Jiuxiang Dai

Nature, Published online: 25 March 2024; doi:10.1038/d41586-024-00832-z

This 2D material is only the second to exhibit the fractional quantum anomalous Hall effect, and theorists are still debating how it works.

MoS₂ Phototransistors with epitaxial ferroelectric (Hf_0.5Zr_0.5)O₂ as a gate dielectric layer are reported. Polarization-dependent ambipolar behavior is observed in the FETs, and relatively low power consumption and hysteresis-free loop are achieved in the FeFETs. The anomalous negative photoconductivity is observed as well with high responsivity of −8.44 × 10³ A W⁻¹. The photodetectors show great potential in the CMOS-compatible circuits for multifunctional devices.

Abstract

Ferroelectric field effect transistors (FeFETs), characterized by their low power consumption and polarization effect, can be employed in photodetectors based on 2D materials. In this paper, a MoS₂ phototransistor with epitaxial ferroelectric (Hf_0.5Zr_0.5)O₂ (HZO) is reported as a gate dielectric layer. Gate-dielectric-polarization-dependent ambipolar behavior is observed in the FET, and relatively low power consumption and hysteresis-free loop are achieved in the FeFET. The anomalous negative photoconductivity (NPC) is observed as well. Possible reasons for such phenomenon are clarified including the photogating effect originating from the interface traps and the polarization-dependent electric-field control through ferroelectric gating. The high responsivity of −8.44 × 10³ A W⁻¹ in the negative photoconductivity as well as the response time of 500 ms are reported. The demonstrated Molybdenum disulfide (MoS₂) FeFET photodetectors show great potential in the on-chip complementary metal-oxide semiconductor (CMOS)-compatible circuits for multifunctional devices.

A universal and sustainable process is developed for large-scale production of various 2D nanosheets of hexagonal boron nitride, graphene, molybdenum disulfide, and tungsten disulfide nanosheets with a yield of more than 90% and a large aspect ratio by combining mechanochemistry, supercritical CO2 and polystyrene. The nanosheets are rapidly peeled, fragmentation is prevented, and exfoliated 2D nanosheets display good properties.

Abstract

The 2D materials exhibit numerous technological applications, but their scalable production is a core challenge. Herein, ball milling exfoliation in supercritical carbon dioxide (scCO₂) and polystyrene (PS) is demonstrated to completely exfoliate hexagonal boron nitride nanosheets (BNNSs), graphene, molybdenum disulfide (MoS₂), and tungsten disulfide (WS₂). The exfoliation yield of 91%, 93%, 92%, and 92% and average aspect ratios of 743, 565, 564, and 502 for BNNSs, graphene, MoS₂, and WS_2, respectively, are achieved. Integrating exfoliated BNNSS in the polystyrene matrix, 3768 % thermal conductivity in the axial direction and 316% in the cross-plane direction at 12 wt.% loading is increased. Also, the in-plane and cross-plane electrical conductivity of 6.3 × 10⁻⁴ S m⁻¹ and 6.6 × 10⁻³ S m⁻¹, respectively, and the electromagnetic interference (EMI) of 63.3 dB is achieved by exfoliated graphene nanosheets based composite. High thermal and electrical conductivities and EMI shielding are attributed to the high aspect ratio and ultrathin morphology of the exfoliated nanosheets, which exert high charge mobility and form better the percolation network in the composite films due to their high surface area. The process demonstrate herein can produce substantial quantities of diverse 2D nanosheets for widespread commercial utilization.

A set of efficient dark blue room-temperature phosphorescent materials with tunable-lifetime have been prepared. The phosphorescence lifetime of the doped films can be continuously increased from 32.8 ms to 1925.8 ms. The reason is that the electron-donating ability of the substituent group can modulate the HOMO–LUMO and singlet-triplet energy gap, as well as the interactive force with methyl benzoate derivatives and polyvinyl alcohol.

Abstract

Tunable-lifetime room-temperature phosphorescence (RTP) materials have been widely studied due to their broad applications. However, only few reports have achieved wide-range lifetime modulation. In this work, ultra-wide range tunable-lifetime efficient dark blue RTP materials were realized by doping methyl benzoate derivatives into polyvinyl alcohol (PVA) matrix. The phosphorescence lifetimes of the doped films can be increased from 32.8 ms to 1925.8 ms. Such wide range of phosphorescence lifetime modulation is extremely rare in current reports. Moreover, the phosphorescence emission of the methyl 4-hydroxybenzoate-doped film is located in the dark blue region and the phosphorescence quantum yield reaches as high as 15.4 %, which broadens their applications in organic optoelectronic information. Further studies demonstrated that the reason for the tunable lifetime was that the magnitude of the electron-donating ability of the substituent group modulates the HOMO–LUMO and singlet-triplet energy gap of methyl benzoate derivatives, as well as the ability to non-covalent interactions with PVA. Moreover, the potential applications of luminescent displays and optical anti-counterfeiting of these high-performance dark blue RTP materials have been conducted.

A method of creating air-stable small-molecule n-type organic mixed ionic-electronic conductors is reported with helical perylene-diimide trimer (hPDI[3]) as the model material. Alkyl sidechains are grafted onto the molecular semiconductors to increase its thin-film solution processability, then removed to create films with better ion transport and stability. High-transconductance organic electrochemical transistors are made with side-chainless hPDI[3] as the active material.

Abstract

A new method is reported to make air-stable n-type organic mixed ionic-electronic conductor (OMIEC) films for organic electrochemical transistors (OECTs) using a solution-processable small molecule helical perylene diimide trimer, hPDI[3]-C₁₁. Alkyl side chains are attached to the conjugated core for processability and film making, which are then cleaved via thermal annealing. After the sidechains are removed, the hPDI[3] film becomes less hydrophobic, more ordered, and has a deeper lowest unoccupied molecular orbital (LUMO). These features provide improved ionic transport, greater electronic mobility, and increased stability in air and in aqueous solution. Subsequently, hPDI[3]-H is used as the active material in OECTs and a device with a transconductance of 44 mS, volumetric capacitance of ≈250 F cm⁻³, µC^* value of 1 F cm⁻¹ V⁻¹ s⁻¹, and excellent stability (> 5 weeks) is demonstrated. As proof of their practical applications, a hPDI[3]-H-based OECTs as a glucose sensor and electrochemical inverter is utilized. The approach of side chain removal after film formation charts a path to a wide range of molecular semiconductors to be used as stable, mixed ionic-electronic conductors.

Nature Reviews Materials, Published online: 25 March 2024; doi:10.1038/s41578-024-00673-2

An article in Nature Materials reports the use of a co-doping strategy to produce a Cu2Se-based superionic material that has a figure of merit of 3 at 1,050 K, an efficiency of over 13% when integrated into a thermoelectric module and good operational stability.

Upon heating, symmetry reduction around Eu³⁺ site caused by anisotropic contraction of MIL-68-In framework and Boltzmann population between ⁷F₀ and ⁷F₁ levels of Eu³⁺, together lead to thermally enhanced luminescence. Further modulation of Eu³⁺ concentration in MIL-68-In/Eu allows modulation of thermal-responsive emissions toward advanced information encryption.

Abstract

Applications of luminescence at high temperature such as high-power lighting, lasing, thermophotovoltaics, and photonic coding, are severely prevented due to the notorious thermal quenching (TQ). Although anti-TQ luminescence (anti-TQL) is reported using highly oxygen-coordinated solid-state oxide as host in virtue of the rigid skeleton that resists lattice vibration at elevated temperatures, it is meaningful to extend anti-TQL to other hosts. Herein, taking advantage of the ligand-metal antenna effect and the negative thermal expansion feature of Eu³⁺ doped MIL-68-In (MIL-68-In/xEu), adjustable anti-TQL is realized for the first time, that is, anti-TQ, zero-TQ, and TQ at x = 5%, 10%, and 50%, respectively. Therefore, except for added novel mechanisms, this work has also expanded the hosts available for high-temperature luminescence and enabled advanced photonic coding in terms of facial synthesis, rich information, and visual changes of emission intensity instead of device-dependent analogous.

Recent advances in tribo-dielectric materials for TENGs are comprehensively reviewed in terms of principle, method, and application. The contact electrification and charge transport mechanism of dielectric materials for TENGs are introduced, followed by highlighting the modification mechanisms, strategies, and applications of advanced tribo-dielectrics based power sources and self-powered sensors, serving as guidelines for developing high-performance TENGs.

Abstract

Triboelectric nanogenerator (TENG) manifests distinct advantages such as multiple structural selectivity, diverse selection of materials, environmental adaptability, low cost, and remarkable conversion efficiency, which becomes a promising technology for micro-nano energy harvesting and self-powered sensing. Tribo-dielectric materials are the fundamental and core components for high-performance TENGs. In particular, the charge generation, dissipation, storage, migration of the dielectrics, and dynamic equilibrium behaviors determine the overall performance. Herein, a comprehensive summary is presented to elucidate the dielectric charge transport mechanism and tribo-dielectric material modification principle toward high-performance TENGs. The contact electrification and charge transport mechanism of dielectric materials is started first, followed by introducing the basic principle and dielectric materials of TENGs. Subsequently, modification mechanisms and strategies for high-performance tribo-dielectric materials are highlighted regarding physical/chemical, surface/bulk, dielectric coupling, and structure optimization. Furthermore, representative applications of dielectric materials based TENGs as power sources, self-powered sensors are demonstrated. The existing challenges and promising potential opportunities for advanced tribo-dielectric materials are outlined, guiding the design, fabrication, and applications of tribo-dielectric materials.

InP/ZnS quantum dots (QDs) can be relevant for in vivo platelet imaging. It shows that careful selection of QD phase transfer agent is critical to maintaining platelet function. These results indicate that platelet-QD interaction can occur across a wide range of concentrations. It can image the platelet-QD interaction via FLIM, and use platelet functional assays to monitor platelet activation.

Abstract

InP/ZnS quantum dots (QDs) have received a large focus in recent years as a safer alternative to heavy metal-based QDs. Given their intrinsic fluorescent imaging capabilities, these QDs can be potentially relevant for in vivo platelet imaging. The InP/ZnS QDs are synthesized and their biocompatibility investigated through the use of different phase transfer agents. Analysis of platelet function indicates that platelet-QD interaction can occur at all concentrations and for all QD permutations tested. However, as the QD concentration increases, platelet aggregation is induced by QDs alone independent of natural platelet agonists. This study helps to define a range of concentrations and coatings (thioglycolic acid and penicillamine) that are biocompatible with platelet function. With this information, the platelet-QD interaction can be identified using multiple methods. Fluorescent lifetime imaging microscopy (FLIM) and confocal studies have shown QDs localize on the surface of the platelet toward the center while showing evidence of energy transfer within the QD population. It is believed that these findings are an important stepping point for the development of fluorescent probes for platelet imaging.

The work breaks a bottleneck of synthesizing high quality single-crystal GaN on amorphous SiO₂/Si(100) and demonstrates the monolithically integrated photonic chips on CMOS-compatible substrate for the first time. The self-powered PD affords a rapid response below 250 µs under adjacent LED radiation, demonstrating the high responsivity and detectivity of 2.01 × 10⁵ A W⁻¹ and 4.64 × 10¹³ Jones.

Abstract

The realization of high quality (0001) GaN on Si(100) is paramount importance for the monolithic integration of Si-based integrated circuits and GaN-enabled optoelectronic devices. Nevertheless, thorny issues including large thermal mismatch and distinct crystal symmetries typically bring about uncontrollable polycrystalline GaN formation with considerable surface roughness on standard Si(100). Here a breakthrough of high-quality single-crystalline GaN film on polycrystalline SiO₂/Si(100) is presented by quasi van der Waals epitaxy and fabricate the monolithically integrated photonic chips. The in-plane orientation of epilayer is aligned throughout a slip and rotation of high density AlN nuclei due to weak interfacial forces, while the out-of-plane orientation of GaN can be guided by multi-step growth on transfer-free graphene. For the first time, the monolithic integration of light-emitting diode (LED) and photodetector (PD) devices are accomplished on CMOS-compatible SiO₂/Si(100). Remarkably, the self-powered PD affords a rapid response below 250 µs under adjacent LED radiation, demonstrating the responsivity and detectivity of 2.01 × 10⁵ A/W and 4.64 × 10¹³ Jones, respectively. This work breaks a bottleneck of synthesizing large area single-crystal GaN on Si(100), which is anticipated to motivate the disruptive developments in Si-integrated optoelectronic devices.

A liquid crystal elastomer soft robot capable of self-sustained continuous movement, with a specific motion mode that can be gate-controlled by either substrate adhesion or remote light. It is mechanically trained to undergo continuous snapping actions to ensure its self-sustained locomotion. By on-demand setting, the autonomous soft robot can perform sophisticated tasks, including rolling, jumping, making stops, decelerating, backing up, and even turning around obstacles.

Abstract

Self-oscillation phenomena observed in nature serve as extraordinary inspiration for designing synthetic autonomous moving systems. Converting self-oscillation into designable self-sustained locomotion can lead to a new generation of soft robots that require minimal/no external control. However, such locomotion is typically constrained to a single mode dictated by the constant surrounding environment. In this study, a liquid crystal elastomer (LCE) robot capable of achieving self-sustained multimodal locomotion, with the specific motion mode being controlled via substrate adhesion or remote light stimulation is presented. Specifically, the LCE is mechanically trained to undergo repeated snapping actions to ensure its self-sustained rolling motion in a constant gradient thermal field atop a hotplate. By further fine-tuning the substrate adhesion, the LCE robot exhibits reversible transitions between rolling and jumping modes. In addition, the rolling motion can be manipulated in real time through light stimulation to perform other diverse motions including turning, decelerating, stopping, backing up, and steering around complex obstacles. The principle of introducing an on-demand gate control offers a new venue for designing future autonomous soft robots.

A novel method is developed for graphene growth in air. A sandwich-like sample, comprising of a graphite plate embedded by a poly-dopamine coated glass and a support substrate, provides an anaerobic atmosphere. As the induction coil moves, the graphite plate is heated instaneously and graphene forms on the glass inner surface via transform of the polymer precursor film.

Abstract

The scalable, efficient, and cost-economic preparation method of graphene is the key to promoting the real applications of graphene. In recent years researchers have made intensive efforts to enhance the synthesis efficiency and reduce the production costs of the manufacturing processes, especially for the chemical vapor deposition methods. However, the efficiency and uniformity are difficult to further improve due to its complicated synthesis conditions. A high-efficiency synthesis method to provide a large uniform production area suitable for graphene growth remains a great challenge until now. In this work, a facile and scalable ultrafast quenching method for growing graphene in air is developed by using scanning electromagnetic induction (SEMI) equipment. This method is successfully applied to grow a 400 mm × 400 mm graphene glass within 2 min in the air with a lab-grade instrument. Thus-produced multiple-layered graphene glass is of a high uniformity, film adhesion, and full coverage, showing a surface resistance (Rs) below 500 Ω sq⁻¹. Outstanding electrothermal capabilities up to 1000 °C are demonstrated for their promising potential for transparent heating devices. The SEMI method, including the product size and growth rate, can be easily up-scaled, which is believed to provide an effective route to grow graphene aiming at its real applications.

Broadband polarization-sensitive based on (TaSe₄)₂I nanowire is demonstrated. The exciting experimental results include a high R of 110.5 A/W, very low NEP of 1.2 × 10⁻¹⁴ WHz^−1/2, competitive high D* of 4.8 × 10¹⁰ cmHz^1/2 W⁻¹ in the MWIR spectrum range and high dichroic ratio of 2.32 under 637 nm laser. This find promotes the development of uncooled polarization-sensitive MWIR photodetectors.

Abstract

Polarization-sensitive infrared (IR) photodetection plays an important role in fiber optic communication, environmental monitoring, and remote sensing imaging. Semiconductors with quasi-1D crystal structures exhibit unique optical and electrical properties due to their 1D carrier transport channels and large surface area-to-volume ratio, offering the possibility of high-performance photodetectors with high photogain (G), polarization sensitivity photodetection. Herein, an ultra-broadband photodetection (405 nm–10.6 µm) based on a quasi-1D (TaSe₄)₂I single-crystal nanowire is reported. The (TaSe₄)₂I photodetector exhibits excellent polarization-sensitive photodetection, with a high dichroic ratio of I _max/I _min = 2.32 under 637 nm illumination. Notably, the (TaSe₄)₂I nanowire photodetector exhibits a competitive performance in uncooled mid-wave infrared (MWIR) detection with a high photoresponsivity (R) of 110.5 AW⁻¹ and specific detectivity (D*) of 4.8 × 10¹⁰ cmHz^1/2W⁻¹. Moreover, in the long-wave infrared (LWIR) spectral range, an R of 67.6 mAW⁻¹ is demonstrated at room temperature (RT). The (TaSe₄)₂I nanowire photodetector enables significant advancements for polarization-sensitive and uncooled MWIR and LWIR photodetection.

Shen et al. develop a four-state domain wall memory on LiNbO₃ ferroelectric thin films, where each state can be stably encoded at a specific low voltage, demonstrating excellent fatigue resistance and retention performance. With the advantage of embedded selectors within the constructed crossbar array, it is successfully exhibited for convolutional neural network computations.

Abstract

Low-power and parallel processing Neuromorphic computing that imitates on the human brain's extraordinary data processing and learning capabilities is promising in non-von Neumann application platforms in the post-Moore era. Ferroelectric domain walls appearing as nanoscale topological defects in solids exhibit coexisting ordering parameters besides the spontaneous polarization, leading to the emergence of rich physics and electronic effects in the development of neuromorphic electronics that go beyond the conventional CMOS. In this study, the four-state domain wall memory is developed on LiNbO₃ ferroelectric thin films integrated with Si substrates, where each state can be stably manipulated at a specific low voltage, showcasing outstanding fatigue resistance and retention performance. The constructed crossbar array that functions as a kernel for image convolution can be used to implement processing operations like image filtering, sharpness enhancement, and edge detection. Additional simulation from a convolutional neural network model shows 96.98% accuracy on the Modified National Institute of Standards and Technology handwritten digits dataset. The stable multi-state domain wall memory provides a new approach for computing and promotes research in domain wall electronics to meet future enormous demands of big data.

CrB and Co₂CO₂, renowned for their outstanding electronic properties, are combined to create a superlattice material. Employing Density Functional Theory (DFT) and ML techniques utilizing multiple crystal descriptors, the electronic characteristics of this superlattice are examined. The study reveals that CrB/Co₂CO₂ exhibits structural stability, excellent electronic properties, and potential applications as a ferroelectric laser material.

Abstract

In recent times, newly unveiled 2D materials exhibiting exceptional characteristics, such as MBenes and MXenes, have gained widespread application across diverse domains, encompassing electronic devices, catalysis, energy storage, sensors, and various others. Nonetheless, numerous technical bottlenecks persist in the development of high-performance, structurally flexible, and adjustable electronic device materials. Research investigations have demonstrated that 2D van der Waals superlattices (vdW SLs) structures comprising materials exhibit exceptional electrical, mechanical, and optical properties. In this work, the advantages of both materials are combined and compose the vdW SLs structure of MBenes and MXenes, thus obtaining materials with excellent electronic properties. Furthermore, it integrates machine learning (ML) with first-principles methods to forecast the electrical properties of MBene/MXene superlattice materials. Initially, various configurations of MBene/MXene superlattice materials are explored, revealing that distinct stacking methods exert significant influence on the electronic structure of MBene/MXene materials. Specifically, the BABA-type stacking of CrB (layer A) and Co₂CO₂ MXene (layer B) is most stable configureation. Subsequently, multiple descriptors of the structure are constructed to predict the density of states  of vdW SLs through the employment of ML techniques. The best model achieves a mean absolute error (MAE) as low as 0.147 eV.

The study presents a unique fabrication method for vertically aligned (2D BN and Graphite films) within a silicon rubber composite, demonstrating higher through-plane thermal conductivity. The films exhibit a highly oriented and dense structure, resulting in low thermal resistance and low compression modulus. Practical tests reveal the composite's significant heat dissipation capabilities and outstanding resilience, for advanced thermal management.

Abstract

The relentless drive toward miniaturization in microelectronic devices has sparked an urgent need for materials that offer both high thermal conductivity (TC) and excellent electrical insulation. Thermal interface materials (TIMs) possessing these dual attributes are highly sought after for modern electronics, but achieving such a combination has proven to be a formidable challenge. In this study, a cutting-edge solution is presented by developing boron nitride (BN) and graphite films layered silicone rubber composites with exceptional TC and electrical insulation properties. Through a carefully devised stacking-cutting method, the high orientation degree of both BN and graphite films is successfully preserved, resulting in an unprecedented through-plane TC of 23.7 Wm⁻¹ K⁻¹ and a remarkably low compressive modulus of 4.85 MPa. Furthermore, the exceptional properties of composites, including low thermal resistance and high resilience rate, make them a reliable and durable option for various applications. Practical tests demonstrate their outstanding heat dissipation performance, significantly reducing CPU temperatures in a computer cooling system. This research work unveils the possible upper limit of TC in BN-based TIMs and paves the way for their large-scale practical implementation, particularly in the thermal management of next-generation electronic devices.

The work demonstrates a framework to design triangular magnets with atomically precise control of competing intralayer and interlayer magnetic exchange interactions. Careful considerations of isotope purity, nuclear and electronic spins, lattice symmetry, frontier orbitals, and electronic states for CaMnTeO₆ result in the realization of strong quantum fluctuations. This provides a powerful tool for enhancing coherent quantum dynamics in real materials.

Abstract

Noncentrosymmetric triangular magnets offer a unique platform for realizing strong quantum fluctuations. However, designing these quantum materials remains an open challenge attributable to a knowledge gap in the tunability of competing exchange interactions at the atomic level. Here, a new noncentrosymmetric triangular S = 3/2 magnet CaMnTeO₆ is created based on careful chemical and physical considerations. The model material displays competing magnetic interactions and features nonlinear optical responses with the capability of generating coherent photons. The incommensurate magnetic ground state of CaMnTeO₆ with an unusually large spin rotation angle of 127°(1) indicates that the anisotropic interlayer exchange is strong and competing with the isotropic interlayer Heisenberg interaction. The moment of 1.39(1) µB, extracted from low-temperature heat capacity and neutron diffraction measurements, is only 46% of the expected value of the static moment 3 µB. This reduction indicates the presence of strong quantum fluctuations in the half-integer spin S = 3/2 CaMnTeO₆ magnet, which is rare. By comparing the spin-polarized band structure, chemical bonding, and physical properties of AMnTeO₆ (A = Ca, Sr, Pb), how quantum-chemical interpretation can illuminate insights into the fundamentals of magnetic exchange interactions, providing a powerful tool for modulating spin dynamics with atomically precise control is demonstrated.

The successful synthesis of highly crystalline 2D FeCr₂S₄ in 2D form with pure cubic spinel structure, which exhibits perpendicular magnetic anisotropy, thickness independent of T _C and excellent air stability. The work promotes further exploration of the fundamental aspects of 2D magnets, and paves the way for the application of the 2D robust ferrimagnetic material in multiferroic and spintronic devices.

Abstract

The discovery of intrinsic 2D magnetic materials has opened up new opportunities for exploring magnetic properties at atomic layer thicknesses, presenting potential applications in spintronic devices. Here a new 2D ferrimagnetic crystal of nonlayered FeCr₂S₄ is synthesized with high phase purity using chemical vapor deposition. The obtained 2D FeCr₂S₄ exhibits perpendicular magnetic anisotropy, as evidenced by the out-of-plane/in-plane Hall effect and anisotropic magnetoresistance. Theoretical calculations further elucidate that the observed magnetic anisotropy can be attributed to its surface termination structure. By combining temperature-dependent magneto-transport and polarized Raman spectroscopy characterizations, it is discovered that both the measured Curie temperature and the critical temperature at which a low energy magnon peak disappeared remains constant, regardless of its thickness. Magnetic force microscopy measurements show the flipping process of magnetic domains. The exceptional air-stability of the 2D FeCr₂S₄ is also confirmed via Raman spectroscopy and Hall hysteresis loops. The robust anisotropic ferrimagnetism, the thickness-independent of Curie temperature, coupled with excellent air-stability, make 2D FeCr₂S₄ crystals highly attractive for future spintronic devices.

This paper reports an approach to maximize the electrocatalytic performance of mechanically exfoliated WS₂ through sequential plasma treatments. This dry process can spatially tune the level of surface oxidation as well as the concentration of sulfur vacancies such that compositionally graded, mixed-domain electrochemical catalysts induced hydrogen evolution reaction performance greater than platinum with high stability over centimeter-scale areas.

Abstract

Electrocatalytic water splitting is crucial to generate clean hydrogen fuel, but implementation at an industrial scale remains limited due to dependence on expensive platinum (Pt)-based electrocatalysts. Here, an all-dry process to transform electrochemically inert bulk WS₂ into a multidomain electrochemical catalyst that enables scalable and cost-effective implementation of the hydrogen evolution reaction (HER) in water electrolysis is reported. Direct dry transfer of WS₂ flakes to a gold thin film deposited on a silicon substrate provides a general platform to produce the working electrodes for HER with tunable charge transfer resistance. By treating the mechanically exfoliated WS₂ with sequential Ar-O₂ plasma, mixed domains of WS₂, WO₃, and tungsten oxysulfide form on the surfaces of the flakes, which gives rise to a superior HER with much greater long-term stability and steady-state activity compared to Pt. Using density functional theory, ultraefficient atomic sites formed on the constituent nanodomains are identified, and the quantification of atomic-scale reactivities and resulting HER activities fully support the experimental observations.