Laser-induced the enhancement of Raman scattering performance in WO3-x/Ag composite films.

Non-stoichiometric tungsten oxide (WO3-x) has controllable defects, high charge density, and good synergy with other materials to exhibit good surface-enhanced Raman scattering (SERS) properties. Its heterojunction structure provides an opportunity to develop high-quality and low-cost SERS substrates. This study obtained WO3-x/Ag composite thin films were obtained by Nd: YAG fiber pulsed laser modification at ambient conditions. The effects of interactions between heterojunctions and laser modification on the samples' morphology, composition, and optical properties were investigated. The absorption peaks exhibited a red shift by varying the laser scan speeds, and the SERS properties of the sample were evaluated by methylene blue (MB) dye. The results show that the laser-modified WO3-x/Ag films have good stability as SERS substrates. The characteristic peaks of MB can still be detected after 90 days in the air. The WO3-x/Ag films also have good homogeneity and a low detection limit, with a limit of detection (LOD) as low as 10-7 M, and an enhancement factor as high as 1.34 × 104. The simulated results by the finite difference in time domain (FDTD) showed substantial agreement with those of the experimental ones.

From defects to catalysis: mechanism and optimization of NO electroreduction synthesis of NH3.

Ammonia (NH3) is a crucial industrial raw material, but the traditional Haber-Bosch process is energy-intensive and highly polluting. Electrochemical methods for synthesizing ammonia using nitric oxide (NO) as a precursor offer the advantages of operating under ambient conditions and achieving both NO reduction and resource utilization. Defect engineering enhances electrocatalytic performance by modulating electronic structures and coordination environments. In this brief review, the catalytic reaction mechanism of electrocatalytic NO reduction to NH3 is elucidated, with a focus on synthesis strategies involving vacancy defects and doping defects. From this perspective, the latest advances in various catalytic reduction systems for nitric oxide reduction reaction (NORR) are summarized and synthesized. Finally, the research prospects for NO reduction to NH3 are discussed.

Fracture Mechanisms and Crack Propagation in Monolayer Ti3C2Tx under Nanoindentation: The Influence of Surface Terminations and Vacancy Defects.

Monolayer MXenes are a novel class of two-dimensional transition metal carbides/nitrides with fascinating physicochemical properties. Despite recent advances in the study of MXenes' mechanical properties, a comprehensive understanding of the fundamental physical mechanisms that affect fracture due to surface terminations and vacancy defects in MXenes under nanoindentation remains largely unexplored. Here, we address this gap using molecular dynamics simulations and nanoindentation theory to investigate the effects of surface terminations and vacancy defects on the fracture behavior of Ti3C2Tx MXenes. By inducing the rupture of monolayer MXenes through nanoindentation, we find that bare Ti3C2 exhibits brittle fracture behavior. The presence of surface terminations and vacancy defects reduces the load-carrying capacity and flexibility of MXenes. Interestingly, surface terminations increase the stiffness of the structure, while vacancy defects have the opposite effect. We also find that high concentrations of surface oxidation impart ductile fracture characteristics to MXenes and increase the maximum crack length at failure. Additionally, defects exceeding the critical concentration can effectively prevent brittle crack propagation by causing frequent crack deflection and blunting crack tips. Combining these findings, we propose a new strategy to synergistically enhance the fracture toughness of MXenes through high concentrations of surface oxidation and vacancy defects exceeding the critical concentration without significantly affecting strength and stiffness, thereby avoiding catastrophic failure in MXene monolayers due to brittle fracture. This work provides fundamental insights into the mechanical properties and fracture mechanisms of monolayer MXenes.

Effect of strain on the photoelectric properties of molybdenum ditelluride under vacancy defects: a DFT investigation.

CONTEXT: This study explores the impact of deformation on the electrical and optical characteristics of monolayer cadmium telluride (MoTe2) with vacancies, using the foundational principles of density functional theory. It was discovered that both strain and imperfections alter the electrical characteristics of monolayer MoTe2. Under VTe-MoTe2, a direct-to-indirect band-gap transition occurs. In DTe-MoTe2, the band-gap value reduces dramatically, the conduction band changes downward, and the carrier concentration rises. The DVTe-induced band gap state is closer to the Fermi energy level than the VTe-induced band gap state. In this paper, DTe-MoTe2 is chosen for tensile deformation. The results show that the band-gap value tends to decrease by increasing tensile deformation. When the stretching value reaches 10%, the lower bound of the conduction band and the top of the valence band overlap, and the system is converted from a semiconductor to a metal. Considering the density of states, the missing state MoTe2 is mainly contributed by the participation of Te-s, Te-p, and Mo-d orbitals. In terms of optical qualities, the absorption and reflection peaks are red-shifted and blue-shifted, respectively. It is hoped that these effects on the optoelectronic properties will be widely applied. METHODS: In this study, we utilize the generalized gradient approximation plane-wave pseudopotential method, incorporating Perdew-Burke Ernzerhof (PBE) generalized functions and following the fundamental principles of the density functional theory framework. A 3 × 3 × 1 supercell was constructed as an undoped model based on a MoTe2 monolayer, which consists of 9 Mo atoms and 18 Te atoms. The vacuum flat plate was set to 15 Å along the z-direction to avoid interactions between the monolayers. For electronic structure calculations, the energy cutoff was set to 450 eV. Each model's computational process and structural optimization were carried out using the Monkhorst-Pack specialized K-point sampling approach. Crystal optimization computations used a 3 × 3 × 1 Monkhorst-Pack K-point grid for molybdenum ditelluride monolayers and a 9 × 9 × 1 K-point grid for electronic system analysis, analyzing state density and optical characteristics, respectively. For the structural optimization, the convergence requirements for maximum force, maximum atom displacement, maximum stress, and energy change were defined at 0.03 eV/Å, 0.001 Å, 0.05 Gpa, and 1.0 × 10-5 eV/atom, respectively.

Effects of vacancy defects and atomic doping on the electronic and magnetic properties of puckered penta-like PdPSe monolayer: anAb initiostudy.

The experimental knowledge of two-dimensional penta-like PdPSe monolayer is largely based on a recent publication (Liet al2021Adv. Mater. 2102541). Therefore, the aim of our research is consequently to explore the effect of vacancy defects and substitutional doping on the electronic properties of the novel penta-PdPSe monolayer by using first-principles calculations. Penta-like PdPSe is a semiconductor with an indirect bandgap of 1.40 eV. We show that Pd and Se vacancy defected structures are semiconductors with band gaps of 1.10 eV and 0.95 eV respectively. While P single vacancy and double vacancy defected structures are metals. The doping with Ag (at Pd site) and Si (at P site) convert the PdPSe to nonmagnetic metallic monolayer while the doping with Rh (at Pd site), Se (at P site) and As (at site Se) convert it to diluted magnetic semiconductors with the magnetic moment of 1µB. The doping with Pt (at the Pd site), As (at the P site), S and Te (at Se site) are indirect semiconductors with a bandgap of ∼1.2 eV. We undertook this theoretical study to inspire many experimentalists to focus on penta-like PdPSe monolayer growth incorporating different impurities and by defect engineering to tune the novel two dimensional materials (PdPSe) properties for the advanced nanoelectronic application.

Phonon transport in vacancy induced defective stanene/hBN van der Waals heterostructure.

In this study, Non-Equilibrium Molecular Dynamics (NEMD) simulation is employed to investigate the phonon thermal conductivity (PTC) of Sn/hBN van der Waals heterostructures with different vacancy-induced defects. We deliberately introduce three types of vacancies in Sn/hBN bilayer point vacancies, bivacancies, and edge vacancies at various concentrations ranging from 0.25% to 2%, to examine their effects on PTC across temperatures from 100 K to 600 K. The key findings of our work are (i) PTC declines monotonically with increasing vacancy concentration for all types of vacancies, with a maximum reduction of ∼62% observed at room temperature compared to its pristine form. (ii) The position of defects has an impact on PTC, with a larger decrease observed when defects are present in the hBN layer and a smaller decrease when defects are in the Sn layer. (iii) The type of vacancy also influences PTC, with point vacancies causing the most substantial reduction, followed by bivacancies, and edge vacancies having the least effect. A 2% defect concentration results in a ∼62% decrease in PTC for point vacancies, ∼51% for bivacancies, and ∼32% for edge vacancies. (iv) Finally, our results indicate that for a given defect concentration, PTC decreases as temperature increases. The impact of temperature on thermal conductivity is less pronounced compared to the effect of vacancies for the defective Sn/hBN bilayer. The presence of vacancies and elevated temperatures enhance phonon-defect and phonon-phonon scattering, leading to changes in the phonon density of states (PDOS) profile and the distribution of phonons across different frequencies of Sn/hBN bilayer, thus affecting its thermal conductivity. This work offers new insights into the thermal behavior of vacancy-filled Sn/hBN heterostructures, suggesting potential pathways for modulating thermal conductivity in bilayer van der Waals heterostructures for applications in thermoelectric, optoelectronics, and nanoelectronics in future.

Stereochemically Active Lone Pairs Stabilizing Intrinsic Vacancy Defects in Thermoelectric InTe.

Harvesting waste heat efficiently with thermoelectric energy conversion requires materials with low thermal conductivity. Recently, it was demonstrated how dynamic lone pair expression in thermoelectric InTe is responsible for giant anharmonicity leading to a very low lattice thermal conductivity. InTe also contains correlated disorder of intrinsic defects due to vacancies, and this contributes to additional lowering of the thermal conductivity. Here we use the three-dimensional difference pair distribution function (3D-ΔPDF) to analyze 25 K single crystal diffuse X-ray scattering from InTe to unravel the local defect structure, and propose a microscopic structural model. Extended off-centering of In+ ions induced by vacancies allows for the local expression of stereochemically active lone pairs. The associated electronic stabilization is proposed to be a driving force for the formation of In+ vacancy defects in InTe.

Ruthenium Single Atomic Sites Surrounding the Support Pit with Exceptional Photocatalytic Activity.

Single-metal atomic sites and vacancies can accelerate the transfer of photogenerated electrons and enhance photocatalytic performance in photocatalysis. In this study, a series of nickel hydroxide nanoboards (Ni(OH)x NBs) with different loadings of single-atomic Ru sites (w-SA-Ru/Ni(OH)x) were synthesized via a photoreduction strategy. In such catalysts, single-atomic Ru sites are anchored to the vacancies surrounding the pits. Notably, the SA-Ru/Ni(OH)x with 0.60 wt % Ru loading (0.60-SA-Ru/Ni(OH)x) exhibits the highest catalytic performance (27.6 mmol g-1 h-1) during the photocatalytic reduction of CO2 (CO2RR). Either superfluous (0.64 wt %, 18.9 mmol g-1 h-1; 3.35 wt %, 9.4 mmol-1 h-1) or scarce (0.06 wt %, 15.8 mmol g-1 h-1; 0.29 wt %, 21.95 mmol g-1 h-1; 0.58 wt %, 23.4 mmol g-1 h-1) of Ru sites have negative effect on its catalytic properties. Density functional theory (DFT) calculations combined with experimental results revealed that CO2 can be adsorbed in the pits; single-atomic Ru sites can help with the conversion of as-adsorbed CO2 and lower the energy of *COOH formation accelerating the reaction; the excessive single-atomic Ru sites occupy vacancies that retard the completion of CO2RR.

Disclosing the intrinsic nature of efficient removal of antibiotics in N/S dual-doped porous carbon-based materials: The manipulation of internal electric field.

N/S co-doping has emerged as a prevailing strategy for carbon-based adsorbents to facilitate the antibiotic removal efficiency. Nevertheless, the underlying interplay among N, S, and their adjacent vacancy defects remains overlooked. Herein, we present a novel in situ strategy for fabricating pyridinic-N dominated and S dual-doped porous carbon adsorbent with rich vacancy defects (VNSC). The experimental results revealed that N (acting as the electron donor) and S (acting as the electron acceptor) form an internal electric field (IEF), with a stronger IEF generated between pyridinic-N and S, while their adjacent vacancy defects activate carbon π electrons, thus enhancing the charge transfer of the IEF. Density functional theory (DFT) calculations further demonstrated that the rich charge transfer in the IEF facilitated the π-π electron donor-acceptor (EDA) interaction between VNSC and tetracycline (TC) as well as norfloxacin (NOR), and thus is the key to adsorption performance of VNSC. Consequently, VNSC exhibited high adsorption capacities toward TC (573.1 mg g-1) and NOR (517.0 mg g-1), and its potential for environmental applications was demonstrated by interference, environmentally relevant concentrations, fixed-bed column, and regeneration tests. This work discloses the natures of adsorption capacity for N/S dual-doped carbon-based materials for antibiotics.

Efficient detection of 45 ppb ammonia at room temperature using Ni-doped CeO2 octahedral nanostructures.

To meet the requirements in air quality monitors for the public and industrial safety, sensors are required that can selectively detect the concentration of gaseous pollutants down to the parts per million (ppm) and ppb (parts per billion) levels. Herein, we report a remarkable NH3 sensor using Ni-doped CeO2 octahedral nanostructure which efficiently detects NH3 as low as 45 ppb at room temperature. The Ni-doped CeO2 sensor exhibits the maximum response of 42 towards 225 ppm NH3, which is ten-fold higher than pure CeO2. The improved sensing performance is caused by the enhancement of oxygen vacancy, bandgap narrowing, and redox property of CeO2 caused by Ni doping. Density functional theory confirms that O vacancy with Ni at Ce site (VONiCe) augments the sensing capabilities. The Bader charge analysis predicts the amount of charge transfer (0.04 e) between the Ni-CeO2 surface and the NH3 molecule. As well, the high negative adsorption energy (≈750 meV) and lowest distance (1.40 Å) of the NH3 molecule from the sensor surface lowers the detection limit. The present work enlightens the fabrication of sensing elements through defect engineering for ultra-trace detection of NH3 to be useful further in the field of sensor applications.

Oxygen Vacancy Defect Enhanced NIR-II Photothermal Performance of BiOxCl Nanosheets for Combined Phototherapy of Cancer Guided by Multimodal Imaging.

Narrow photo-absorption range and low carrier utilization are significant barriers that restrict the antitumor efficiency of 2D bismuth oxyhalide (BiOX, X = Cl, Br, I) nanosheets (NSs). Introducing oxygen vacancy (OV) defects can expand the absorption range and improve carrier utilization, which are crucial but also challenging. In this study, a series of BiOxCl NSs with different OV defect concentrations (x = 1, 0.7, 0.5) is developed, which shows full spectrum absorption and strong absorption in the second near-infrared region (NIR-II). Density functional theory calculations are utilized to calculate the crystal structure and density states of BiOxCl, which confirm that part of the carriers is separated by OV enhanced internal electric field to improve carrier utilization. The carriers without redox reaction can be trapped in the OV, leading to great majority of photo-generated carriers promoting the photothermal performance. Triggered by single NIR-II (1064 nm), BiOxCl NSs' bidirectional efficient utilization of carriers achieves synchronously combined phototherapy, leading to enhanced tumor ablation and multimodal diagnostic in vitro and vivo. It is thus believed that this work provides an innovative strategy to design and construct nanoplatforms of indirect band gap semiconductors for clinical phototheranostics.

Ascorbic Acid Induced the Improved Oxygen Vacancy Defects of Bi4O5Br2 and Its Application on Photoelectrochemical Detection of DNA Demethylase MBD2 with Improved Detection Sensitivity.

Oxygen vacancy defects (OVs) are one of the main strategies for nanomaterials modification to improve the photoactivity, but current methods for fabricating OVs are usually complicated and harsh. It is important to develop simple, rapid, safe, and mild methods to fabricate OVs. By studying the effects of different weak reducing agents, the concentration of the reducing agent and the reaction time on fabrication of OVs, it is found that L-ascorbic acid (AA) gently and rapidly induces the increase of OVs in Bi4O5Br2 at room temperature. The increased OVs not only improve the adsorption of visible light, but also enhance the photocurrent response. Based on this, the preparation of OVs in Bi4O5Br2 is employed to the development of a photoelectrochemical biosensor for the detection of DNA demethylase of methyl-CpG binding domain protein 2 (MBD2). The biosensor shows a wide linear range of 0.1-400 ng mL-1 and a detection limit as low as 0.03 ng mL-1 (3σ). In addition, the effect of plasticizers on MBD2 activity is evaluated using this sensor. This work not only provides a novel method to prepare OVs in bismuth rich materials, but also explores a new novel evaluation tool for studying the ecotoxicological effects of contaminants.

Effect of doping and defects on the optoelectronic properties of ZrSe2 based on the first principle.

CONTEXT: Based on the first principles under the framework of density functional theory, it calculates the effect of vacancy defects in single Zr and single Se atoms and the replacement of Se atoms in ZrSe2 with O, Se, and Te atoms on the optoelectronic properties of monolayer ZrSe2, including geometry, energy band structure, electronic density of states, and optical properties. The doping of the three non-metallic atoms was n-type doping for the O and S atoms and p-type doping for the Te atom. Defects in the Zr atoms and O-atom doping significantly affect the peak reflectance and absorption coefficient of the ZrSe2 system. METHODS: All Density Functional Theory calculations were carried out using the CASTEP module in the Materials-Studio (MS) software. The generalized gradient approximation plane-wave pseudopotential method and the Perdew-Burke-Ernzerfhof (PBE) generalized function were used for structural optimization and total energy calculation of the defect and doping systems. After convergence tests, the plane wave truncation energy was set to 500 eV, and the Brillouin zone K-point grid was set to 4 × 4 × 1. The atomic energy convergence criterion is 1.0 × 10-6 eV/atom, the interatomic interaction force convergence criterion is 0.02 eV/Å, the maximum atomic displacement convergence criterion is 0.001 Å, and the internal crystal stress convergence criterion is 0.05 GPa. In order to avoid the influence of the interaction forces between the layers, a vacuum layer of 15 Å is placed in the Z-axis direction.

The Controllable Mechanical Properties of Coiled Carbon Nanotubes with Stone-Wales and Vacancy Defects.

Coiled carbon nanotubes (CCNTs) as a promising nanometer scale spring are investigated for the effect of the defects on the tensile mechanical properties of CCNTs by using molecular dynamics (MD) simulations. Six samples of defective CCNTs are constructed by introducing the defects in the different positions. The results show an obvious decrease in the spring constant and elastic limit of defective CCNTs, which results in the lower energy storage ability during the elastic range compared with the perfect CCNTs. However, the defected CCNTs exhibit better ductility (138.9%) and higher energy absorbing ability (1539.93 J/g) during the fracture process since introduced defects change the deformation pattern. Furthermore, among the defected CCNTs, the stiffness (1.48~1.93 nN/nm), elastic limit (75.2~88.7%), ductility (108.5~138.9%), and deformation pattern can be adjusted by changing the position or the type of defects. This study firstly provides insight into the effects of Stone-Wales (SW) and vacancy defects on the mechanical properties of CCNTs, and the obtained results are meaningful for designing CCNTs with specified properties by introducing defects.

Deciphering Vacancy Defect Evolution of 2D MoS2 for Reliable Transistors.

Two-dimensional (2D) MoS2 is an excellent candidate channel material for next-generation integrated circuit (IC) transistors. However, the reliability of MoS2 is of great concern due to the serious threat of vacancy defects, such as sulfur vacancies (VS). Evaluating the impact of vacancy defects on the service reliability of MoS2 transistors is crucial, but it has always been limited by the difficulty in systematically tracking and analyzing the changes and effects of vacancy defects in the service environment. Here, a simulated initiator is established for deciphering the evolution of vacancy defects in MoS2 and their influence on the reliability of transistors. The results indicate that VS below 1.3% are isolated by slow enrichment during initiation. Over 1.3% of VS tend to enrich in pairs and over 3.5% of the enriched VS easily evolve into nanopores. The enriched VS with electron doping in the channel cause the threshold voltage (Vth) negative drift approaching 6 V, while the expanded nanopores initiate the Vth roll-off and punch-through of transistors. Finally, sulfur steam deposition has been proposed to constrain VS enrichment, and reliable MoS2 transistors are constructed. Our research provides a new method for deciphering and identifying the impact of defects.

Self-Assembled 1D/3D Perovskite Heterostructure for Stable All-Air-Processed Perovskite Solar Cells with Improved Open-Circuit Voltage.

Environmental instability and photovoltage loss induced by defects are inevitable obstacles in the development of all-air-processed perovskite solar cells (PSCs). In this study, the ionic liquid 1-ethyl-3-methylimidazolium iodide ([EMIM]I) is introduced into the hole transport layer/three-dimensional (3D) perovskite interface to form a self-assembled 1D/3D perovskite heterostructure, which significantly reduces iodine vacancy defects and modulates band energy alignment, resulting in pronouncedly improved open-circuit voltage (Voc ). As a result, the corresponding device exhibits a high power conversion efficiency with negligible hysteresis and a high Voc of 1.14 V. Most importantly, together with the high stability of the 1D perovskite, remarkable high environmental and thermal stabilities of the 1D/3D PSC devices are achieved, which maintain 89 % of unencapsulated device initial efficiency after 1320 h in air and retain 85 % of the initial efficiency when heated at 85 °C for 22 h. This study affords an effective strategy to fabricate high-performance all-air-processed PSCs with outstanding stability.

Pt single atoms and defect engineering of TiO2-nanosheet-assembled hierarchical spheres for efficient room-temperature HCHO oxidation.

Achieving high atomic utilization and low cost of desirable Pt/TiO2 catalysts is a major challenge for room temperature HCHO oxidation. Here, the strategy of anchoring stable Pt single atoms by abundant oxygen vacancies over TiO2-nanosheet-assembled hierarchical spheres (Pt1/TiO2-HS) was designed to eliminate HCHO. A superior HCHO oxidation activity and CO2 yield (∼100% CO2 yield) at relative humidity (RH) > 50% over Pt1/TiO2-HS is achieved for long-term run. We attribute the excellent HCHO oxidation performance to the stable isolated Pt single atoms anchored on the defective TiO2-HS surface. The Ptδ+ on the Pt1/TiO2-HS surface has a facile intense electron transfer with the support by forming Pt-O-Ti linkages, driving HCHO oxidation effectively. Further in situ HCHO-DRIFTS revealed that the dioxymethylene (DOM) and HCOOH/HCOO- intermediates were further degraded via active OH- and adsorbed oxygen on the Pt1/TiO2-HS surface, respectively. This work may pave the way for the next generation of advanced catalytic materials for high-efficiency catalytic HCHO oxidation at room temperature.

Effect of vacancy defect and strain on the structural, electronic and magnetic properties of carbon nitride 2D monolayers by DFTB method.

We investigate the electronic and magnetic properties of CnNm(C6N6, C2N, C3N and C3N4) using density functional tight-binding (DFTB) method. We find that these compounds are dynamically stable and their electronic band gaps are in the range of 0.59-3.28 eV. We show that the electronic structure is modulated by strain and the semiconducting behavior is well preserved except for C3N at +5% biaxial strain, where a transition from semiconductor to metal was observed. Under +3% biaxial strain, C3N4undergoes a transition from an indirect (K-Γ) to a direct (Γ-Γ) band gap. Moreover, band gap of C2N transforms from direct (Γ-Γ) to indirect (M-Γ) under +4% biaxial strain. However, no change in the nature of the band gap of C6N6. Further, when the studied materials under uniaxial tensile strain, their bandgaps reduce. Our theoretical study showed that an indirect-to-direct nature transition may occur for C6N6and for C3N4, which broadens their applications. On the other hand, magnetism is observed in all N-vacancy defected CnNm, which encourages its application in spintronic. Moreover, calculations of formation energies indicate that N-vacancy is energetically more favorable than C-vacancy in both C2N and C3N4. Opposite behavior found for C6N6and C3N.

Regulating Spin Polarization through Cationic Vacancy Defects in Bi4 Ti3 O12 for Enhanced Molecular Oxygen Activation.

Molecular oxygen (O2 ) activation technology is of great significance in environmental purification due to its eco-friendly operation and cost-effective nature. However, the activation of O2 is limited by spin-forbidden transitions, and efficient molecular oxygen activation depends on electronic behavior and surface adsorption. Herein, we prepared cationic defect-rich Bi4 Ti3 O12 (BTO-MV2) catalysts containing Ti vacancies (VTi ) for O2 activation in water purification. The VTi on BTO nanosheets can induce electron spin polarization, increasing the number of spin-down photogenerated electrons and reducing the recombination of electron-hole pairs. An active surface VTi is also formed, serving as a center for adsorbing O2 and extracting electrons, effectively generating ⋅OH, O2 ⋅- and 1 O2 . The degradation rate constant of tetracycline achieved by BTO-MV2 is 3.3 times faster than BTO, indicating a satisfactory prospect for practical application. This work provides an efficient pathway to activate molecular oxygen by constructing new active sites through cationic vacancy modification technology.

Facile and Scalable Mechanochemical Synthesis of Defective MoS2 with Ru Single Atoms Toward High-Current-Density Hydrogen Evolution.

Designing a facile strategy to prepare catalysts with highly active sites are challenging for large-scale implementation of electrochemical hydrogen production. Herein, a straightforward and eco-friendly method by high-energy mechanochemical ball milling for mass production of atomic Ru dispersive in defective MoS2 catalysts (Ru1 @D-MoS2 ) is developed. It is found that single atomic Ru doping induces the generation of S vacancies, which can break the electronic neutrality around Ru atoms, leading to an asymmetrical distribution of electrons. It is also demonstrated that the Ru1 @D-MoS2 exhibits superb alkaline hydrogen evolution enhancement, possibly attributing to this electronic asymmetry. The overpotential required to deliver a current density of 10 mA cm-2 is as low as 107 mV, which is much lower than that of commercial MoS2 (C-MoS2 , 364 mV). Further density functional theory (DFT) calculations also support that the vacancy-coupled single Ru enables much higher electronic distribution asymmetry degree, which could regulate the adsorption energy of intermediates, favoring the water dissociation and the adsorption/desorption of H*. Besides, the long-term stability test under 500 mA cm-2 further confirms the robust performance of Ru1 @D-MoS2 . Our strategy provides a promising and practical way towards large-scale preparation of advanced HER catalysts for commercial applications.