Formulating N-Doped Carbon Hollow Nanospheres with Highly Accessible Through-Pores to Isolate Fe Single-Atoms for Efficient Oxygen Reduction.

It is challenging yet promising to design highly accessible N-doped carbon skeletons to fully expose the active sites inside single-atom catalysts. Herein, mesoporous N-doped carbon hollow spheres with regulatable through-pore size can be formulated by a simple sequential synthesis procedure, in which the condensed SiO2 is acted as removable dual-templates to produce both hollow interiors and through-pores, meanwhile, the co-condensed polydopamine shell is served as N-doped carbon precursor. After that, Fe─N─C hollow spheres (HSs) with highly accessible active sites can be obtained after rationally implanting Fe single-atoms. Microstructural analysis and X-ray absorption fine structure analysis reveal that high-density Fe─N4 active sites together with tiny Fe clusters are uniformly distributed on the mesoporous carbon skeleton with abundant through-pores. Benefitted from the highly accessible Fe─N4 active sites arising from the unique through-pore architecture, the Fe─N─C HSs demonstrate excellent oxygen reduction reaction (ORR) performance in alkaline media with a half-wave potential up to 0.90 V versus RHE and remarkable stability, both exceeding the commercial Pt/C. When employing Fe─N─C HSs as the air-cathode catalysts, the assembled Zn-air batteries deliver a high peak power density of 204 mW cm-2 and stable discharging voltage plateau over 140 h.

Low-Potential Iodide Oxidation Enables Dual-Atom CoFe─N─C Catalysts for Ultra-Stable and High-Energy-Efficiency Zn-Air Batteries.

The low energy efficiency and limited cycling life of rechargeable Zn-air batteries (ZABs) arising from the sluggish oxygen reduction/evolution reactions (ORR/OERs) severely hinder their commercial deployment. Herein, a zeolitic imidazolate framework (ZIF)-derived strategy associated with subsequent thermal fixing treatment is proposed to fabricate dual-atom CoFe─N─C nanorods (Co1 Fe1 ─N─C NRs) containing atomically dispersed bimetallic Co/Fe sites, which can promote the energy efficiency and cyclability of ZABs simultaneously by introducing the low-potential oxidation redox reactions. Compared to the mono-metallic nanorods, Co1 Fe1 ─N─C NRs exhibit remarkable ORR performance including a positive half-wave potential of 0.933 V versus reversible hydrogen electrode (RHE) in alkaline electrolyte. Surprisingly, after introducing the potassium iodide (KI) additive, the oxidation overpotential of Co1 Fe1 ─N─C NRs to reach 10 mA cm-2 can be significantly reduced by 395 mV compared to the conventional destructive OER. Theoretical calculations show that the markedly decreased overpotential of iodide oxidation can be ascribed to the synergistic effects of neighboring Co─Fe diatomic sites as the unique adsorption sites. Overall, aqueous ZABs assembled with Co1 Fe1 ─N─C NRs and KI as the air-cathode catalyst and electrolyte additive, respectively, can deliver a low charging voltage of 1.76 V and ultralong cycling stability of over 230 h with a high energy efficiency of ≈68%.

Defect Emission and Its Dipole Orientation in Layered Ternary Znln2 S4 Semiconductor.

Defect engineering is promising to tailor the physical properties of 2D semiconductors for function-oriented electronics and optoelectronics. Compared with the extensively studied 2D binary materials, the origin of defects and their influence on physical properties of 2D ternary semiconductors are not clarified. Here, the effect of defects on the electronic structure and optical properties of few-layer hexagonal Znln2 S4 is thoroughly studied via versatile spectroscopic tools in combination with theoretical calculations. It is demonstrated that the Zn-In antistructural defects induce the formation of a series of donor and acceptor energy levels and sulfur vacancies induce donor energy levels, leading to rich recombination paths for defect emission and extrinsic absorption. Impressively, the emission of donor-acceptor pair in Znln2 S4 can be significantly tailored by electrostatic gating due to efficient tunability of Fermi level (Ef ). Furthermore, the layer-dependent dipole orientation of defect emission in Znln2 S4 is directly revealed by back focal plane imagining, where it presents obviously in-plane dipole orientation within a dozen-layer thickness of Znln2 S4 . These unique features of defects in Znln2 S4 including extrinsic absorption, rich recombination paths, gate tunability, and in-plane dipole orientation are definitely a benefit to the advanced orientation-functional optoelectronic applications.

Self-Sacrificing Template Synthesis of Carbon Nanosheets Assembled Hollow Spheres with Abundant Active Fe-N4 O1 Moieties for Electrocatalytic Oxygen Reduction.

Single-atom Fe-N-C (Fe1 -N-C) materials represent the benchmarked electrocatalysts for oxygen reduction reaction (ORR). However, single Fe atoms in the carbon skeletons cannot be fully utilized due to the mass transfer limitation, severely restricting their intrinsic ORR properties. Herein, a self-sacrificing template strategy is developed to fabricate ultrathin nanosheets assembled Fe1 -N-C hollow microspheres (denoted as Fe1 /N-HCMs) by rational carbonization of Fe3+ chelating polydopamine coated melamine cyanuric acid complex. The shell of Fe1 /N-HCMs is constructed by ultrathin nanosheets with thickness of only 2 nm, which is supposed to be an ideal platform to isolate and fully expose single metal atoms. Benefiting from unique hierarchical hollow architecture with highly open porous structure, 2 nm-thick ultrathin nanosheet subunits and abundant Fe-N4 O1 active sites revealed by X-ray absorption fine structure analysis, the Fe1 /N-HCMs exhibit high ORR performance with a positive half-wave potential of 0.88 V versus the reversible hydrogen electrode and robust stability. When served as air-cathode catalysts with ultralow loading mass of 0.25 mg cm-2 , Fe1 /N-HCMs based Zn-air batteries present a maximum power density of 187 mW cm-2 and discharge specific capacity of 806 mA h gZn -1 in primary Zn-air batteries, all exceeding those of commercial Pt/C.

Revisiting the Hetero-Interface of Electrolyte/2D Materials in an Electric Double Layer Device.

Electric double layer (EDL) devices based on 2D materials have made great achievements for versatile electronic and opto-electronic applications; however, the ion dynamics and electric field distribution of the EDL at the electrolyte/2D material interface and their influence on the physical properties of 2D materials have not been clearly clarified. In this work, by using Kelvin probe force microscope and steady/transient optical techniques, the character of the EDL and its influence on the optical properties of monolayer transition metal dichalcogenides (TMDs) are probed. The potential drop, unscreened EDL potential distribution, and accumulated carriers at the electrolyte/TMD interface are revealed, which can be explained by nonlinear Thomas-Fermi theory. By monitoring the potential distribution along the channel, the evolution of the electric field-induced lateral junction in the TMD EDL transistor is accessed, giving rise to the better exploration of EDL device physics. More importantly, EDL gate-dependent carrier recombination and exciton-exciton annihilation in monolayer TMDs on lithium-ion solid state electrolyte (Li2 Al2 SiP2 TiO13 ) are evaluated for the first time, benefiting from the understanding of the interaction between ions, carriers, and excitons. The work will deepen the understanding of the EDL for the exploitation of functional device applications.

Transition Metal (Co, Ni, Fe, Cu) Single-Atom Catalysts Anchored on 3D Nitrogen-Doped Porous Carbon Nanosheets as Efficient Oxygen Reduction Electrocatalysts for Zn-Air Battery.

Exploring highly active and cost-efficient single-atom catalysts (SACs) for oxygen reduction reaction (ORR) is critical for the large-scale application of Zn-air battery. Herein, density functional theory (DFT) calculations predict that the intrinsic ORR activity of the active metal of SACs follows the trend of Co > Fe > Ni ≈ Cu, in which Co SACs possess the best ORR activity due to its optimized spin density. Guided by DFT calculations, four kinds of transition metal single atoms embedded in 3D porous nitrogen-doped carbon nanosheets (MSAs@PNCN, M = Co, Ni, Fe, Cu) are synthesized via a facile NaCl-template assisted strategy. The resulting MSAs@PNCN displays ORR activity trend in lines with the theoretical predictions, and the Co SAs@PNCN exhibits the best ORR activity (E1/2  = 0.851 V), being comparable to that of Pt/C under alkaline conditions. X-ray absorption fine structure (XAFS) spectra verify the atomically dispersed Co-N4 sites are the catalytically active sites. The highly active CoN4 sites and the unique 3D porous structure contribute to the outstanding ORR performance of Co SAs@PNCN. Furthermore, the Co SAs@PNCN catalyst is employed as cathode in Zn-air battery, which can deliver a large power density of 220 mW cm-2 and maintain robust cycling stability over 530 cycles.

2D Indium Phosphorus Sulfide (In2 P3 S9 ): An Emerging van der Waals High-k Dielectrics.

2D van der Waals (vdW) semiconductors hold great potentials for more-than-Moore field-effect transistors (FETs), and the efficient utilization of their theoretical performance requires compatible high-k dielectrics to guarantee the high gate coupling efficiency. The deposition of traditional high-k dielectric oxide films on 2D materials usually generates interface concerns, thereby causing the carrier scattering and degeneration of device performance. Here, utilizing a space-confined epitaxy growth approach, the authors successfully obtained air-stable ultrathin indium phosphorus sulfide (In2 P3 S9 ) nanosheets, the thickness of which can be scaled down to monolayer limit (≈0.69 nm) due to its layered structure. 2D In2 P3 S9 exhibits excellent insulating properties, with a high dielectric constant (≈24) and large breakdown voltage (≈8.1 MV cm-1 ) at room temperature. Serving as gate insulator, ultrathin In2 P3 S9 nanosheet can be integrated into MoS2 FETs with high-quality dielectric/semiconductor interface, thus providing a competitive electrical performance of device with subthreshold swings (SS) down to 88 mV dec-1 and a high ON/OFF ratio of 105 . This study proves an important strategy to prepare 2D vdW high-k dielectrics, and greatly facilitates the ongoing research of 2D materials for functional electronics.

Isolating Fe Atoms in N-Doped Carbon Hollow Nanorods through a ZIF-Phase-Transition Strategy for Efficient Oxygen Reduction.

Transition metal-nitrogen-carbon (TM-N-C) catalysts have been intensely investigated to tackle the sluggish oxygen reduction reactions (ORRs), but insufficient accessibility of the active sites limits their performance. Here, by using solid ZIF-L nanorods as self-sacrifice templates, a ZIF-phase-transition strategy is developed to fabricate ZIF-8 hollow nanorods with open cavities, which can be subsequently converted to atomically dispersed Fe-N-C hollow nanorods (denoted as Fe1 -N-C HNRs) through rational carbonization and following fixation of iron atoms. The microstructure observation and X-ray absorption fine structure analysis confirm abundant Fe-N4 active sites are evenly distributed in the carbon skeleton. Thanks to the highly accessible Fe-N4 active sites provided by the highly porous and open carbon hollow architecture, the Fe1 -N-C HNRs exhibit superior ORR activity and stability in alkaline and acidic electrolytes with very positive half-wave potentials of 0.91 and 0.8 V versus RHE, respectively, both of which surpass those of commercial Pt/C. Remarkably, the dynamic current density (JK ) of Fe1 -N-C HNRs at 0.85 V versus RHE in alkaline media delivers a record value of 148 mA cm-2 , 21 times higher than that of Pt/C. The assembled Zn-air battery using Fe1 -N-C HNRs as cathode catalyst exhibits a high peak power density of 208 mW cm-2 .

Mechanical Anisotropy in Two-Dimensional Selenium Atomic Layers.

Two-dimensional (2D) trigonal selenium (t-Se) has become a new member in 2D semiconducting nanomaterial families. It is composed of well-aligned one-dimensional Se atomic chains bonded via van der Waals (vdW) interaction. The contribution of this unique anisotropic nanostructure to its mechanical properties has not been explored. Here, for the first time, we combine experimental and theoretical analyses to study the anisotropic mechanical properties of individual 2D t-Se nanosheets. It was found that its fracture strength and Young's modulus parallel to the atomic chain direction are much higher than along the transverse direction, which was attributed to the weak vdW interaction between Se atomic chains as compared to the covalent bonding within individual chains. Additionally, two distinctive fracture modes along two orthogonal loading directions were identified. This work provides important insights into the understanding of anisotropic mechanical behaviors of 2D semiconducting t-Se and opens new possibilities for future applications.

Topotactic Growth of Free-Standing Two-Dimensional Perovskite Niobates with Low Symmetry Phase.

Here, we report a novel topotactic method to grow 2D free-standing perovskite using KNbO3 (KN) as a model system. Perovskite KN with monoclinic phase, distorted by as large as ∼6 degrees compared with orthorhombic KN, is obtained from 2D KNbO2 after oxygen-assisted annealing at relatively low temperature (530 °C). Piezoresponse force microscopy (PFM) measurements confirm that the 2D KN sheets show strong spontaneous polarization (Ps) along [101̅]pc direction and a weak in-plane polarization, which is consistent with theoretical predictions. Thickness-dependent stripe domains, with increased surface displacement and PFM phase changes, are observed along the monoclinic tilt direction, indicating the preserved strain in KN induces the variation of nanoscale ferroelectric properties. 2D perovskite KN with low symmetry phase stable at room temperature will provide new opportunities in the exploration of nanoscale information storage devices and better understanding of ferroelectric/ferroelastic phenomena in 2D perovskite oxides.

Bifunctional WC-Supported RuO2 Nanoparticles for Robust Water Splitting in Acidic Media.

We report the strong catalyst-support interaction in WC-supported RuO2 nanoparticles (RuO2 -WC NPs) anchored on carbon nanosheets with low loading of Ru (4.11 wt.%), which significantly promotes the oxygen evolution reaction activity with a η10 of 347 mV and a mass activity of 1430 A gRu -1 , eight-fold higher than that of commercial RuO2 (176 A gRu -1 ). Theoretical calculations demonstrate that the strong catalyst-support interaction between RuO2 and the WC support could optimize the surrounding electronic structure of Ru sites to reduce the reaction barrier. Considering the likewise excellent catalytic ability for hydrogen production, an acidic overall water splitting (OWS) electrolyzer with a good stability constructed by bifunctional RuO2 -WC NPs only requires a cell voltage of 1.66 V to afford 10 mA cm-2 . The unique 0D/2D nanoarchitectures rationally combining a WC support with precious metal oxides provides a promising strategy to tradeoff the high catalytic activity and low cost for acidic OWS applications.

Lowering the Contact Barriers of 2D Organic F16 CuPc Field-Effect Transistors by Introducing Van der Waals Contacts.

2D organic crystals exhibit efficient charge transport and field-effect characteristics, making them promising candidates for high-performance nanoelectronics. However, the strong Fermi level pinning (FLP) effect and large Schottky barrier between organic semiconductors and metals largely limit device performance. Herein, by carrying out temperature-dependent transport and Kelvin probe force microscopy measurements, it is demonstrated that the introducing of 2D metallic 1T-TaSe2 with matched band-alignment as electrodes for F16 CuPc nanoflake filed-effect transistors leads to enhanced field-effect characteristics, especially lowered Schottky barrier height and contact resistance at the contact and highly efficient charge transport within the channel, which are attributed to the significantly suppressed FLP effect and appropriate band alignment at the nonbonding van der Waals (vdW) hetero-interface. Moreover, by taking advantage of the improved contact behavior with 1T-TaSe2 contact, the optoelectronic performance of F16 CuPc nanoflake-based phototransistor is drastically improved, with a maximum photoresponsivity of 387 A W-1 and detectivity of 3.7 × 1014 Jones at quite a low Vds of 1 V, which is more competitive than those of the reported organic photodetectors and phototransistors. The work provides an avenue to improve the electrical and optoelectronic properties of 2D organic devices by introducing 2D metals with appropriate work function for vdW contacts.

Two-Dimensional van der Waals Materials with Aligned In-Plane Polarization and Large Piezoelectric Effect for Self-Powered Piezoelectric Sensors.

Piezoelectric two-dimensional (2D) van der Waals (vdWs) materials are highly desirable for applications in miniaturized and flexible/wearable devices. However, the reverse-polarization between adjacent layers in current 2D layered materials results in decreasing their in-plane piezoelectric coefficients with layer number, which limits their practical applications. Here, we report a class of 2D layered materials with an identical orientation of in-plane polarization. Their piezoelectric coefficients (e22) increase with layer number, thereby allowing for the fabrication of flexible piezotronic devices with large piezoelectric responsivity and excellent mechanical durability. The piezoelectric outputs can reach up to 0.363 V for a 7-layer α-In2Se3 device, with a current responsivity of 598.1 pA for 1% strain, which is 1 order of magnitude higher than the values of the reported 2D piezoelectrics. The self-powered piezoelectric sensors made of these newly developed 2D layered materials have been successfully used for real-time health monitoring, proving their suitability for the fabrication of flexible piezotronic devices due to their large piezoelectric responses and excellent mechanical durability.

PEGylated Tantalum Nanoparticles: A Metallic Photoacoustic Contrast Agent for Multiwavelength Imaging of Tumors.

Elemental tantalum is a well-known biomedical metal in clinics due to its extremely high biocompatibility, which is superior to that of other biomedical metallic materials. Hence, it is of significance to expand the scope of biomedical applications of tantalum. Herein, it is reported that tantalum nanoparticles (Ta NPs), upon surface modification with polyethylene glycol (PEG) molecules via a silane-coupling approach, are employed as a metallic photoacoustic (PA) contrast agent for multiwavelength imaging of tumors. By virtue of the broad optical absorbance from the visible to near-infrared region and high photothermal conversion efficiency (27.9%), PEGylated Ta NPs depict high multiwavelength contrast capability for enhancing PA imaging to satisfy the various demands (penetration depth, background noise, etc.) of clinical diagnosis as needed. Particularly, the PA intensity of the tumor region postinjection is greatly increased by 4.87, 7.47, and 6.87-fold than that of preinjection under 680, 808, and 970 nm laser irradiation, respectively. In addition, Ta NPs with negligible cytotoxicity are capable of eliminating undesirable reactive oxygen species, ensuring the safety for biomedical applications. This work introduces a silane-coupling strategy for the surface engineering of Ta NPs, and highlights the potential of Ta NPs as a biocompatible metallic contrast agent for multiwavelength photoacoustic image.

Enhanced Light Emission from the Ridge of Two-Dimensional InSe Flakes.

InSe, a newly rediscovered two-dimensional (2D) semiconductor, possesses superior electrical and optical properties as a direct-band-gap semiconductor with high mobility from bulk to atomically thin layers and is drastically different from transition-metal dichalcogenides, in which the direct band gap only exists at the single-layer limit. However, absorption in InSe is mostly dominated by an out-of-plane dipole contribution, which results in the limited absorption of normally incident light that can only excite the in-plane dipole at resonance. To address this challenge, we have explored a unique geometric ridge state of the 2D flake without compromising the sample quality. We observed the enhanced absorption at the ridge over a broad range of excitation frequencies from photocurrent and photoluminescence (PL) measurements. In addition, we have discovered new PL peaks at low temperatures due to defect states on the ridge, which can be as much as ∼60 times stronger than the intrinsic PL peak of InSe. Interestingly, the PL of the defects is highly tunable through an external electrical field, which can be attributed to the Stark effect of the localized defects. InSe ridges thus provide new avenues for manipulating light-matter interactions and defect engineering that are vitally crucial for novel optoelectronic devices based on 2D semiconductors.

Liquid Exfoliation of Colloidal Rhenium Disulfide Nanosheets as a Multifunctional Theranostic Agent for In Vivo Photoacoustic/CT Imaging and Photothermal Therapy.

Near-infrared light-mediated theranostic agents with superior tissue penetration and minimal invasion have captivated researchers in cancer research in the past decade. Herein, a probe sonication-assisted liquid exfoliation approach for scalable and continual synthesis of colloidal rhenium disulfide nanosheets, which is further explored as theranostic agents for cancer diagnosis and therapy, is reported. Due to high-Z element of Re (Z = 75) and significant photoacoustic effect, the obtained PVP-capped ReS2 nanosheets are evaluated as bimodality contrast agents for computed tomography and photoacoustic imaging. In addition, utilizing the strong near-infrared absorption and ultrahigh photothermal conversion efficiency (79.2%), ReS2 nanosheets could also serve as therapeutic agents for photothermal ablation of tumors with a tumor elimination rate up to 100%. Importantly, ReS2 nanosheets show no obvious toxicity based on the cytotoxicity assay, serum biochemistry, and histological analysis. This work highlights the potentials of ReS2 nanosheets as a single-component theranostic nanoplatform for bioimaging and antitumor therapy.

Unraveling the Raman Enhancement Mechanism on 1T'-Phase ReS2 Nanosheets.

2D transition metal dichalcogenides materials are explored as potential surface-enhanced Raman spectroscopy substrates. Herein, a systematic study of the Raman enhancement mechanism on distorted 1T (1T') rhenium disulfide (ReS2 ) nanosheets is demonstrated. Combined Raman and photoluminescence studies with the introduction of an Al2 O3 dielectric layer unambiguously reveal that Raman enhancement on ReS2 materials is from a charge transfer process rather than from an energy transfer process, and Raman enhancement is inversely proportional while the photoluminescence quenching effect is proportional to the layer number (thickness) of ReS2 nanosheets. On monolayer ReS2 film, a strong resonance-enhanced Raman scattering effect dependent on the laser excitation energy is detected, and a detection limit as low as 10-9 m can be reached from the studied dye molecules such as rhodamine 6G and methylene blue. Such a high enhancement factor achieved through enhanced charge interaction between target molecule and substrate suggests that with careful consideration of the layer-number-dependent feature and excitation-energy-related resonance effect, ReS2 is a promising Raman enhancement platform for sensing applications.

Up-regulation of receptor interaction protein 140 promotes glucolipotoxicity-induced damage in MIN6 cells.

The receptor interaction protein 140 (RIP140) cofactor is a key regulator of metabolic balance, but its function in glucose- and lipid-mediated damage in islet ß cells is unknown and was investigated in this study. RIP140 expression and distribution was evaluated in MIN6 cells under high glucose and lipid conditions using real-time Polymerase Chain Reaction (PCR), western blotting and confocal laser scanning microscopy. Cells were separately treated with 500 µM palmitic acid and 25 mM glucose when RIP140 expression was upregulated or downregulated, and cell viability, apoptosis rate, the level of oxidative stress and insulin secretion was assessed, as was the expression of related genes. Increased glucose and palmitic acid elevated RIP140 expression and distribution in nuclei. Overexpression of RIP140 promoted apoptosis but inhibited cell viability in MIN6 cells, and basal insulin secretion and glucose-stimulated insulin secretion levels were altered following treatment with glucose and palmitic acid. In addition, oxidative stress was elevated, phosphorylated extracellular signal-regulated kinases 1/2 and uncoupling protein 2 messenger RNA (mRNA) abundance were increased, B-cell lymphoma-2 protein levels were decreased, and peroxisome proliferators activated receptor gamma co-activator 1 alpha, phosphoenolpyruvate carboxykinase , and pancreatic and duodenal homeobox-1 mRNA levels were downregulated. Furthermore, glucolipotoxicity-induced damage was reversed when RIP140 expression was downregulated by small interfering RNA (SiRNA). RIP140 promotes islet ß cells damage caused by glucolipotoxicity.

[Understanding of and attitude towards sperm donation among males in Shandong Province and their influencing factors and countermeasures].

Objective: To investigate the understanding of and attitude towards sperm donation among males of the right age in Shandong Province a provide some reference for improving the propaganda for sperm donation and the recruitment of sperm donors. Methods: We conducted a questionnaire survey among the male students and other men of the right age for sperm donation in the three cities of Shandong Province, Jinan, Qingdao and Yantai, with the questionnaires distributed randomly and filled in anonymously on the spot. Then we performed statistical analysis on the 2 000 valid copies collected. Results: Among the 2 000 males, only 227(11. 35%) accepted sperm donation,997(49. 85%) knew that sperm donation was harmless to health, and merely 9. 95% had donated or considered donating sperm. The misgivings about sperm donation mainly included possible ethical problems, personal privacy, the complicated procedure, and high requirements. Conclusion: Most males of the right age have misgivings about sperm donation. The propaganda for sperm donation in Shandong human sperm banks are relatively monotonous and needs to be improved.

Hierarchical ß-Mo2 C Nanotubes Organized by Ultrathin Nanosheets as a Highly Efficient Electrocatalyst for Hydrogen Production.

Production of hydrogen by electrochemical water splitting has been hindered by the high cost of precious metal catalysts, such as Pt, for the hydrogen evolution reaction (HER). In this work, novel hierarchical ß-Mo2 C nanotubes constructed from porous nanosheets have been fabricated and investigated as a high-performance and low-cost electrocatalyst for HER. An unusual template-engaged strategy has been utilized to controllably synthesize Mo-polydopamine nanotubes, which are further converted into hierarchical ß-Mo2 C nanotubes by direct carburization at high temperature. Benefitting from several structural advantages including ultrafine primary nanocrystallites, large exposed surface, fast charge transfer, and unique tubular structure, the as-prepared hierarchical ß-Mo2 C nanotubes exhibit excellent electrocatalytic performance for HER with small overpotential in both acidic and basic conditions, as well as remarkable stability.