Highly intense wildfires exhibiting extreme combustion phenomena are becoming more common globally, yet little is known of their combustion temperatures compared to smaller fires. Fire behavior, postfire ecosystem recovery, and smoke constituents are sensitive to combustion temperature; while in-situ thermocouple measurements from experimental fires record temperatures <1500 degrees C, comparable measurements from extreme wildfires do not exist. Here, we investigate temperatures in the June 2023 megafires in Quebec via scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) analysis of the atomic ordering and nanoscale structure of carbon aerosols from the wildfire smoke, where higher combustion temperatures increase sp(2) CC bonding and ordered graphitic layering. From both direct lattice imaging and fine structure in EELS spectra, we observe features that are only present for highly graphitic carbons formed at heating regimes of 1900-2500 degrees C, temperatures that are >400-1000 degrees C higher than reported measurements of wildfire temperature. We interpret this disparity to result from a combination of extreme combustion phenomena such as pyrocumulonimbus clouds, which proliferated in Canada during the summer 2023 megafires, and limitations in the performance of thermocouples at such high temperatures. Although this study is limited in scope, our intention is to inspire researchers to question and revisit the convention on wildfire combustion temperatures and the processes that generate them. We propose that wider recognition of ultrahigh wildfire combustion temperatures may warrant a new paradigm in fire management, fire ecology, and air pollution for highly intense fires.

Scaling ferroelectrics to nanometer thicknesses remains a central challenge for low-power, nonvolatile electronics, as leakage currents increasingly dominate with reduced dimensions. Alkali-based, lead-free ferroelectrics offer an environmentally sustainable alternative to lead-based systems, yet their scaling is severely limited by leakage arising from volatile alkali constituents. Here, we show that this intrinsic limitation can be transformed into an advantageous degree of freedom through defect engineering. By precisely modulating alkali deficiency during thin-film synthesis, we engineer clustered defect complexes that function as deep trap states, strongly suppressing leakage and enabling robust ferroelectric operation in ultrathin films down to the sub-10 nm regime at voltages below 100 mV. Our results establish defect-enabled scaling as a viable pathway for advancing environmentally benign ferroelectrics toward ultra-low-power, non-volatile electronic technologies.

Scaling ferroelectrics to nanometer thicknesses remains a central challenge for low-power, nonvolatile electronics, as leakage currents increasingly dominate at reduced dimensions. Alkali-based, lead-free ferroelectrics offer an environmentally sustainable alternative to lead-based systems, yet their scaling is severely limited by leakage arising from volatile alkali constituents. Here, we show that this intrinsic limitation can be transformed into an advantageous degree of freedom through defect engineering. By precisely modulating alkali deficiency during thin-film synthesis, we engineer clustered defect complexes that function as deep trap states, strongly suppressing leakage and enabling robust ferroelectric operation in ultrathin films down to the sub-10 nm regime at voltages below 100 mV. Our results establish defect-enabled scaling as a viable pathway for advancing environmentally benign ferroelectrics toward ultra-low-power, nonvolatile electronic technologies.

Enhancing intrinsic catalytic activity through material engineering remains a key objective in electrocatalysis research. To achieve this, constructing/assembling nanoscale core-shell structures has proven a particularly effective strategy, as it can simultaneously enhance catalytic activity and optimize atom utilization. The altered/modulated electrocatalytic properties of the shell can arise from lattice strain, induced by core-shell lattice mismatch, together with ligand effects, reflecting electronic interactions between heteroatoms. However, synthetically, it is difficult to isolate/separate the strain effect from electronic interactions, making the specific contribution/attribution to altered catalytic activity ambiguous. Here, we report a Pd@Pt core-shell nanocube (NC) system in which the Pd core, with expanded lattice parameters, minimizes its strain effect on the Pt shell. The Pt shell exhibits a more than 10-fold increase in catalytic activity compared to pure Pt NCs for both the hydrogen oxidation (HOR) and oxygen reduction (ORR) reactions under alkaline conditions. X-ray photoelectron spectroscopy analysis revealed a downshift of the Pt d-band center, and density functional theory calculations indicate that this change arises predominantly from electronic effects rather than strain effects, weakening the binding strength of reaction intermediates and thereby enhancing electrocatalytic activity. This work highlights the significance of electronic effects in tuning electrocatalytic activity.

Two-dimensional (2D) magnets provide a versatile platform for exploring emergent quantum phases and developing next-generation spintronic devices. Despite this potential, high-throughput chemical vapor deposition (CVD) of ternary phase 2D magnets remains a significant challenge and is rarely explored. Here, we report a seeded-CVD method to synthesize nanoplates of a 2D magnetic material, Fe3GeTe2 (FGT), with lateral sizes of 10 μm and thicknesses of 20-80 nm. Synthesized nanoplates exhibit high Curie temperature (Tc ∼ 206 K) and large coercive field (∼1 T) based on reflective magnetic circular dichroism (RMCD) measurements. Cross-sectional scanning transmission electron microscopy and multislice electron ptychography directly reveal widespread and 3D-inhomogeneous Fe intercalation within the vdW gaps that is quantified to be Fe3+xGeTe2 with x ≈ 0.4, which resolves the atomic structural origins of the magnetic enhancement. These results enable a scalable route to synthesize 2D ternary magnet Fe3GeTe2 directly for property studies and device integration.

Local structural features in zeolites-such as crystal surfaces, interfaces, and defects-critically influence molecular transport and catalysis, yet their nonperiodic nature renders 3D, high-resolution characterization difficult. Here, we show that multislice electron ptychography (MEP) opens new opportunities to address this limitation. Through simulation-guided optimization of acquisition parameters and the use of low electron doses to avoid structural damage, MEP attains atomic-scale lateral and nanometer-scale depth resolution, enabling visualization of diverse local structures in the MFI-type zeolite ZSM-5. This depth sensitivity reveals nanometric surface roughness, [010]/[100] intergrowth with an intervening MEL-type domain, and a previously unreported planar defect involving intra-crystalline translational offsets. These findings highlight pronounced structural inhomogeneity in this widely studied zeolite and demonstrate the potential of MEP for probing 3D nonperiodic structures in other zeolites and in similarly beam-sensitive materials.

Pinpointing the active sites where electrocatalytic reactions occur requires atomic resolution and is fundamental to rational catalyst design. In water electrolysis, the oxygen evolution reaction (OER) is driven by highly oxidizing potentials that typically transform electrocatalysts into metastable structures with high oxidation states, often reaching +4, even to +6. However, these metastable structures relax back once the potential is removed, complicating the identification of the true active structure and undermining long-term catalyst stability 13. Using atomic-resolution cryogenic scanning transmission electron microscopy (Cryo-STEM), we directly visualized the metastable structure of a widely used OER electrocatalyst, nickel–iron (oxy)hydroxides, under operating conditions. Combining in-situ X-ray absorption spectroscopy, Cryo-STEM and electrochemical measurements, we find low(er) oxidation states (Fe3+ and Ni2+) are preserved during catalysis and are sufficient to drive the reaction efficiently, contrary to conventional expectations that high-oxidation-state sites are essential for strongly oxidizing reactions. Meanwhile, this electrocatalyst exhibits 2.2 A/cm2 at 1.8 V, in anion exchange membrane water catalysts, a state-of-the-art performance. These findings experimentally demonstrate an apparent thermodynamic anomaly: that low(er)-oxidation-state sites can efficiently drive highly oxidizing reactions, paving the way to design durable OER electrocatalysts.

Electrocatalysts, suitable for at-scale applications, must integrate high activity, long-term durability, and cost-effectiveness, with the latter presenting a major challenge for platinum-group-metal (PGM) electrocatalysts. Alkaline systems enable the use of cost-effective transition metals. However, developing non-PGM electrocatalysts that can catalyze the high-potential oxygen evolution reaction (OER) with high stability remains challenging. Here, we report on metallic Ni catalysts with a Co- and Fe-rich shell (Ni@FeCo), which, during OER operation, transforms into an active oxide shell. Anion exchange membrane water electrolyzers (AEMWEs) employing Ni@FeCo catalysts exhibited excellent performance, reaching 10 A cm-2 at 2.18 V. Operando X-ray characterizations revealed the oxidation of Co and Fe, while Ni remained mostly metallic across all AEMWE operating potentials. Structural characterization, by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS), revealed that the active Ni@FeCo catalysts feature a metallic Ni core and a Ni-Fe-Co spinel oxide shell. This metal-core/oxide-shell heterostructure provides efficient electron transport and OER activity while remaining stable under AEMWE operating potentials. The Ni@FeCo catalysts operated stably for over 1700 h in an AEMWE, highlighting their potential for practical applications and demonstrating a viable strategy for designing nonprecious metal-based electrocatalysts.

High-quality, multifunctional two-dimensional (2D) titanium oxynitide (TiNO) thin films and one-dimensional (1D) TiNO nanowires have been synthesized using a pulsed laser deposition, a simple, fast, and congruent evaporation method. First-principles calculations as a function of surface orientation and termination indicate that surface oxidation of TiNO nanowires can stabilize the (110) orientation observed experimentally. The specific capacitance value for the TiNO nanowire samples (2725 mF/cm2) has been found to be nearly six times more than that of the TiNO thin film samples (400 mF/cm2), which is attributed to the high packing density of TiNO nanowires over a given area. The nanowire samples have also been found to exhibit a significantly higher energy density (1.35 μWh/cm2) than the TiNO thin-film samples (0.33 μWh/cm2). Thus, the TiNO material system in thin-film and nanowire forms has been demonstrated to be a promising candidate for use as an electrode material in supercapacitors and other charge-storage applications.

The lack of mechanistic understanding and catalyst design principles for alkaline electrolytes, especially for the sluggish oxygen reduction reaction, has impeded the advancement of alkaline fuel cells. Here we propose a modified volcano plot and apply this rationale to strategically design Pt nanosheets with PdHx nanosheets substrates. This catalyst exhibited high stability with a specific activity of 1.71 mA cm−2 at 0.95 V versus the reversible hydrogen electrode, surpassing the benchmark of Pt/C by 49-fold. Spectroscopic, electrochemical and electron microscopic characterizations revealed that such performance enhancement originated from tensile-strained Pt{111} facets, improving oxidative stability and suppressing carbon corrosion. In fuel cell testing, the catalyst enabled a peak power density of 1.67 W cm−2 with a loading of 10 µgPGM Cathode cm−2. Further optimization delivered a peak power density of 21.7 W mg−1PGM Cathode+Anode with a total specific catalyst cost US$1.27 kW−1, surpassing the US Department of Energy’s Pt group metal loading and cost targets. This study provides valuable insights into catalyst design for the alkaline oxygen reduction reaction. Volcano plots are useful catalyst design tools for acidic oxygen reduction reaction, but have proved less successful for alkaline oxygen reduction reaction. Here, a modified volcano plot for this environment is developed and used to design PdHx@Pt nanosheets with high oxygen reduction reaction performance.

The development of nonprecious-metal-based hydrogen oxidation reaction (HOR) electrocatalysts remains as the bottleneck for achieving high-performance, platinum group metal-free (PGM-free) alkaline/anion exchange membrane fuel cells. Numerous efforts have been dedicated toward enhancing the HOR activity of Ni catalysts due to the lack of alternative choices. However, mechanistic insights relating to electrocatalytic activity and degradation remain a matter of debate, and proposed models tend to lack conclusive experimental evidence. Here, we studied the state of Ni catalysts using scanning transmission electron microscopy and electron energy loss spectroscopy, together with in situ high energy resolution fluorescence detected X-ray absorption spectroscopy. The results revealed that a metallic Ni surface is crucial for effectively catalyzing the HOR, and that the formation of α-Ni(OH)2 at potentials positive of +0.3 V vs. RHE leads to deactivation of the catalyst. Further analysis with theoretical calculations revealed a strong interaction between the Ni surface and graphene, resulting in a tightly sealed carbon shell that protects the Ni surface. The analysis further indicates that HOR occurs on graphene-protected Ni@C catalysts through the transport of hydrogen and protons across the carbon shell, particularly at self-healing larger holes. Using the Ni@C catalyst, together with evidence-informed experimental protocols to avoid oxidation before, during, and after membrane electrode assembly fabrication and testing, we achieved a milestone PGM-free AEMFC peak power density performance of 1.0 W/cm2. This is a demonstration of a Watt-scale performance for a PGM-free AEMFC.

Scaling ferroelectrics to nanometer thicknesses remains a central challenge for low-power, nonvolatile electronics, as leakage currents increasingly dominate at reduced dimensions. Alkali-based, lead-free ferroelectrics offer an environmentally sustainable alternative to lead-based systems, yet their scaling is severely limited by leakage arising from volatile alkali constituents. Here, we show that this intrinsic limitation can be transformed into an advantageous degree of freedom through defect engineering. By precisely modulating alkali deficiency during thin-film synthesis, we engineer clustered defect complexes that function as deep trap states, strongly suppressing leakage and enabling robust ferroelectric operation in ultrathin films down to the sub-10 nm regime at voltages below 100 mV. Our results establish defect-enabled scaling as a viable pathway for advancing environmentally benign ferroelectrics toward ultra-low-power, nonvolatile electronic technologies.

Rechargeable zinc-air batteries (ReZAB) have emerged as the next-generation batteries with several advantages over the conventional lithium-ion battery. In this work, single nanocrystals of inverse-type high-entropy spinel oxides (HESOx, particle size of 10-12 nm) confined in highly curved defective onion-like carbons (HESOx/OLCAT) as efficient electrocatalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and ReZAB, have been synthesized. The HESOx materials were thoroughly characterized using several analytical techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), Raman, and electron paramagnetic resonance (EPR). HESOx/OLCAT catalyst was tested for ReZAB using literature-recommended parameters that would allow for real technological application. These parameters include a current loading of 10 mA cm-2 and a discharge areal energy density of 35 mWh cmgeometric -2, which maps a Li-ion battery pack-level specific energy of 120 Wh kgpack -1. HESOx/OLCAT electrocatalysts allowed for continuous discharging and charging at a current loading of 10 mA cm-2 with discharge areal energy densities between 37 and 74 mWh cmgeometric -2, thus outperforming the recommended threshold of 35 mWh cmgeometric -2. Considering that most studies (>90%) hardly meet the recommended threshold for technological application of ReZAB, the present work represents one of the top-performing electrocatalysts for ReZAB. The excellent electrocatalytic properties of defect-rich HESOx/OLCAT toward ORR/OER and ReZAB are governed by the strong electronic modulation arising from d-π hybridization, the availability of multiple catalytic sites for intermediates, and weakened d-band centers of the rate-determining intermediates (i.e., *O adsorption for ORR and *OOH formation for OER) compared to the pristine HESOx. This work introduces an effective approach for the design and synthesis of single nanocrystals of high-entropy electrocatalysts for the development of low-cost, robust, and technologically relevant rechargeable zinc-air batteries.

When hydrogen atoms occupy interstitial sites in metal lattices, they form metal hydrides (MHx), whose structural and electronic properties can differ significantly from those of the host metals. Determining where the hydrogen is located within the MHx is crucial for predicting and understanding the resultant unique physical and electronic properties of the hydride. Yet, directly imaging hydrogen within a host material remains a major challenge due to its weak signal in conventional X-ray and electron imaging techniques. Here, we employ electron ptychography, a scanning transmission electron microscopy (STEM) technique, to image the three-dimensional (3D) distribution of H atoms in palladium hydride (PdHx) nanocubes, one of the most studied and industrially relevant MHx materials. We observe an unexpected one-dimensional superlattice ordering of hydrogen within the PdHx nanocubes and 3D hydrogen clustering in localized regions within the PdHx nanocubes, revealing spatial heterogeneity in metal hydride nanoparticles previously inaccessible by other methods.

The colloidal synthesis of high entropy oxide (HEO) nanocrystals requires navigating and balancing competing reaction pathways, which are often unknown. There is also a limited understanding of HEO nanocrystal formation and growth pathways, which hinders morphological control. Here, we report on the colloidal synthesis of rocksalt-type (FeCoMnMgZn)O nanocrystals with different morphologies. Reaction pathway studies show a Fe-rich spinel-type intermediate and indicate that competing chemical reactivities dictate the final compositions and morphologies. Atomic resolution imaging analysis of concave cubic and dendritic (FeCoMnMgZn)O nanocrystals indicate a 1.73% lattice expansion relative to bulk FeO. The (FeCoMnMgZn)O nanocrystals are active electrocatalysts for the oxygen evolution reaction in alkaline media.

High-entropy semiconducting nanocrystals involving the random incorporation of five or more metals within a single, disordered lattice are receiving significant research interest as catalytic materials. Among these, high-entropy sulfide (HES) nanocrystals demonstrate potential as electrocatalysts but have been slower to gain research interest compared to other high-entropy systems due to the complications introduced by multistep, high-temperature synthesis techniques and the issues of material stability during performance. In this work, we report a simple, reproducible, and scalable HES synthesis to produce star-like nanocrystals. The HES nanocrystals show promise as electrocatalysts with high stability by maintaining a uniform overpotential within 1.5% of the initial value for over 2,200 cycles while rotating, with values as low as 313 mV at 10 mA/cm2 for the oxygen evolution reaction (OER) in alkaline media. Our work provides a low-temperature, colloidal method in the formation of highly complex, phase-pure thiospinel high-entropy sulfide nanocrystals.

Mechanical bonds arise between molecules that contain interlocked subunits, such as one macrocycle threaded through another. Within polymers, these linkages will confer distinctive mechanical properties and other emergent behaviors, but polymerizations that form mechanical bonds efficiently and use simple monomeric building blocks are rare. In this work, we introduce a solid-state polymerization in which one monomer infiltrates crystals of another to form a macrocycle and mechanical bond at each repeat unit of a two-dimensional (2D) polymer. This mechanically interlocked 2D polymer is formed as a layered solid that is readily exfoliated in common organic solvents, enabling spectroscopic characterization and atomic-resolution imaging using advanced electron microscopy techniques. The 2D mechanically interlocked polymer is easily prepared on multigram scales, which, along with its solution processibility, enables the facile fabrication of composite fibers with Ultem that exhibit enhanced stiffness and strength.

Capturing the active state of (electro)catalysts under operating conditions, namely operando, is the ultimate objective of (electro)catalyst characterization, enabling the unraveling of reaction mechanisms and advancing (electro)catalyst development. Operando insights advance our understanding of the correlations between electrochemical tests and device-level performances. However, operando characterization of electrocatalysts is challenging due to the complexity of electrochemical devices and instrumental limitations. As a result, the majority of electrocatalyst characterizations have been limited to half-cell in situ studies. Here, we present an operando X-ray absorption spectroscopic study of Mn spinel oxide electrocatalysts in an operating fuel cell employing a custom-designed cell. Our results reveal that in anion exchange membrane fuel cells, the Mn valence state, within spinel Mn3O4/C, increases to above 3+, adopting an octahedral coordination devoid of Jahn-Teller distortions. This structural change results in an AEMFC performance equivalent to that of Co1.5Mn1.5O4/C, a composition that outperforms Mn3O4/C in rotating disk electrode tests. Our results underscore the importance of operando characterizations in elucidating the active state of electrocatalysts and understanding the correlation(s) between electrochemical tests and device performance.