Recent advances in cobalt phosphide-based materials for electrocatalytic water splitting:From catalytic mechanism and synthesis method to optimization design

Electrochemical water splitting has long been considered an effective energy conversion technology for trans-ferring intermittent renewable electricity into hydrogen fuel,and the exploration of cost-effective and high-performance electrocatalysts is crucial in making electrolyzed water technology commercially viable.Cobalt phosphide(Co-P)has emerged as a catalyst of high potential owing to its high catalytic activity and durability in water splitting.This paper systematically reviews the latest advances in the development of Co-P-based materials for use in water splitting.The essential effects of P in enhancing the catalytic performance of the hydrogen evolution reaction and oxygen evolution reaction are first outlined.Then,versatile synthesis techniques for Co-P electrocatalysts are summarized,followed by advanced strategies to enhance the electrocatalytic performance of Co-P materials,including heteroatom doping,composite construction,integration with well-conductive sub-strates,and structure control from the viewpoint of experiment.Along with these optimization strategies,the understanding of the inherent mechanism of enhanced catalytic performance is also discussed.Finally,some existing challenges in the development of highly active and stable Co-P-based materials are clarified,and pro-spective directions for prompting the wide commercialization of water electrolysis technology are proposed.

The hydrogen storage performance and catalytic mechanism of theMgH_(2)-MoS_(2)composite

In this work,we synthesized MoS_(2)catalyst via one-step hydrothermal method,and systematically investigated the catalytic effect of MoS_(2)on the hydrogen storage properties of MgH_(2).The MgH_(2)-5MoS_(2)composite milled for 5 h starts to release hydrogen at 259℃.Furthermore,it can desorb 4.0 wt.%hydrogen within 20 min at 280℃,and absorb 4.5 wt.%hydrogen within 5 min at 200℃.Mo and MoS_(2)coexistedin the ball milled sample,whereas only Mo was kept in the sample after dehydrogenation and rehydrogenation,which greatly weakens theMg-H bonds and facilitates the dissociation of MgH_(2)on the surface of Mo(110).The comparative study show that the formed MgS has nocatalytic effect for MgH_(2).We believed that the evolution and the catalytic mechanism of MoS_(2)will provide the theoretical guidance for theapplication of metal sulfide in hydrogen storage materials.

The newly-assisted catalytic mechanism of surface hydroxyl species performed as the promoter in syngas-to-C2 species on the Cu-based bimetallic catalysts

In the conversion process of syngas-to-C_(2)species,the OH species are inevitably produced accompanying the production of key intermediates CH_(x)(x=1-3),traditionally,the function of surface OH species is generally accepted as the hydrogenating reactive species.This work for the first time proposed and confirmed the assisted catalytic mechanism of surface OH species that performed as the promoter for syngas-to-C_(2)species on Cu-based catalysts.DFT and microkinetic modeling results reveal that the produced OH species accompanying the intermediates CH_(x)production on the MCu(M=Co,Fe,Rh)catalysts can stably exist to form OH/MCu catalysts,on which the presence of surface OH species as the promoter not only presented better activity and selectivity toward CH_(x)(x=1-3)compared to MCu catalysts,but also significantly suppressed CH_(3)OH production,providing enough CH_(x)sources to favor the production of C_(2)hydrocarbons and oxygenates.Correspondingly,the electronic properties analysis revealed the essential relationship between the electronic feature of OH/MCu catalysts and catalytic performance,attributing to the unique electronic micro-environment of the catalysts under the interaction of surface OH species.This new mechanism is called as OH-assisted catalytic mechanism,which may be applied in the reaction systems related to the generation of OH species.

Revealing the catalytic mechanism of an ionic liquid with an isotope exchange method

The alkylation mechanism catalyzed by an ionic liquid （as a Lewis acid） may be different from the traditional alkylation mechanism catalyzed by Br nsted acid,especially as their initiation steps are still not clear.In this paper,an isotope exchange method is used to investigate the catalytic mechanism of AlCl 3 /butyl-methyl-imidazolium chloride ionic liquid in the alkylation of benzene with 1-dodecene.The proposed catalytic mechanism was confirmed by analysis of ionic liquid before and after reaction and of the alkylation products of deuterated benzene （C 6 D 6） with 1-dodecene.The proposed mechanism consists of the equilibrium reaction between [Al 2 Cl 7 ] ＋H ＋ and [AlHCl 3 ] ＋ ＋[AlCl 4 ],in which the Br nsted acid [AlHCl 3 ] ＋ is supplied by the reaction of 2-H on the imidazolium ring and [Al 2 Cl 7 ].The alkylation reaction is initiated by the Br nsted acid [AlHCl 3 ] ＋ which reacts with 1-dodecene to form a carbonium ion,then the carbonium ion reacts with benzene to form an unstable σ complex,leading to the formation of 2-phenyldodecane.

Recent Advances in Constructing Interfacial Active Catalysts Based on Layered Double Hydroxides and Their Catalytic Mechanisms

The interaction between the metal and the support of supported metal catalysts, which are widely used in industry, is the primary focus of the study of such catalysts. With the developing understanding of the metal–support interaction, the intrinsic factor that influences the catalytic performance has been determined to be the structure of interfacial sites. Layered double hydroxides(LDHs, a class of two-dimensional layered anion clay) possess several unique characteristics, such as the following:(1) tunable elemental component, homogeneous distribution of metal cations.(2) anchoring eff ect.(3) multiple layered structure for exfoliation or intercalation and special memory eff ect;and(4) internal/external confinement eff ects during topological transformation. Taking LDHs and their derivatives as precursors or supports shows superior advantages in designing interfacial active catalysts with tunable properties. Therefore, this review is mainly focused on constructing interfacial active catalysts by LDHs and revealing the interfacial eff ects(including electronic, geometric, and bifunctional eff ects) on the catalytic performance that will provide new perspectives and approaches for the development of heterogeneous catalysis.

A first-principles study of the catalytic mechanism of the dehydriding reaction of LiNH_2 through adding Ti catalysts

Experiments on a ball milled mixture with a 1：1 molar ratio of LiNH2 and LiH with a small amount （1 mol %） of Ti^nano, TICl3 and TiO2^nano have revealed a superior catalytic effect on Li N H hydrogen storage materials. In the x-ray diffraction profiles, no trace of Ti^nano, TICl3 and TiO2^nano was found in these doped composites, by which we deduced that Ti atoms enter LiNH2 by partial element substitution. A first-principles plane-wave pseudopotential method based on density functional theory has been used to investigate the catalytic effects of Ti catalysts on the dehydrogenating properties of LiNH2 system. The results show that Ti substitution can reduce the dehydrogenation reaction activation energy of LiNH2 and improve the dehydrogenating properties of LiNH2. Based on the analysis of the density of states and overlap populations for LiNH2 before and after Ti substitution, it was found that the stability of the system of LiNH2 is reduced, which originates from the increase of the valence electrons at the Fermi level （EF） and the decrease of the highest occupied molecular orbital （HOMO） lowest unoccupied molecular orbital （LUMO） gap （△EH-L） near EF. The catalytic effect of Ti on the dehydrogenating kinetics of LiNH2 may be attributed to the reduction of average populations between N-H per unit bond length （nm-1）, which leads to the reduction of the chemical bond strength of NH.

The age of vanadium-based nanozymes: Synthesis, catalytic mechanisms, regulation and biomedical applications

Nanomaterials with enzyme-mimic(nanozyme) activity have garnered considerable attention as a potential alternative to natural enzymes, thanks to their low preparation cost, high activity, ease of preservation, and unique physicochemical properties. Vanadium(V) is a transition metal that integrates the benefits of valence-richness, low cost, and non-toxicity, making it a desirable candidate for developing a range of emerging nanozymes. In this review, we provide the first systematic summary of recent research progress on V-based nanozymes. First, we summarize the preparation of V-based nanozymes using both top-down and bottom-up synthesis methods. Next, we review the mechanism of V-based nanozymes that mimic the activity of various enzymes. We then discuss methods for regulating V-based nanozyme activity, including morphology, size, valence engineering, defect engineering, external triggering, and surface engineering. Afterward, we outline various biomedical applications, including therapeutic, anti-inflammatory, antibacterial, and biosensing. Finally, we prospect the challenges and countermeasures for V-based nanozymes based on their development. By summarizing recent research progress on V-based nanozymes, we hope to provide useful insights for researchers to further explore their potential applications and overcome their existing challenges.

High entropy materials based electrocatalysts for water splitting:Synthesis strategies,catalytic mechanisms,and prospects

Among various electrocatalysts,high entropy materials(HEMs)have attracted great attention due to the distinctive designing concept and unique properties with captivating electrocatalytic activity and stability.To date,HEMs have been a new family of advanced electrocatalysts in the research field of water electrolysis.In this work,the structural features and synthesis strategies of high entropy catalysts are reviewed,especially,their performances for catalyzing hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in water electrolysis are presented,in which the crucial roles of structure,composition,multisites synergy,and“four core effects”for enhancing catalytic activity,stability,and resistance of electrochemical corrosion are introduced.Besides,the design tactics,main challenges,and future prospects of HEM-based electrocatalysts for HER and OER are discussed.It is expected to provide valuable information for the development of low-cost efficient HEM-based electrocatalysts in the field of water electrolysis.

Deep Insight of Design,Mechanism,and Cancer Theranostic Strategy of Nanozymes

Since the discovery of enzyme-like activity of Fe3O4 nanoparticles in 2007,nanozymes are becoming the promising substitutes for natural enzymes due to their advantages of high catalytic activity,low cost,mild reaction conditions,good stability,and suitable for large-scale production.Recently,with the cross fusion of nanomedicine and nanocatalysis,nanozyme-based theranostic strategies attract great attention,since the enzymatic reactions can be triggered in the tumor microenvironment to achieve good curative effect with substrate specificity and low side effects.Thus,various nanozymes have been developed and used for tumor therapy.In this review,more than 270 research articles are discussed systematically to present progress in the past five years.First,the discovery and development of nanozymes are summarized.Second,classification and catalytic mechanism of nanozymes are discussed.Third,activity prediction and rational design of nanozymes are focused by highlighting the methods of density functional theory,machine learning,biomimetic and chemical design.Then,synergistic theranostic strategy of nanozymes are introduced.Finally,current challenges and future prospects of nanozymes used for tumor theranostic are outlined,including selectivity,biosafety,repeatability and stability,in-depth catalytic mechanism,predicting and evaluating activities.

Quantum chemical study on the catalytic mechanism of Na/K on NO-char heterogeneous reactions during the coal reburning process

Quantum chemical simulation was used to investigate the catalytic mechanism of Na/K on NO-char heterogeneous reactions during the coal reburning process. Both NO-char and NO-Na/K reactions were considered as three-step processes in this calculation. Based on geometry optimizations made using the UB3LYP/6-31G(d) method, the activation energies of NO-char and NO-Na/K reactions were calculated using the QCISD(T)/6-311G(d, p) method; Results showed that the activation energy of the NO-Na/K reaction (107.9/82.0 kJ/mol) was much lower than that of the NO-char reaction (245.1 kJ/mol). The reactions of NaO/KO and Na2O/K2O reduced by char were also studied, and their thermodynamics were calculated using the UB3LYP/6-31G(d) method; Results showed that both Na and K can be refreshed easily and rapidly by char at high temperature during the coal reburning process. Based on the calculations and analyses, the catalytic mechanism of Na/K on NO-char het-erogeneous reactions during the coal reburning process was clarified.

Epigenetic modification enzymes: catalytic mechanisms and inhibitors

Epigenetic modifications alter chromatin structures and consequently affect transcription and cellular functions.Major epigenetic markers include DNA methylation and histone acetylation and methylation.The modifications are reversible and are achieved in aid of relative enzymes.Much effort has been directed at the understanding of the chemical mechanisms of individual catalytic reactions,which can serve as a foundation for inhibitor development.Among the many methods deployed,structural studies have proven the most effective for understanding enzyme-mediated modifications and have provided support for the development of lead-candidate drug inhibitors.This review briefly summarizes the existing knowledge on the catalytic mechanisms of the major epigenetic modification enzymes,with an emphasis on the structural information and inhibitors of these enzymes.

Structural insights into the catalytic mechanism of aldehyde-deformylating oxygenases

The fatty alk（a/e）ne biosynthesis pathway found in cyanobacteria gained tremendous attention in recent years as a promising alternative approach for biofuel production. Cyanobacterial aldehyde-deformylating oxygenase （cADO）, which catalyzes the conversion of Cn fatty aldehyde to its corresponding Cn-1 alk（ale）ne, is a key enzyme in that pathway. Due to its low activity, alk（a/e）ne production by cADO is an inefficient process. Previous biochemical and structural investi. gations of cADO have provided some information on its catalytic reaction. However, the details of its cata- lytic processes remain unclear. Here we report five crystal structures of cADO from the Synechococcus elongates strain PCC7942 in both its iron-free and iron-bound forms, representing different states during its catalytic process. Structural comparisons and functional enzyme assays indicate that Giu144, one of the iron-coordinating residues, plays a vital role in the catalytic reaction of cADO. Moreover, the helix where Glu144 resides exhibits two distinct conformations that correlates with the different binding states of the di-iron center in cADO structures. Therefore, our results provide a structural explanation for the highly labile feature of cADO di-iron center, which we pro- posed to be related to its low enzymatic activity. On the basis of our structural and biochemical data, a possible catalytic process of cADO was proposed, which could aid the design of cADO with improved activity.

Metal organic framework supported niobium pentoxide nanoparticles with exceptional catalytic effect on hydrogen storage behavior of MgH_(2)

Nb_(2)O_(5)nanoparticles with an average particle size of 10 nm supported on a rhombic dodecahedral metal organic framework(MOF)were successfully synthesized by a facile one-pot hydrothermal reaction and subsequent calcination process.Experimental results demonstrated that the prepared catalyst drastically improved the hydrogen storage behavior of MgH_(2).7 wt%Nb_(2)O_(5)@MOF doped MgH_(2)started to desorb hydrogen at 181.9℃and 6.2 wt%hydrogen could be released within 2.6 min and 6.3 min at 275℃and 250℃,respectively.The fully dehydrogenated composite also displayed excellent hydrogenation by decreasing the onset absorption temperature to 25℃and taking up4.9 wt%and 6.5 wt%hydrogen within 6 min at 1750C and 1500C,respectively.Moreover,the corresponding activation energy was calculated to be 75.57±4.16 kJ mol^(-1)for desorption reaction and 51.38±1.09 kJ mol^(-1)for absorption reaction.After 20 cycles,0.5 wt%hydrogen capacity was lost for the MgH_(2)+7 wt%Nb_(2)O_(5)@MOF composite,much lower than 1.5 wt%of the MgH_(2)+7 wt%Nb_(2)O_(5)composite.However,the addition of Nb_(2)O_(5)@MOF had limited effect on reducing the dehydrogenation enthalpy of MgH_(2).Microstructure analysis revealed that Nb_(2)O_(5)particles were uniformly distributed on surface of the MgH_(2)matrix and synergistically improved the hydrogen storage property of MgH_(2)with MOF.

Properties and catalytic mechanism of γ-glutamyltranspeptidase from B.subtilis NX-2

Sinceγ-glutamyltranspeptidase(GGT)especially catalyses the transfer of theγ-glutamyl moiety to a variety of amino acids and short peptides,GGT has important practical value for enzymatic synthesis ofγ-glutamyl compounds.In this paper,the GGT produced from Bacillus subtilis NX-2 was purified by a combination of ammonium sulfate fractionation and ion exchange chromatography,and the properties of purified GGT were investigated.At the conditions of pH 10.0,D-glutamine(D-Gln)/L-tryptophan(L-Trp)with a molar ratio of 5:7,a temperature 40℃ and a reaction time of 4 h,a higher conversion rate of 42%was obtained.According to the time course,the catalytic mechanism of enzymatic synthesis ofγ-D-glutamyl-L-tryptophan(γ-D-Gln-L-Trp)was discussed.It was demonstrated that the GGT can catalyze not only the reaction of transpeptidation,but also the irreversible hydrolysis of the products which results in the decrease of the yield of the products.The affinity parameter of GGT to D-Gln(Km)was 5.08 mmol·L-1 and the maximum reaction rate of transpeptidation(rmax)was determined as 0.034 mmol·min-1·L-1,while the affinity parameter of GGT toγ-D-Gln-L-Trp(K’m)was 2.267 mmol·L-1,and the maximum reaction rate of hydrolysis(r’max)was 0.012 mmol·min-1·L-1.

A Review on the Mechanism of NO Selective Catalytic Oxidation

In this paper,the research status and catalytic mechanism of activated carbon catalysts,molecular sieve catalysts,noble metal catalysts and transition metal oxide catalysts used for NO catalytic oxidation were studied to provide reference for future research.

Sulfur poisoning mechanism of three way catalytic converter and its grey relational analysis

Combining a detailed catalytic surface reaction mechanism with noble metal and promoter elementary reactions, a new three-way catalytic converter(TWC) reaction mechanism is established. Based on the new mechanism, steady condition numerical simulation is carried out, and the change of light-off temperatures and conversion efficiency with various SO2 contents is obtained. By grey relational analysis(GRA), the relational grade between conversion efficiency and SO2 content is obtained. And, the result shows that SO2 content has the most important influence on C3H6 and NOX conversion efficiency. This provides an important reference to the improvement of activity design of TWC, and may provide guidance for the condition design and optimization of TWC.

Catalytic applications of amorphous alloys in wastewater treatment: A review on mechanisms, recent trends, challenges and future directions

Amorphous alloys,with unique atomic structures and metastable nature,are treated as superior candi-dates for environmental wastewater remediation due to their superior catalytic capabilities.Given the strong demand for environmental protection,the field of amorphous alloys in wastewater treatment has great development prospects,and numerous research results have been published in recent years.As a promising catalyst,it was demonstrated that amorphous alloys could exhibit many excellent proper-ties in wastewater treatment,such as high catalytic efficiency,easily adjustable parameters and reliable sustainability.This paper aims to summarize recent research trends regarding amorphous alloys in the field of catalysis,focusing on the preparation methods,physical performance,catalytic mechanisms and environmental application.Meanwhile,this review also investigates the challenges encountered and fu-ture perspectives of amorphous alloys,offering new research opportunities to enlarge their applicability spectra.

Understanding the catalysis of chromium trioxide added magnesium hydride for hydrogen storage and Li ion battery applications

This study explores how the chemical interaction between magnesium hydride(MgH_(2))and the additive CrO_(3) influences the hydrogen/lithium storage characteristics of MgH_(2).We have observed that a 5 wt.%CrO_(3) additive reduces the dehydrogenation activation energy of MgH_(2) by 68 kJ/mol and lowers the required dehydrogenation temperature by 80℃.CrO_(3) added MgH_(2) was also tested as an anode in an Li ion battery,and it is possible to deliver over 90%of the total theoretical capacity(2038 mAh/g).Evidence for improved reversibility in the battery reaction is found only after the incorporation of additives with MgH_(2).In depth characterization study by X-ray diffraction(XRD)technique provides convincing evidence that the CrO_(3) additive interacts with MgH_(2) and produces Cr/MgO byproducts.Gibbs free energy analyses confirm the thermodynamic feasibility of conversion from MgH_(2)/CrO_(3) to MgO/Cr,which is well supported by the identification of Cr(0)in the powder by X ray photoelectron spectroscopy(XPS)technique.Through high resolution transmission electron microscopy(HRTEM)and energy dispersive spectroscopy(EDS)we found evidence for the presence of 5 nm size Cr nanocrystals on the surface of MgO rock salt nanoparticles.There is also convincing ground to consider that MgO rock salt accommodates Cr in the lattice.These observations support the argument that creation of active metal–metal dissolved rock salt oxide interface may be vital for improving the reactivity of MgH_(2),both for the improved storage of hydrogen and lithium.

Effect of electrolyte cation-mediated mechanism on electrocatalytic carbon dioxide reduction

The steep reduction in costs and systematic optimization of renewable electricity has ignited an intensifying interest in harnessing electroreduction of carbon dioxide(CO_(2)RR)for the generation of chemicals and fuels.The focus of research over the past few decades has been on the optimization of the electrode and the electrolyte environment.Notably,cation species in the latter have recently been found to dramatically alter the selectivity of CO_(2)RR and even their catalytic activity by multiple orders of magnitude.As a result,the selection of cations is a critical factor in designing catalytic interfaces with high selectivity and efficiency for targeted products.Informed decision-making regarding cation selection relies on a comprehensive understanding of prevailing electrolyte effect models that have been used to elucidate observed experimental trends.In this perspective,we review the hypotheses that explain how electrolyte cations influence CO_(2)RR by mechanisms such as through tuning of the interfacial electric field,buffering of the local pH,stabilization of the key intermediates and regulation of the interfacial water.Our endeavor is to elucidate the molecular mechanisms underpinning cation effects,thus fostering the evolution of more holistic and universally applicable predictive models.In this regard,we highlight the current challenges in this area of research,while also identifying potential avenues for future investigations.

Graphene-loaded nickel−vanadium bimetal oxides as hydrogen pumps to boost solid-state hydrogen storage kinetic performance of magnesium hydride

To modify the thermodynamics and kinetic performance of magnesium hydride(MgH_(2))for solid-state hydrogen storage,Ni_(3)V_(2)O_(8)-rGO(rGO represents reduced graphene oxide)and Ni_(3)V_(2)O_(8)nanocomposites were prepared by hydrothermal and subsequent heat treatment.The beginning hydrogen desorption temperature of 7 wt.%Ni_(3)V_(2)O_(8)-rGO modified MgH_(2)was reduced to 208℃,while the additive-free MgH_(2)and 7 wt.%Ni_(3)V_(2)O_(8)doped MgH_(2)appeared to discharge hydrogen at 340 and 226℃,respectively.A charging capacity of about 4.7 wt.%H_(2)for MgH_(2)+7 wt.%Ni_(3)V_(2)O_(8)-rGO was achieved at 125℃ in 10 min,while the dehydrogenated MgH_(2)took 60 min to absorb only 4.6 wt.%H_(2)at 215℃.The microstructure analysis confirmed that the in-situ generated Mg_(2)Ni/Mg_(2)N_(i)H_(4) and metallic V contributed significantly to the enhanced performance of MgH_(2).In addition,the presence of rGO in the MgH_(2)+7 wt.%Ni_(3)V_(2)O_(8)-rGO composite reduced particle aggregation tendency of Mg/MgH_(2),leading to improving the cyclic stability of MgH_(2)during 20 cycles.