Fe-Co heteronuclear atom pairs as catalytic sites for efficient oxygen electroreduction.

Single-site Fe-N-C catalysts are the most promising Pt-group catalyst alternatives for the oxygen reduction reaction, but their application is impeded by their relatively low activity and unsatisfactory stability as well as production costs. Here, cobalt atoms are introduced into an Fe-N-C catalyst to enhance its catalytic activity by utilizing the synergistic effect between Fe and Co atoms. Meanwhile, phenanthroline is employed as the ligand, which favours stable pyridinic N-coordinated Fe-Co sites. The obtained catalysts exhibit excellent ORR performance with a half-wave potential of 0.892 V and good stability under alkaline conditions. In addition, the excellent ORR activity and durability of FeCo-N-C enabled the constructed zinc-air battery to exhibit a high power density of 247.93 mW cm-2 and a high capacity of 768.59 mA h gZn-1. Moreover, the AEMFC based on FeCo-N-C also achieved a high open circuit voltage (0.95 V) and rated power density (444.7 mW cm-2), surpassing those of many currently reported transition metal-based cathodes. This work emphasizes the feasibility of this non-precious metal catalyst preparation strategy and its practical applicability in fuel cells and metal-air batteries.

Computed tomography perfusion deficit volume predicts the functional outcome of endovascular therapy for basilar artery occlusion.

OBJECTIVES: To investigate the relationship between baseline computed tomography perfusion deficit volumes and functional outcomes in patients with basilar artery occlusion (BAO) undergoing endovascular therapy. METHODS: This was a single-center study in which the data of 64 patients with BAO who underwent endovascular therapy were retrospectively analyzed. All the patients underwent multi-model computed tomography on admission. The posterior-circulation Acute Stroke Prognosis Early Computed Tomography Score was applied to assess the ischemic changes. Perfusion deficit volumes were obtained using Syngo.via software. The primary outcome of the analysis was a good functional outcome (90-day modified Rankin Scale score ≤ 3). Logistic regression and receiver operating characteristic curves were used to explore predictors of functional outcome. RESULTS: A total of 64 patients (median age, 68 years; 72 % male) were recruited, of whom 26 (41 %) patients achieved good functional outcomes, while 38 (59 %) had poor functional outcomes. Tmax > 10 s, Tmax > 6 s, and rCBF < 30 % volume were independent predictors of good functional outcomes (odds ratio range, 1.0-1.2; 95 % confidence interval [CI], 1.0-1.4]) and performed well in the receiver operating characteristic curve analyses, exhibiting positive prognostic value; the areas under the curve values were 0.85 (95 % CI, 0.75-0.94), 0.81 (95 % CI, 0.70-0.90), and 0.78 (95 % CI, 0.67-0.89). CONCLUSION: Computed tomography perfusion deficit volume represents a valuable tool in predicting high risk of disability and mortality in patients with BAO after endovascular treatment.

Current advances in modulating tumor hypoxia for enhanced therapeutic efficacy.

Hypoxia is a common feature of most solid tumors, which promotes the proliferation, invasion, metastasis, and therapeutic resistance of tumors. Researchers have been developing advanced strategies and nanoplatforms to modulate tumor hypoxia to enhance therapeutic effects. A timely review of this rapidly developing research topic is therefore highly desirable. For this purpose, this review first introduces the impact of hypoxia on tumor development and therapeutic resistance in detail. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are also systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We provide a detailed discussion of the rationale and research progress of these strategies. Through a review of current trends, it is hoped that this comprehensive overview can provide new prospects for clinical application in tumor treatment. STATEMENT OF SIGNIFICANCE: As a common feature of most solid tumors, hypoxia significantly promotes tumor progression. Advanced nanoplatforms have been developed to modulate tumor hypoxia to enhanced therapeutic effects. In this review, we first introduce the impact of hypoxia on tumor progression. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We discuss the rationale and research progress of the above strategies in detail, and finally introduce future challenges for treatment of hypoxic tumors. By reviewing the current trends, this comprehensive overview can provide new prospects for clinical translatable tumor therapy.

The value of computed tomography perfusion deficit volumes in acute isolated brainstem infarction.

Purpose: Diagnosis of acute isolated brainstem infarction is challenging owing to non-specific, variable symptoms, and the effectiveness of non-contrast computed tomography (NCCT) is poor owing to limited spatial resolution and artifacts. Computed tomography perfusion (CTP) imaging parameters are significantly associated with functional outcomes in posterior circulation acute ischemic stroke; however, the role of CTP in isolated brainstem infarction remains unclear. We aimed to determine the value of CTP imaging parameters in predicting functional outcomes for affected patients. Methods: In total, 116 consecutive patients with isolated pontine/midbrain hypoperfusion who underwent CTP and follow-up by magnetic resonance imaging (MRI) between January 2018 and March 2022, were retrospectively analyzed. Perfusion deficit volumes on all maps, and the final infarction volume (FIV) on MRI were quantified. "Good" functional outcome was defined as a 90-day modified Rankin Scale score of 0 and 1. Statistical analysis included uni- and multivariate regression analyses, binary logistic regressions, and receiver operating characteristics (ROC) analyses. Results: In total, 113 patients had confirmed isolated pontine/midbrain infarction on follow-up MRI. Onset-to-scan time, visibility of ischemic lesions on NCCT, the baseline National Institutes of Health Stroke Scale (NIHSS) score, and perfusion deficit volumes on all CTP maps were significantly associated with FIV (p < 0.05). In a multivariate linear regression model, adjusted for age, sex, NIHSS score, onset-to-scan time, and visibility of NCCT, perfusion deficit volumes remained significantly associated with FIV. In binary logistic regression analyses, perfusion deficit volumes on all CTP maps remained independent predictors of a good functional outcome. In ROC analyses, the cerebral blood flow deficit volume showed a slightly higher discriminatory value with the largest area under the curve being 0.683 [(95% CI, 0.587-0.780), p = 0.001]. Conclusion: Perfusion deficit volumes of CTP imaging could reflect the FIV and contain prognostic information on functional outcomes in patients with acute isolated brainstem infarction.

Avoiding Sabatier's Limitation on Spatially Correlated Pt-Mn Atomic Pair Sites for Oxygen Electroreduction.

The development of highly active and low-cost oxygen reduction reaction (ORR) catalysts is crucial for the practical application of hydrogen fuel cells. However, the linear scaling relation (LSR) imposes an inherent Sabatier's limitation for most catalysts including the benchmark Pt with an insurmountable overpotential ceiling, impeding the development of efficient electrocatalysts. To avoid such a limitation, using earth-abundant metal oxides with different crystal phases as model materials, we propose an effective and dynamic reaction pathway through constructing spatially correlated Pt-Mn pair sites, achieving an excellent balance between high activity and low Pt loading. Experimental and theoretical calculations demonstrate that manipulating the intermetallic distance and charge distribution of Pt-Mn pairs can effectively promote O-O bond cleavage at these sites through a bridge configuration, circumventing the formation of *OOH intermediates. Meanwhile, the dynamic adsorption configuration transition from the bridge configuration of O2 to the end-on configuration of *OH improves *OH desorption at the Mn site within such pairs, thereby avoiding Sabatier's limitation. The well-designed Pt-Mn/ß-MnO2 exhibits outstanding ORR activity and stability with a half-wave potential of 0.93 V and barely any activity degradation for 70 h. When applied to the cathode of a H2-O2 anion-exchange membrane fuel cell, this catalyst demonstrates a high peak power density of 287 mW cm-2 and 500 h of stability under a cell voltage of 0.6 V. This work reveals the adaptive bonding interactions of atomic pair sites with multiple reactant/intermediates, offering a new avenue for rational design of highly efficient atomic-level dispersed ORR catalysts beyond the Sabatier optimum.

Progress in Manipulating Dynamic Surface Reconstruction via Anion Modulation for Electrocatalytic Water Oxidation.

The development of efficient and economical electrocatalysts for oxygen evolution reaction (OER) is of paramount importance for the sustainable production of renewable fuels and energy storage systems; however, the sluggish OER kinetics involving multistep four proton-coupled electron transfer hampers progress in these systems. Fortunately, surface reconstruction offers promising potential to improve OER catalyst design. Anion modulation plays a crucial role in controlling the extent of surface reconstruction and positively persuading the reconstructed species' performances. This review starts by providing a general explanation of how various types of anions can trigger dynamic surface reconstruction and create different combinations with pre-catalysts. Next, the influences of anion modulation on manipulating the surface dynamic reconstruction process are discussed based on the in situ advanced characterization techniques. Furthermore, various effects of survived anionic groups in reconstructed species on water oxidation activity are further discussed. Finally, the challenges and prospects for the future development directions of anion modulation for redirecting dynamic surface reconstruction to construct highly efficient and practical catalysts for water oxidation are proposed.

Metal Oxide-Supported Metal Catalysts for Electrocatalytic Oxygen Reduction Reaction: Characterization Methods, Modulation Strategies, and Recent Progress.

The sluggish kinetics of the oxygen reduction reaction (ORR) with complex multielectron transfer steps significantly limits the large-scale application of electrochemical energy devices, including metal-air batteries and fuel cells. Recent years witnessed the development of metal oxide-supported metal catalysts (MOSMCs), covering single atoms, clusters, and nanoparticles. As alternatives to conventional carbon-dispersed metal catalysts, MOSMCs are gaining increasing interest due to their unique electronic configuration and potentially high corrosion resistance. By engineering the metal oxide substrate, supported metal, and their interactions, MOSMCs can be facilely modulated. Significant progress has been made in advancing MOSMCs for ORR, and their further development warrants advanced characterization methods to better understand MOSMCs and precise modulation strategies to boost their functionalities. In this regard, a comprehensive review of MOSMCs for ORR is still lacking despite this fast-developing field. To eliminate this gap, advanced characterization methods are introduced for clarifying MOSMCs experimentally and theoretically, discuss critical methods of boosting their intrinsic activities and number of active sites, and systematically overview the status of MOSMCs based on different metal oxide substrates for ORR. By conveying methods, research status, critical challenges, and perspectives, this review will rationally promote the design of MOSMCs for electrochemical energy devices.

Engineering interfacial band bending over bismuth vanadate/carbon nitride by work function regulation for efficient solar-driven water splitting.

Nature-inspired artificial Z-scheme photocatalyst offers great promise in solar overall water splitting, but its rational design, construction and interfacial charge transfer mechanism remain ambiguous. Here, we design an approach of engineering interfacial band bending via work function regulation, which realizes directional charge transfer at interface and affords direct Z-scheme pathway. Taking BiVO4 as prototype, its oxygen vacancy concentration is reduced by slowing down the crystallization rate, thereby changing the work function from smaller to larger than that of polymeric carbon nitride (PCN). Consequently, the photoinduced charge transfer pathway of BiVO4/PCN is switched from type-II to Z-scheme as evidenced by synchronous illuminated X-ray photoelectron spectroscopy (XPS) and femtosecond transient absorption spectroscopy. Specifically, the direct Z-scheme BiVO4/PCN shows superior photocatalytic performance in water splitting. This work provides deep insights and guidelines to constructing heterojunction photocatalysts for solar utilization.

Manipulating the Spin State of Fe Sites via Fe-O-Si Bridge Bonds for Enhanced Polysulfide Redox Kinetics in the Li-S Battery.

Transition metals with 3d unoccupied orbitals have superior catalytic activity, but inherent high spin suppresses their adsorption capability, leading to sluggish polysulfide conversion kinetics for Li-S batteries. Herein, we provide Fe-O-Si bridge bonds to manipulate eg filling and induce a high-to-medium spin transition of Fe3+ sites, which enhances polysulfide adsorption and facilitates sulfur redox reaction kinetics. The resultant cathodes exhibit outstanding performances under high sulfur loading, which can deliver a high battery specific energy of 1061 mA h·g-1 even after 100 cycles in Li-S pouch batteries. This work provides new insights into the kinetic and multi-step conversion mechanism of the sulfur redox reaction process, helping in the understanding and design of spin-dependent catalysts.

Carbon doping endows silicon oxide with enhanced redox kinetics of polysulfides.

Carbon-doped SiO2 is synthesized by the in situ carbonization of halloysite. Carbon atoms partially substitute O atoms to form Si-C bonds and manipulate the localized electronic states of Si atoms, thereby endowing SiO2 with suitable adsorption strength and reducing the activation energy barrier for polysulfides in the sulfur redox. The C-SiO2/S cathodes for Li-S batteries exhibited superior electrochemical performance.

The Analysis of Causality and Risk Spillover between Crude Oil and China's Agricultural Futures.

This paper aims to apply the time-varying Granger causality test (TVGC) and the DY Spillover Index (Diebold and Yilmaz, 2012) to measure the Granger causality and dynamic risk spillover effects of the international crude oil futures market on China's agricultural commodity futures market from the perspectives of return and volatility spillovers. Empirical evidence relating to the TVGC test suggests the existence of unidirectional Granger causality between crude oil futures and agricultural product futures. This relationship shows a strong time-varying property, in particular for sudden or extreme events such as financial crises and natural disasters. On the other hand, the volatility spillover in crude oil and agricultural product futures markets responds asymmetrically and bidirectionally according to the result of the DY Spillover index, and the periodicity of total volatility spillover correlates closely with the occurrence of global economic events, which indicates that the spillover effect between crude oil and agricultural commodity futures markets will be exacerbated in turbulent financial and economic times. Such findings are expected to help in formulating policy recommendations, portfolio design, and risk-management decisions.

Surface Design Strategy of Catalysts for Water Electrolysis.

Hydrogen, a new energy carrier that can replace traditional fossil fuels, is seen as one of the most promising clean energy sources. The use of renewable electricity to drive hydrogen production has very broad prospects for addressing energy and environmental problems. Therefore, many researchers favor electrolytic water due to its green and low-cost advantages. The electrolytic water reaction comprises the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Understanding the OER and HER mechanisms in acidic and alkaline processes contributes to further studying the design of surface regulation of electrolytic water catalysts. The OER and HER catalysts are mainly reviewed for defects, doping, alloying, surface reconstruction, crystal surface structure, and heterostructures. Besides, recent catalysts for overall water splitting are also reviewed. Finally, this review paves the way to the rational design and synthesis of new materials for highly efficient electrocatalysis.

Manipulating the Conversion Kinetics of Polysulfides by Engineering Oxygen p-Band of Halloysite for Improved Li-S Batteries.

Polar oxides are widely used as the cathodes to impede the shuttle effect in lithium-sulfur batteries, but suffer from the sluggish desorption and conversion of polysulfides due to too strong affinity of polysulfides on oxygen sites. Herein, employing halloysite as a model, an approach to overcome these shortcomings is proposed via engineering oxygen p-band center by loading titanium dioxide nanoparticles onto Si-O surface of halloysite. Using density functional theory calculations, it is predicted that electron transfer from titanium dioxide nanoparticles to interfacial O sites results in downshift of p-band center of O sites that promote desorption of polysulfides and the cleavage of Li-S and S-S, accelerating the conversion kinetics of polysulfides. The designed composite cathode material delivers outstanding electrochemical performance in Li-S batteries, outperforming the recently reported similar cathodes. The concept could provide valuable insight into the design of other catalysts for Li-S batteries and beyond.

Pd/Fe2O3 with Electronic Coupling Single-Site Pd-Fe Pair Sites for Low-Temperature Semihydrogenation of Alkynes.

Dispersing single palladium atoms on a support is promising to minimize the usage of palladium and improve the selectivity for alkyne semihydrogenation, but its activity is often very low as a result of unfavorable H2 activation. Here, we load palladium onto α-Fe2O3(012) to construct highly active and stable single-site Pd-Fe pairs with luxuriant d-electron domination near the Fermi level driven by strong electronic coupling and prove that Pd-Fe pairs cooperatively adsorb H2 and dissociate an H─H bond, whereas solo Pd sites enable preferential desorption of C═C intermediate, thus achieving both high activity and high selectivity for alkyne hydrogenation. This catalyst exhibits state-of-the-art performance in purifying acetylene of ethylene stream, with 99.6% and 100% conversion and 96.7% and 94.7% selectivity at 353 and 393 K, respectively, and excellent stability with negligible activity decay after a 200 h test. This single-site pair inherits the advantage but overcomes the weakness of both Pd ensemble and single Pd atoms, enabling ultralow-Pd-loading catalysts for selective hydrogenation.

Hydrogen-Catalyzed Acid Transformation for the Hydration of Alkenes and Epoxy Alkanes over Co-N Frustrated Lewis Pair Surfaces.

Hydrogen (H2) is widely used as a reductant for many hydrogenation reactions; however, it has not been recognized as a catalyst for the acid transformation of active sites on solid surface. Here, we report the H2-promoted hydration of alkenes (such as styrenes and cyclic alkenes) and epoxy alkanes over single-atom Co-dispersed nitrogen-doped carbon (Co-NC) via a transformation mechanism of acid-base sites. Specifically, the specific catalytic activity and selectivity of Co-NC are superior to those of classical solid acids (acidic zeolites and resins) per micromole of acid, whereas the hydration catalysis does not take place under a nitrogen atmosphere. Detailed investigations indicate that H2 can be heterolyzed on the Co-N bond to form Hδ--Co-N-Hδ+ and then be converted into OHδ--Co-N-Hδ+ accompanied by H2 generation via a H2O-mediated path, which significantly reduces the activation energy for hydration reactions. This work not only provides a novel catalytic method for hydration reactions but also removes the conceptual barriers between hydrogenation and acid catalysis.

Contrasting Photochemical Activity of Two Sub-layers for Natural 2D Nanoclay with an Asymmetric Layer Structure.

The two-dimensional (2D) materials with asymmetric sub-layers have recently attracted tremendous interest in many fields, and investigating the structure-performance relationship of different sub-layers is critical but challenging. Herein, we report that natural kaolinite (Kaol) nanosheets with an asymmetric layer structure possess a contrasting photocatalytic activity on its Al-O and Si-O sub-layers. The experimental and theoretical results reveal that the ion isovalent structure of Fe3+ and Al3+ not only results in a high iron doping concentration in the Al-O sub-layer but also causes superb intrinsic photochemical activity of the Al-O sub-layer compared with the Si-O sub-layer. Thus, the Al-O sub-layers of Kaol NSs have more excellent photogenerated charge generation and separation efficiency than Si-O sub-layers, resulting in about 1-2 orders of magnitude higher photocatalytic performance. This study not only unravels the structure-performance relationship of different sub-layers of 2D nanoclay but also sheds new light on the design of 2D materials with the asymmetric sub-layer.

Bi5O7I/g-C3N4 Heterostructures With Enhanced Visible-Light Photocatalytic Performance for Degradation of Tetracycline Hydrochloride.

Bi5O7I/g-C3N4 p-n junctioned photocatalysts were synthesized by alcohol-heating and calcination in air. The structures, morphologies and optical properties of as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS). Photocatalytic activity of the heterojunctioned composites were evaluated by degradation of Rhodamine B (RhB) and tetracycline hydrochloride (TCH) under visible light illumination. The results indicated that the composites exhibited superior efficiencies for photodegradation of RhB and TCH in comparison with pure BiOI, Bi5O7I and g-C3N4. An effective built-in electric field was formed by the interface between p-type Bi5O7I and n-type g-C3N4, which promoted the efficient separation of photoinduced electron-hole pairs. In addition, 8% Bi5O7I/g-C3N4 composite showed excellent photostability in a five-cycle photocatalytic experiment. Experiments on scavenging active intermediates revealed the roles of active species.

Comparative transcriptome analysis of root, stem, and leaf tissues of Entada phaseoloides reveals potential genes involved in triterpenoid saponin biosynthesis.

BACKGROUND: Entada phaseoloides (L.) Merr. is an important traditional medicinal plant. The stem of Entada phaseoloides is popularly used as traditional medicine because of its significance in dispelling wind and dampness and remarkable anti-inflammatory activities. Triterpenoid saponins are the major bioactive compounds of Entada phaseoloides. However, genomic or transcriptomic technologies have not been used to study the triterpenoid saponin biosynthetic pathway in this plant. RESULTS: We performed comparative transcriptome analysis of the root, stem, and leaf tissues of Entada phaseoloides with three independent biological replicates and obtained a total of 53.26 Gb clean data and 116,910 unigenes, with an average N50 length of 1218 bp. Putative functions could be annotated to 42,191 unigenes (36.1%) based on BLASTx searches against the Non-redundant, Uniprot, KEGG, Pfam, GO, KEGG and COG databases. Most of the unigenes related to triterpenoid saponin backbone biosynthesis were specifically upregulated in the stem. A total of 26 cytochrome P450 and 17 uridine diphosphate glycosyltransferase candidate genes related to triterpenoid saponin biosynthesis were identified. The differential expressions of selected genes were further verified by qPT-PCR. CONCLUSIONS: The dataset reported here will facilitate the research about the functional genomics of triterpenoid saponin biosynthesis and genetic engineering of Entada phaseoloides.

Ni-modified MoS2 nanoflake arrays with stepped sites on carbon nanotubes for efficient hydrodesulfurization of coal-to-liquid fuel.

Carbon nanotube (CNT)-supported Ni-modified MoS2 catalysts with ultra-high loading were synthesized with the assistance of citric acid. The morphology of the nanoflake arrays could be controlled to give abundant stepped sites, which favored the hydrogenation desulfurization pathway of dibenzothiophene. The catalyst exhibited excellent performance and stability for hydrodesulfurization of model oil and coal-to-liquid fuel.

Ultra-smooth TiO2 thin film based optical humidity sensor with a fast response and recovery.

An ultra-smooth $\text{TiO}_2$TiO2 thin film based optical humidity sensor was fabricated via a modified dip coating process. The $\text{TiO}_2$TiO2 film possessed a root mean square roughness of ${2.6 \pm 0.3}\;\text{nm}$2.6±0.3nm. Measurement of relative humidity (RH) was performed by modulation in the intensity of laser transmitted at room temperature. The optical humidity sensor based on $\text{TiO}_2$TiO2 film exhibited two-segmented linearity in the whole RH range. The response time and recovery time were determined to be 27 s and 23 s, respectively. To our knowledge, the optical humidity sensor achieved the fastest recovery to date among those modulated in optical power. The fast response and recovery are attributed to the smooth surface of sensing film, which allows the rapid equilibrium between adsorption and desorption of water molecules on the film surface. In addition, this optical humidity sensor possessed an excellent reproducibility and long-term stability after aging. The sensing mechanism is based on the chemisorption of water molecules in the low RH range and formation of water droplets in the high RH range on the surface of ${\text{TiO}_2}$TiO2 film.