Abstract Graphene edges and topological defects are two important active sites in metal-free carbon-based electrocatalysts for various energy-related reactions such as the oxygen reduction reaction (ORR). However, quantitative measurement and exploration of the atomic origin of the activities of these defects remain challenging, largely due to the structural complexity and heterogeneity of carbon-based electrocatalysts. Their ORR selectivity toward either the two-electron pathway producing hydrogen peroxide or the four-electron pathway leading to water also remains controversial. Herein, we fabricate well-defined model electrocatalysts via chemical vapor deposition of nanocrystalline graphene domains with tunable edge densities. The ORR activities are determined to be dominated by the two-electron pathway producing hydrogen peroxide and scale linearly with the edge density, enabling the quantification of the specific activity per unit edge length. Using atomic-resolution differential phase contrast scanning transmission electron microscopy, we identified the favorable formation of topological defects at the edges, with significant fluctuations in localized electron states, providing an important atomic origin for their enhanced ORR activity. This was corroborated by the deliberate introduction of topological defects by Ar plasma treatment, leading to two-dimensional amorphous carbon and significantly enhanced two-electron ORR activity.

Twisted bilayer MoS2 forms a quantum-engineered sensing platform, where the moiré superlattice creates a configurable surface potential for molecular control. Here we present a periodically modulated landscape in bilayer MoS2 by twist-angle tuning, and use it for molecular trapping and selective sensing. The native 54 meV moiré potential confines aromatic molecules (e.g., rhodamine 6G, R6G; methylene blue, MB) at AA-stacking sites. Introducing extended vacancies deepens confinement to 238 meV, enhancing adsorption. Twist angle enables band alignment with molecules, driving charge-transfer resonances. This integrated design, moiré potentials, defect-enhanced trapping and band-aligned charge transfer, synergistically amplifies Raman signals, achieving single-molecule sensitivity down to 10−20 M. Importantly, the platform exhibits molecule-specific selectivity: R6G is optimally detected at 10° and 50° bilayer MoS2, while MB responds at 15° and 45°, demonstrating twist-angle encoding of molecular recognition. Our twisted MoS2 with extended vacancies establishes a moiré system as a versatile platform for selective molecular sensing. Twisted layers of van der Waals materials can generate moiré superlattices, forming reconfigurable surface potentials with nanoscale periodicity. Here, the authors show that the moiré potential in twisted bilayer MoS2 can be used to confine aromatic molecules, improving the surface-enhanced Raman spectroscopy sensitivity and selectivity of this platform.

Carbon catalysts featuring basal etheric C & horbar;O & horbar;C structures are promising for 2e-ORR, with etheric carbon (Cetheric) serves as the active sites, but their controlled synthesis remains challenging. Here, we propose a thermodynamics-guided methodology for predicting the formation probability of carbon active sites. Based on this framework, cobalt (Co) atoms are employed as coordination-induced structural directors to experimentally realize the targeted sites. Statistical thermodynamic and DFT analyses reveal that Co incorporation thermodynamically promotes the formation of C & horbar;O & horbar;C moieties in CoC3O1 and CoC2O2 configurations, while maintaining favorable 2e-ORR activity and selectivity. Guided by these insights, a Co-induced etheric carbon catalyst (C & horbar;O & horbar;C(Co)) was successfully synthesized, which features the coexistence of CoC3O1 and CoC2O2 configurations and exhibits a 1.5-fold increase in Cetheric active site density compared to Co-free catalysts. The C & horbar;O & horbar;C(Co) catalyst delivers outstanding 2e-ORR performance, achieving a 0.68 V onset potential and similar to 95% H2O2 selectivity across a broad potential range. Practical applicability was validated through integration into PEMFC-type devices, where the system could simultaneously generate electrical power and electrosynthesize H2O2. This work presents a thermodynamics-guided, metal-directed approach for rational design of carbon active sites, offering a predictive framework for functional carbon materials.

The durability of platinum (Pt) electrocatalysts in electrochemical energy conversion is fundamentally challenged by surface oxidation and dissolution during electrochemical operation. Although Pt surface oxidation has commonly been discussed in terms of a "place exchange" mechanism between Pt and oxygen, atomic-scale insight into its potential-dependent progression has remained limited. Herein, we directly visualize atomic electrooxidation and dissolution of {111}-terminated surfaces of octahedral Pt nanoparticles by employing ex situ differential-phase-contrast scanning transmission electron microscopy combined with online inductively coupled-plasma mass spectroscopy and density functional theory calculations. We reveal the atomistic structural evolution of the {111} nanoparticle surface with progressively increasing electrode potentials (0.8-1.5 V), from the initial lattice expansion induced by adsorbed oxygen, to vacancy-induced formation of two-dimensional, lattice-contracted PtOx monolayers, and finally to a dimensional transition to three-dimensional PtO2 growth. Furthermore, we demonstrate how the potential cycling protocols (triangular versus square wave cycling) decisively control the final oxide's dimensionality (multilayer versus single layer) and stability. These atomic-scale insights establish how electrochemical conditions dictate Pt oxidation pathways and atomistic structural evolution, providing a mechanistic basis for understanding and improving the durability of Pt-based electrocatalysts.

Antimony-doped tin oxide (ATO) serves as a promising corrosion-resistant and conductive support for reducing iridium (Ir) loading in oxygen evolution reaction (OER) catalysts for proton-exchange membrane electrolysis. While metal-support interactions (MSIs) are well-known to modify the catalyst activity and stability in heterogeneous thermal catalysis, their role in electrocatalysis-particularly for the ATO-supported Ir-based OER catalysts-remains underexplored. Herein, we disclose a thermally induced MSI during the synthesis of ATO-supported IrO x catalysts, which decisively controls the OER activity and stability. Upon air annealing of the ATO-supported Ir chloride precursor, Ir nanoparticles initially formed at 300 degrees C, transforming into an epitaxial rutile phase IrOx surface layer partially covered by ATO at 400 degrees C and finally evolving into an Ir-Sn mixed rutile oxides surface at 600 degrees C, demonstrating a strong MSI under high temperatures. This further leads to declined OER activity with increasing temperature, highlighting the importance of temperature control during the catalyst annealing. We further demonstrate that residual chlorine from the precursors markedly suppresses OER performance. Annealing under H-2 removes chlorine but weakens the MSI and induces nanoparticle agglomeration, compromising the catalytic stability. In contrast, using nitrate precursors under low-temperature air annealing effectively eliminates chlorine while preserving high IrO x dispersion, yielding simultaneous gains in both activity and durability. These results provide critical guidance for rational synthesis of ATO-supported Ir-based electrocatalysts with a finely tuned MSI through a controlled annealing atmosphere and precursor chemistry.

Erbium-based materials have long been recognized for their important telecom-band applications, yet their widespread adoption in integrated optoelectronics has been hindered by two fundamental limitations: the difficulty in achieving high erbium density without concentration quenching which leads to small optical gain in doped materials, and the difficulty in fabricating a practical device with single crystal nanowires that demonstrated high optical gain previously1,2. Here, we overcome these limitations by synthesizing 2D single crystal ErOCl that has an Er density of 1.75*1022 cm-3. The high-quality single crystal material significantly reduces the density-related quenching effect that dominates in randomly doped materials with high Er concentration. This results in a record optical gain coefficient over 1500 dB/cm at 1536 nm band, at least larger by an order of magnitude than the previous gain record in Er materials. Leveraging this exceptional gain medium, we demonstrate room-temperature continuous-wave lasing operation by integrating with a photonic crystal microcavity, achieving a record-low threshold of 7 μW with the most compact size of any Er-based lasers. Furthermore, the unique Stark splitting characteristics of ErOCl provide optical gain in three wavelength bands and lead to lasing in these wavelengths by engineering the cavity. This is the first time that optical gain has been shown in three different wavelength bands in Er materials, together with the smallest size of laser cavity, could have many important applications in on-chip sensing and optical communication.

The local structure and chemical environment critically govern transport properties in quantum and energy materials, but their atomic-scale manifestations remain elusive. Here we uncovered the atomic characteristics, intrinsic origin, and thermoelectric implications of chemical inhomogeneity in Bi2Te3-based materials with varying Se alloying. Using aberration-corrected electron microscopy, chemical bonding analysis, and thermodynamic modeling, we revealed pronounced Se enrichment in the central layer of a quintuple structure and constructed precise atomic models for this intrinsic inhomogeneity. Atomic-scale charge-density and valence-state measurements provided direct experimental evidence for chemical bonding disparity in Bi2Te3, with more covalent bonding in central layers and greater ionic bonding in outer layers. We also showed that this bonding disparity, coupled with entropy-enthalpy competition, drove the observed site preference and local chemical segregation in Bi2Te3-xSex (x = 0.5, 1.0, 1.5, 2.0, and 2.5). The site-resolved bonding analyses further demonstrated that selective Se occupation tuned both ionic and covalent components of Bi-X bonds in Bi2Te3-xSex. Therefore, this intrinsic chemical inhomogeneity modulated bonding polarity, the electronic band gap, and the Seebeck coefficient, serving as a fundamental determinant of thermoelectric performance. Our findings highlight atomic-scale chemical inhomogeneity as a key factor in tailoring functional properties of layered quantum materials beyond thermoelectrics.

While metal-oxide interfaces can profoundly modulate the performance of (electro)catalysts, their dynamic nature under operational conditions remains poorly understood, and a compromise between activity and stability persists as a central challenge. Herein, we reveal a dynamic, "breathing" interface behavior in MOx/Pt (M = In, Sn, Sb) systems during the cathodic oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells. By constructing well-defined Pt octahedra decorated with ultrathin p-block metal oxide overlayers, we demonstrate that an oxygen-deficient M-Pt interface forms at reducing potentials and improves the ORR activity following a trend of In-Pt > Sn-Pt ∼ Sb-Pt via interfacial charge transfer, while oxidizing potentials generate an oxygen-enriched M-O-Pt structure that effectively suppresses Pt dissolution and improves catalytic durability, particularly with SnOx overlayers. We further validate that harnessing the dynamic metal-oxide interfaces represents a new and generalizable strategy to break the activity and stability trade-off for a wide range of shaped or non-shaped Pt and Pt-bimetallic catalysts, most notably in InSnOx-decorated PtCo catalysts.

Electrochemical polarization under oxygen evolution conditions often induces structural reconstruction from the parent phase in transition‐metal‐based catalysts, which are frequently interpreted as active intermediate species. Here, we investigate the relaxation behavior of electrochemically induced intermediates in spinel and hydroxide catalysts at controlled non‐operando conditions by correlated spectroscopy and microscopy techniques. The oxyhydroxide phase formed at high anodic potentials remains stable after potential removal as long as electrochemical environments are maintained. In contrast, once the electrode is disconnected and the electrolyte is gradually removed, the intermediate state progressively relaxes back to the parent structure. Further drying treatments reveal that decreasing electrolyte activity markedly accelerates such structural recovery. These findings demonstrate that electrochemically induced intermediate structures should be regarded as boundary‐condition‐dependent states rather than intrinsically stable phases, highlighting the strong environment dependence of catalyst structural insights obtained under non‐operando conditions.

Electron tomography (ET) is crucial for determining the three-dimensional (3D) structure of materials in real space but challenging due to the inherent missing wedge, high dose, and limited depth-of-field. Although deep learning can address these challenges in principle, the scarcity of ET data severely limits its application. In this study, we propose a general data-driven ET reconstruction framework that uses extensive and readily available random high-entropy projections to construct large-scale datasets. By integrating both real structural priors and depth-dependent imaging physics, the framework enables high-quality 3D reconstruction independent of specific materials or resolutions. Using this strategy, we successfully determine the 3D atomic structure of a 13-nm Pt nanoparticle containing 52 138 atoms, achieving a root-mean-square displacement of 22.6 pm; the projection consistency error is significantly reduced, effectively expanding the depth-of-field limit of atomic-scale ET.

Solar-driven overall water splitting offers a sustainable route for producing hydrogen and hydrogen peroxide, yet achieving high H2O2 selectivity remains challenging due to competing proton-coupled electron transfer pathways. Here we construct an S-scheme heterojunction composed of carbon quantum dots (CQDs) and K3PW12O40, where the built-in electric field at the interface enhances charge separation and promotes proton transfer, creating a favorable microenvironment for selective H2O2 generation. This catalyst achieves H2 and H2O2 production rates of 603 and 586 μmol/g·h simultaneously under visible light irradiation. The tailored electronic structure lowers energy barriers for key intermediates, facilitating selective H2O2 production. These findings demonstrate that interfacial proton regulation combined with broad light absorption and efficient charge separation can guide the design of multifunctional photocatalysts for scalable solar-driven H2O2 synthesis.

Atomic electron tomography (AET) is a powerful technique for determining the three-dimensional atomic structure of matter in real space. However, conventional AET requires numerous projections across a wide angular range. The high dose and prolonged acquisition severely limit its application. Here, we propose an interpretable and universal algorithm for low-dose, fast and tilt-constrained AET: null-space iterative reconstruction (NSIRE), which uses an unsupervised diffusion model to iteratively compute null-space solutions of projection equations, thereby generating tomograms consistent with both projection constraints and atomic potential prior. NSIRE can resolve a wide range of complex materials under 6-12° sparse projection or within ±29° small tilt-range without retraining. Using the NSIRE, we determine the three-dimensional atomic structures of a 4-nm Pt nanoparticle with grain boundaries and a 3-nm PtCo nanoalloy (the smallest one resolved so far), achieving a root-mean-square displacement of <20 pm and high projection consistency, overcoming the scale, dose and time limitations of AET.

Nitrogen-doped carbon materials have emerged as promising metal-free electrocatalysts for oxygen reduction reaction (ORR) in fuel cells and metal-air batteries. However, the structural inhomogeneity, particularly the coexistence of four nitrogen doping structures-pyridinic, graphitic, pyrrolic, and oxidized nitrogen-makes assessing their respective contributions challenging and controversial. The current understanding of the four nitrogen doping structures may be also oversimplified and even problematic. The development of a distinctive graphitic-N-doped carbon electrocatalyst is presented in which graphitic nitrogen coordinated with pentagon defects is selectively constructed. Contrary to the previously held belief that graphitic nitrogen has little effect on ORR electrocatalysis, the unique graphitic N configuration exhibited significantly enhanced four-electron ORR activity in both alkaline and acidic media. In situ electrochemical Raman spectroscopy combined with density functional theory calculations further revealed that graphitic nitrogen, when coordinated with pentagon defects, optimized the density of states near the Fermi level, leading to optimized binding energies with oxygen-containing intermediates. The results rationalize the long-standing controversy over the role of different nitrogen dopants in ORR electrocatalysis and suggest that there is considerable potential to precisely construct new nitrogen doping configurations to achieve superior electrocatalytic performance.

Future 6G communication includes underwater and cross-media scenarios, in which visible light laser communication (VLLC) has inherent advantages such as large capacity and transmission security. GaN-based laser diodes (LDs) are expected to play important roles in future VLLC systems, leveraging their capability in short-wavelength visible light spectrum, especially in the blue-green transmission window of water. Large bandwidth, high-speed blue/green laser devices could provide desirable channel capacity for wavelength-division full-duplex communication systems. In this paper, through theoretical analysis based on the bandwidth formula of LDs derived from the carrier rate equation, combined with numerical calculations, we design blue and green InGaN/GaN Fabry-P & eacute;rot (FP) cavity LD structures to increase bandwidth. High-bandwidth blue and green LDs for short-distance high-speed communication are fabricated by simultaneously shortening cavity length, reducing waveguide layer thickness, and increasing end-face reflectivity. The blue and green LDs achieve the -3dB E-E bandwidth of 5.4 GHz and 3.5 GHz, respectively, enabling a 21.79/17.49 Gbps full-duplex system with 21.79 Gbps downlink and 17.49 Gbps uplink using the discrete multi-tone (DMT) bit-loading modulation format. These results set a record for bandwidth and communication rate in blue and green VLLC full-duplex systems, paving the way for future high-speed applications in visible light wireless access infrastructures.

Platinum-group metal-free single-atom catalysts (SACs) are vital for cost-effective fuel cells, yet their adoption is hindered by performance limitations and challenges in scalable production. While Fe-N-C SACs offer high activity, their stability is severely compromised by Fenton-induced degradation. To address this, Co-N-C SACs have emerged as promising alternatives due to their much lower Fenton activity and hence improved durability. However, conventional synthesis relies on solvent-intensive methods, limiting large-scale, environmentally friendly production and precise structural control. Here, we report a solid-phase synthesis strategy via the Kirkendall effect for the kilogram-scale production of Co-doped zeolitic imidazolate framework-8 (Co-ZIF-8) with high reproducibility and precise compositional control. Further pyrolysis at high temperatures enables the formation of structurally well-defined Co-N-C SACs with tunable composition, high site density, and superior scalability. The optimized catalyst, when integrated as the cathode in a representative proton exchange membrane fuel cell (PEMFC) system, delivers remarkable power densities of 0.70 W cm-2 and 0.39 W cm-2 in O2 and air conditions, respectively, outperforming most reported Co-based catalysts. This work establishes a generalizable and environmentally sustainable route for the large-scale production of high-performance non-precious metal electrocatalysts, advancing PEMFC technology and broader electrochemical energy applications.

Solid-state lithium metal batteries are facing huge challenges under practical working conditions1,2. Even when the ionic conductivity of composite solid-state electrolytes is increased to 1 mS cm-1, it is still difficult to realize long-life cycling of solid-state batteries above a current density of 1 mA cm-2 and an areal capacity of 1 mAh cm-2 (ref. 3). The fundamental cause is the brittle nature of the solid-electrolyte interphase (SEI) with sluggish lithium-ion transport and the resulting lithium dendrites and severe side reactions. Here we report a ductile inorganic-rich SEI that retains its structural integrity while allowing easy ion diffusion at high current densities and areal capacities. The ductility of the SEI is ascribed to the Ag2S and AgF components, which are formed by a substitution reaction between Li2S/LiF in the SEI and AgNO3 in the dielectric composite electrolytes. Even at a high current density of 15 mA cm-2 and an areal capacity of 15 mAh cm-2, a symmetrical lithium cell with such an SEI has a long cycle life of over 4,500 hours. Furthermore, the ductile SEI also works over 7,000 hours at -30 °C, even under practical conditions of 5 mA cm-2 and 5 mAh cm-2.

Fenton technology is promising for removing recalcitrant and toxic organic contaminants for wastewater purification. Neutral Fenton technology is preferred for its reduced acid usage and improved operational convenience. However, the challenges are the low production of reactive species and the limited conversion of high-valent iron (Fe) to low-valent Fe. This study introduced a new cycle employing high-valent iron-oxo species [Fe(IV)=O], which directly participates in degradation, facilitating Fe regeneration. To achieve it, we developed an O-doped single Fe atom catalyst (SACs, Fe-N3O1) to promote the efficient Fe(IV)=O generation. The O-doping improved the acetaminophen degradation rate constant and turnover frequency of Fe-N3O1 by approximately tenfold, and elevated the steady-state concentration of Fe(IV)=O 65 times over. The normalized degradation rate constant of Fe-N3O1/H2O2 was superior to other reported catalysts. Density functional theory calculations indicated that O-doping decreased the charge density of Fe site, enhanced the metal-oxygen bond strength, and reduced the energy barrier for the key reaction intermediate (*O + *H2O), facilitating the efficient and selective formation of Fe(IV)=O. Fe-N3O1/H2O2 demonstrated wide pH tolerance, high resistance to complex water matrices, and excellent stability, making it promising for practical applications. This study provides a new perspective on controlling the selective generation of reactive species to achieve sustainable neutral Fenton-like reactions.

Electrocatalysts support crucial industrial processes and emerging decarbonization technologies, but their design is hindered by structural and compositional changes during operation, especially at application-relevant current densities. Here we use operando X-ray spectroscopy and modelling to track, and eventually direct, the reconstruction of iron sulfides and oxides for the oxygen evolution reaction. We show that inappropriate activation protocols lead to uncontrollable Fe oxidation and irreversible catalyst degradation, compromising stability and reliability and precluding predictive design. Based on these, we develop activation programming strategies that, considering the thermodynamics and kinetics of surface reconstruction, offer control over precatalyst oxidation. This enables reliable predictions and the design of active and stable electrocatalysts. In a NixFe1-xS2 model system, this leads to a threefold improvement in durability after programmed activation, with a cell degradation rate of 0.12 mV h-1 over 550 h (standard operation: 0.29 mV h-1, constrained to 200 h), in an anion exchange membrane water electrolyser operating at 1 A cm-2. This work bridges predictive modelling and experimental design, improving the electrocatalyst reliability for industrial water electrolysis and beyond at high current densities.