Both heterojunction and core-shell photocatalysts have demonstrated promising performance in photocatalytic CO2 conversions to fuels. However, fundamental knowledge of heterojunctions in core-shell structures is highly desired to facilitate the design of future photocatalysts. By combining advanced experimental characterizations and density functional theory (DFT) calculations, the role of the Cu2O@MoS2 heterojunction in photocatalytic CO2 conversions to fuels was investigated. We discovered that the charge dynamics and electron transfer properties of Cu2O@MoS2 photocatalysts are altered by the heterojunction and Cu2O underlayer due to the electron transfer from Cu2O to MoS2 and the change in CO2 adsorption strength on the hybrid catalyst surface. Consequently, more electrons can travel to the surrounding liquid environment to be consumed by CO2 reduction. This study provides experimental and theoretical investigations of the fundamental mechanisms of heterojunction core-shell photocatalysts.

A complete and thorough understanding of the complicated heterogeneous structure of polyamide separation membranes is crucial to improving their performance. Electron tomography has been used to study density variations in dense polymer membranes; however, the nonuniformity of membrane thickness and surface morphology present major challenges to the accuracy of that method. In this article, we show that nanoscale 2D electron energy loss spectroscopy (EELS) maps can be correlated with 3D scanning transmission electron microscopy (STEM) tomography to improve the quantitative mapping of density. We reveal quantitative nanoscale structural differences between commercial seawater and brackish water polyamide thin film composite reverse osmosis membranes and compare them to thin uniform printed membranes. To reduce electron beam damage, we employ a high-speed direct electron detector for low-dose EELS, which allows for membrane thickness and electron scattering measurements to be spatially correlated to improve the measurement of density. We resolve nanoscale differences between three polyamide membranes which have distinctly different separation performances. Our work provides a framework for the use of STEM and EELS to extract heterogeneous density variations in structurally complex membranes.

Anode-free lithium metal batteries (AFLMBs) represent the ultimate solution to mankind's quest for the Holy Grail of batteries, where the cell-level energy density is maximized on the assumption that lithium (Li0) must be fully utilized with near 100% Coulombic efficiency. Although substantial progress has been made since the anode-free concept was first proposed, the challenges presented by the most powerful anode material that can be found on the periodic table still remain unresolved due to its extreme reactive nature, which not only makes it impossible to retain 100% reversibility but also induces inhomogeneity during repeated plating/stripping cycles and persistent capacity loss over a long period of time. The isolated study approaches, emphasizing either individual electrolyte components or interphasial chemistry engineering, but mostly focused on the negative-electrode current collector, hinder insight into issues arising when these components are assembled into cells and forced to interface with each other. In this review, we attempt to examine this high-dimensional topic from a panoramic perspective, with the focus placed on the liquid electrolytes. We first outline the fundamental operating principles of key individual battery components, together with practical perspectives for evaluating lithium utilization and reversibility in AFLMBs. We then discuss how these components interact when assembled into full cells, how such interactions give rise to heterogeneous electrochemical and mechanical behaviors, and how these phenomena can be characterized and regulated. It is also outlined that a hierarchical perspective on lithium behavior, spanning from the nano- to cell-scale, is essential to enable plating, stripping, and recovery in AFLMBs. Finally, we present perspectives from leading researchers actively working on the various elements that constitute AFLMBs and integrate these viewpoints to clarify the future research directions of this field. By providing a system-level framework for understanding AFLMBs, this review aims to guide future research efforts and contribute to addressing the broader challenges of sustainable energy storage.

Sodium metal batteries offer high theoretical energy density but are hindered by nonuniform sodium nucleation, dendritic growth, and poor plating/stripping reversibility on conventional current collectors. Here, a coating-free, intrinsically sodiophilic three-dimensional carbon host is formed via electrochemical co-intercalation of Na-solvent complexes into graphitic carbon paper (I-CP). Structural and surface analyses confirm Na-solvent co-intercalation within graphitic domains while preserving the structural integrity of the carbon framework. Compared with Al foil and graphite controls, I-CP substantially lowers the sodium nucleation overpotential and enables uniform, void-filling sodium deposition throughout the interconnected carbon network, suppressing dendrite formation and dead sodium accumulation. As a result, I-CP achieves a high average Coulombic efficiency of 99.6% over 500 cycles at 1 mA cm−2, and symmetric Na@I-CP cells exhibit stable operation for over 1000 h at 0.5 mA cm−2 / 0.5 mAh cm−2 with an overpotential of ∼20 mV. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry reveal the formation of a chemically homogeneous, vertically graded solid electrolyte interphase comprising an organic-rich outer layer and an inorganic-rich inner region. These interfacial advantages translate to improved full-cell performance: Na@I-CP paired with Na0.44MnO2 and Na3V2(PO4)3 cathodes retains over 85% capacity after 500 cycles at 1 C, while I-CP||Na3V2(PO4)3 cells operated under reduced sodium inventory conditions deliver 81.5 mAh g−1 over 150 cycles at C/2. This work establishes co-intercalated graphitic carbon paper as a scalable and effective current-collector platform for stable and highly reversible sodium metal batteries.

Iridium-containing complex oxides are attractive catalysts for the oxygen evolution reaction (OER) in acidic media, but the link between their structure and long-term performance remains poorly defined. We synthesize a library of Ir-containing double perovskites (' with A = Sr, Ba, and B' = Fe, Co, In, Y, La, Ce, Pr, Nd, Tb) to systematically probe how composition influences restructuring dynamics and steady-state OER activity. Using surface-sensitive spectroscopy, electron microscopy, and rotating disk electrode measurements, we show that all compositions converge to a similar intrinsic activity for the OER after restructuring, but do so at different rates. The B'-site cation dictates dissolution kinetics, with more oxophilic cations showing slower restructuring. These results reveal that while changing the composition of complex Ir oxides has little influence on the intrinsic OER activity of these materials, it has an important effect on dissolution rates and restructuring dynamics, offering a means to engineer catalyst durability under acidic OER conditions.

Chromium trihalides, like CrCl3, are part of an emerging class of van der Waals materials that have been showing promise for their magnetic properties. However, CrCl3 has been produced only by mechanical tape exfoliation, a low yield method, and by liquid exfoliation in organic solvents, with a negative impact on the environment and human health. Here, CrCl3 was produced for the first time by liquid-phase exfoliation (LPE) in aqueous medium, in the presence of polyvinylpyrrolidone (PVP10) or sodium dodecyl sulfate (SDS), followed by ultrasonication. It was also the first time that CrCl3 was obtained with nanometric size (<100 nm), and its photothermal, magnetic, and water stability performances were studied. Results showed that CrCl3 + SDS (zeta potential = -19.9 mV) had better water stability than CrCl3 + PVP10 (zeta potential = 8.6 mV). CrCl3 + SDS and CrCl3 + PVP10 were obtained with a mean particle lateral size of 39.4 +/- 15.9 and 65.6 +/- 47.4 nm and a mean thickness of 4.4 +/- 3.9 and 7.1 +/- 5.3 nm, respectively. Both materials revealed a similar ability to convert near-infrared light into heat, showing a temperature increase of 4.7 degrees C (CrCl3 + SDS) and 5.8 degrees C (CrCl3 + PVP10) after 30 min of irradiation. Results show that the presence of SDS during production leads to a loss of Cl atoms when compared to PVP10, but crystallinity is preserved. Magnetometry measurements show a N & eacute;el temperature of 15 K +/- 2.0 K for both samples, showing its antiferromagnetism. A Curie-Weiss analysis indicates a ferromagnetic dominant paramagnetic phase due to the positive Curie-Weiss temperatures, with the calculated effective moments as 4.20 mu(B) +/- 0.63 mu(B) and 3.95 mu(B) +/- 0.49 mu(B) for CrCl3 + PVP10 and CrCl3 + SDS, respectively. These results show that LPE of CrCl3 with PVP10 or SDS produces 2D CrCl3, preserving crystallinity and magnetic properties, and demonstrating potential for spintronic applications.

Batteries consist of complex, layered interfaces, and their performance‐limiting mechanisms are best understood through nanoscale structural analysis of both anodes and cathodes in realistic full‐cell architectures. This has been challenging for liquid‐electrolyte‐based batteries due to limitations imposed by handling liquid electrolytes and size constraints in most high‐resolution electron microscopes, while cryogenic focused ion beam (cryo‐FIB) milling has typically been limited to a single electrode. Here, a full‐cell cryo‐FIB milling process is presented that reveals anode, cathode, and seprator interfaces in a liquid electrolyte cell with a sodium metal anode and Na 0.44 MnO 2 cathode. This full‐cell cryo‐milled battery stack enables visualization of interfaces at both electrodes, allowing characterization of the entire cell while comparing the effects of two solvents, ethlyene carbonat/diethyl carbonate and digylme, in a NaPF 6 salt‐based electrolyte. It is demonstrated that after moderate cycling (10–50 cycles), degradation pathways differ between carbonate‐ and ether‐based electrolytes. Carbonate‐based cells degrade rapidly, driven largely by electrolyte depletion resulting from excessive solid electrolyte interphase (SEI) formation at the anode. In contrast, diglyme‐based exhibit improved cycling stability but ultimately also experience electrolyte depletion, which instead arises from electrolyte degradation at the cathode. These findings provide insight into solvent‐specific degradation mechanisms relevant to future battery development.

Nanopores embedded within monolayer hexagonal boron nitride (h-BN) offer possibilities of creating atomically thin ceramic membranes with unique combinations of high permeance (atomic thinness), high selectivity (via molecular sieving), increased thermal stability, and superior chemical resistance. However, fabricating size-selective nanopores in monolayer h-BN via scalable top-down processes remains nontrivial due to its chemical inertness, and characterizing nanopore size distribution over a large area remains extremely challenging. Here, we demonstrate a facile and scalable approach of exploiting the chemical vapor deposition (CVD) process temperature to enable direct incorporation of subnanometer/nanoscale pores into the monolayer h-BN lattice, in combination with manufacturing compatible polymer casting to fabricate centimeter-scale nanoporous atomically thin ceramic membranes. We leverage diffusive transport of analytes including size-selective Ficoll sieving to characterize subnanometer-scale and nanoscale defects that manifest as pores in centimeter-scale h-BN membranes, overcoming previous limitations in large-area characterization of nanoscale defects in h-BN. Our approach opens a new frontier to advance atomically thin membranes to 2D ceramic materials, such as h-BN via facile and direct formation of nanopores, for size-selective separations.

A design of experiments (DoE) approach is applied to the study of nitrogen (N)-doped carbons prepared via a molten salt templating method using the eutectic salt lithium chloride/potassium chloride (LiCl/KCl) and the precursors sucrose and melamine (N precursor). This approach is used to deconvolute effects from surface composition and porosity on the electrocatalytic performance of N-doped carbons as oxygen reduction reaction (ORR) electrocatalysts. Additionally, DoE is implemented to reveal the synthesis-structure-function relationship for the prepared materials over an entire design space. From this work, it is evident that the N precursor content has the greatest impact on the tunability of material properties (e.g., N-content, pyridinic N content, surface area, pore size distribution, etc.) followed by pyrolysis temperature and salt mass. Additionally, without adequate porosity (surface area ≥ 500 m2 g-1, micropore volume > 0.15 cc g-1, etc.) and electrochemically active surface area, activity and selectivity for the ORR via N-functionalization is significantly reduced. Optimization of the studied design space indicates that an N precursor content of 35 wt.%-38 wt.%, pyrolysis temperature ≤ 900 °C, and a salt mass < 15 g would garner the necessary N-content (∼7-8 at%) and porosity to achieve the most active and selective N-doped carbon ORR electrocatalysts.

Improved oxygen evolution reaction (OER) electrocatalysts based on an additional understanding of surface changes that occur upon metal dissolution are needed to enable the efficient use of electrochemical water splitting. This work integrates theoretical and experimental studies of the effects of metal dissolution from the RuO2 and Ru1-x Ti x O2 surfaces on the OER activity and electrochemical stability. Our computational analysis shows that the energetic barriers for metal dissolution depend highly on the surface site and Ti-substituent location. Metal dissolution induces the formation of new active surface sites with different electronic density distributions. In addition to dissolution-induced changes to the surface composition, electron density changes occur in the interfacial electrolyte components. Surface reconstruction changes the activation barriers for the OER steps. Our experimental analysis of RuO2 and Ru0.8Ti0.2O2 using a two-step durability test in acidic electrolytes shows that the OER activity, surface, and metal dissolution change over the durability tests. Ti-substitution exhibits improved electrochemical stability with cycling. For RuO2, changes in the mass activity of RuO2 with cycling are directly correlated with Ru dissolution and lowering of the electrochemical surface area (ECSA). In contrast, Ru0.8Ti0.2O2 showed a 19 times lower Ru dissolution rate, and metal dissolution results in increasing the ECSA and new active sites. Our STEM and EELS analysis supports that repeated cycling under OER conditions results in surface reconstruction for both RuO2 and Ru0.8Ti0.2O2, with the formation of a disordered RuO2 surface and changes to the distribution of Ru and Ti at the Ru0.8Ti0.2O2 surface. The experimentally observed changes in activity and surface structure after cycling are consistent with computational analysis, which shows how metal dissolution may alter the OER activation barriers. Combining experimental and computational insights, this work reveals the effects of metal dissolution on the surface atomic and electronic structure and OER activity and advances our comprehension of metal dissolution dynamics and surface reconstruction, which may have implications for other catalytic processes.

Bimetallic heterostructures, including core-shell and Janus configurations, often offer unique electrocatalytic properties compared to monometallic nanoparticles. However, achieving precise control over both elemental composition and spatial arrangement within these structures remains a challenge. Here, an electrosynthesis method is introduced that enables the fabrication of heterostructured bimetallic nanoparticles with precise, independent control of their elemental distribution. By leveraging dual-channel scanning electrochemical cell microscopy (SECCM), the local ionic environment is dynamically modulated in situ, adjusting the deposition bias between channels to achieve selective electrodeposition. This approach allows temporal control over the solution conditions within the SECCM droplet, facilitating the synthesis of multi-layer core-shell nanoparticles with tunable thickness, number, and sequence of layers. This technique is demonstrated with Pt-Cu and Pt-Ni systems, synthesizing arrays of Cu@Pt and Pt@Cu core-shell structures, which are then screened for catalytic activity in hydrogen evolution (HER) and oxygen reduction (ORR) reactions. The high spatial resolution and on-demand control over the composition and structure make this method well-suitable for creating arrays of complex, multi-metallic heterostructures, which is expected to accelerate the discovery of advanced electrocatalytic materials, offering a platform for efficient and scalable electrocatalyst screening.

In the landscape of proton exchange membrane fuel cells (PEMFCs), there is a strong need for durable, low hydrogen crossover membranes that retain high current output and proton conductivity during operation. This study presents the use of UV-Ozone induced defects in graphene to eliminate the proton conductivity penalty commonly associated with traditional crossover mitigation strategies. We report a defect engineered graphene material that demonstrates an increase in hydrogen/proton selectivity of 27%, a decrease in H2 crossover of 24%, with limited to no impact on current output. Furthermore, we demonstrate a membrane that is 39% more durable than state of the art GORE Select membranes and shows no loss in performance after a 100 h accelerated stress test (AST). This study illustrates the viability of 2D material membranes to sieve between H2 and H3O+ in industrial testing conditions and serve as highly scalable and durable fuel cell membranes that represent a significant upgrade over current state of the art membranes for hydrogen fuel cell vehicles and clean energy generation.

In alignment with the Materials Genome Initiative and as the product of a workshop sponsored by the US National Science Foundation, we define a vision for materials laboratories of the future in alloys, amorphous materials, and composite materials; chart a roadmap for realizing this vision; identify technical bottlenecks and barriers to access; and propose pathways to equitable and democratic access to integrated toolsets in a manner that addresses urgent societal needs, accelerates technological innovation, and enhances manufacturing competitiveness. Spanning three important materials classes, this article summarizes the areas of alignment and unifying themes, distinctive needs of different materials research communities, key science drivers that cannot be accomplished within the capabilities of current materials laboratories, and open questions that need further community input. Here, we provide a broader context for the workshop, synopsize the salient findings, outline a shared vision for democratizing access and accelerating materials discovery, highlight some case studies across the three different materials classes, and identify significant issues that need further discussion.

Reverse osmosis (RO) has constituted most of the installed desalination capacity in recent decades. Commercial membranes offer excellent selectivity and reasonable productivity. These membranes, however, suffer from several weaknesses that stem from the use of interfacial polymerization as a means of manufacturing. The inability to control thickness, adjust easily to new chemistries, and avoid surface roughness that enhances foulilng propensity are a few of the weaknesses to conventional membrane fabrication. Numerous materials have been proposed as alternatives to polyamide for RO in recent decades. However, in spite of numerous publications on these new materials, it is remarkable to see how none has even come close to succeeding in replacing conventional RO membrane materials in a commercial setting. This is largely because many of these new materials are incompatible with existing membrane manufacturing approaches such as interfacial polymerization. We must be able to process new materials into thin, defect-free films on conventional supports. This is a significant hurdle for new material adoption in membranes today. New manufacturing methods are needed to address the inherent weaknesses of interfacial polymerization for polyamide and the general processing of newly discovered materials into thin film composite membranes for RO and nanofiltration platforms.

The authentic active sites of oxide-derived copper (OD-Cu), namely grain boundaries (GBs) and oxidized Cu delta+ species, is still debatable, and their role in governing CH4 conversion remains unclear. Herein, this study answers these questions using bimetallic catalysts by novel electro-shock strategy with controllable GBs for the oxidization of Cu delta+ species by modulating Ag loading. The Ag enrichment at the GBs facilitates the bonding of oxygen with the uncoordinated Cu atoms, resulting in GB oxidation effect. The obtained CH4 selectivity is twice that of GBs or nanoalloy effect. The enhanced performance is attributed to the stable Cu delta+ species and unique electron transfer mechanism from GB oxidation structure. Operando attenuated-total-reflection Fourier-transform-infrared-spectroscopy unveils the reaction pathway of CO2-to-CH4 and the sluggish reversible quenching processes of intermediates. Theoretical calculations indicate that the weak *CO adsorption on GB oxidation structure facilitates *CO hydrogenation, promoting CO2-to-CH4 conversion.

Point defect qubits in semiconductors have demonstrated their outstanding capabilities for high spatial resolution sensing generating broad multidisciplinary interest. Hexagonal boron nitride (hBN) hosting point defect qubits have recently opened up new horizons for quantum sensing by implementing sensing foils. The sensitivity of point defect sensors in hBN is currently limited by the linewidth of the magnetic resonance signal, which is broadened due to strong hyperfine couplings. Here, we report on a vacancy-related spin qubit with an inherently low symmetry configuration, the VB2 center, giving rise to a reduced magnetic resonance linewidth at zero magnetic fields. The VB2 center is also equipped with a classical memory that can be utilized for storing population information. Using scanning transmission electron microscopy imaging, we confirm the existence of the VB2 configuration in free-standing monolayer hBN.

The ability to scale two-dimensional (2D) material thickness down to a single monolayer presents a promising opportunity to realize high-speed energy-efficient memristors. Here, we report an ultra-fast memristor fabricated using atomically thin sheets of 2D hexagonal Boron Nitride, exhibiting the shortest observed switching speed (120 ps) among 2D memristors and low switching energy (2pJ). Furthermore, we study the switching dynamics of these memristors using ultra-short (120ps-3ns) voltage pulses, a frequency range that is highly relevant in the context of modern complementary metal oxide semiconductor (CMOS) circuits. We employ statistical analysis of transient characteristics to gain insights into the memristor switching mechanism. Cycling endurance data confirms the ultra-fast switching capability of these memristors, making them attractive for next generation computing, storage, and Radio-Frequency (RF) circuit applications.

Given the growing emphasis on energy efficiency, environmental sustainability, and agricultural demand, there’s a pressing need for decentralized and scalable ammonia production. Converting nitrate ions electrochemically, which are commonly found in industrial wastewater and polluted groundwater, into ammonia offers a viable approach for both wastewater treatment and ammonia production yet limited by low producibility and scalability. Here we report a versatile and scalable solution-phase synthesis of high-entropy single-atom nanocages (HESA NCs) in which Fe and other five metals-Co, Cu, Zn, Cd, and In-are isolated via cyano-bridges and coordinated with C and N, respectively. Incorporating and isolating the five metals into the matrix of Fe resulted in Fe-C5 active sites with a minimized symmetry of lattice as well as facilitated water dissociation and thus hydrogenation process. As a result, the Fe-HESA NCs exhibited a high selectivity toward NH3 from the electrocatalytic reduction of nitrate with a Faradaic efficiency of 93.4% while maintaining a high yield rate of 81.4 mg h−1 mg−1. Converting nitrate from waste sources into ammonia provides an effective method for both wastewater treatment and ammonia production. Here the authors report a scalable solution-phase synthesis of high-entropy single-atom nanocage catalysts for efficient nitrate-to-ammonia conversion.

2D memristors have demonstrated attractive resistive switching characteristics recently but also suffer from the reliability issue, which limits practical applications. Previous efforts on 2D memristors have primarily focused on exploring new material systems, while damage from the metallization step remains a practical concern for the reliability of 2D memristors. Here, the impact of metallization conditions and the thickness of MoS 2 films on the reliability and other device metrics of MoS 2 ‐based memristors is carefully studied. The statistical electrical measurements show that the reliability can be improved to 92% for yield and improved by ≈16× for average DC cycling endurance in the devices by reducing the top electrode (TE) deposition rate and increasing the thickness of MoS 2 films. Intriguing convergence of switching voltages and resistance ratio is revealed by the statistical analysis of experimental switching cycles. An “effective switching layer” model compatible with both monolayer and few‐layer MoS 2 , is proposed to understand the reliability improvement related to the optimization of fabrication configuration and the convergence of switching metrics. The Monte Carlo simulations help illustrate the underlying physics of endurance failure associated with cluster formation and provide additional insight into endurance improvement with device fabrication optimization.

Nanowires composed of a 1:1 stoichiometry of transition metals and chalcogen ions can be fabricated from two-dimensional transition metal dichalcogenides (TMDs) by using electron beam irradiation. Wires fabricated through in situ experiments can be geometrically connected to TMD sheets in various ways, and their physical properties can vary accordingly. Understanding the structural transformation caused by electron beams is critical for designing wire-sheet structures for nanoelectronics. In this study, we report the behavior of nanowires formed inside a monolayer MoS2 sheet by combining phase-contrast images and large-scale atomistic modeling. We investigate the effect of vacancies on the dynamic evolution of wires, such as rotations with different edge structures and breaking, by considering the interactions between MoS wires and MoS2 nanosheets. The obtained insights can be applied to other monolayer TMDs to guide the behavior of TMD wires and fabricate favorable geometries for various applications.