Mo₂C Nanoparticles Decorated Graphitic Carbon Sheets: Biopolymer-Derived Solid-State Synthesis and Application as an Efficient Electrocatalyst for Hydrogen Generation

The present work reports on the preparation of Mo₂C nanoparticles decorated graphitic carbon sheets (Mo₂C/GCSs) via a biopolymer-derived solid-state reaction between (NH₄)₆Mo₇O₂₄·4H₂O and sodium alginate at 900 °C under Ar. As a novel hydrogen evolution reaction electrocatalytst, the Mo₂C/GCSs hybrids exhibit high activity in acidic solutions with an onset potential of 120 mV, a Tafel slope of 62.6 mV dec^–1, and an exchange current density of 12.5 × 10^–3 mA cm^–2. Moreover, such Mo₂C/GCSs catalysts also show excellent durability during long-term 3000 cycles

Effect of Heat Treatment Temperature on the Crystallization Behavior and Microstructural Evolution of Amorphous NbCo_1.1Sn

Heat treatment-induced nanocrystallization of amorphous precursors is a promising method for nanostructuring half-Heusler compounds as it holds significant potential in the fabrication of intricate and customizable nanostructured materials. To fully exploit these advantages, a comprehensive understanding of the crystallization behavior of amorphous precursors under different crystallization conditions is crucial. In this study, we investigated the crystallization behavior of the amorphous NbCo1.1Sn alloy at elevated temperatures (783 and 893 K) using transmission electron microscopy and atom probe tomography. As a result, heat treatment at 893 K resulted in a significantly finer grain structure than heat treatment at 783 K owing to the higher nucleation rate at 893 K. At both temperatures, the predominant phase was a half-Heusler phase, whereas the Heusler phase, associated with Co diffusion, was exclusively observed at the specimen annealed at 893 K. The Debye–Callaway model supports that the lower lattice thermal conductivity of NbCo1.1Sn annealed at 893 K is primarily attributed to the formation of Heusler nanoprecipitates rather than a finer grain size. The experimental findings of this study provide valuable insights into the nanocrystallization of amorphous alloys for enhancing thermoelectric properties

Nickel single atom-decorated carbon nanosheets as multifunctional electrocatalyst supports toward efficient alkaline hydrogen evolution

Tailoring catalysts with balanced adsorption capabilities toward multiple reaction intermediates is highly desirable for complex electrocatalytic reactions, but rather challenging. Here, Ni single atom-decorated carbon nanosheets are developed as multifunctional supports for engineering heterostructured electrocatalysts toward hydrogen evolution in alkaline media. The Ni single atoms (Ni–N ) are actively dedicated to cleaving the H–OH bonds as well as facilitating H spillover to metallic Pt sites. For the case of supported Pt electrocatalysts, a Pt/PtO configuration is generated at the heterointerface via Pt–O–C (Ni) interfacial bonding, with oxidized Pt species located at the interface and metallic Pt formed in the near-interface area. Further, the oxidized Pt species are also active for boosting the water dissociation step. These findings not only open up a new avenue toward the development of multifunctional catalyst supports but also demonstrate the importance of regulating interface chemistry of heterostructured electrocatalysts at atomic level. 4 ad

Gallium-Indium-Tin Liquid Metal Nanodroplet-Based Anisotropic Conductive Adhesives for Flexible Integrated Electronics

Compared with traditional solder joint bonding, an anisotropic conductive adhesive (ACA) provides an efficient and simple method for the interconnection of small-scale electronics. The wider application of ACAs for nanoelectronics is still suppressed, however, by the lack of durable and cost-effective conductive components. Herein, a series of core-shell eutectic gallium-indium-tin liquid metal (LM) nanodroplets (NDs) with different diameters have been successfully synthesized and regulated by a combination of laser irradiation and sonication. Due to their high conductivity and good fluidity, these LM NDs were used as soft conductive filler micro/nanoparticles for fabricating ACAs. The as-prepared ND-based ACAs present satisfactory anisotropic conductivity when used to interconnect small-scale electronic circuits. Highly durable anisotropic electrical performance was also maintained in flexible packed devices, even under bending or twisting operation modes

FeN₄ Active Sites Electronically Coupled with PtFe Alloys for Ultralow Pt Loading Hybrid Electrocatalysts in Proton Exchange Membrane Fuel Cells

The exorbitant cost of Pt-based electrocatalysts and the poor durability of non-noble metal electrocatalysts for proton exchange membrane fuel cells limited their practical application. Here, FeN4 active sites electronically coupled with PtFe alloys (PtFe-FeNC) were successfully prepared by a vapor deposition strategy as an ultralow Pt loading (0.64 wt %) hybrid electrocatalyst. The FeN4 sites on the FeNC matrix are able to effectively anchor the PtFe alloys, thus inhibiting their aggregation during long-life cycling. These PtFe alloys, in turn, can efficiently restrain the leaching of the FeN4 sites from the FeNC matrix. Thus, the PtFe-FeNC demonstrated an improved Pt mass activity of 2.33 A mgPt–1 at 0.9 V toward oxygen reduction reaction, which is 12.9 times higher than that of commercial Pt/C (0.18 A mgPt–1). It demonstrated great stability, with the Pt mass activity decreasing by only 9.4% after 70,000 cycles. Importantly, the fuel cell with an ultralow Pt loading in the cathode (0.012 mgPt cm–2) displays a high Pt mass activity of 1.75 A mgPt–1 at 0.9 ViR-free, which is significantly better than commercial MEA (0.25 A mgPt–1). Interestingly, PtFe-FeNC catalysts possess enhanced durability, exhibiting a 12.5% decrease in peak power density compared to the 51.7% decrease of FeNC

Atomic Ru-Doped Ni_0.85Se Nanosheets as Efficient Electrocatalysts toward Simulated Seawater Hydrogen Evolution

The development of affordable and efficient catalysts for seawater hydrogen evolution is highly desirable but presents significant challenges. In this study, we prepared an exceptionally efficient electrocatalyst, atomic Ru-doped Ni0.85Se supported on carbon cloth (Ru–Ni0.85Se/CC–12 h), for the hydrogen evolution reaction (HER) in both a 1 M KOH solution and an alkaline-simulated seawater environment (1 M KOH and 0.5 M NaCl). Notably, Ru–Ni0.85Se/CC–12 h exhibited excellent performance with remarkably low overpotentials of 34.1 and 44.2 mV at 10 mA/cm2 in the 1 M KOH solution and the alkaline-simulated seawater environment, respectively. Furthermore, it demonstrated remarkable durability, showing negligible performance degradation even after continuous 18 h at 10 mA/cm2. The outstanding HER performance of Ru–Ni0.85Se/CC–12 h in both alkaline solution and alkaline-simulated seawater can be attributed to the atomic Ru doping in Ni0.85Se, which modifies its geometric and electronic structure, thereby enhancing its activity and resistance to chloride ion poisoning and erosion simultaneously

A general synthesis of inorganic nanotubes as high-rate anode materials of sodium ion batteries

Inorganic tubular materials have an exceptionally wide range of applications, yet developing a simple and universal method to controllably synthesize them remains challenging. In this work, we report a vapor-phase-etching hard-template method that can directly fabricate tubes on various thermally stable oxide and sulfide materials. This synthesis method features the introduction of a vapor-phase-etching process to greatly simplify the steps involved in preparing tubular materials and avoids complicated post-processing procedures. Furthermore, the in-situ heating transmission electron microscopy (TEM) technique is used to observe the dynamic formation process of TiO2−x tubes, indicating that the removal process of the Sb2S3 templates first experienced the Rayleigh instability, then vapor-phase-etching process. When used as an anode for sodium ion batteries, the TiO2−x tube exhibits excellent rate performance of 134.6 mA h g−1 at the high current density of 10 A g−1 and long-term cycling over 7000 cycles. Moreover, the full cell demonstrates excellent cycling performance with capacity retention of 98% after 1000 cycles, indicating that it is a promising anode material for batteries. This method can be expanded to the design and synthesis of other thermally-stable tubular materials such as ZnS, MoS2, and SiO2

Atomically Dispersed Dual-Site Cathode with a Record High Sulfur Mass Loading for High-Performance Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT-Na/S) batteries possess high potential for grid-scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur-doped graphene frameworks supporting atomically dispersed 2H-MoS2 and Mo1 (S@MoS2-Mo1/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT-Na/S batteries. Impressively, the as-prepared S@MoS2-Mo1/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g−1 at 0.1 A g−1 and a low-capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction and density-functional theory calculations reveal that atomic-level Mo in this integrated dual-active-site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high-performance dual-site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level

Toward enhanced alkaline hydrogen electrocatalysis with transition metal-functionalized nitrogen-doped carbon supports

Superior catalyst supports are crucial to developing advanced electrocatalysts toward heterogeneous catalytic reactions. Herein, we systematically investigate the role of transition metal-functionalized N-doped carbon nanosheets (M-N-C, M = Mn, Fe, Co, Ni, Cu, Mo, and Ag) as the multifunctional electrocatalyst supports toward hydrogen evolution/oxidation reactions (HER/HOR) in alkaline media. The results demonstrate that all the M-N-C nanosheets, except Cu-N-C and Ag-N-C, can promote the alkaline HER/HOR electrocatalytic activity of Pt by accelerating the sluggish Volmer step, among which Mn plays a more significant role. Analyses reveal that the promotion effect of M-N-C support is closely associated with the electronegativity of the metal dopants and the relative filling degree of their d-orbitals. For one, the metal dopant in M-N-C with smaller electronegativity would provide more electrons to oxygen and hence tune the electronic structure of Pt via the M-O-Pt bonds at the interface. For another, the transition metal in M-N4 moieties with more empty d orbitals would hybridize with O 2p orbitals more strongly that promotes the adsorption of water/hydroxyl species. The results demonstrate the conceptual significance of multifunctional supports and would inspire the future development of advanced electrocatalysts

Epitaxial growth of an atom-thin layer on a LiNi0.5Mn1.5O4 cathode for stable Li-ion battery cycling

Transition metal dissolution in cathode active material for Li-based batteries is a critical aspect that limits the cycle life of these devices. Although several approaches have been proposed to tackle this issue, this detrimental process is not yet overcome. Here, benefitting from the knowledge developed in the semiconductor research field, we apply an epitaxial method to construct an atomic wetting layer of LaTMO3 (TM = Ni, Mn) on a LiNi0.5Mn1.5O4 cathode material. Experimental measurements and theoretical analyses confirm a Stranski–Krastanov growth, where the strained wetting layer forms under thermodynamic equilibrium, and it is self-limited to monoatomic thickness due to the competition between the surface energy and the elastic energy. Being atomically thin and crystallographically connected to the spinel host lattices, the LaTMO3 wetting layer offers long-term suppression of the transition metal dissolution from the cathode without impacting its dynamics. As a result, the epitaxially-engineered cathode material enables improved cycling stability (a capacity retention of about 77% after 1000 cycles at 290 mA g−1) when tested in combination with a graphitic carbon anode and a LiPF6-based non-aqueous electrolyte solution