Smart surface coatings of silicon (Si) nanoparticles are shown to be good examples for dramatically improving the cyclability of lithium-ion batteries. Most coating materials, however, face significant challenges, including a low initial Coulombic efficiency, tedious processing, and safety assessment. In this study, a facile sol-gel strategy is demonstrated to synthesize commercial Si nanoparticles encapsulated by amorphous titanium oxide (TiO ), with core-shell structures, which show greatly superior electrochemical performance and high-safety lithium storage. The amorphous TiO shell (≈3 nm) shows elastic behavior during lithium discharging and charging processes, maintaining high structural integrity. Interestingly, it is found that the amorphous TiO shells offer superior buffering properties compared to crystalline TiO layers for unprecedented cycling stability. Moreover, accelerating rate calorimetry testing reveals that the TiO -encapsulated Si nanoparticles are safer than conventional carbon-coated Si-based anodes.

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An ex situ strategy for fabrication of graphene oxide (GO)/metal oxide hybrids without assistance of surfactant is introduced. Guided by this strategy, GO/Al2O3 hybrids are fabricated by two kinds of titration methods in which GO and Al2O3 colloids are utilized as titrant for hybrids of low and high GO content respectively. After sintered by spark plasma sintering, few‐layer graphene (FG)/Al2O3 nanocomposites are obtained and GO is well reduced to FG simultaneously. A percolation threshold as low as 0.38 vol.% is achieved and the electrical conductivity surpasses 103 Sm−1 when FG content is only 2.35 vol.% in FG/Al2O3 composite, revealing the homogeneous dispersion and high quality of as‐prepared FG. Furthermore, it is found that the charge carrier type changes from p‐ to n‐type as graphene content becomes higher. It is deduced that this conversion is related to the doping effect induced by Al2O3 matrix and is thickness‐dependent with respect to FG.

received widespread attention during the past decades. It enables direct conversion between heat and electricity which has been used in space exploration, microelectronics, automobiles and so on. [1] However, the widespread application of thermoelectric devices in daily life is severely limited by the low thermoelectric conversion efficiency, which is mainly related to the dimensionless figure of merit ZT = α 2 σT/κ, where α, σ, and T are the Seebeck coefficient, electrical conductivity, absolute temperature, respectively and thermal conductivity κ is composed of electronic (κ e ) and lattice (κ l ) contributions. [2] Among the developed TE materials with high ZT (≥1), the V 2 VI 3 (V represents Group V elements Sb and Bi, and VI is Group VI elements S, Se and Te) compounds and derivatives have been intensively investigated for a long history since 1950s, which are widely considered as the benchmark of high performance TE materials in low-to mid-temperature range. [3] The outstanding TE performance of V 2 VI 3 materials represented by Sb 2 Te 3 , Bi 2 Te 3 , and Bi 2 Se 3 can be ascribed to its high power factor (PF) due to the suitable carrier concentration and low κ derived from the layered structure weakly bonded by van der Waals interaction. [3] Optimized by isoelectronic extrinsic doping, much improved TE performance with the maximum ZT around 1 has been The (Bi,Sb) 2 Te 3 (BST) compounds have long been considered as the benchmark of thermoelectric (TE) materials near room temperature especially for refrigeration. However, their unsatisfactory TE performances in wide-temperature range severely restrict the large-scale applications for power generation. Here, using a self-assembly protocol to deliver a homogeneous dispersion of 2D inclusion in matrix, the first evidence is shown that incorporation of MXene (Ti 3 C 2 T x ) into BST can simultaneously achieve the improved power factor and greatly reduced thermal conductivity. The oxygen-terminated Ti 3 C 2 T x with proper work function leads to highly increased electrical conductivity via hole injection and retained Seebeck coefficient due to the energy barrier scattering. Meanwhile, the alignment of Ti 3 C 2 T x with the layered structure significantly suppresses the phonon transport, resulting in higher interfacial thermal resistance. Accordingly, a peak ZT of up to 1.3 and an average ZT value of 1.23 from 300 to 475 K are realized for the 1 vol% Ti 3 C 2 T x /BST composite. Combined with the high-performance composite and rational device design, a record-high thermoelectric conversion efficiency of up to 7.8% is obtained under a temperature gradient of 237 K. These findings provide a robust and scalable protocol to incorporate MXene as a versatile 2D inclusion for improving the overall performance of TE materials toward high energy-conversion efficiency.

Obtaining bifunctional electrocatalysts with high activity for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is a main hurdle in the application of rechargeable metal-air batteries. Earth-abundant 3d transition metal-based catalysts have been developed for the OER and ORR; however, most of these are based on oxides, whose insulating nature strongly restricts their catalytic performance. This study describes a metallic Ni-Fe nitride/nitrogen-doped graphene hybrid in which 2D Ni-Fe nitride nanoplates are strongly coupled with the graphene support. Electronic structure of the Ni-Fe nitride is changed by hybridizing with the nitrogen-doped graphene. The unique heterostructure of this hybrid catalyst results in very high OER activity with the lowest onset overpotential (150 mV) reported, and good ORR activity comparable to that for commercial Pt/C. The high activity and durability of this bifunctional catalyst are also confirmed in rechargeable zinc-air batteries that are stable for 180 cycles with an overall overpotential of only 0.77 V at 10 mA .

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Electrolytic gas evolution is a significant phenomenon in many electrochemical technologies from water splitting, chloralkali process to fuel cells. Although it is known that gas evolution may substantially affect the ohmic resistance and mass transfer, studies focusing on the electrochemistry of individual bubbles are critical but also challenging. Here, we report an approach using scanning electrochemical cell microscopy (SECCM) with a single channel pipet to quantitatively study individual gas bubble nucleation on different electrode substrates, including conventional polycrystalline Pt and Au films, as well as the most interesting two-dimensional semiconductor MoS 2 . Due to the confinement effect of the pipet, well-defined peak-shaped voltammetric features associated with single bubble nucleation and growth are consistently observed. From stochastic bubble nucleation measurement and finite element simulation, the surface H 2 concentration corresponding to bubble nucleation is estimated to be ∼218, 137, and 157 mM, with critical nuclei contact angles of ∼156°, ∼161°, and ∼160°at polycrystalline Pt, Au, and MoS 2 substrates, respectively. We further demonstrated the surface faceting at polycrystalline Pt is not specifically correlated with the bubble nucleation behavior.

Graphene aerogel (GA) possessing good electrical conductivity and low weight has been widely considered as a promising candidate for high-performance microwave-absorbing (MA) materials. However, simultaneous realization of high reflection loss (RL), low thickness, and light weight remains very challenging for GA because of the trade-off between impedance match and attenuation ability. Herein, through use of (3-aminopropyl)­triethoxysilane as a surface modifier and cross-linker, the GA materials with precisely controlled density are fabricated via a unique solvothermal protocol of zero-volume shrinkage. The density-controlled GA (4.5 mg·cm–3) exhibits a remarkable minimum RL (RLmin) of −50 dB at a thickness of 1.14 mm in the K-band, owing to the optimized dielectric properties. Moreover, even higher attenuation ability without sacrificed impedance match is obtained by incorporating magnetic Fe3O4@C microspheres into the density-controlled GA. Superior MA performance involving unprecedented RLmin of −54.0 dB and qualified bandwidth covering 80% of the K-band has been achieved in the superlight Fe3O4@C/GA composite at a thickness less than 1 mm, which is highly desirable for MA material applied in mobile devices.