Iron-nitrogen-carbon materials are promising nonprecious-metal catalysts for oxygen reduction reaction, yet their active-site density is inherently limited by conventional high-temperature synthesis. Herein, we introduce a precursor-mediated synthesis strategy that overcomes this bottleneck by using ferrous oxalate as a highly dispersed iron source. Controlled low-temperature decomposition generates ultrafine FeOx nanoparticles, which are subsequently converted into atomically dispersed Fe-N4 sites during pyrolysis. The concomitant release of CO2 concurrently etches the carbon matrix, creating additional defects and microporosity. This approach achieves a high site density of 1.18 × 1020 sites g-1 (3.4 ± 0.6 atoms nm-2). The resulting catalyst exhibits outstanding ORR performance in acidic medium, with a half-wave potential of 0.825 V vs RHE, and achieves a peak power density of 1.43 W cm-2 in a practical H2-O2 fuel cell. Operando X-ray absorption spectroscopy further reveals the reversible structural dynamics of the Fe-N4 sites, which switch between tetra- and penta-coordinated configurations during the reaction, directly evidencing that such coordination flexibility optimizes intermediate adsorption/desorption and enhances catalytic activity. This work provides a practical route to break the site-density ceiling in Fe-N-C catalysts and delivers insights into coordination-environment evolution of single-atom centers under working conditions.

The degradation mechanism of Fe-N-C catalysts in practical proton exchange membrane fuel cells remains unclear. Well-controlled rotating disk electrode (RDE) tests often fail to replicate the degradation processes under device‑relevant conditions. Here we reveal a device-operation-specific degradation mechanism for the active high‑spin D1 sites. The high current densities in operating fuel cells create a unique interfacial microenvironment—simultaneously alkaline-shift and rich in hydroxyl radicals—which drives D1 conversion into a metastable D4 intermediate. The D4 state, featuring an FeN4 center surrounded by a deeply-oxidized carbon coordination shell, dissolves rapidly following pH recovery. The fate of dissolved Fe ions in running fuel cells will either be carried away with electrolyte flow or aggregate into Fe oxides, depending on interfacial fluid flows. In contrast, under milliampere-level RDEs, D1 sites dissolve directly without forming this D4 intermediate. This D4 pathway challenges the long-held view of immediate Fe dissolution. Furthermore, the deactivation of the D4 state is identified as electron‑transfer blocking by its over‑oxidized carbon periphery, a previously unidentified deactivation mechanism. These findings underscore that catalyst degradation mechanism can be dictated by operationally-induced microenvironments, a concept likely relevant beyond fuel cells.

An in-situ tender X-ray absorption spectroscopy (XAS) technique was developed to enhance the characterization of key light elements, including P, S, Cl, K, etc., which are indispensable for studies in new energy materials, environmental pollutant monitoring, and biological toxins analysis. A quick-scanning XAS (QXAS) technique was established for the tender X-ray energy range (2–5 keV), improving temporal resolution from tens of minutes to a few seconds. Effective noise suppression was achieved via incorporating an analog low-pass filter for QXAS acquisition. In addition, a digital Butterworth filter was applied for comparison. Quick-scanning at the maximum speed enabled the acquisition of XAS spectra for S, Cl, and K elements in less than 18s, 12s, and 7s, respectively. The resulting data exhibited good consistency with conventional measurements, confirming the reliability of the QXAS system. As a proof-of-concept, in-situ QXAS monitoring of the sulfur K-edge during lithium–sulfur battery (LSB) discharge demonstrated the system’s capability for observing dynamic electrochemical processes. An integrated QXAS system for the tender X-ray regime has been developed, achieving second-scale time resolution through rapid and periodic monochromator scanning. The analog low-pass filter effectively suppresses noise under quick-scanning conditions. This system shows strong potential for advancing the mechanistic understanding of complex dynamic processes.

The 1W1B beamline, a vital hard X-ray absorption spectroscopy facility in northern China, has been running for over 20 years. It has attracted a large user community and achieved high productivity. However, the available beam time is severely insufficient to meet the growing user demand. Furthermore, a new upgrade project was implemented in 2024, and the higher flux necessitates a reevaluation of thermal deformation in optical components of the beamline. In recent years, substantial efforts have been made to enhance beam performance, develop many important techniques and improve experimental efficiency. Following the new upgrade project in 2024, a set of water-cooled switchable carbon film filters was installed in the front end of the beamline to better manage the heat load. Additionally, a newly-designed double crystal monochromator has replaced the old one to enhance stability during energy scans. These improvements are expected to ensure the safe and stable operation of 1W1B beamline following the upgrade project, and also provide improved beam performance for the XAFS user community.

The pursuit of high-energy solid-state lithium metal batteries (ssLMBs) is challenging, due to the sluggish ion transport in solid electrolytes and unstable electrode-electrolyte interfaces. Herein, we showcase regulating Li+ solid-state coordination as a feasible strategy. By constructing Li+ coordination with poly-1,3-dioxolane chains and anions, an in situ polymerized solid electrolyte (PDTE) is obtained with an ionic conductivity of 1.45 mS cm-1, Li+ transference number of 0.67, and high interfacial compatibility. As the bifunctional promoter, it alleviates Li+ hopping barriers via the ligand-field effects and establishes the conformal solid/cathode-electrolyte interfaces. Its derived Li|PDTE|LiFePO4 ssLMBs maintains cycling for over 1000 cycles at 2 C with 92.5% retention in capacity, and at the fast-charging rate up to 20 C. When coupled with a LiNi0.8Co0.1Mn0.1O2 cathode, PDTE further showcases promises in stable operation under a wide voltage window from 2.8 to 4.5 V and a low-temperature range down to -20 °C. Toward practical promises, 5.7 Ah solid-state pouch cells are further assembled with an energy density of 513 Wh kg-1 and the elevated safety for thermal runaway.

Learning from nature has garnered significant attention in the scientific community for its potential to inspire creative solutions in material or catalyst design. The study reports a biomimetic single selenium (Se) site‐modified carbon (C) moiety that retains the unique reactivity of selenoenzyme with peroxides, aiming to selectively catalyze the oxygen reduction reaction (ORR). The as‐designed Se‐C demonstrates nearly 100% 4‐electron selectivity, evidenced by 0.039% of H2O2 yield at 0.5 V versus reversible hydrogen electrode, outperforming commercial platinum (Pt) by 65 times. In‐situ X‐ray absorption spectroscopy and theoretical calculations attribute this exceptional selectivity to the enzyme‐like behaviors of the Se site to steal an O atom from peroxide intermediates. The second achievement is the significantly increased consecutive 2+2 electron selectivity. Benefiting from the enzyme‐like H2O2 reduction activity with a higher onset potential of 0.915 V compared to Pt at 0.875 V, the Se‐C as a secondary catalytic site reduced the H2O2 yields of the Co‐N‐C, Fe‐N‐C, and N‐C catalysts by 96%, 67%, and 98%, respectively, via a consecutive 2+2 electron pathway. This also leads to more stable catalysts via protecting the active sites from oxidative attacks. This work establishes new pathways for precise tuning of reaction selectivity in ORR and beyond.

Hydrophobic polymer encapsulation enhances the water stability of lead halide perovskites but often lacks precise control over the perovskite-polymer interfaces, limiting luminescence tunability. Herein, we propose a synergistic hydrophilic-hydrophobic polymer strategy to engineer the local coordination environment of MAPbBr(3) in luminescent fibers via electrospinning. Combining the hydrophobic polymer PMMA with the hydrophilic copolymer PMN, it is demonstrated that the PMN/PMMA weight ratio could modulate the Pb coordination environment (i.e. Pb-O vs Pb-Br bond), and subsequently tune the crystallinity of MAPbBr(3), by synchrotron radiation X-ray absorption fine structure spectroscopy (XAFS), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS) characterization. This coordination engineering, coupled with crystallinity regulation, tailors the photoluminescence, resulting in a photoluminescence quantum yield (PLQY) enhancement of similar to 48 % at the optimal weight ratio (PMN/PMMA = 0.08). Crucially, PMN endows the fibers with unique water-responsive behavior: moderate moisture could induce the increasing photoluminescence of MAPbBr(3) through recrystallization, whereas excessive water could result in degrading the unencapsulated MAPbBr(3) outside the fibers. This work establishes a polymer-mediated coordination control paradigm for developing waterproof, tunable perovskite luminescent materials.

Lithium-rich layered oxide (LRLO) cathodes are recognized for their high energy densities, primarily driven by oxygen-related anionic redox activities, yet substantial activation of this process simultaneously induces structural instability. The typical voltage range in academic studies spans 2.0–4.8 V. Although 2.5–4.5 V are generally considered in industrial applications for enhanced capacity retention and electrolyte compatibility, this moderate voltage window leads to reduced capacity. To address energy density limitations, several top battery suppliers propose to separately increase the formation voltage during the initial cycle to enhance capacity, while other companies (e.g., Contemporary Amperex Technology Co., Ltd., CATL) claim that this high-voltage formation protocol would exacerbate cycling capacity fading. Herein, we systemically demonstrate that high-voltage formation promotes substantial Li + extraction from the transition metal (TM) layers, creating vacancies (in TM layer) that drive in-plane TM migration. This migration triggers a transformation in the OM 6 (M, cation) configuration from O4 (OLi x TM 2 ) to O5 (OLi y TM 1 ). Such evolution simultaneously enhances both anionic and cationic redox activity, collectively boosting capacity. Nonetheless, the induced in-plane TM migration would further aggravate out-of-plane TM migration, leading to progressive structural degradation, which has been elucidated as the main reason for cycling capacity fading.

Pulsed electrochemical methods have emerged as a simple and effective approach for increasing catalyst durability and improving product selectivity. However, mechanistic understanding is primarily derived from traditional experimental techniques or theoretical calculations, which only provide ex situ information and prevent accurate analysis of electrochemical processes. In this study, we developed a novel potential modulated difference X-ray absorption fine structure (PM-diffXAFS) spectroscopy technique for the in situ observation of the dynamic evolution of Pt catalysts in pulsed electrolysis at the atomic level. The near-surface layers of the Pt catalyst underwent periodic oxidation and reduction within a few seconds, while the oxygen species that entered the bulk of the Pt catalyst were maintained, while the oxidation state was much lower at high potential under pulsed conditions than that under steady conditions, which was helpful for preventing the overoxidation of Pt catalysts. Besides, the tailored oxidation state could be achieved by adjusting the pulsed potential and duration. The present study provides a novel approach to understanding the pulse electrolysis process, and the strategy developed in this work offers guidance for optimizing the stability and selectivity of catalysts.

DNA methylation regulates fruit ripening in tomato, and disruption of the DNA demethylase DEMETER-LIKE 2 (DML2) results in genome-wide DNA hypermethylation and impaired ripening. We report here that the transcription factors Ripening Inhibitor (RIN) and FRUITFULL 1 (FUL1) play critical roles in mediating the effect of DNA methylation on tomato fruit ripening. RIN and FUL1 are silenced in dml2 mutant plants, and the defective ripening phenotype of dml2 is mimicked by the rin/ful1 double mutant. Restoration of RIN expression in dml2 partially rescues its ripening defects. DNA methylation controls ripening not only by regulating the expression of RIN and FUL1 but also by interfering with the genomic binding of RIN. In dml2 mutant plants, RIN cannot bind to some of its targets in vivo even though DNA methylation does not interfere with RIN binding in vitro; this inhibited binding in vivo is correlated with increased DNA methylation and histone H3 enrichment within 100 bp of the binding site. Our work uncovers the molecular mechanisms underlying DNA methylation control of fruit ripening in tomato.

Efforts to improve the specific capacity and energy density of lithium nickel-cobalt-manganese oxide (NCM) cathodes focus on operating at high voltages or increasing nickel content. However, both approaches necessitate a thorough understanding of the charge compensation mechanism. Traditional ionic-bonding models which separate transition metal (TM) and oxygen redox processes prove inadequate as anionic redox becomes significant, ignoring crucial metal-oxygen interactions. In this study, we systematically investigate the charge compensation process in low-nickel and high-nickel NCMs under high-voltage conditions. Here, the involvement of oxygen is critical in redox, as it shares electrons with TM to form a strong TM-O covalent bond. Compared to low-Ni NCMs, high-Ni NCMs exhibit an oxygen dimerization stage with trapped O2, which leads to the aggregation of vacancies in the transition metal layer, thereby accelerating structural destabilization. This variation in oxygen dimerization behavior among NCMs is closely correlated with differences in elemental composition, spin states, and stacking faults. Our findings comprehensively reveal the redox behaviors of transition metals and oxygen, particularly highlighting oxygen behavior at each delithiation state, helping to optimize the utilization of oxygen redox reactions in commercial NCM compounds for high-capacity and high-energy-density lithium-ion batteries.

In order to expand the range of synchrotron radiation structural characterization modes, an automated in-situ X-ray absorption fine structure (XAFS) spectroscopy characterization for electrochemical research has been established. An in-situ control system equipped with an automatic trigger capability facilitates automated acquisition of XAFS and electrochemical data. Furthermore, the quick scanning XAFS (QXAFS) terminal, in-situ server and data storage were all controlled by remote users, enabling remote measurement to be achieved. Using this system, the evolution of the local structure near Fe atoms during the charging and discharging of lithium-sulfur battery (LSB) cathode materials was observed, which provides deep insights into the sulfur reaction pathway in LSBs by leveraging structural information. The system established here paves the way for fully automated and intelligent in-situ XAFS experiments.

Electrocatalytic acetylene semi-hydrogenation (EASH) offers a promising and environmentally friendly pathway for the production of C2H4, a widely used petrochemical feedstock. While the economic feasibility of this route has been demonstrated in three-electrode systems, its viability in practical device remains unverified. In this study, we designed a highly efficient electrocatalyst based on a PdCu alloy system utilizing the hydrogen spillover mechanism. The catalyst achieved an operational current density of 600 mA cm-2 in a zero-gap membrane electrode assembly (MEA) reactor, with the C2H4 selectivity exceeding 85%. This data confirms the economic feasibility of EASH in real-world applications. Furthermore, through in situ Raman spectroscopy and theoretical calculations, we elucidated the catalytic mechanism involving interfacial hydrogen spillover. Our findings underscore the economic viability and potential of EASH as a greener and scalable approach for C2H4 production, thus advancing the field of electrocatalysis in sustainable chemical synthesis.

The efficacy of the oxygen reduction reaction(ORR)in fuel cells can be significantly enhanced by optimiz-ing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e-pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,signifi-cantly reducing the production of hydrogen peroxide(H2O2).Remarkably,the optimized catalyst demon-strated superior fuel cell performance,with peak power densities of 1.32 W cm-2 in oxygen and 0.61 W cm-2 in air environments,respectively.A significant decrease in H2O2 by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.

Pressure-induced structural phase transitions play a pivotal role in unlocking novel material functionalities and facilitating innovations in materials science. Nonetheless, unveiling the mechanisms of densification, which relies heavily on precise and comprehensive structural analysis, remains a challenge. Herein, we investigated the archetypal B4 -> B1 phase transition pathway in ZnO by combining x-ray absorption fine structure (XAFS) spectroscopy with machine learning. Specifically, we developed an artificial neural network (NN) to decipher the extended-XAFS spectra by reconstructing the partial radial distribution functions of Zn-O/Zn pairs. This provided us with access to the evolution of the structural statistics for all the coordination shells in condensed ZnO, enabling us to accurately track the changes in the internal structural parameter u and the anharmonic effect. We observed a clear decrease in u and an increased anharmonicity near the onset of the B4 -> B1 phase transition, indicating a preference for the iT phase as the intermediate state to initiate the phase transition that can arise from the softening of shear phonon modes. This study suggests that NN-based approach can facilitate a more comprehensive and efficient interpretation of XAFS under complex in-situ conditions, which paves the way for highly automated data processing pipelines for high-throughput and real-time characterizations in next-generation synchrotron photon sources.

The single-atom Fe−N−C is a prominent material with exceptional reactivity in areas of sustainable energy and catalysis research. It is challenging to obtain the dense Fe-N 4 site without the Fe nanoparticles (NPs) sintering during the Fe−N−C synthesis via high-temperature pyrolysis. Thus, a novel approach is devised for the Fe−N−C synthesis at low temperatures. Taking FeCl 2 as Fe source, a hydrogen environment can facilitate oxygen removal and dichlorination processes in the synthesis, efficiently favouring Fe-N 4 site formation without Fe NPs clustering at as low as 360 °C. We shed light on the reaction mechanism about hydrogen promoting Fe-N 4 formation in the synthesis. By adjusting the temperature and duration, the Fe-N 4 structural evolution and site density can be precisely tuned to directly influence the catalytic behaviour of the Fe−N−C material. The FeNC-H 2 -360 catalyst demonstrates a remarkable Fe dispersion (8.3 wt %) and superior acid ORR activity with a half-wave potential of 0.85 V and a peak power density of 1.21 W cm −2 in fuel cell. This method also generally facilitates the synthesis of various high-performance M−N−C materials (M=Fe, Co, Mn, Ni, Zn, Ru) with elevated single-atom loadings.

Although Ru-based materials are among the outstanding catalysts for the oxygen evolution reaction (OER), the instability issue still haunts them and impedes the widespread application. The instability of Ru-based OER catalysts is generally ascribed to the formation of soluble species through the over-oxidation of Ru and structural decomposition caused by involvement of lattice oxygen. Herein, an effective strategy of selectively activating the lattice oxygen around Ru site is proposed to improve the OER activity and stability. Our synthesized spinel-type electrocatalyst of Ru and Zn co-doped Co 3 O 4 showed an ultralow overpotential of 172 mV at 10 mA cm −2 and a long-term stability reaching to 100 hours at 10 mA cm −2 for alkaline OER. The experimental results and theoretical simulations demonstrated that the lattice oxygen site jointly connected with the octahedral Ru and tetrahedral Zn atoms became more active than other oxygen sites near Ru atom, which further lowered the reaction energy barriers and avoided generating excessive oxygen vacancies to enhance the structural stability of Ru sites. The findings hope to provide a new perspective to improve the catalytic activity of Ru-incorporated OER catalysts and the stability of lattice-oxygen-mediated mechanism.

Replacement of expensive and rare platinum with metal-nitrogen-carbon catalysts for oxygen reduction reactions in proton exchange membrane fuel cells is hindered by their inferior activity. Herein, we report a highly active iron-nitrogen-carbon catalyst by optimizing the carbon structure and coordination environments of Fe-N-4 sites. A critical high-temperature treatment with ammonium chloride and ammonium bromide not only enhances the intrinsic activity and density of Fe-N-4 sites, but also introduces numerous defects, trace Br ions and creates mesopores in the carbon framework. Notably, surface Br ions significantly improve the interaction between the ionomer and catalyst particles, promoting ionomer infiltration and optimizing the O-2 transport and charge transfer at triple-phase boundary. This catalyst delivers a high peak power density of 1.86Wcm(-2) and 54mAcm(-2) at 0.9 ViR-free in a H-2-O-2 fuel cells at 80 degrees C. Our findings highlight the critical role of interface microenvironment regulation. Replacing expensive and rare platinum with metal-nitrogen-carbon catalysts in proton exchange membrane fuel cells is limited by their lower activity and stability for oxygen reduction reactions. The authors report Fe-N-C catalyst with trace Br ions to enhance Fe-N4 density and introduce defects and mesopores, achieving high activity for oxygen reduction reaction in proton exchange membrane fuel cell.

Quasi-2D perovskites show great potential as photovoltaic devices with superior stability, but the power conversion efficiency (PCE) is limited by poor carrier transport. Here, it is simultaneously affected the hole transport layer (HTL) and the perovskite layer by incorporating pyridine-based materials into poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) to address the key problem above in 2D perovskites. With this approach, the enhanced optoelectronic performance of the novel PEDOT:PSS is due to electron transfer between the additives and PEDOT or PSS, as well as a dissociation between PEDOT and PSS based on experimental and theoretical studies, which facilitates the charge extraction and transfer. Concurrently, in-situ X-ray scattering studies reveal that the introduction of pyridine-based molecules alters the transformation process of the perovskite intermediate phase, which leads to a preferred orientation and ordered distribution caused by the Pb─N chemical bridge, achieving efficient charge transport. As a result, the pyridine-treated devices achieve an increased short-circuit current density (Jsc) and PCE of over 17%.

AbstractIn pursuing cheap and effective oxygen reduction catalysts, the Fe/N/C system emerges as a promising candidate. Nevertheless, the structural transformations of starting materials into Fe- and N-doped carbon catalysts remains poorly characterized under pyrolytic conditions. Here, we explore the evolution of Fe species and track the formation of Fe–N4 site development by employing diverse in-situ diagnostic techniques. In-situ heating microscopy reveals the initial formation of FeOx nanoparticles and subsequent internal migration within the carbon matrix, which stops once FeOx is fully reduced. The migration and decomposition of nanoparticles then leads to carbon layer reconstruction. Experimental and theoretical analysis reveals size-dependent behavior of FeOx where nanoparticles below 7 nm readily release Fe atoms to form Fe–N4 while nanoparticles with sizes >10 nm tend to coalesce and impede Fe–N4 site formation. The work visualizes the pyrolysis process of Fe/N/C materials, providing theoretical guidance for the rational design of catalysts.