Stacking Faults Enabled Second Harmonic Generation in Centrosymmetric van der Waals RhI3.

Second harmonic generation (SHG) in van der Waals (vdW) materials has garnered significant attention due to its potential for integrated nonlinear optical and optoelectronic applications. Stacking faults in vdW materials are a typical kind of planar defect that introduces a degree of freedom to modulate the crystal symmetry and resultant SHG response. However, the physical origin and tunability of stacking-fault-governed SHG in vdW materials remain unclear. Here, taking the intrinsically centrosymmetric vdW RhI3 as an example, we theoretically reveal the origin of stacking-fault-governed SHG response, where the SHG response comes from the energetically favorable AC̅ stacking fault of which the electrical transitions along the high-symmetry paths Γ-M and Γ-K in the Brillion zone play the dominant role at 810 nm. Such a stacking-fault-governed SHG response is further confirmed via structural characterizations and SHG measurements. Furthermore, by applying hydrostatic pressure on RhI3, the correlation between structural evolution and SHG response is revealed with SHG enhancement up to 6.9 times, where the decreased electronic transition energies and higher momentum matrix elements due to the stronger interlayer interactions upon compression magnify the SHG susceptibility. This study develops a promising foundation for nonlinear nano-optics applications through the strategic design of stacking faults.

Out-of-plane Emission Dipole of Second Harmonic Generation in Odd- and Even-layered vdWs Janus Nb3SeI7.

Integration of atomically thin nonlinear optical (NLO) devices demands an out-of-plane (OP) emission dipole of second harmonic generation (SHG) to enhance the spontaneous emission for nanophotonics. However, the research on van der Waals (vdWs) materials with an OP emission dipole of SHG is still in its infancy. Here, by coupling back focal plane (BFP) imaging with numerical simulations and density functional theory (DFT) calculations, we demonstrate that vdWs Janus Nb3SeI7, ranging from bulk to the monolayer limit, exhibits a dominant OP emission dipole of SHG owing to the breaking of the OP symmetry. Explicitly, even-layered Nb3SeI7 with C6v symmetry is predicted to exhibit a pure OP emission dipole attributed to the only second-order susceptibility coefficient χzxx. Meanwhile, although odd-layered Nb3SeI7 with C3v symmetry has both OP and IP dipole components (χzxx and χyyy), the value of χzxx is 1 order of magnitude greater than that of χyyy, leading to an approximate OP emission dipole of SHG. Moreover, the crystal symmetry and OP emission dipole can be preserved under hydrostatic pressure, accompanied by the enhanced χzxx and the resulting 3-fold increase in SHG intensity. The reported stable OP dipole in 2D vdWs Nb3SeI7 can facilitate the rapid development of chip-integrated NLO devices.

Phase Transformation on Multilayer 2M-WS2 for Improved Surface-enhanced Raman Scattering.

In recent years, two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been widely recognized as an ideal platform for surface-enhanced Raman scattering (SERS). Given their rich structural phases, phase transformation in 2D TMDCs is an efficient strategy to tailor their SERS performance. In this paper, we present the great SERS performance of multilayer 2M-WS2 and then investigate the effect of its phase transformation on SERS performance. It is observed that multilayer 2M-WS2 nanosheets undergo a thermally induced single-crystal phase transition from 2M-WS2 to 2H-WS2 upon thermal annealing or laser treatment. Distinguishing from the commercially available pure 2H-WS2 (P-2H-WS2), 2H-WS2 obtained by annealing and laser treatment still retain SERS properties comparable to those of 2M-WS2, among which the detection limits for CV molecules (10-8 M) are 3 orders of magnitude lower than that of P-2H-WS2 and the Raman intensity enhancements are ∼10-37 times higher. In contrast to the charge transfer (CT) mechanism governed by the Fermi level in metallic-phase 2M-WS2, 2H-WS2 obtained by phase transition exhibits accelerated CT facilitated by the bandgap reduction and reorganization resulting from the abundance of vacancies. This study introduces an interesting perspective and potential avenue for enhancing SERS through metal-to-semiconductor phase transitions in 2D TMDCs materials.

Enzymatic Reaction Enhanced Diffusion Accelerates Cargo Transport through Micro/Nano-Channels.

Energy conversion and transfer of enzyme-catalyzed reactions at molecular level are an interesting and challenging scientific topic that helps understanding biological processes in nature. In this study, it is demonstrated that enzyme-catalyzed reactions can enhance diffusion of surrounding molecules and thus accelerate cargo transport within 1D micro/nanochannels. Specifically, urease is immobilized on the inner walls of silica micro/nano-tubes to construct bio-catalytically active micro/nanochannels. The catalytic reaction inside the channels drives a variety of cargoes, including small dye molecules, polymers, and rigid nanoparticles (e.g., quantum dots, QDs), to pass through these micro/nanochannels much faster than they will by free diffusion. The enhanced diffusion of molecular species inside the channels is validated by direct observation of the Brownian motion of tracer particles, and further confirmed by significantly enhanced Raman intensity of reporter molecules. Finite element and Brownian dynamics simulations provide a theoretical understanding of these experimental observations. Furthermore, the effect of the channels' size on the diffusion enhancement is examined. The acceleration effect of the cargo transport through these enzymatically active micro/nanochannels can be turned on or off via chemical activators or inhibitors. This study provides valuable insights on the design of biomimetic channels capable of controlled and efficient transmembrane transport.

Recent Advances of Aminopeptidases-Responsive Small-Molecular Probes for Bioimaging.

Aminopeptidases, enzymes with critical roles in human body, are emerging as vital biomarkers for metabolic processes and diseases. Aberrant aminopeptidase levels are often associated with diseases, particularly cancer. Small-molecule probes, such as fluorescent, fluorescent/photoacoustics, bioluminescent, and chemiluminescent probes, are essential tools in the study of aminopeptidases-related diseases. The fluorescent probes provide real-time insights into protein activities, offering high sensitivity in specific locations, and precise spatiotemporal results. Additionally, photoacoustic probes offer signals that are able to penetrate deeper tissues. Bioluminescent and chemiluminescent probes can enhance in vivo imaging abilities by reducing the background. This comprehensive review is focused on small-molecule probes that respond to four key aminopeptidases: aminopeptidase N, leucine aminopeptidase, Pyroglutamate aminopeptidase 1, and Prolyl Aminopeptidase, and their utilization in imaging tumors and afflicted regions. In this review, the design strategy of small-molecule probes, the variety of designs from previous studies, and the opportunities of future bioimaging applications are discussed, serving as a roadmap for future research, sparking innovations in aminopeptidase-responsive probe development, and enhancing our understanding of these enzymes in disease diagnostics and treatment.

Intercorrelated Ferroelectricity and Bulk Photovoltaic Effect in Two-Dimensional Sn2P2S6 Semiconductor for Polarization-Sensitive Photodetection.

A two-dimensional (2D) ferroelectric semiconductor, which is coupled with photosensitivity and room-temperature ferroelectricity, provides the possibility of coordinated conductance modulation by both electric field and light illumination and is promising for triggering the revolution of optoelectronics for monolithic multifunctional integration. Here, we report that semiconducting Sn2P2S6 crystals can be achieved in a 2D morphology using a chemical vapor transport approach with the assistant of space confinement and experimentally demonstrate the robust ferroelectricity in atomic-thin Sn2P2S6 nanosheet at room temperature. The intercorrelated programming of ferroelectric order along out-of-plane (OOP) and in-plane (IP) directions enables a tunable bulk photovoltaic (BPV) effect through multidirectional electrical control. By combining the capability of anisotropic in-plane optical absorption, a highly integrated Sn2P2S6 optoelectronic device vertically sandwiched with graphene electrodes yields the polarization-dependent open-circuit photovoltage with a dichroic ratio of 2.0 under 405 nm light illumination. The reintroduction of ferroelectric Sn2P2S6 to the 2D asymmetric semiconductor family provides possibilities to hardware implement of the self-powered polarization-sensitive photodetection and spotlights the promising applications for next-generation photovoltaic devices.

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.

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%.

Neuro-inspired optical sensor array for high-accuracy static image recognition and dynamic trace extraction.

Neuro-inspired vision systems hold great promise to address the growing demands of mass data processing for edge computing, a distributed framework that brings computation and data storage closer to the sources of data. In addition to the capability of static image sensing and processing, the hardware implementation of a neuro-inspired vision system also requires the fulfilment of detecting and recognizing moving targets. Here, we demonstrated a neuro-inspired optical sensor based on two-dimensional NbS2/MoS2 hybrid films, which featured remarkable photo-induced conductance plasticity and low electrical energy consumption. A neuro-inspired optical sensor array with 10 × 10 NbS2/MoS2 phototransistors enabled highly integrated functions of sensing, memory, and contrast enhancement capabilities for static images, which benefits convolutional neural network (CNN) with a high image recognition accuracy. More importantly, in-sensor trajectory registration of moving light spots was experimentally implemented such that the post-processing could yield a high restoration accuracy. Our neuro-inspired optical sensor array could provide a fascinating platform for the implementation of high-performance artificial vision systems.

Femtosecond Laser-Driven Phase Engineering of WS2 for Nano-Periodic Phase Patterning and Sub-ppm Ammonia Gas Sensing.

Laser-driven phase transition of 2D transition metal dichalcogenides has attracted much attention due to its high flexibility and rapidity. However, there are some limitations during the laser irradiation process, especially the unsatisfied surface ablation, the inability of nanoscale phase patterning, and the unexploited physical properties of new phase. In this work, the well-controlled femtosecond (fs) laser-driven transformation from the metallic 2M-WS2 to the semiconducting 2H-WS2 is reported, which is confirmed to be a single-crystal to single-crystal transition without layer thinning or obvious ablation. Moreover, a highly ordered 2H/2M nano-periodic phase transition with a resolution of ≈435 nm is achieved, breaking through the existing size bottleneck of laser-driven phase transition, which is attributed to the selective deposition of plasmon energy induced by fs laser. It is also demonstrated that the achieved 2H-WS2 after laser irradiation contains rich sulfur vacancies, which exhibits highly competitive ammonia gas sensing performance, with a detection limit below 0.1 ppm and a fast response/recovery time of 43/67 s at room temperature. This study provides a new strategy for the preparation of the phase-selective transition homojunction and high-performance applications in electronics.

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.

Two-dimensional semiconducting SnP2Se6 with giant second-harmonic-generation for monolithic on-chip electronic-photonic integration.

Two-dimensional (2D) layered semiconductors with nonlinear optical (NLO) properties hold great promise to address the growing demand of multifunction integration in electronic-photonic integrated circuits (EPICs). However, electronic-photonic co-design with 2D NLO semiconductors for on-chip telecommunication is limited by their essential shortcomings in terms of unsatisfactory optoelectronic properties, odd-even layer-dependent NLO activity and low NLO susceptibility in telecom band. Here we report the synthesis of 2D SnP2Se6, a van der Waals NLO semiconductor exhibiting strong odd-even layer-independent second harmonic generation (SHG) activity at 1550 nm and pronounced photosensitivity under visible light. The combination of 2D SnP2Se6 with a SiN photonic platform enables the chip-level multifunction integration for EPICs. The hybrid device not only features efficient on-chip SHG process for optical modulation, but also allows the telecom-band photodetection relying on the upconversion of wavelength from 1560 to 780 nm. Our finding offers alternative opportunities for the collaborative design of EPICs.

Synaptic plasticity realized by selective oxidation of TiS3 nanosheet for neuromorphic devices.

Memristive devices operating analogous to biology synapses demonstrate great potential for neuromorphic applications. Here, we reported the space-confined vapor synthesis of ultrathin titanium trisulfide (TiS3) nanosheets, and subsequent laser manufacturing of a TiS3-TiOx-TiS3 in-plane heterojunction for memristor applications. Due to the flux-controlled migration and aggregation of oxygen vacancies, the two-terminal memristor demonstrates reliable "analog" switching behaviors, in which the channel conductance can be incrementally adjusted by tuning the duration and sequence of programming voltage. The device allows the emulation of basic synaptic functions, featuring excellent linearity and symmetry in conductance change during long-term potentiation/depression processes. The small asymmetric ratio of 0.15 enables it to be integrated into a neural network for the pattern recognition task with a high accuracy of 90%. The results demonstrate the great potential of TiS3-based synaptic devices for neuromorphic applications.

Glioma-associated microglia/macrophages (GAMs) in glioblastoma: Immune function in the tumor microenvironment and implications for immunotherapy.

Glioma is a mixed solid tumor composed of neoplastic and non-neoplastic components. Glioma-associated macrophages and microglia (GAMs) are crucial elements of the glioma tumor microenvironment (TME), regulating tumor growth, invasion, and recurrence. GAMs are also profoundly influenced by glioma cells. Recent studies have revealed the intricate relationship between TME and GAMs. In this updated review, we provide an overview of the interaction between glioma TME and GAMs based on previous studies. We also summarize a series of immunotherapies targeting GAMs, including clinical trials and preclinical studies. Specifically, we discuss the origin of microglia in the central nervous system and the recruitment of GAMs in the glioma background. We also cover the mechanisms through which GAMs regulate various processes associated with glioma development, such as invasiveness, angiogenesis, immunosuppression, recurrence, etc. Overall, GAMs play a significant role in the tumor biology of glioma, and a better understanding of the interaction between GAMs and glioma could catalyze the development of new and effective immunotherapies for this deadly malignancy.

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.

Co-dependent regulation of p-BRAF and potassium channel KCNMA1 levels drives glioma progression.

BRAF mutations have been found in gliomas which exhibit abnormal electrophysiological activities, implying their potential links with the ion channel functions. In this study, we identified the Drosophila potassium channel, Slowpoke (Slo), the ortholog of human KCNMA1, as a critical factor involved in dRafGOF glioma progression. Slo was upregulated in dRafGOF glioma. Knockdown of slo led to decreases in dRafGOF levels, glioma cell proliferation, and tumor-related phenotypes. Overexpression of slo in glial cells elevated dRaf expression and promoted cell proliferation. Similar mutual regulations of p-BRAF and KCNMA1 levels were then recapitulated in human glioma cells with the BRAF mutation. Elevated p-BRAF and KCNMA1 were also observed in HEK293T cells upon the treatment of 20 mM KCl, which causes membrane depolarization. Knockdown KCNMA1 in these cells led to a further decrease in cell viability. Based on these results, we conclude that the levels of p-BRAF and KCNMA1 are co-dependent and mutually regulated. We propose that, in depolarized glioma cells with BRAF mutations, high KCNMA1 levels act to repolarize membrane potential and facilitate cell growth. Our study provides a new strategy to antagonize the progression of gliomas as induced by BRAF mutations.

A polarization-sensitive photothermoelectric photodetector based on mixed-dimensional SWCNT-MoS2 heterostructures.

Mixed-dimensional van der Waals (vdW) integration has been demonstrated to be effective for the modulation of the physical properties of homogeneous materials. Herein, we reported the enhancement of photothermal conversion and decrease of thermal conductivity in metallic single-walled carbon nanotube (SWCNT) films with the integration of chemical vapor deposition-grown monolayer MoS2 films. The induced temperature gradient in SWCNT-MoS2 hybrid films drives carrier diffusion to generate photocurrent via the photothermoelectric (PTE) effect, and a self-powered photodetector working in the visible band range from 405 to 785 nm was demonstrated. The maximum responsivity of the device increases by 6 times compared to that of the SWCNT counterpart. More importantly, the mixed-dimensional device exhibits polarization-dependent photogeneration, showing a large anisotropy ratio of 1.55. This work paves a way for developing high-performance, polarization-sensitive photodetectors by mixed-dimensional integration.

A medium-entropy transition metal oxide cathode for high-capacity lithium metal batteries.

The limited capacity of the positive electrode active material in non-aqueous rechargeable lithium-based batteries acts as a stumbling block for developing high-energy storage devices. Although lithium transition metal oxides are high-capacity electrochemical active materials, the structural instability at high cell voltages (e.g., >4.3 V) detrimentally affects the battery performance. Here, to circumvent this issue, we propose a Li1.46Ni0.32Mn1.2O4-x (0 < x < 4) material capable of forming a medium-entropy state spinel phase with partial cation disordering after initial delithiation. Via physicochemical measurements and theoretical calculations, we demonstrate the structural disorder in delithiated Li1.46Ni0.32Mn1.2O4-x, the direct shuttling of Li ions from octahedral sites to the spinel structure and the charge-compensation Mn3+/Mn4+ cationic redox mechanism after the initial delithiation. When tested in a coin cell configuration in combination with a Li metal anode and a LiPF6-based non-aqueous electrolyte, the Li1.46Ni0.32Mn1.2O4-x-based positive electrode enables a discharge capacity of 314.1 mA h g-1 at 100 mA g-1 with an average cell discharge voltage of about 3.2 V at 25 ± 5 °C, which results in a calculated initial specific energy of 999.3 Wh kg-1 (based on mass of positive electrode's active material).

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 .