Intermediate Species Research Articles

Kinetically Accelerating Ni and C Dual Active Sites Via Pyrrolic-N for Water Dissociation and Alkaline Hydrogen Production

Green hydrogen, which is one of the most promising solutions to environmental issues and energy crises, can be produced through water electrolysis using renewable electricity as eco-friendly and sustainable route. However, the cathodic hydrogen evolution reaction (HER) has been a subject of extensive research due to the slow kinetics of proton-coupled electron transfer, which lowers the overall efficiency. In particular, the rate of HER in alkaline media appears two to three times slower than that in acidic or neutral media. This is because in order to form adsorbed hydrogen, additional water dissociation must first proceed in the Volmer step (H2O + e- → Had + OH-), followed by the coupling of adsorbed hydrogen in the Heyrovsky or Tafel steps (H2O + Had + e- → H2 + OH- / Had + Had → H2). The hydrogen adsorption-free energy (ΔGH*) has traditionally been considered the primary factor influencing the kinetics of the HER at the Heyrovsky and Tafel steps. However, it is important to note that sufficient proton supply to the catalytic sites relies on water adsorption capacity and the ability to cleave the HO-H bond. As a results, a proper strategy for achieving high hydrogen coverage (M-Had) must incorporate both water dissociation and hydrogen combination. Unfortunately, the activation of O- and H- containing intermediates for water dissociation and proton combination requires different catalytic properties, which highly presents a challenge. Therefore, it is crucial to understand the correlation between the catalytic chemical state, adsorption energy of intermediate species (H2O, OH, Had), and the kinetic mechanism of the HER from a theoretical standpoint.Pt-based materials are currently recognized as the most efficient catalysts for the HER. However, they exhibit unsatisfactory intrinsic kinetics under alkaline conditions due to the slow dissociation rate of water caused by the additional energy barrier of HO-H bond dissociation. Furthermore, their scarcity and high price limit their industrial applications. As an alternative, Ni-based materials are considered promising catalysts due to their Pt-like hydrogen adsorption-free energy and the possibility of optimizing water dissociation through chemical state modulation. Recent studies have shown that modulating the surface electronic structure of Ni-based materials through synergistic interactions is an effective way to activate intermediates for alkaline HER. However, most studies on chemical state reorganization focus on a single site, which underestimates the mechanism-based kinetics and makes it difficult to simultaneously control water dissociation and proton adsorption. Therefore, introducing dual active sites that optimize O- and H- affinity independently can be an effective strategy to reduce the energy barrier for Volmer, Heyrovsky and Tafel steps. Moreover, considering the proton pathway within Ni-based catalysts to accelerate alkaline HER kinetics, it is essential to simultaneously govern thermodynamics and kinetics through a kinetic-oriented design.In this study, we present a novel design approach that focuses on alkaline HER kinetics by incorporating dual active sites using Ni nanoparticles embedded in pyrrolic-N-rich carbon nanoplates (Ni@NCP), resulting in robust alkaline HER kinetics. The introduction of N-functional-rich polydopamine (PDA) serves two purposes: it ensures the uniform distribution of reduced Ni nanoparticles within the carbon substrate, and it enriches the ratio of pyrrolic-N in defective carbon, thereby regulating the properties of the Ni metal and the C atoms near the pyrrolic-N. Consequently, the Ni@NCP catalyst exhibits remarkable alkaline HER performance, with a low overpotential of 42 mV at a current density of 10 mA/cm2 and a Tafel slope of 94.9 mV/dec. These results outperform those of previously reported transition metal-based or single metal phase-based HER electrocatalysts. Further validation through the utilization of in-situ/operando Surface Enhanced Raman Spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations confirmed that the alkaline HER kinetics were significantly optimized by the pyrrolic-N-induced asymmetric electronic distribution, specifically by (ⅰ) shifting the d-band center (εd ) of the nearby Ni atoms towards the Fermi energy level to enhance the interaction with -H in H2O molecules and optimize the proton adsorption energy, (ⅱ) increasing the adsorption affinity of nearby C atoms towards H2O and -OH to optimize H2O adsorption, and (ⅲ) elongating the HO-H bonds, facilitating bond cleavage, and promoting simultaneous proton supply into Ni atoms. The kinetic-oriented design of dual active sites significantly reduces the kinetic energy barrier during Volmer step of water dissociation, resulting in facilitates the supply of sufficient protons for accelerated alkaline HER kinetics, ultimately enhancing the overall catalytic activity. Moreover, in a two-electrode system with Ni@NCP as the cathode for water electrolysis, Ni@NCP||IrO2 outperforms the commercial Pt/C||IrO2 system at the current density over 2.3 A/cm2, which shows superior potential for the practical application. Figure 1

Enhanced Design: A User-Friendly 3D-Printed Electrochemical Cell for In Situ Raman Spectroscopy

In energy conversion devices like electrolyzers and batteries, monitoring electrode surfaces during electrochemical processes is crucial for understanding their operation mechanisms. In situ Raman spectroscopy is a promising technique for this purpose, allowing analysis of electrode surface structure, surface species (reaction intermediate species), and localized electrolyte species.1 However, commercially available electrochemical cells designed for in situ Raman spectroscopy are often costly and complex, presenting a bottleneck for widespread use.To address these issues, some research groups have introduced 3D-printed spectroelectrochemical cells with lower cost and complexity.2,3 However, existing designs typically limit the sample types to specific particles. There is a need for a more versatile, cost-effective, and user-friendly spectroelectrochemical cell that can accommodate a wider range of sample types.This study presents an innovative spectroelectrochemical cell design capable of accommodating diverse sample types, such as metal foil strips, fluorine-doped tin oxide-coated glass, indium tin oxide-coated glass, and particles. Notably, we feature updates from the previous year's ECS fall conference (i.e., 244th ECS Meeting). Leveraging stereolithography (SLA) 3D printing with resin as the printing material, our cell design prioritizes versatility, affordability, and simplicity. Using the SLA 3D-printed spectroelectrochemical cell, we will demonstrate its practical utility and effectiveness in electrolyzer and battery applications. References W. Zheng, Chemistry–Methods, 3, e202200042 (2023).M. F. dos Santos et al., Anal. Chem., 91, 10386–10389 (2019).G. D. da Silveira et al., Anal. Chim. Acta, 1141, 57–62 (2021).

(Invited) Electrocatalytic Ammonia Splitting to Enable the Nitrogen Economy

Synthesis of NH3 using the most abundant renewable energy resources (sun/wind), and abundant chemical feedstocks on Earth (H2O and N2) via the energy efficient, large-scale and cost-effective Haber-Bosch (HB) process enables the possibility of producing carbon-free, high energy density liquid fuel on the TW scale. The HB reaction is almost thermoneutral, which means hydrogen’s intrinsic energy is largely retained in ammonia, making NH3 likely the best candidate for storing and transporting renewable H2. The conversion of NH3 to electricity via a direct ammonia fuel cell or back to H2 via electrolysis has received little attention until very recently, however, and is primarily limited by the ammonia oxidation half reaction. This talk will present our recent investigation of homogeneous electrocatalysts to drive the NH3 splitting reaction at room temperature and ambient pressure. Our recent efforts aimed at understanding the mechanism of the ammonia oxidation reaction with [Ru(tpy)(dmabpy)NH3]2+, using a variety of spectroscopic (NMR and optical) and electrochemical methods will be presented. Interestingly, reactions [Ru(tpy)(dmabpy)NH3]3+ with various Lewis bases are shown to trigger a catalytic reaction which results in formation of a characterized N2-bridged dimer intermediate species. Alternative ammines coordinated to the Ru center are also oxidized to form surprising highly oxidized products. The effect of solvent on the overpotential and catalysis will be discussed as well as preliminary results of next-generation Ru and Os catalysts.

NMR Studies of High Voltage Electrolyte Decomposition Reactions

Lithium-ion batteries have become an irreplaceable part of daily life, yet state-of-art LIBs could not meet the growing demand of higher energy density partially due to limited choices for the cathode and the electrolyte that can provide the desired safety and reliability. One of the solutions is to move towards higher voltage systems. To rationalize the CEI design, on the electrolyte side, fundamental studies of electrochemical decomposition behavior at high voltage of common electrolytes, typically using carbonate-based organic solvent, remain incomplete despite experimental and computational efforts. Several decomposition products of EC were identified, mostly pointing at ring-opened linear molecules such as CO, CO2, glycolic acid and oxalic acid with the presence of active/singlet oxygen or PEO-like polymer owing to Lewis acid induced polymerization. However, in some cases there were no ring opening observed with EC forming vinylene carbonate (VC) or poly-EC instead. While the mechanism of ring-opening reactions that involve deprotonation, nucleophilic and/or electrophilic reactions are straightforward and widely reported, full reaction mechanisms pathways are not yet realized. In this study we combined experimental and computational NMR to track the dynamic evolution of intermediate species to discover their chemical nature by following their NMR fingerprints. The findings will be presented to provide a clearer picture of the effects of high voltage on electrolyte systems in general and their implications on overall battery chemistry.

Advancing the C[formula omitted] low-temperature oxidation chemistry through species measurements in a rapid compression machine, Part A: 1-Butene

Alkene chemistry plays a crucial role in the autoignition and oxidation of larger hydrocarbons. Unlike its other isomers, 1-butene is characterized by a two-stage ignition process. Various previous studies of 1-butene oxidation have used experimental techniques, including the measurement of ignition delay times in rapid compression machines (RCM) and in shock tubes, the determination of flame velocities, and the measurement of species concentrations in flames and in jet-stirred reactors (JSR). JSR studies provide an important insight into intermediate species formation at low temperatures but are constrained to low pressures and/or highly diluted conditions. To bridge the gap between JSR and engine-relevant conditions, this study presents species concentration measurements during the oxidation of 1-butene at 733 K and 30 bar under stoichiometric ’air-like’ conditions in an RCM, complemented by IDT measurements in the temperature range of 680–910 K. We designed an innovative 2-valve sampling setup to reduce quantitative uncertainties and the time required for species measurements. Our results indicate that existing 1-butene models fail to accurately predict the IDTs and the formation of the key oxidation intermediates. In response, potential optimizations for an improved kinetic model based on NUIGMech1.3 are discussed. Rate parameters for predominantly fuel consumption pathways, along with other reactions and thermochemical properties in the Waddington mechanism, have been altered within expected uncertainty limits to reflect the experimentally observed IDTs and species concentrations of this study and other validation data from the literature. However, the refined model does not predict the formation of 2-ethenyloxirane and ethene, indicating a gap in our understanding of the chemistry of these components. Overall, this study demonstrates the importance of measuring intermediates under the same conditions as IDTs to accurately address deficiencies in current kinetic mechanisms, and represents the first phase of a comprehensive investigation advancing the understanding of C4 oxidation chemistry.Novelty and significance statementThe novelty of this research lies in the design of an innovative sampling system for RCM species measurements, lowering the time for experimental execution and the uncertainties of the measurements. This enabled first-time species measurements during the oxidation of butene isomers in an RCM at high pressure and low level of dilution, contributing to the refinement of the 1-butene sub-mechanism within the NUIGMech1.3 framework. This research contributes to the understanding of the oxidation of alkenes, an important class of intermediates in gasoline and biofuel combustion. It emphasizes the need to measure intermediate species at the same conditions as ignition delay times, which are essential for understanding oxidation pathways under engine-relevant conditions. This research is part of a broader investigation of C4 oxidation chemistry, along with our companion work on n-butane. The resulting kinetic model is capable of reproducing most of the available n-butane and 1-butene validation targets.

Spontaneous flows and quantum analogies in heterogeneous active nematic films

Incorporating the inherent heterogeneity of living systems into models of active nematics is essential to provide a more realistic description of biological processes such as bacterial growth, cell dynamics and tissue development. Spontaneous flow of a confined active nematic is a fundamental feature of these systems, in which the role of heterogeneity has not yet been considered. We therefore determine the form of spontaneous flow transition for an active nematic film with heterogeneous activity, identifying a correspondence between the unstable director modes and solutions to Schrödinger’s equation. We consider both activity gradients and steps between regions of distinct activity, finding that such variations can change the signature properties of the flow. The threshold activity required for the transition can be raised or lowered, the fluid flux can be reduced or reversed and interfaces in activity induce shear flows. In a biological context fluid flux influences the spread of nutrients while shear flows affect the behaviour of rheotactic microswimmers and can cause the deformation of biofilms. All the effects we identify are found to be strongly dependent on not simply the types of activity present in the film but also on how they are distributed.

Does the active surface area determine the activity of silica supported nickel catalysts in CO2 methanation reaction?

Two series of silica supported catalysts with comparable nickel contents varying from 2.5 to 20 wt.% were prepared by wet impregnation method in the absence and presence of citric acid in the impregnation solution. Temperature-programmed reduction, X-ray diffraction and electron microscopy studies indicated changes of reducibility of nickel oxide species in the corresponding catalysts and formation of nickel nanoparticles of different size and morphology. A gradual increase in the performance of catalysts in the CO2 methanation reaction was observed with increasing Ni loading. The application of a modified impregnation method led to a reduction in the size of the nickel crystallites, which increased the active surface area of the catalysts, improving their activity and selectivity towards methane at low temperatures, as well as their stability at high temperatures. It was shown that the high active surface area of silica-supported nickel catalysts, due to the presence of small crystallites, is a key factor in increasing their activity. However, other catalyst properties may also play an important role. Hydrogen temperature-programmed desorption and in-situ DRIFTS adsorption/desorption of CO, CO2 and CO2 hydrogenation reaction studies indicated that modification of the method of catalyst synthesis led to changes in the surface properties of the catalysts, affecting the way CO2 and H2 activation and the transformation of resulted intermediate species to the final reaction products.

Trimetallic FeNiCu Atomic Clusters Supported on Carbon Matrix: Highly Active Catalysts for C3H6-SCR of NO.

C3H6-SCR denitrification technology faces catalyst deactivation problems and low catalytic performance at medium-low temperatures. This study utilized the intermetallic synergies to prepare atomic cluster catalysts (FeNiCu/NC) by anchoring Fe-Ni-Cu on a carbon matrix to enhance the C3H6-SCR performance at medium-low temperatures. The synergistic effect of the Fe-Ni-Cu is reflected in the differences in the physicochemical properties of the catalysts, which is proved by several characterization techniques. Results showed that the FeNiCu/NC catalyst had a larger surface area (541.4 m2/g) and there were no metal oxides on the surface of the catalyst but abundant defective sites that anchored Fe/Ni/Cu atoms through N atoms to form M-Nx active sites and atomic clusters. The hollow carbon morphology provides sufficient active sites for C3H6-SCR. The coordination environments of active sites were M-Nx-C, Fe2/FeCu2/FeNi2, Ni3/NiFe/NiCu2, and Cu4/CuFe2/CuNi2, where the synergistic action of trimetal leads to the presence of Fe-Ni-Cu-Nx-C. The synergistic action of the Fe-Ni-Cu significantly improved the C3H6-SCR performance at medium-low temperatures. The FeNiCu/NC exhibited an 81% NO conversion at 150 °C under 2% O2, 15% and 20% higher than FeNi/NC and FeCu/NC catalysts, respectively. Even at 4% O2, the FeNiCu/NC catalyst was active to remove 78% NO and achieve a 93% N2 selectivity at 150 °C and maintained a 100% NO conversion at 300-425 °C. The DRIFTS results demonstrated that NO and C3H6 could combine with active O at metal cluster, M-Nx, or defective oxygen sites to produce various intermediate species, wherein acetates and nitrates were the main active intermediates. Based on the DRIFTS results, a reaction pathway for C3H6-SCR over the FeNiCu/NC catalyst was proposed.

A new and large monofenestratan reveals the evolutionary transition to the pterodactyloid pterosaurs

For over a century, there was a major gap in our understanding of the evolution of the flying Mesozoic reptiles, the pterosaurs, with a major morphological gap between the early forms and the derived pterodactyloids.1 Recent discoveries have found a cluster of intermediate forms that have the head and neck of the pterodactyloids but the body of the early grade,2 yet this still leaves fundamental gaps between these intermediates and both earlier and more derived pterosaurs. Here, we describe a new and large Jurassic pterosaur,Skiphosoura bavaricagen. et sp. nov., preserved in three dimensions, that helps bridge the gap between current intermediate pterosaurs and the pterodactyloids. A new phylogeny shows that there is a general progression of key characteristics of increasing head size, increasing length of neck and wing metacarpal, modification to the fifth toe that supports the rear wing membrane, and gradual reduction in tail length and complexity from earlier pterosaurs into the first pterodactyloids. This also shows a clear evolution of the increasing terrestrial competence of derived pterosaurs. Furthermore, this closes gaps between the intermediates and their ancestors and descendants, and it firmly marks the rhamphorhynchines and ctenochasmatid clades as, respectively, being the closest earliest and latest groups to this succession of transitional forms.

Contact-electro-luminescence triggered by triboelectric charge

Luminol, a prominent chemiluminescent reagent, is extensively employed in biochemical and environmental analyses for its ability to produce rapid luminescence through oxidation in aqueous solutions. However, the lack of comprehensive studies on the observation and regulation of intermediate species during this luminescent reaction may limit its effectiveness in detection applications. Understanding these intermediates is crucial for enhancing the accuracy and reliability of luminol-based detection methods. To solve the above problems, this work proposes a straightforward and effective approach to directly oxidize luminol via reactive oxygen species (ROS) generated from contact electrification (CE) between inert solid dielectrics and deionized (DI) water, termed contact-electro-luminescence (CEL). Metal-free, cost-effective solid dielectrics present a promising alternative to expensive metal-based catalysts, aligning well with the principles of green chemistry and sustainable development. In such reaction system, ROS can be regulated by various solid dielectrics and additives (such as xylitol and p-benzoquinone), thereby tuning the luminol reaction. More importantly, two distinct luminescent emission peaks are directly observed and the intensity of the emission peaks of the two intermediate states can be regulated. The observation of intermediate is beneficial to reveal the intrinsic of luminescence reactions, exploiting the effective and tunable luminescence system. Moreover, CEL provides a new mechanical-photonic conversion paradigm to study luminol luminescence via triboelectric charge from the CE effect. CEL can offer distinct characteristic signals, offering potential applications in high-efficiency and specific detection for environmental monitoring, biomedical diagnosis and food safety testing etc.

Programmable C−N Bond Formation through Radical‐Mediated Chemistry in Plasma‐Microdroplet Fusion

AbstractNon‐thermal plasma discharge produced in the wake of charged microdroplets is found to facilitate catalyst‐free radical mediated hydrazine cross‐coupling reactions without the use of external light source, heat, precious metal complex, or trapping agents. A plasma‐microdroplet fusion platform is utilized for introduction of hydrazine reagent that undergoes homolytic cleavage forming radical intermediate species. The non‐thermal plasma discharge that causes the cleavage originates from a chemically etched silica capillary. The coupling of the radical intermediates gives various products. Plasma‐microdroplet fusion occurs online in a programmable reaction platform allowing direct process optimization and product validation via mass spectrometry. The platform is applied herein with a variety of hydrazine substrates, enabling i) self‐coupling to form secondary amines with identical N‐substitutions, ii) cross‐coupling to afford secondary amine with different N‐substituents, iii) cross‐coupling followed by in situ dehydrogenation to give the corresponding aryl‐aldimines with two unique N‐substitutions, and iv) cascade heterocyclic carbazole derivatives formation. These unique reactions were made possible in the charged microdroplet environment through our ability to program conditions such as reagent concentration (i. e., flow rate), microdroplet reactivity (i. e., presence or absence of plasma), and reaction timescale (i. e., operational mode of the source). The selected program is implemented in a co‐axial spray format, which is found to be advantageous over the conventional one‐pot single emitter electrospray‐based microdroplet reactions.

Programmable C-N Bond Formation through Radical-Mediated Chemistry in Plasma-Microdroplet Fusion.

Non-thermal plasma discharge produced in the wake of charged microdroplets is found to facilitate catalyst-free radical mediated hydrazine cross-coupling reactions without the use of external light source, heat, precious metal complex, or trapping agents. A plasma-microdroplet fusion platform is utilized for introduction of hydrazine reagent that undergoes homolytic cleavage forming radical intermediate species. The non-thermal plasma discharge that causes the cleavage originates from a chemically etched silica capillary. The coupling of the radical intermediates gives various products. Plasma-microdroplet fusion occurs online in a programmable reaction platform allowing direct process optimization and product validation via mass spectrometry. The platform is applied herein with a variety of hydrazine substrates, enabling i) self-coupling to form secondary amines with identical N-substitutions, ii) cross-coupling to afford secondary amine with different N-substituents, iii) cross-coupling followed by in situ dehydrogenation to give the corresponding aryl-aldimines with two unique N-substitutions, and iv) cascade heterocyclic carbazole derivatives formation. These unique reactions were made possible in the charged microdroplet environment through our ability to program conditions such as reagent concentration (i. e., flow rate), microdroplet reactivity (i. e., presence or absence of plasma), and reaction timescale (i. e., operational mode of the source). The selected program is implemented in a co-axial spray format, which is found to be advantageous over the conventional one-pot single emitter electrospray-based microdroplet reactions.

The relationship between spectral signals and retinal sensitivity in dendrobatid frogs.

Research on visually driven behavior in anurans has often focused on Dendrobatoidea, a clade with extensive variation in skin reflectance, which is perceived to range from cryptic to conspicuous coloration. Because these skin patterns are important in intraspecific and interspecific communication, we hypothesized that the visual spectral sensitivity of dendrobatids should vary with conspecific skin spectrum. We predicted that the physiological response of frog retinas would be tuned to portions of the visible light spectrum that match their body reflectance. Using wavelength-specific electroretinograms (ERGs; from 350-650 nm), spectrometer measurements, and color-calibrated photography of the skin, we compared retinal sensitivity and reflectance of two cryptic species (Allobates talamancae and Silverstoneia flotator), two intermediate species (Colostethus panamansis and Phyllobates lugubris), and two conspicuous aposematic species (Dendrobates tinctorius and Oophaga pumilio). Consistent with the matched filter hypothesis, the retinae of cryptic and intermediate species were sensitive across the spectrum, without evidence of spectral tuning to specific wavelengths, yielding low-threshold broadband sensitivity. In contrast, spectral tuning was found to be different between morphologically distinct populations of O. pumilio, where frogs exhibited retinal sensitivity better matching their morph's reflectance. This sensory specialization is particularly interesting given the rapid phenotypic divergence exhibited by this species and their behavioral preference for sympatric skin reflectances. Overall, this study suggests that retinal sensitivity is coevolving with reflective strategy and spectral reflectance in dendrobatids.

Adsorption Structure-Activity Correlation in the Photocatalytic Chemistry of Methanol and Water on TiO2(110).

ConspectusPhotocatalysis, a process involving light absorption (band gap excitation), charge separation, interfacial charge transfer, and surface redox reactions, has attracted intensive attention because of the potential applications in solar to fuel conversion. Despite the great efforts devoted to the design of materials and optimization of charge separation and overall efficiency, the molecular mechanism of photocatalytic reactions, for example, water oxidation, is still unclear, mainly because of the complexity of powder catalysts and the aqueous environment which prevent the direct experimental detection of adsorption sites, surface species, and charge/energy transfer dynamics. Without direct evidence, the charge transfer and elementary reaction steps remain elusive, and misleading conclusions are sometimes drawn. For instance, the positively charged 5-fold coordinated Ti sites (Ti5cs) on TiO2 surfaces are argued to propel holes and therefore cannot be active sites for oxidative reactions, regardless of the demonstration by scanning tunneling microscopy (STM). Direct site-specific measurements are thus highly demanded. Surface science studies, which rely on well-defined single crystals and ultrahigh vacuum based techniques, can identify the active sites and active species at the catalyst surfaces and measure the interfacial electronic structure and energy of desorbing species for charge transfer analysis, providing direct evidence for investigating the photocatalytic reaction mechanism at the molecular level.In this Account, the elementary photocatalytic chemistry of methanol and water on TiO2, which are investigated by surface science techniques such as atom-resolved STM, ensemble-averaged mass spectrometer based temperature-programmed desorption/time-of-flight spectroscopy, and photoelectron spectroscopy in combination with theoretical calculations, will be described. Both methanol and water can be photocatalytically oxidized at Ti5cs, producing adsorbed formaldehyde and gaseous •OH radicals, respectively, under ultraviolet (UV) light irradiation. The photocatalytic activity shows salient adsorption structure including adsorption site (terminal/bridging), adsorption state (molecular/dissociative) and adsorption configuration (monomer/cluster) dependence, which comes from the ability to generate terminal anions which are capable of capturing photogenerated holes and exhibit superior photocatalytic activity over their parent molecules. These studies reveal the origin of the correlation between photocatalytic activity and adsorption structure of CH3OH and H2O on TiO2 surfaces and suggest that the simple criteria widely used to analyze the feasibility of charge transfer, i.e., the relative position of the band edges and the molecular orbitals of adsorbates, should be replaced by the change of Gibbs free energy of the charge trapping reaction from the thermodynamic point of view. These results contribute to the fundamental understanding of photocatalysis. Based on our research, future state-resolved and time-resolved studies can provide deeper insight into the charge and energy transfer and transient intermediate species, which will benefit the depiction of the overall photocatalytic reactions, for example, the photocatalyzed oxygen evolution reaction from water.

Transition metal atoms embedded graphyne as effective catalysts for nitrate electroreduction to ammonia: A theoretical study

Electrocatalytic nitrate reduction reaction (NO3RR) to ammonia has been proved to be a viable approach to dispose of nitrates pollution and simultaneously fabricate valuable ammonia at room temperature and pressure. It is essential to explore high-performance and selective electrocatalysts for NO3RR to overcome the sluggish kinetics. Herein, through adopting a four-step screening route based upon the calculation of density functional theory (DFT), we have performed a comprehensive investigation on the NO3RR catalytic activities for single-atom catalysts (SACs), taking transition metal atom embedded graphyne (TM-GY, TM = 3d ∼ 5d) as example. The computation results show that the electrochemical conversion of nitrate-to-ammonia can be realized on Cr-GY candidate with an extremely low limiting potential (−0.36 V) and high selectivity, which can be ascribed to the moderate adsorption strength between the intermediate species and Cr atom derived from its distinct electronic property. Our study not only reveals the NO3RR catalytic origin of TM-GY, but also provides a new route for the rational design of electrocatalysts for nitrate reduction to ammonia.

Unveiling the impact of Leptospira TolC efflux protein on host tissue adherence, complement evasion, and diagnostic potential.

The TolC family protein of Leptospira is a type I outer membrane efflux protein. Phylogenetic analysis revealed significant sequence conservation among pathogenic Leptospira species (83%-98% identity) compared with intermediate and saprophytic species. Structural modeling indicated a composition of six β-strands and 10 α-helices arranged in two repeats, resembling bacterial outer membrane efflux proteins. Recombinant TolC (rTolC), expressed in a heterologous host and purified via Ni-NTA chromatography, maintained its secondary structural integrity, as verified by circular dichroism spectroscopy. Polyclonal antibodies against rTolC detected native TolC expression in pathogenic Leptospira but not in nonpathogenic ones. Immunoassays and detergent fractionation assays indicated surface localization of TolC. The rTolC's recognition by sera from leptospirosis-infected hosts across species suggests its utility as a diagnostic marker. Notably, rTolC demonstrated binding affinity for various extracellular matrix components, including collagen and chondroitin sulfate A, as well as plasma proteins such as factor H, C3b, and plasminogen, indicating potential roles in tissue adhesion and immune evasion. Functional assays demonstrated that rTolC-bound FH retained cofactor activity for C3b cleavage, highlighting TolC's role in complement regulation. The rTolC protein inhibited both the alternative and the classical pathway-mediated membrane attack complex (MAC) deposition in vitro. Blocking surface-expressed TolC on leptospires using specific antibodies reduced FH acquisition by Leptospira and increased MAC deposition on the spirochete. These findings indicate that TolC contributes to leptospiral virulence by promoting host tissue colonization and evading the immune response, presenting it as a potential target for diagnostic and therapeutic strategies.

Oxidation of glyoxal with the Mo-oxime complex in a benzalkonium chloride interface: Raghavan and Srinivasan kinetic model

Gaining an understanding of the glucose oxidation product (glyoxal) interaction with the metal–organic complex in a biological environment is pivotal to its usage. Thus, the glyoxal (Gyx) oxidation with Mo-oxime complex (MC) is studied with the spectrophotometric method, following a pseudo-phase approach. The result highlights the inclusion of hydrolysis, ion catalysis, the neutral primary salt effect, and radical generation as the essential factors in Gyx oxidation, with the exclusion of intermediate species formation. The hydrolysis of Gxy is observed to actively engage MC without charge inhibition as charge-neutral reacting species are involved, thus, implicating neutral primary salt effect where the variation of ionic strength of the system keeps the redox rate unchanged. The involvement of charge-neutral specie at the rate controlling step encouraged electrostatic attraction when Mg2+ ion additive is incorporated into the system, leading to ion catalysis. The generation of free radical from Gxy aids the emergence of formic acid. The zero intercept of Michaelis–Menten type plot and the non-appreciable shift in the maximum absorption wavelength of the reaction system and MC rule-out the presence of intermediate species. The contribution of thermodynamic enthalpy is instrumental in the redox process, leading to the formic acid product. The inclusion of benzalkonium chloride (BZC) hastens the Gxy oxidation, which is supported by Raghavan and Srinivasan’s model.

Spatial pattern of woody plant species richness and composition in primary warm temperate evergreen forest in Kasugayama Hill, Japan

Plant species richness and composition are influenced by complex interactions between biotic and abiotic factors that operate on different spatial scales. Since spatial scales vary continuously in nature, it is expected that multiple factors simultaneously affect species richness and composition at an intermediate spatial scale (i.e., the mesoscale landscape level). Previous studies have shown that local topography and elevation are important factors for shaping intermediate spatial scale plant species richness; however, the relative importance of these factors has rarely been examined. Here, we used spatially explicit woody plant data to examine the factors that characterize the spatial pattern of primary evergreen forest biodiversity at the intermediate spatial scale. We found that the spatial pattern of species diversity in a predominantly warm temperate evergreen forest at the landscape level is mainly characterized by shifts in species composition along the elevation gradient. Our study also found that compositional shift along the elevational gradient was mainly caused by habitat specialization among congeneric species, suggesting that niche partitioning among closely-related species is a fundamentally important feature of the intermediate spatial scale species richness pattern. Furthermore, we found that specialization in a habitat of closely-related species can be established even within a limited environmental gradient. This suggests that biotic interactions among closely-related species may be an important factor driving habitat specialization, and biotic interactions may play an important role in shaping landscape-scale biodiversity patterns.

Gallium-Mediated switching in product selectivity for CO2 hydrogenation over Ni/CeO2 catalysts

Achieving high activity and selectivity for the reverse water–gas shift (RWGS) reaction at low-temperatures continues to pose a significant challenge. Ni-based catalysts have been widely employed in CO2 hydrogenation due to their strong capacity to dissociate H2, but it exhibits low selectivity for CO. Herein, we successfully altered the product selectivity for CO2 hydrogenation via controlling the distribution of Ga species on Ni/CeO2 catalysts. When Ga was combined with Ni to form the spinel of NiGa2O4 (NiGa2O4/CeO2), the main product selectivity was CO. While, the Ga was doped into CeO2 to support Ni (Ni/Ga4-CeO2), the product selectivity was the CH4. The NiGa2O4 spinel supported on CeO2 exhibits excellent performance in the RWGS reaction, with a CO selectivity over 99 %, and a production rate as high as 74.5 mmol/gcat·h at 450 °C and 24000 mL/gcat·h, without any loss of activity after 72 h. The Ni/Ga4-CeO2, containing metallic Ni species and abundant oxygen vacancies, enhances the methanation process, with a CO2 conversion as high as 81.38 %, and a CH4 production rate of 136 mmol/gcat·h. The CO-TPD analysis and density functional theory calculation reveals that the NiGa2O4/CeO2 catalyst exhibits weak adsorption of CO*, which plays a key role in enhancing the selectivity towards CO. Subsequent in-situ DRIFTS analysis further confirms that the differences in CO2 hydrogenation product obtained from NiGa4/CeO2 and Ni/Ga4-CeO2 can be attributed to the formation of different intermediate species over their surface, leading to a change in the selectivity of CO2 hydrogenation products. This study provides an insight to switch the product selectivity for CO2 reduction by controlling the distribution of Ga species.

Decay Bc+→D(s)(*)+ℓ+ℓ− within covariant confined quark model

We study the rare semileptonic decays of Bc mesons within the effective field theoretical framework of covariant confined quark model. The transition form factors corresponding to Bc+→D(*)+ and Bc+→Ds(*)+ are computed in the entire q2 range. Using form factors, we compute the branching fractions and compare them with the available theoretical results. We also compute various physical observables such as forward-backward asymmetry, longitudinal and transverse polarizations, as well as clean angular observables. Published by the American Physical Society 2024