, and the composition and flow rates of inner and outer liquids. As‐obtained HCMs were comprised of ultrafine nanocrystals of ZrO2, SiO2, ZrC, and SiC, which can enhance the interfacial polarization effect. Through optimization of microstructure and composition, the electromagnetic shielding performance of HCMs reached up to 45 dB in the frequency range of 12–18 GHz. This work demonstrates a facile and general method for the fabrication of monodispersed HCMs.

Phosphorus-doped TiO2 mesoporous nanocrystals for anodes in high-current-rate lithium ion batteries

Limited by the intrinsic low electronic conductivity and inferior electrode kinetics, the use of TiO2 as an anode material for lithium ion batteries (LIBs) is hampered. Nanoscale surface-engineering strategies of morphology control and particle size reduction have been devoted to increase the lithium storage performances. It is found that the ultrafine nanocrystal with mesoporous framework plays a crucial role in achieving the excellent electrochemical performances due to the surface area effect. Herein, a promising anode material for LIBs consisting of phosphorus-doped TiO2 mesoporous nanocrystals (P-TMC) with ultrafine size of 2–8 nm and high specific surface area (234.164 m2 g–1) has been synthesized. It is formed through a hydrothermal process and NaBH4 assisted heat treatment for anatase defective TiO2 (TiO2–x) formation followed by a simple gas phosphorylation process in a low-cost reactor for P-doping. Due to the merits of the large specific surface area for providing more reaction sites for Li+ ions to increase the storage capacity and the presence of oxygen vacancies and P-doping for enhancing material’s electronic conductivity and diffusion coefficient of ions, the as-designed P-TMC can display improved electrochemical properties. As a LIB anode, it can deliver a high reversible discharge capacity of 187 mAh g–1 at 0.2 C and a good long cycling performance with ∼82.6% capacity retention (101 mAh g–1) after 2500 cycles at 10 C with an average capacity loss of only 0.007% per cycle. Impressively, even the current rate increases to 100 times of the original rate, a satisfactory capacity of 104 mAh g−1 can be delivered, displaying good rate capacity. These results suggest the P-TMC a viable choice for application as an anode material in LIB applications. Also, the strategy in this work can be easily extended to the design of other high-performance electrode materials with P-doping for energy storage.

Nanoarchitectonics of ultrafine molybdenum carbide nanocrystals into three-dimensional nitrogen-doped carbon framework for capacitive deionization.

Molybdenum carbide (MoC) has emerged as a promising material for capacitive deionization (CDI), but the poor electrochemical kinetics in conventional MoC owing to the bulk structure and low electric conductivity limit its CDI performance. To address this challenge, herein, we develop a novel strategy to synthesize ultrafine MoC nanocrystals that are embedded within a three-dimensional nitrogen-doped carbon framework (NC/MoC). This synthesis method involves the space-confined pyrolysis of molybdate precursors within metal-organic frameworks (MOFs). In this process, molybdates are confined into the MOF crystalline structure, where MOFs provide a confined reactor and carbon source. The resulting NC/MoC with the uniformly distributed MoC nanocrystals provides sufficient active sites for the electrosorption of salt ions, while the MOF-derived NC matrix facilitates charge transfer and provides the space-confined effect for preventing the possible aggregations of MoC nanocrystals during the CDI process. The NC/MoC exhibits an impressive salt adsorption capacity (SAC, 84.2 mg g-1, 1.2 V), rapid desalination rate, and high cycling stability (91.4% SAC retention after 200 cycles), better than those of most previously reported carbon-based CDI materials. Besides, the possible mechanisms are systematically investigated by ex situ characterization and density functional theory calculations. This study opens up new avenues for the construction of metal carbide-based nanocrystals for CDI and other electrochemical applications.

Cyanosol-enabled ultrafine alloy nanocrystals on graphene as a hybridization matrix for long-life and high-rate silicon anodes

A cyanosol-derived electrostatic assembly and pyrolysis route has been developed to construct homogeneous silicon/metal/carbon (Si/M/C) ternary materials, enabling improved lithium-storage kinetics and performance.

One-pot synthesis of an ultrafine Cu2O nanocrystal/porous polymer heterostructure for photocatalytic hydrogen production

This work provides a facile method for inorganic/organic heterostructures synthesis in a one-pot “click” reaction, in which ultrafine and uniform Cu2O nanocrystals were in situ deposited on triazole polymer nanosheets for the first time.

(Invited) MOF-Derived Nanosheet Arrays As Advanced Electrocatalysts for Water Splitting

Developing efficient, nanostructured electrocatalysts with desired compositions and structures is of great significance for improving the efficiency of water splitting toward hydrogen production. In this regard, metal organic framework (MOF) derived nanoarrays have attracted great attention as promising electrocatalysts because of their diverse compositions and adjustable structures. This presentation summarizes our recent work on the design and fabrication of MOF-derived nanosheet arrays toward enhanced catalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) as well as overall water splitting.First, heterostructured inter-doped ruthenium-cobalt oxide ((Ru-Co)Ox) hollow nanosheet arrays were prepared on carbon cloth for efficient overall water splitting. Benefiting from the desirable compositional and structural advantages of more exposed active sites, optimized electronic structure, and interfacial synergy effect, the (Ru-Co)Ox nanoarrays exhibited outstanding performance as a bifunctional catalyst. Particularly, they showed a remarkable hydrogen evolution reaction (HER) activity with an overpotential of 44.1 mV at 10 mA cm–2 and a small Tafel slope of 23.5 mV dec–1, as well as an excellent oxygen evolution reaction (OER) activity with an overpotential of 171.2 mV at 10 mA cm−2. As a result, a very low cell voltage of 1.488 V was needed at 10 mA cm–2 for alkaline overall water splitting.Second, Mo-doped ruthenium–cobalt oxide (Mo-RuCoOx) nanosheet arrays were produced for high-efficiency water splitting through combining electronic and vacancy engineering. The unique Mo-RuCoOx nanosheet arrays were able to act as a high-performance bifunctional electrocatalyst toward both HER and OER. Theoretical calculations and experimental results reveal that the incorporation of Ru and Mo can effectively tune the electronic structure, and the controllable Mo dissolution coupling with the oxygen vacancy generation during surface reconstruction is able to optimize the adsorption energy of hydrogen/oxygen intermediates, thus greatly accelerating the kinetics for both HER and OER. As a result, the Mo-RuCoOx nanoarrays exhibit remarkably low overpotentials of 41 mV and 156 mV at 10 mA cm–2 for HER and OER in 1 M KOH, respectively. Furthermore, the two-electrode electrolyzer assembled by the Mo-RuCoOx nanoarrays requires a cell voltage as low as 1.457 V to achieve 10 mA cm–2 for alkaline overall water splitting.Third, hollow nanosheet arrays assembled by ultrafine ruthenium-cobalt phosphide nanocrystals were fabricated toward exceptional pH-universal hydrogen evolution. The development of high-efficiency electrocatalysts for pH-universal HER is promising for constructing feasible water splitting systems at all pH values, but it remains challenging. A facile approach toward hollow nanosheet arrays assembled by ultrafine ruthenium-cobalt phosphide (Ru-CoxP) nanocrystals was developed through conversion from the MOF template. The synergic effects of optimized electronic structure, increased active sites, and rapid charge/mass transfer endowed the Ru-CoxP nanoarrays with outstanding electrocatalytic performance toward pH-universal HER. While exhibiting remarkably low overpotentials of 34.6 mV and 22.7 mV at 10 mA cm–2 in 1 M KOH and 0.5 M H2SO4, respectively, the Ru-CoxP nanoarrays showed an extremely low overpotential of 21.6 mV at 10 mA cm–2 in 1 M phosphate buffer solution (PBS). Furthermore, they were able to stably drive a Pt-free neutral electrolyzer for overall water splitting at 10 mA cm−2 with a cell voltage as low as 1.557 V.

Grain refinement mechanism in chip and the machined subsurface during high-speed machining of Inconel 718 alloy

Microstructural defects on the machined surface of Inconel 718 alloy can be a significant source of fatigue cracks, potentially leading to failures of the structural components of aerospace engines. This work focused on the grain refinement mechanism induced by the dynamic recrystallization (DRX) behavior in both the chip and machined subsurface during high-speed machining (HSM) of Inconel 718 alloy. Multiscale metallurgical observations were conducted using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and precession electron diffraction (PED) to characterize the crystal structures, including the grain size, grain boundary distribution, dislocation density, and grain orientation distribution. Finite element (FE) simulations were performed to obtain the strain, strain rate, and cutting temperature to analyze the microstructure evolution mechanism under the effect of severe deformation conditions in HSM. The results indicate that grain refinement in the chip primarily occurs in the shear band and secondary deformation zone. The primary cause of the variation in the final grain size is attributed to the distinct thermomechanical loading conditions experienced by the material. The microstructure observed in the machined subsurface reveals a significant gradient distribution, characterized by the presence of an amorphous structure, nanocrystallites, refined grains, and elongated grains along the depth direction. The equiaxed ultrafine nanocrystals observed in the machined near-surface result from both continuous DRX (cDRX) and discontinuous DRX (dDRX) mechanisms. In the deeper zone, the presence of numerous subgrains and a high geometrically necessary dislocation (GND) density reaching up to 1016/m2 within the grains indicate that the refined grains in this zone result from the cDRX mechanism. The variation in DRX mechanisms observed in the machined subsurface are closely related to the gradient distribution of the thermomechanical load generated in HSM.

Effect of ultralow Dy and Gd contents on surface crystallization and domain wall motion of FeCuSiBNbMo alloys

Surface crystallization of Fe-based melt-spun ribbons with high saturation induction leads to the formation of coarse grains after nanocrystallization, which results in a deterioration of the soft magnetic properties. Herein, doping with an ultralow concentration (0.1 at.%) of RE (RE = Dy and Gd) inhibits the surface crystallization of melt-spun FeCuSiBNbMo samples using industrial-grade Nb–Fe raw materials. This inhibition of surface crystallization promotes the formation of uniform and ultrafine nanograins after optimal annealing. Furthermore, the movement of domain wall is significantly affected by the presence of large grains (∼600 nm) in the free surface, which exerts a strong pinning effect on the domain wall motion. This pinning effect can be attributed to the higher magnetic anisotropy energy of the free surface compared to that of the nanocrystal region. The low coercivity observed in the samples with 0.1 at.% Dy and Gd addition is ascribed to the presence of dense and ultrafine nanocrystals, low effective magnetic anisotropy, and a weak pinning effect. This work provides insights into the relationship between surface crystallization, coercivity, domain wall motion, and magnetic anisotropy energy in Fe-based nanocrystalline ribbons.

Electrochemical oxidation induced in-situ transformation of lamellar cobalt nitrate-hydroxide to oxygen vacancy-rich porous Ce Doped-CoOOH nanosheet for efficient oxygen evolution reaction

Two-dimensional transition metal (2D TM)-based oxyhydroxides are widely used for electrocatalytic OER due to their high activity and low price. However, the limited active sites and insufficient intrinsic activity restrict their commercial applications. In this work, we develop a novel electrochemical oxidation etching-induced in-situ doping strategy to construct 2D oxygen vacancy (Ov)-rich porous Ce-doped CoOOH ultrathin nanosheets consisting of ultrafine nanocrystals on carbon cloth (Ce–CoOOH/CC) using lamellar cobalt nitrate-hydroxide on CC (CoLNH/CC) as the precursor for electrocatalytic OER. Benefiting from the abundant active sites and efficient mass/electron transfer rooted in the 2D ultrathin porous structure, as well as the optimized electronic structure resulting from Ce doping and Ov introducing, the Ce–CoOOH/CC exhibits a superior OER activity, with a low overpotential of 306 mV at 50 mA cm−2 and a small Tafel slope of 72.2 mV dec−1, compared to that of Co LHN/CC (368 mV and 93.9 mV dec−1), CeO2/Co LHN/CC (359 mV and 94.3 mV dec−1), and CoOOH/CC (337 mV and 75.9 mV dec−1) counterparts. Meanwhile, it shows good stability, with negligible current attenuation after 3000 cyclic voltammetry cycles or 24 h of continuous test. This study provides a feasible strategy for constructing various metal-doped porous transition metal oxyhydroxide-based electrocatalysts.

Highly dispersed conductive and electrocatalytic mediators enabling rapid polysulfides conversion for lithium sulfur batteries

The practical application of Li-S batteries encounters hurdles in maintaining cycling durability and rate capability under realistic conditions. Electrostatic self-assembly stands as a captivating avenue for exploring new frontiers in nanoscale catalysis. Leveraging renewable bio-oil both as a carbon source and self-polymerization precursor, ultrafine Mo2C nanocrystals anchored on bio-oil-derived 3D hierarchical carbon matrix (Mo2C@BOC) are fabricated by a facile NaCl template-assisted electrostatic self-assembly and followed annealing procedure. Densely anchored ultrafine Mo2C nanocrystals, intertwined with highly conductive carbon nanosheets, unveil an enhanced exposure of catalytically active sites for lithium polysulfide immobilization, conversion, and supply amply nucleation sites to mediate the fast precipitation of Li2S2/Li2S. Attributed to these favorable features, Li-S cells based on the as-designed catalytic host attain satisfactory cyclability with a minimum capacity fading rate of 0.0144 % over 1000 cycles and excellent rate capability. Decent performance can be achieved even at a high sulfur loading of 8.0 mg cm−2 and a low electrolyte-to-sulfur ratio of 3.5 µL mg−1. This strategy for solving the shuttle effect under high sulfur loading provides a promising solution for the further development of high-performance Li-S batteries. This work provides a rational strategy for solving the shuttle effect under high sulfur loading and sheds light on the great potential of Mo2C@BOC for developing more practical Li-S batteries.

Ultrafine PtMo Nanocrystals Confined on N‐Doped Carbon Toward Efficient pH‐Universal Hydrogen Evolution Reaction

AbstractPt‐based nanocrystals with tunable electronic structure and optimized atom efficiency are essential for boosting the hydrogen evolution reaction (HER) performance and further industrial application. However, the synthesis of uniform and ordered nanocrystals is still a challenge due to the uncontrollable size growth of metal particles, restricting the active sites toward the desired catalytic activity. Herein, the synthesis of ultrafine bimetal PtMo nanocrystals on N‐doped carbon (PtMo‐NC) through an anchoring‐sites engineering strategy is reported, in which the N‐rich carbon can provide abundant sites to anchor the metal atoms and suppress the over aggregation. The PtMo‐NC catalyst exhibits superior HER performance in both alkaline and acidic conditions, delivering a smaller overpotential (80 mV and 63 mV) at a current density of 100 mA cm−2 in alkaline and acidic media. Theoretical calculations reveal that the introduction of Mo atom into Pt can reduce the energy barrier of water molecule dissociation and optimize the H intermediate absorption strength on Pt sites, thus boosting the catalytic HER performance. This study offers a universal strategy to design ultrafine nanocatalysts to achieve high‐efficiency electrocatalysis.