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Methods and equations for analysing the kinetics of enzyme-catalysed reactions were developed at the beginning of the 20th century in two centres in particular; in Paris, by Victor Henri, and, in Berlin, by Leonor Michaelis and Maud Menten. Henri made a detailed analysis of the work in this area that had preceded him, and arrived at a correct equation for the initial rate of reaction. However, his approach was open to the important objection that he took no account of the hydrogen-ion concentration (a subject largely undeveloped in his time). In addition, although he wrote down an expression for the initial rate of reaction and described the hyperbolic form of its dependence on the substrate concentration, he did not appreciate the great advantages that would come from analysis in terms of initial rates rather than time courses. Michaelis and Menten not only placed Henri's analysis on a firm experimental foundation, but also defined the experimental protocol that remains standard today. Here, we review this development, and discuss other scientific contributions of these individuals. The three parts have different authors, as indicated, and do not necessarily agree on all details, in particular about the relative importance of the contributions of Michaelis and Menten on the one hand and of Henri on the other. Rather than force the review into an unrealistic consensus, we consider it appropriate to leave the disagreements visible. [ABSTRACT FROM AUTHOR]

CsPbX3 perovskite nanocrystal (NC) is considered as an excellent optical material and is widely applied in optoelectronics. However, its poor water stability impedes its study in enzyme‐like activity, and further inhibits its application in biomimetic cascade catalysis. Herein, for the first time, the oxidase‐like and ascorbate oxidase‐like activities of an amphiphilic polymer capped CsPbX3 are demonstrated, and its catalytic mechanism is further explored. Furthermore, an all‐nanozyme cascade system (multifunctional CsPbBr3@Zr‐metal organic framework (Zr‐MOF) and Prussian blue as oxidase‐like and peroxidase‐like nanozyme) is constructed with a portable paper‐based device for realizing the dual‐mode (ratiometric fluorescence and colorimetric) detection of ascorbic acid in a point‐of‐care (POC) fashion. This is the first report on the utilization of all‐inorganic CsPbX3 perovskite NC in biomimetic cascade catalysis, which opens a new avenue for POC clinical disease diagnosis. [ABSTRACT FROM AUTHOR]

The commercialization of Li−S batteries is seriously hindered by polysulfides with severe shuttle effect, and the inherent insulating properties and slow reaction kinetics of insoluble Li2S products. Transition metal sulfides (TMSs) have a high adsorption capacity for polysulfides and have been shown to have a strong catalytic effect on polysulfide conversion reactions. This paper reviews the research on the application of Unary TMSs, heterostructures, etc. in Li−S batteries, and gives some research methods for TMD catalysts in Li−S batteries. Finally, it points out the main focuses and direction of future Li−S battery research and development. It aims to provide some insights into the design and manufacture of advanced Li−S batteries for commercial use. [ABSTRACT FROM AUTHOR]

A high-flux beamline optimized for non-resonant X-ray emission spectroscopy (XES) in the tender X-ray energy range has been constructed at the BESSY II synchrotron source. The beamline utilizes a cryogenically cooled undulator that provides X-rays over the energy range 2.1 keV to 9.5 keV. This energy range provides access to XES [and in the future X-ray absorption spectroscopy (XAS)] studies of transition metals ranging from Ti to Cu (Kα, Kβ lines) and Zr to Ag (Lα, Lβ), as well as light elements including P, S, Cl, K and Ca (Kα, Kβ). The beamline can be operated in two modes. In PINK mode, a multilayer monochromator (E/ΔE ≃ 30-80) provides a high photon flux (1014 photons s-1 at 6 keV and 300 mA ring current), allowing non-resonant XES measurements of dilute substances. This mode is currently available for general user operation. X-ray absorption near-edge structure and resonant XAS techniques will be available after the second stage of the PINK commissioning, when a high monochromatic mode (E/ΔE ≃ 10000-40000) will be facilitated by a double-crystal monochromator. At present, the beamline incorporates two von Hamos spectrometers, enabling time-resolved XES experiments with time scales down to 0.1 s and the possibility of two-color XES experiments. This paper describes the optical scheme of the PINK beamline and the endstation. The design of the two von Hamos dispersive spectrometers and sample environment are discussed here in detail. To illustrate, XES spectra of phosphorus complexes, KCl, TiO2 and Co3O4 measured using the PINK setup are presented. [ABSTRACT FROM AUTHOR]

Catalytic Janus colloids, with one hemi‐sphere covered by a hydrogen peroxide reduction catalyst such as platinum, represent one of the most experimentally explored examples of self‐motile active colloid systems. This paper comparatively investigates the motile behavior of symmetrical catalytic colloids produced by a solution‐based metal salt reduction process. Despite the significant differences in the distribution of catalytic activity, this study finds that the motion produced by symmetrical colloids is equivalent to that previously reported for Janus colloids. It also shows that introducing a Janus structure to the symmetrical colloids via masking does not significantly modify their motion. These findings could indicate that very subtle variations in surface reactivity can be sufficient to produce Janus‐like active Brownian particle‐type motion, or that a symmetry‐breaking phenomena is present. The study will consequently motivate fresh theoretical attention and also demonstrate a straightforward route to access large quantities of motile active colloids, which are expected to show subtly different phenomenology compared to those with Janus structures. [ABSTRACT FROM AUTHOR]

The various toxic contaminants such as dyes, heavy metals, pesticides, rare‐earth elements, and hazardous chemicals are the major threats to all the flora and fauna. Owing to the harmful ill effects caused by the toxic contaminants, it is necessary to eliminate these compounds from the authors' ecosystem. The chitosan magnetic nanomaterials (CMNPs) are one of the superior materials used in the wastewater treatment through various conventional technologies. The chitosan is a natural source obtained from the crustacean shells of crabs, prawns etc. The magnetic nanomaterial prepared by the reinforcement of chitosan is highly effective in the removal of heavy metals, dyes, organic matter, and harmful chemicals. It is used in various technologies such as adsorption, flocculation, immobilisation, photocatalytic technology, and bioremediation. This possesses unique surface and magnetic characteristics, Moreover, it is simple, economically feasible, and eco‐friendly material used efficiently in wastewater treatment. This review paper depicts the overview of CMNP in the industrial effluent treatment. [ABSTRACT FROM AUTHOR]

Droplet impact on solid surfaces is essential both in nature and industry. Precisely regulating the dynamic behavior of droplet impact is of great significance for energy harvesting, anti-icing, inkjet printing, pesticide spraying, and many other fields. Various rebounding behaviors (deposition, rebounding, rotation, instability control, and so on) and rebounding intrinsic parameters (such as contact time) after droplets impacting on solid surfaces can be regulated by surface engineering. This paper reviews the advances in regulating droplet impact behavior from the perspective of symmetry by modifying solid surfaces from the following aspects: chemical modification and physical structure regulation, in which the symmetry is discussed from mirror symmetry and rotational symmetry. Firstly, the symmetry of the droplet impact dynamics and its influencing factors are introduced. Then the modulation of droplet impact symmetry, using homogeneous and heterogeneous chemically modified solid surfaces, is summarized. The following presents the influence of physical structures, from micro to macro scale compared to the droplet size, on the droplet impact symmetry. Finally, the future challenges and opportunities of the droplet impact behavior regulation are discussed. [ABSTRACT FROM AUTHOR]

A series of new pyrazolate and mixed pyrazolate/pyrazole magnesium complexes is described and their reactivity toward carbon dioxide is examined. The dimeric complex [Mg(pztBu,tBu)2]2 inserts CO2 instantly and quantitatively forming the tetrameric complex [Mg(CO2·pztBu,tBu)2]4 and monomeric donor‐stabilized [Mg(CO2·pztBu,tBu)2(thf)2]. Complexes of the type [Mgx(pzR,R)2x(HpzR,R)y]n (R = iPr, tBu) engage in similar insertion reactions involving dissociation of the carbamic acid HOOCpzR,R. Even solid polymeric derivatives [Mg(pzR,R)2]n (R = Me, H) react instantaneously and exhaustively with CO2, the resulting [Mg(CO2·pz)2]m featuring a CO2 capacity of 35.7 wt% (8.2 mmol g−1). All described magnesium pyrazolates display completely reversible CO2 uptake in solution and in the solid state, respectively, as monitored via VT 1H NMR and in situ FTIR spectroscopy as well as thermogravimetric analysis. Fluorinated [Mg2(pzCF3,CF3)4(thf)3] does not yield any isolable CO2 insertion product but exhibits the highest activity in the catalytic transformation of epoxides and CO2 to cyclic carbonates. [ABSTRACT FROM AUTHOR]

The world is facing grand challenges in energy security, environmental pollution, and sustainable use (and re‐use) of resources. Electrochemical processes, incorporating electrosynthesis, electrochemical catalysis, and electrochemical energy storage devices, provide pathways to address these challenges via green chemistry. However, the applicability of electrochemical processes for these systems is limited by the required energy input, the "electrons" in electrochemistry. Electrocatalysis as a subset of electrochemistry is set to underpin many of the United Nations Sustainable Development Goals, including "Affordable and Clean Energy" through the production of future fuels and abatement of carbon emissions; "Responsible Consumption and Production" through recycling and degradation of waste; and "Climate Action" through CO2 (and other greenhouse gas) remediation. The rise of green photovoltaic power has lowered the carbon cost of these electrons, making electrocatalysis an even more viable, green(er), chemical conversion pathway. This perspective highlights the need for comprehensive understanding of catalyst structure via in situ and operando analysis to complement device design considerations. The challenges faced by the field of electrocatalysis in data reporting, elimination of electrochemical artifacts, catalyst stability, and scaling to industrial relevance, along with opportunities, emerging tools, are discussed with a view to achieve the maximum 'potential' of electrocatalysis. [ABSTRACT FROM AUTHOR]

Allostery is an important property of biological macromolecules which regulates diverse biological functions such as catalysis, signal transduction, transport, and molecular recognition. However, the concept was expressed using two different definitions by J. Monod and, over time, more have been added by different authors, making it fuzzy. Here, we reviewed the different meanings of allostery in the current literature and found that it has been used to indicate that the function of a protein is regulated by heterotropic ligands, and/or that the binding of ligands and substrates presents homotropic positive or negative cooperativity, whatever the hypothesized or demonstrated reaction mechanism might be. Thus, proteins defined to be allosteric include not only those that obey the two‐state concerted model, but also those that obey different reaction mechanisms such as ligand‐induced fit, possibly coupled to sequential structure changes, and ligand‐linked dissociation‐association. Since each reaction mechanism requires its own mathematical description and is defined by it, there are many possible 'allosteries'. This lack of clarity is made even fuzzier by the fact that the reaction mechanism is often assigned imprecisely and/or implicitly in the absence of the necessary experimental evidence. In this review, we examine a list of proteins that have been defined to be allosteric and attempt to assign a reaction mechanism to as many as possible. [ABSTRACT FROM AUTHOR]

2020 and 2021 marked major milestones for the catalysis community in Canada. The Catalysis Division of The Chemical Institute of Canada marked its 50‐year anniversary in 2021, and the Canadian Catalysis Foundation celebrated its 30th anniversary in 2020. Both organizations have been instrumental in supporting and advancing the broad and evolving field of catalysis in Canada. This article summarizes the genesis of these organizations and highlights the key roles that they serve for the catalysis community. The health and vibrancy of the catalysis community in 2022 is a testament to the vision, insights, and efforts of those in the community in the 1960s and 1970s who created a framework that helped to bridge the gaps between science and engineering in the field of catalysis. The establishment of the Division in 1971 pulled together a critical mass of people with common professional interests in all aspects of catalysis and catalyst technology. The division structure facilitated collaborations, formalizing and organizing biennial catalysis symposia, administering award programs, and, now, acting as a pipeline for members and directors of the Canadian Catalysis Foundation. [ABSTRACT FROM AUTHOR]

To celebrate the 100th volume of The Canadian Journal of Chemical Engineering (CJCE) in 2022, we briefly narrate its history and accomplishments. The CJCE's journey began in 1929 with the launch of the Canadian Journal of Research (CJR), which transformed to the Canadian Journal of Technology (CJT) in 1951, and finally to its present name in 1957 as the flagship publication of the Canadian Society for Chemical Engineering (CSChE). Using statistical data and keywords mined from Clarivate's Web of Science (WoS) together with manual searches of the articles published in the CJR and CJT, we describe how the scope of chemical engineering has continued to evolve, over the past 90+ years, in becoming ever more multifaceted. Chemical engineering encompasses traditional areas, such as polymers, thermodynamics, transport phenomena, transfer and separation processes, reactor design, energy conversion, process simulation and control, and environmental science; however, it has been expanding to include biotechnology, biomedical, food processing, novel composite materials, nanotechnology, renewable/green energy, CO2 capture and transformation, and numerical techniques like neural networks, artificial intelligence, discrete element methods, etc. Like all scientific journals, the growth and success of the CJCE are attributed to the commitment of its contributing authors. We recognize and celebrate the contributions of several prominent Canadian and international researchers, who published their articles in the CJCE. With a number of new initiatives launched in the last decade, we foresee continued improvements in the stature of the CJCE as a top‐ranked journal for publishing impactful research, leading to advancements in chemical sciences and engineering. [ABSTRACT FROM AUTHOR]

The intermediates for the production of nonionic surfactants can be derived from petrochemicals and/or from renewable raw materials. In both, the role of catalysis is fundamental. In this paper the main results reported in the literature related with the catalysis for ethoxylation of fatty esters will be reviewed. The main open challenges for these technologies will be outlined. [ABSTRACT FROM AUTHOR]

Noncrystalline nickel phosphide (Ni-P) nanoparticles have drawn great attention due to their high potential as catalysts. However, the structure of noncrystalline Ni-P nanoparticles is still unknown, which may shed light on explaining the catalysis mechanism of the Ni-P nanoparticles. In this paper, noncrystalline Ni-P nanoparticles were synthesized. Their morphology, particle size, element contents, local atomic structures, as well as the catalysis in the thermal decomposition of ammonium perchlorate were studied. The results demonstrate that the as-prepared Ni-P nanoparticles are spherical with an average diameter of about 13.5 nm. The Ni and P contents are, respectively, 78.15% and 21.85%. The noncrystalline nature of the as-prepared Ni-P nanoparticles can be attributed to cross-linkage between P-doping f.c.c.-like Ni centers and Ni3P-like P centers. The locally ordered Ni centers and P centers are the nuclei sites, which can explain well the origin of initial nuclei to form the crystalline phases after high-temperature annealing. The starting temperature of high-temperature decomposition of ammonium perchlorate was found having a significant decrease in the presence of the noncrystalline Ni-P nanoparticles. Therefore, the as-prepared noncrystalline Ni-P nanoparticles can be used as a potential catalyst in the thermal decomposition of ammonium perchlorate. [ABSTRACT FROM AUTHOR]

Metal borides have received a lot of attention recently as a potentially useful material for a wide range of applications. In particular, molybdenum‐based borides and MBenes are of great significance, due to their remarkable properties like good electronic conductivity, considerable stability, high surface area, and environmental harmlessness. Therefore, in this article, the progress made in molybdenum‐based borides and MBenes in recent years is reviewed. The first step in understanding these materials is to begin with an overview of their structural and electronic properties. Then synthetic technologies for the production of molybdenum borides, such as high‐temperature/pressure methods, physical vapor deposition (PVD), chemical vapor deposition (CVD), element reaction route, molten salt‐assisted, and selective etching methods are surveyed. Then, the critical performance of these materials in numerous applications like energy storage, catalysis, biosensors, biomedical devices, surface‐enhanced Raman spectroscopy (SERS), and tribology and lubrication are summarized. The review concludes with an analysis of the current progress of these materials and provides perspectives for future research. Overall, this review will offer an insightful reference for the understanding molybdenum‐based borides and their development in the future. [ABSTRACT FROM AUTHOR]

In recent years, there has been a surge in annual plastic production, which has contributed to growing environmental challenges, particularly in the form of microplastics. Effective management of plastic and microplastic waste has become a critical concern, necessitating innovative strategies to address its impact on ecosystems and human health. In this context, catalytic degradation of microplastics emerges as a pivotal approach that holds significant promise for mitigating the persistent effects of plastic pollution. In this article, we critically explored the current state of catalytic degradation of microplastics and discussed the definition of degradation, characterization methods for degradation products, and the criteria for standard sample preparation. Moreover, the significance and effectiveness of various catalytic entities, including enzymes, transition metal ions (for the Fenton reaction), nanozymes, and microorganisms are summarized. Finally, a few key issues and future perspectives regarding the catalytic degradation of microplastics are proposed. [ABSTRACT FROM AUTHOR]

Homogenous catalysis is an essential tool within the commercial manufacture of bulk and fine chemicals. Within this, phosphine ligands, such as tricyclohexylphosphine, otherwise known as CYTOP® 366, are a crucial component. When designing a pathway to your ligand of choice, some key considerations include safety, yield and quality, but at commercial volumes we must also balance cost and consider the technologies readily available. Herein, we report the synthetic route that was chosen to manufacture tricyclohexylphosphine at commercial scale. We also consider, with the use of computational calculations, why traditional hydrophosphination methods failed, where the selected pathway succeeded. [ABSTRACT FROM AUTHOR]

The paper analyses how the control of material flows needed by living systems determines evolutionary patterns. A simplification of Miller's living systems theory, distinguishing only three functional units, (i) production systems, (ii) storage, and (iii) controller structures, is used to investigate the importance of these units on various evolutionary stages. In the internal evolution of biological systems, storage is crucial to control the availability of intermediate products of autocatalytic cycles. This is the base for continuous production and maintenance of controller structures (brains). In the external, technical evolution storage enables building external production systems and controller structures (like computers). In the dyadic coevolution of living systems, control of material flows and/or storage enable power positions in interaction patterns ranging from competition for scarce resources, via market relations, to egalitarian cooperation. Such power positions open access to different markets and exclusive evolutionary options. Economic theory widely ignores that. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Metabolic control analysis [Kacser and Burns (1973) Symp. Soc. Exp. Biol. 27, 65-104; Heinrich and Rapoport (1974) Eur. J. Biochem. 42, 89-95] leads to a description of the systemic properties of a metabolic system (expressed as control coefficients) in terms of the local kinetic properties of the individual enzyme-catalyzed reactions (expressed as elasticity coefficients). This paper describes a non-algebraic diagrammatic method which generates the mathematical expressions for flux or concentration-control coefficients in terms of elasticity coefficients. According to a set of simple rules, 'flux-control patterns' or 'concentration-control patterns' are drawn on a metabolic diagram. Each control pattern represents a product of elasticity coefficients that occurs as a term in the expression for a control coefficient. The rules also generate the correct sign that precedes each term. The control patterns are then used to build the expressions for control coefficients. The procedure was developed in such a way that each control pattern can be understood in terms of a 'chain of local effects' which shows how a perturbation in the activity of an enzyme is propagated through the metabolic pathway. [ABSTRACT FROM AUTHOR]

Electrochemical ammonia oxidation reaction (eAOR) regains interest due to ammonia being an interesting alternative to hydrogen for fuel cell technologies. In the present review, we first discuss some of the most important findings on eAOR with solid catalysts, including mechanistic and feasibility aspects for practical implementation. We then examine the reports on molecular catalysis of eAOR that have recently emerged. We finally discuss immobilization strategies of these molecular catalysts, and discuss intrinsic advantages of those strategies, so as to guide the design of efficient catalytic systems able to compete with heterogeneous, solid catalysts. [ABSTRACT FROM AUTHOR]

A family of transition metal complexes of meso‐aryl‐2‐aza‐21‐carbaporphyrin (N‐confused porphyrin, NCP) derivatives acting as ortho‐metallating ligands for ruthenium(II), rhodium(III), and iridium(III) is synthesized and characterized by XRD, spectroscopic, and electrochemical methods. The chirality of these systems is shown by the separation of the enantiomers and analyzed by circular dichroism and DFT. A preliminary catalytic study indicates the activity of the iridium(III) ortho‐metallated complexes in the N‐heterocyclization of primary amines with diols. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of complicated multiphase conversions and the severe shuttling effect of lithium polysulfides (LiPSs) significantly hinder the applications of Li‐S battery, which is one of the most promising candidates for the next‐generation energy storage system. Herein, a bifunctional electrocatalyst, indium phthalocyanine self‐assembled with carbon nanotubes (InPc@CNT) composite material, is proposed to promote the conversion kinetics of both reduction and oxidation processes, demonstrating a bidirectional catalytic effect on both nucleation and dissolution of Li2S species. The theoretical calculation shows that the unique electronic configuration of InPc@CNT is conducive to trapping soluble polysulfides in the reduction process, as well as the modulation of electron transfer dynamics also endows the dissolution of Li2S in the oxidation reaction, which will accelerate the effectiveness of catalytic conversion and facilitate sulfur utilization. Moreover, the InPc@CNT modified separator displays lower overpotential for polysulfide transformation, alleviating polarization of electrode during cycling. The integrated spectroscopy analysis, HRTEM, and electrochemical study reveal that the InPc@CNT acts as an efficient multifunctional catalytic center to satisfy the requirements of accelerating charging and discharging processes. Therefore, the Li–S battery with InPc@CNT‐modified separator obtains a discharge‐specific capacity of 1415 mAh g−1 at a high rate of 0.5 C. Additionally, the 2 Ah Li–S pouch cells deliver 315 Wh kg−1 and achieved 80% capacity retention after 50 cycles at 0.1 C with a high sulfur loading of 10 mg cm−2. Our study provides a practical method to introduce bifunctional electrocatalysts for boosting the electrochemical properties of Li–S batteries. [ABSTRACT FROM AUTHOR]

Inhospitable, inaccessible, and extremely remote alike the famed pole of inaccessibility, aka Point Nemo, the isolated locations in deserts, at sea, or in outer space are difficult for humans to settle, let alone to thrive in. Yet, they present a unique set of opportunities for science, economy, and geopolitics that are difficult to ignore. One of the critical challenges for settlers is the stable supply of energy both to sustain a reasonable quality of life, as well as to take advantage of the local opportunities presented by the remote environment, e.g., abundance of a particular resource. The possible solutions to this challenge are heavily constrained by the difficulty and prohibitive cost of transportation to and from such a habitat (e.g., a lunar or Martian base). In this essay, the advantages and possible challenges of integrating Fischer–Tropsch, artificial photosynthesis, and plasma catalysis into a robust, scalable, and efficient self‐contained system for energy harvesting, storage, and utilization are explored. [ABSTRACT FROM AUTHOR]

Alkaline phosphatase (Escherichia coli) was found to catalyze the synthesis of monophosphate esters of serine, ethanolamine, propanolamine, butanol, glycerol, L-glucose, and tris(hydroxymethyl)aminomethane by phosphoryl transfer from cysteamine S-phosphate (donor) to the respective alcohols (acceptors). Maximum enzymic synthesis of the above esters occurred at pH 7.8. The newly-formed phosphate esters were measured quantitatively after separation of the products by the aid of paper high voltage electrophoresis techniques or by an amino acid analyzer. The percentage of the enzyme-catalyzed synthesis of the new phosphate esters varied from 15-39 0/0 using different acceptors under otherwise identical experimental conditions. It is pertinent to note that the same compounds were phosphorylated to essentially the same extent when the donor (substrate) compound was serine O-phosphate, aminoethanol O-phosphate or p-nitrophenyl O-phosphate. The rates of enzymic consumption of cysteamine S-phosphate (vh + va) were measured at different pH values and at different concentrations of acceptor (Tris or aminoethanol) in the presence of 1.5 M NaCl using 3 mM substrate (cysteamine S-phosphate). The presence of either Tris or aminoethanol gave the same pH profile for the rate of consumption (vh + va) of cysteamine S-phosphate with a maximum value around pH 7.8. This value differs from that found for the same reaction in barbital buffer (pH 9.0). The rate of enzymic consumption of cysteamine S-phosphate was also measured at various substrate and Tris concentrations at pH 7.8 under constant ionic strength (Γ/2 = 1.0). The same Km value (0.24 mM) was obtained at Tris concentrations varying from 0.02 M to 0.5 M. The Vmax values derived from these experiments were linearly related to the Tris concentrations up to 0.5 M Tris. The ph profile of the rate of consumption of p-nitrophenyl phosphate as well as the Km value (0.26 mM) were similar to the corresponding values obtained for cysteamine S-phosphate. The rate of hydrolysis (vh) could not be measured when cysteamine S-phosphate served as the donor compound due to the instability of cysteamine S-phosphate under the conditions required for inorganic phosphate assay. Therefore, the rate of transfer (va = vRSH - vP1) could not be estimated. The pH dependence of the rate of transfer, va, was calculated from experimental data obtained when p-nitrophenyl phosphate served as the donor compound and Tris served as the acceptor. The pH profile for the rate of transfer, va, obtained from these measurements was very similar to that obtained by direct measurement of Tris O-phosphate formation using cysteamine as the donor. It is suggested that phosphoryl transfer occurs through a phosphorylated enzyme intermediate, and therefore, the types of compounds that could serve as acceptors are independent of the donor compounds and depend only on the bond energy of the particular phosphorylated enzyme intermediate. [ABSTRACT FROM AUTHOR]

This paper presents a comparison of the activity for methane oxidation of selected commercial platinum, palladium, and platinum-palladium supported catalysts. Precious metal loadings are typical of those found in the catalytic converters for lean-burn natural gas engines. Experiments are presented for de-greened as well as hydrothermally aged catalysts, both in the presence and the absence of water. For the platinum catalyst, fraction conversion of methane is shown to be independent of methane concentration, while for the palladium-containing catalysts a dependence of conversion on methane partial pressure is observed. For catalysts containing palladium, reduction in hydrogen gives an increase in methane conversion activity, although the increase is subsequently lost in the oxidizing atmosphere. Hydrothermal aging of the platinum catalyst causes a relatively large and permanent loss in methane oxidation activity, while the palladium-based catalysts showed more resistance to deactivation. Adding a small amount of palladium to the platinum catalyst provides an overall improvement in performance. [ABSTRACT FROM AUTHOR]

Over the past decades, the design of active catalysts has been the subject of intense research efforts. However, there has been significantly less deliberate emphasis on rationally designing a catalyst system with a prolonged stability. A major obstacle comes from the ambiguity behind how catalyst degrades. Several degradation mechanisms are proposed in literature, but with a lack of systematic studies, the causal relations between degradation and those proposed mechanisms remain ambiguous. Here, a systematic study of a catalyst system comprising of small particles and single atoms of Pt sandwiched between graphene layers, GR/Pt/GR, is studied to unravel the degradation mechanism of the studied electrocatalyst for oxygen reduction reaction(ORR). Catalyst suffers from atomic dissolution under ORR harsh acidic and oxidizing operation voltages. Single atoms trapped in point defects within the top graphene layer on their way hopping through toward the surface of GR/Pt/GR architecture. Trapping mechanism renders individual Pt atoms as single atom catalyst sites catalyzing ORR for thousands of cycles before washed away in the electrolyte. The GR/Pt/GR catalysts also compare favorably to state‐of‐the‐art commercial Pt/C catalysts and demonstrates a rational design of a hybrid nanoarchitecture with a prolonged stability for thousands of operation cycles. [ABSTRACT FROM AUTHOR]

As the atmospheric carbon dioxide (CO2) level keeps hitting the new record, humanity is facing an ever-daunting challenge to efficiently mitigate CO2 from the atmosphere. Though electrochemical CO2 reduction presents a promising pathway to convert CO2 to valuable fuels and chemicals, the general lack of suitable electrocatalysts with high activity and selectivity severely constrains this approach. Herein, a novel class of electrocatalysts is investigated, the quasi-copper-mers, in which the CuN4 rather than Cu atom itself serve as the basic building block. The respective quasi-copper-monomers, -dimers, and -trimers hosted in a graphene-like substrate are first synthesized and then performed both experimental characterization and density functional theory (DFT) calculations to examine their atomic structures, evaluate their electrocatalytical performance and understand their underlying mechanisms. The experimental results show that the quasi-copper-trimers not only outperform the quasi-copper-dimer and quasi-copper-monomer when catalyzing CO2 to CO, it also shows a superior selectivity against the competing hydrogen evolution reaction (HER). The DFT calculations not only support the experimental observations, but also reveal the volcano curve and the physical origin for the qausi-copper-trimer superiority. The present work thus presents a new strategy in the design of high-performance electrocatalysts with high activity and selectivity. [ABSTRACT FROM AUTHOR]

Molecular catalysis of electrochemical reactions is a field of intense activity because of the current interest in electrifying chemical transformations, including both electrosynthesis of organic molecules and production of fuels via small molecule activation. Controlled potential electrolysis (CPE) is often coupled with in situ in operando spectroscopic methods with the aim to gather mechanistic information regarding the catalytic species involved. Herein, considering a simple mechanism for a homogeneous molecular catalysis of an electrochemical reaction, we establish the concentration profile of the catalyst in the electrolysis cell enabling to envision the information that can be obtained from the coupling of this CPE with a spectroscopic probe in the cell compartment. We show how the characteristic parameters of the system (catalytic rate constant, cell dimensions and stirring rate) affect the response with particular emphasis on the transition between two limiting cases, namely a 'fast' catalysis regime where catalysis only takes place in a small layer adjacent to the electrode surface and a 'slow' catalysis regime where catalysis takes place in the bulk of the solution. These formal concepts are then illustrated with an experimental example, the electroreduction of CO2 in dimethylformamide homogeneously catalyzed by iron tetraphenylporphyrin and followed by UV‐vis spectroscopy. [ABSTRACT FROM AUTHOR]

Many kinetic models have appeared in literature in past decades using two main approaches: the traditional global kinetics approach, or the more complex micro-kinetics approach. Whether global or micro-kinetics, kinetic models have been based on experimental data obtained at the end of the monolith. The experimental procedure using end pipe analysis may give an accurate overview of the reaction mechanisms that occur; however, the lack of information from within the catalyst can ultimately lead to inaccuracies in the kinetic model and parameters used. Using SpaciMS, a spatially resolved experimental technique developed at the Queen's University Belfast, information from within the catalyst can be obtained. This minimally invasive technique provides detailed information of the gas concentration and temperature profile from inside the catalytic monolith. This paper presents a kinetic model and simulations validated against experimental data obtained from three positions inside the catalyst monolith at 2, 14, and 26 mm in, using data from the SpaciMS. Also, simulations of end pipe analysis, using a commercial reactor, for the CO oxidation are presented and analyzed. The simulations presented are for varying concentrations of both CO and O2 (0.5 % and 1 % CO, 0.5 % and 2 % O2) for both the global and micro-kinetic approach. [ABSTRACT FROM AUTHOR]

In this paper, industrial grade metatitanic (H2TiO3) from sulphate process was used as the raw material to prepare TiO2 through a series of modification. Granular and honeycomb SCR DeNO X catalysts were made by granulation and molding processes respectively with those TiO2 as the carrier material. The characterisation, mechanical strength and denitration performance of the carrier/catalyst samples were tested and compared with those of commercial anatase nano-TiO2 products. The results showed that the TiO2 sample after the modified operation was remarkably improved in particle diameter, dispersion characteristic (average particle size from 15.79 to 1.746 µm) and the degree of crystallinity (from 93.7% to 98.1%), also the impurity content of K, Na, Ca, Mg, Al, S, etc. was significantly reduced; however, the grain size was increased (from 7.0 to 9.9 nm), and the specific surface area was decreased slightly (from 148.1 to 112.6 m2/g). As a whole, the characterisation was extremely close to commercial anatase nano-TiO2. Catalyst samples prepared with TiO2 after the modified operation had an upgrade on catalytic activity (the maximum denitration rate of granular catalyst from 95.0% to 97.1%; honeycomb catalyst from 92.2% to 93.3%), and the mechanical properties of honeycomb catalysts have been enhanced significantly (compressive strength of axial direction changed from 0.1063 to 0.5965 Mpa). The work indicated that TiO2 prepared with the industrial grade metatitanic from sulphate process was suitable as a carrier material for SCR DeNO X catalyst production. Also the modification was necessary. [ABSTRACT FROM AUTHOR]

Cytosolic nucleotidase II ( cN- II) from Legionella pneumophila ( Lp) catalyzes the hydrolysis of GMP and d GMP displaying sigmoidal curves, whereas catalysis of IMP hydrolysis displayed a biphasic curve in the initial rate versus substrate concentration plots. Allosteric modulators of mammalian c N- II did not activate Lpc N- II although GTP, GDP and the substrate GMP were specific activators. Crystal structures of the tetrameric Lpc N- II revealed an activator-binding site at the dimer interface. A double mutation in this allosteric-binding site abolished activation, confirming the structural observations. The substrate GMP acting as an activator, partitioning between the allosteric and active site, is the basis for the sigmoidicity of the initial velocity versus GMP concentration plot. The Lpc N- II tetramer showed differences in subunit organization upon activator binding that are absent in the activator-bound human c N- II structure. This is the first observation of a structural change induced by activator binding in c N- II that may be the molecular mechanism for enzyme activation. Database The coordinates and structure factors reported in this paper have been submitted to the Protein Data Bank under the accession numbers and . The accession number of GMP complexed Lpc N- II is . Structured digital abstract and by (), and by (), [Structured digital abstract was added on 5 March 2014 after original online publication] [ABSTRACT FROM AUTHOR]

Processive enzymes perform sequential steps of catalysis without dissociating from their polymeric substrate. This mechanism is considered essential for efficient enzymatic hydrolysis of insoluble cellulose (particularly crystalline cellulose), but a theoretical framework for processive kinetics remains to be fully developed. In this paper, we suggest a deterministic kinetic model that relies on a processive set of enzyme reactions and a quasi steady-state assumption. It is shown that this approach is practicable in the sense that it leads to mathematically simple expressions for the steady-state rate, and only requires data from standard assay techniques as experimental input. Specifically, it is shown that the processive reaction rate at steady state may be expressed by a hyperbolic function related to the conventional Michaelis- Menten equation. The main difference is a 'kinetic processivity coefficient', which represents the probability of the enzyme dissociating from the substrate strand before completing n sequential catalytic steps, where n is the mean processivity number measured experimentally. Typical processive cellulases have high substrate affinity, and therefore this probability is low. This has significant kinetic implications, for example the maximal specific rate ( Vmax/E0) for processive cellulases is much lower than the catalytic rate constant ( kcat). We discuss how relationships based on this theory may be used in both comparative and mechanistic analyses of cellulases. [ABSTRACT FROM AUTHOR]

Using free lipase as the catalyst for biodiesel production has drawn increasing attention in recent years due to its advantages of lower cost and faster reaction rate compared to immobilized lipase. Our previous study showed that free lipase NS81006 could effectively catalyze the methanolysis of renewable oil. Ethanol, derived from renewable biomass, has a greater potential for biodiesel production. In this paper, ethanol was explored for the first time as the acyl acceptor for free lipase-mediated biodiesel preparation. The effect of stirring rate, water content, molar ratio of ethanol to oil and ethanol adding strategy was investigated systematically during the process of free lipase NS81006-catalyzed ethanolysis. An ethyl ester yield of 90% was obtained under the optimized conditions. Further study showed that the free lipase could be repeatedly used by simple separation of the water phase from the oil phase and there was no obvious loss in lipase activity after five repeated uses. [ABSTRACT FROM AUTHOR]

This paper reviews amorphous carbon bearing sulfonic acid groups as an efficient solid acid catalyst for the production of various chemicals. The material is produced by the sulfonation of incompletely carbonized organic carbon to yield an insoluble, stable, and inexpensive catalyst with acid catalytic activity comparable to that of sulfuric acid (H2SO4). The carbon material can also be readily separated from liquid products by decantation or filtration, and can be repeatedly reused without any decrease in activity. As a replacement for H2SO4 in industrial chemical production, a carbon-based solid acid catalyst thus has the potential to substantially reduce energy consumption and waste generation. The carbon catalyst also converts crude vegetable oils into biodiesel in a one-step process, demonstrating the potential utility of this material in a wide range of catalytic processes. The remarkable catalytic activity of this material is attributable to the incorporation of reactants into the bulk structure and the high density of strongly acidic SO3H sites. [ABSTRACT FROM AUTHOR]

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The length of the needle ending theYersiniaYsc injectisome is determined by YscP, a protein acting as a molecular ruler. In addition, YscP is required for Yop secretion. In the present paper, by a systematic deletion analysis, we localized accurately the region required for Yop secretion between residues 405 and 500. As this C-terminal region of YscP has also been shown to control needle length it probably represents the substrate specificity switch of the machinery. By a bioinformatics analysis, we show that this region has a globular structure, an originalα/β fold, a P-x-L-G signature and presumably no catalytic activity. In spite of very limited sequence similarities, this structure is conserved among the proteins that are presumed to control the needle length in many different injectisomes and also among members of the FliK family, which control the flagellar hook length. This region thus represents a new protein domain that we called T3S4 forypeecretionubstratepecificitywitch. The T3S4 domain of YscP can be replaced by the T3S4 domain of AscP (Aeromonas salmonicida) or PscP (Pseudomonas aeruginosa) but not by the one from FliK, indicating that in spite of a common global structure, these domains need to fit their partner proteins in the secretion apparatus. [ABSTRACT FROM AUTHOR]

Simultaneously optimizing elementary steps, such as water dissociation, hydroxyl transferring, and hydrogen combination, is crucial yet challenging for achieving efficient hydrogen evolution reaction (HER) in alkaline media. Herein, Ru single atom‐doped WO2 nanoparticles with atomically dispersed Ru–W pair sites (Ru–W/WO2‐800) are developed using a crystalline lattice‐confined strategy, aiming to gain efficient alkaline HER. It is found that Ru–W/WO2‐800 exhibits remarkable HER activity, characterized by a low overpotential (11 mV at 10 mA cm−2), notable mass activity (5863 mA mg−1 Ru at 50 mV), and robust stability (500 h at 250 mA cm−2). The highly efficient activity of Ru–W/WO2‐800 is attributed to the synergistic effect of Ru–W sites through ensemble catalysis. Specifically, the W sites expedite rapid hydroxyl transferring and water dissociation, while the Ru sites accelerate the hydrogen combination process, synergistically facilitating the HER activity. This study opens a promising pathway for tailoring the coordination environment of atomic‐scale catalysts to achieve efficient electro‐catalysis. [ABSTRACT FROM AUTHOR]

Solar energy‐induced catalysis has been attracting intensive interests and its quantum efficiencies in plasmon‐mediated photothermal catalysis (P‐photothermal catalysis) and external heat‐coupled photocatalysis (E‐photothermal catalysis) are ultimately determined by the catalyst structure for photo‐induced energetic hot carriers. Herein, different catalysts of supported (TiO2‐P25 and Al2O3) platinum quantum dots are employed in photo, thermal, and photothermal catalytic dry reforming of methane. Integrated experimental and computational results unveil different active sites (hot zones) on the two catalysts for photo, thermal, and photothermal catalysis. The hot zones of P‐photothermal catalysis are identified to be the metal–support interface on Pt/P25 and the Pt surface on Pt/Al2O3, respectively. However, a change of the active site to the Pt surface on Pt/P25 is for the first time observed in E‐photothermal catalysis (external heating temperature of 700 °C). The hot zones contribute to the significant enhancements in photothermal catalytic reactivity against thermocatalysis. This study helps to understand the reaction mechanism of photothermal catalysis to exploit efficient catalysts for solar energy utilization and fossil fuels upgrading. [ABSTRACT FROM AUTHOR]

Traditional trial‐and‐error experiments and theoretical simulations have difficulty optimizing catalytic processes and developing new, better‐performing catalysts. Machine learning (ML) provides a promising approach for accelerating catalysis research due to its powerful learning and predictive abilities. The selection of appropriate input features (descriptors) plays a decisive role in improving the predictive accuracy of ML models and uncovering the key factors that influence catalytic activity and selectivity. This review introduces tactics for the utilization and extraction of catalytic descriptors in ML‐assisted experimental and theoretical research. In addition to the effectiveness and advantages of various descriptors, their limitations are also discussed. Highlighted are both 1) newly developed spectral descriptors for catalytic performance prediction and 2) a novel research paradigm combining computational and experimental ML models through suitable intermediate descriptors. Current challenges and future perspectives on the application of descriptors and ML techniques to catalysis are also presented. [ABSTRACT FROM AUTHOR]

Designing and synthesizing advanced electrocatalysts with superior intrinsic activity toward hydrogen evolution reaction (HER) in alkaline media is critical for the hydrogen economy. Herein, a novel Ir@Rhene heterojunction electrocatalyst is synthesized via epitaxially confining ultrasmall and low‐coordinate Ir nanoclusters on the ultrathin Rh metallene accompanying the formation of Ir/IrO2 Janus nanoparticles. The as‐prepared heterojunctions display outstanding alkaline HER activity, with an overpotential of only 17 mV at 10 mA cm−2 and an ultralow Tafel slope of 14.7 mV dec−1. Both structural characterizations and theoretical calculations demonstrate that the Ir@Rhene heterointerfaces induce charge density redistribution, resulting in the increment of the electron density around the O atoms in the IrO2 site and thus delivering much lower water dissociation energy. In addition, the dual‐site synergetic effects between IrO2 and Ir/Rh interface trigger and improve the interfacial hydrogen spillover, thereby subtly avoiding the steric blocking of the active site and eventually accelerating the alkaline HER kinetics. [ABSTRACT FROM AUTHOR]

Lithium–sulfur (Li‐S) batteries have emerged as one of the most attractive alternatives for post‐lithium‐ion battery energy storage systems, owing to their ultrahigh theoretical energy density. However, the large‐scale application of Li–S batteries remains enormously problematic because of the poor cycling life and safety problems, induced by the low conductivity , severe shuttling effect, poor reaction kinetics, and lithium dendrite formation. In recent studies, catalytic techniques are reported to promote the commercial application of Li–S batteries. Compared with the conventional catalytic sites on host materials, quantum dots (QDs) with ultrafine particle size (<10 nm) can provide large accessible surface area and strong polarity to restrict the shuttling effect, excellent catalytic effect to enhance the kinetics of redox reactions, as well as abundant lithiophilic nucleation sites to regulate Li deposition. In this review, the intrinsic hurdles of S conversion and Li stripping/plating reactions are first summarized. More importantly, a comprehensive overview is provided of inorganic QDs, in improving the efficiency and stability of Li–S batteries, with the strategies including composition optimization, defect and morphological engineering, design of heterostructures, and so forth. Finally, the prospects and challenges of QDs in Li–S batteries are discussed. [ABSTRACT FROM AUTHOR]

Water constitutes ≈70–90% of the organism's body by mass and is highly important for its survival. Water contains a variety of chemical contaminants introduced by various sectors, resulting in contamination that has a direct impact on the ecosystem. Various approaches are in practice to tackle these issues. Among these, semiconductor photocatalysis appears to be the cutting‐edge technology for the degradation of wastewater contaminants. Herein, the fabrication of Fe3O4−SiO2 nanocomposite via facile co‐precipitation and Stober methods are reported. Various characterization techniques are employed for the structural elucidation, morphology, crystallinity, and stability of the as‐prepared composite. The nanocomposite is employed in catalytic and photocatalytic applications toward the removal of methylene blue (MB) and methyl orange (MO) dyes from a comparative perspective. It is observed that the composite can remove about 93% of MB and 51% of MO within 7 and 6 h, respectively. These findings indicate that the nanocomposite has a higher MB removal effectiveness than the MO. This trend can be accredited to the difference in the chemical structure of both dyes. The nanocomposite is also evaluated for antioxidant and antileishmanial activity, and it is shown to be quite effective even at very low concentrations. [ABSTRACT FROM AUTHOR]

The present study establishes the suitability of a kinetic model for the catalytic cracking of 1, 3, 5‐triisopropylbenze (TIPB) using the data obtained in the Chemical Reactor Engineering Centre (CREC) Riser Simulator. The postulated kinetic model accounts for both the TIPB and the various major products formed experimentally, such as: 1, 3‐diisopropylbenzene, isopropylbenzene, benzene, propylene, and coke. It is proven that the proposed kinetics is suitable to describe the chemical concentration changes in a CREC Riser Simulator at various reaction times, partial pressures, temperatures, and C/O (catalyst/feedstock) ratios. It is demonstrated that the proposed kinetics simulates well the experimental data from the CREC Riser Simulator, including an experimentally observed C/O optimum ratio. It is anticipated that this type of kinetic model, accounting for intrinsic kinetics, coke deactivation, and diffusional phenomena, could have significant value in establishing the influence of catalyst solid fluxes, at set hydrocarbon feed fluxes, in both industrial riser and downer fluid catalytic cracking (FCC) units. [ABSTRACT FROM AUTHOR]