The low utilization of active sites and sluggish reaction kinetics of MoSe severely impede its commercial application as electrocatalyst for hydrogen evolution reaction (HER). To address these two issues, the first example of introducing 1T MoSe and N dopant into vertical 2H MoSe /graphene shell/core nanoflake arrays that remarkably boost their HER activity is herein described. By means of the improved conductivity, rich catalytic active sites and highly accessible surface area as a result of the introduction of 1T MoSe and N doping as well as the unique structural features, the N-doped 1T-2H MoSe /graphene (N-MoSe /VG) shell/core nanoflake arrays show substantially enhanced HER activity. Remarkably, the N-MoSe /VG nanoflakes exhibit a relatively low onset potential of 45 mV and overpotential of 98 mV (vs RHE) at 10 mA cm with excellent long-term stability (no decay after 20 000 cycles), outperforming most of the recently reported Mo-based electrocatalysts. The success of improving the electrochemical performance via the introduction of 1T phase and N dopant offers new opportunities in the development of high-performance MoSe -based electrodes for other energy-related applications.

Increasing the utilization efficiency of sulfur electrodes and suppressing the "shuttle effect" of intermediate polysulfides are the key challenge for high-performance lithium-sulfur batteries (LSBs). Herein a facile combined strategy is reported to fabricate novel porous carbon fibers/vanadium nitride arrays (PCF/VN) composite scaffold for the storage of sulfur via a facile chemical etching united solvothermal-supercritical fluid method. More active sulfur can be stored in the PCF/VN backbone and dual blocking effects associated with "physical block and chemical absorption" for polysulfides are achieved in the PCF/VN/S integrated electrode. The PCF with highly porous structure provides large space to accommodate active sulfur and possesses cross-linked maze channels to physically immobilize the polysulfide species. The VN nanobelt arrays demonstrate strong ability for chemically anchoring the polysulfides, thus retarding the shuttle effect. Due to the unique structure and dual confining effect, the designed PCF/VN/S electrode shows a high reversible capacity of 1310.8 mA h g −1 at 0.1 C, an extended cycle life (1052.5 mA h g −1 after 250 cycles) as well as enhanced rate capability, much better than other counterparts (CF/VN/S, PCF/S, and CF/S). This work opens a new door for fabricating high-performance integrated electrodes for LSBs.

Porous materials have been thriving as promising candidates for vast applications in current electrochemical energy storage field. [1][2][3] The rational design of porous architectures with hierarchical and interconnected pore networks is always strongly considered by scientific community. [4][5][6][7] In parallel with the microporous (pore size ≤ 2 nm) and mesoporous (2 nm ≤ pore size ≤ 50 nm) materials, macroporous (50 nm ≤ pore size) materials emerge and hold tremendous potentials due to their significant advantages with interconnected frameworks offering improved structural stability, as well as large channels for accelerated mass mobilization and accessibility advantageous over micro/mesoporous materials. [8] In addition, many electrochemical energy storage applications require an open cellular structure with a reasonable combination of hierarchical pore size and distribution, of which the macropores work together with mesopores and micropores to accelerate transport mass (e.g., chemicals and electrolyte), thus highlighting the necessity and importance of macropores in a porous hierarchy. [9] Porous macrocellular carbon, one member of macroporous material family, is of particularly great interest due to their excellent chemical, mechanical, and thermal stability coupled with good conductivity and high surface area. Thus, various carbonaceous porous materials (e.g., 3D rGO, [10] porous graphene, [11][12][13] carbon nanorods, [14] carbon nanotube networks, [15] microporous carbon, [16] hierarchical porous carbon, [17] biomass derived carbon, [18][19][20][21] and their hybrids) [22][23][24] are endowed with a wide range of applications in lithium ion batteries, [25] sodium ion batteries, [26] and supercapacitors. [27] Diverse techniques have been developed to fabricate macroporous carbon materials including template, [27] suspension, [28] microfluidics, [29] membrane/microchannel emulsification, [9] and seeded emulsion polymerization, [30] etc. However, such methodologies are tedious, requiring multiple synthetic steps, caustic chemical treatments, and long curing times. Therefore, it is with great interest to develop facile approaches for large-scale construction of macroporous materials.Puffing process has been extensively accepted to produce 3D edible and degradable foam from starch-based materials (e.g., (2 of 8)rice, corn, wheat, potato). [31] As a typical puffing method, the instantaneous puffing (IP) involving compression and instantaneous release processes is widely accepted for popcorn fabrication. In general, the grains are first compressed in a heated and sealed container. Then, the starch-containing feedstocks are puffed/expanded in a flash by instantaneous release of clamping force of the sealed container at a high temperature of ≈200-300 °C and a large pressure of 0.5-1.5 MPa. The bulk starch-containing feedstocks are instantaneously transformed into expanded 3D porous macrocellular materials with volume and surface area increased by dozens of times through the facile IP process. This technolog...

power sources for electric vehicles and electronics. [4][5][6][7] In such a context, nextgeneration LIBs era with Li metal anode is spring up including Li-S, Li-O 2 , and solidstate Li batteries, which require high gravimetric capacity anodes and cathodes. [8][9][10][11][12][13] The maximum gravimetric capacity of cells would be significantly increased if Li is deposited on the anode directly as pure Li metal rather than stored in intercalation compounds such as graphite in LIBs during the charge/discharge processes. The theoretical capacity based on lithiated graphite is about 372 mA h g −1 , while pure Li metal theoretically delivers 3860 mA h g −1 . Therefore, Li metal anode is strongly considered recently. [14][15][16][17] In spite of the huge potential for highenergy-density device, the practical application of Li metal to a rechargeable anode is bumpy and has many challenges. [18,19] The most tough one is that Li metal problematically forms dendrites and related unstable structures during repeated plating/stripping. The fresh metallic deposit acts as an active site inducing reductive decomposition of electrolyte components. Part of the irregular deposition may become electrically isolated, and shedding may also occur. [20] Therefore, the disordered Li deposit gives rise to a poor Coulombic efficiency and a short cycle life. The metallic Li dendrites may easily penetrate into the separator and eventually induce internal short circuit, resulting in severe safety problem. [21,22] To circumvent these issues, great efforts are devoted to exploring dendrite-free Li metal anodes. Many emerging strategies have been investigated to enhance the electrochemical performance of Li metal anode: (1) Electrolyte additive is introduced into the electrolyte to form stable solid electrolyte interphase (SEI) film and reaction interface. [23][24][25][26][27][28] (2) Buffer layer or ion transfer layer is fabricated on the surface of Li metal by physical, chemical, or electrochemical methods and ensures homogeneous deposition of Li during cycling. [29][30][31][32] (3) Solidstate electrolyte is established on the surface of Li and proven to inhibit the dendrite growth. [33][34][35] (4) Highly porous conductive matrix is applied to guide the uniform deposition of Li metal in a working cell. [36][37][38][39][40] If the Li metal can be well protected by stable SEI, extra space is therefore required for the volume expansion/shrink of Li metal. Therefore, design/fabrication of novel porous conductive matrix is particularly important Construction of stable dendrite-free Li metal anode is crucial for the development of advanced Li-S and Li-air batteries. Herein, self-supported TiC/C core/shell nanowire arrays as skeletons and confined hosts of molten Li forming integrated trilayer TiC/C/Li anode are described. The TiC/C core/ shell nanowires with diameters of 400-500 nm exhibit merits of good lithiophilicity, high electrical conductivity, and abundant porosity. The as-prepared TiC/C/Li anode exhibits prominent electrochemical performance...

Tailoring molybdenum selenide electrocatalysts with tunable phase and morphology is of great importance for advancement of hydrogen evolution reaction (HER). In this work, phase- and morphology-modulated N-doped MoSe /TiC-C shell/core arrays through a facile hydrothermal and postannealing treatment strategy are reported. Highly conductive TiC-C nanorod arrays serve as the backbone for MoSe nanosheets to form high-quality MoSe /TiC-C shell/core arrays. Impressively, continuous phase modulation of MoSe is realized on the MoSe /TiC-C arrays. Except for the pure 1T-MoSe and 2H-MoSe , mixed (1T-2H)-MoSe nanosheets are achieved in the N-MoSe by N doping and demonstrated by spherical aberration electron microscope. Plausible mechanism of phase transformation and different doping sites of N atom are proposed via theoretical calculation. The much smaller energy barrier, longer HSe bond length, and diminished bandgap endow N-MoSe /TiC-C arrays with substantially superior HER performance compared to 1T and 2H phase counterparts. Impressively, the designed N-MoSe /TiC-C arrays exhibit a low overpotential of 137 mV at a large current density of 100 mA cm , and a small Tafel slope of 32 mV dec . Our results pave the way to unravel the enhancement mechanism of HER on 2D transition metal dichalcogenides by N doping.