Oxidation Reaction Research Articles

Pt-decorated oxygen-vacancy-tuned high temperature hydrogen-annealed WO3 as an efficient anode electrocatalyst for PEMFC

One of the most significant steps for the widespread application of Proton Exchange Membrane Fuel Cells (PEMFC) is the development of an efficient and corrosion-resistant electrocatalyst for Hydrogen Oxidation Reaction (HOR). To achieve an enhanced electrocatalytic activity towards HOR, we developed a carbon-free electrocatalyst that performs on par with the Pt/C commercial-based catalyst. Pt nanoparticles dispersed on hydrogenated WO3 surfaces were synthesized and experimentally shown to be an efficient HOR electrocatalyst. Furthermore, different characterizations and electrochemical studies validate the performances of all the hydrogenated samples. Pt/a-WO3/H400, hydrogenated at 400 °C, exhibits excellent electrocatalytic activity in terms of onset potential, limiting current density, and electrochemical surface area (ECSA). The membrane electrode assembly (MEA) was fabricated, and its single-cell performance was carried out using Pt/a-WO3/H300, Pt/a-WO3/H400, and Pt/a-WO3/H500 at the anode with Pt loading of 0.125 mg/cm2. The single-cell performance of Pt/a-WO3/H400 as anode electrocatalyst has the highest power density (540 mW/cm2) at 50 °C and high durability, compared to Pt/C. The enhanced electrocatalytic performance is attributed to the synergistic catalytic effect between Pt nanoparticles and the WO3-x interface. This occurs due to the preferential orientation of the highly active (002) facet and the creation of an optimum amount of oxygen vacancies due to the hydrogenation impact.

Phenanthridine-based Covalent Organic Frameworks for Boosting Overall Solar H2O2 Production.

Solar-driven H2O2 production via the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels is green and sustainable, but severely restricted by the sluggish reaction kinetics. Constructing intriguing photocatalysts with effective active centers is a shortcut to breaking the kinetic bottleneck with great significance. Herein, we synthesize two novel neutral phenanthridine-based covalent organic frameworks (PD-COF1 and PD-COF2) for photosynthesizing H2O2. Compared to the no phenanthridine counterpart (AN-COF), the H2O2 photosynthetic activities of PD-COF1 and PD-COF2 are markedly boosted. In air and pure water without sacrificial agents, under Xe lamp and natural sunlight, the H2O2 photogeneration rate of PD-COF2 is 6103 and 3646 μmol g-1 h-1, respectively. Further experimental and theoretical inspections demonstrate that introducing phenanthridine units into COFs smoothly modulates the charge carrier dynamics and thermodynamically favors the generation of crucial OOH* and OH* intermediates in the ORR and WOR paths, respectively. Additionally, this is the first time the neutral phenanthridine moiety serves as the photooxidation unit for 2e- WOR towards H2O2 photoproduction. The current work sheds light on exploring novel catalytic centers for high-performance H2O2 evolution.

Cu3(HITP)2 with peroxidase- and ascorbic acid oxidase-like catalytic activity for fluorescence/chemiluminescence sensing of ascorbic acid

Nanomaterials with intrinsic enzyme mimicking activity have achieved widespread application. However, developing novel nanomaterials with multienzyme mimicry activity remains challenging. Herein, Cu3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) with ascorbic acid oxidase (AAO)- and peroxidase (POD)-like activity are successfully synthesized. Cu3(HITP)2 exhibits excellent AAO-like activity and can specifically catalyze the oxidation reaction of ascorbic acid (AA). Dehydroascorbic acid (DHAA) obtained from the oxidation of AA is allowed to react with nonfluorescent o-phenylenediamine (OPD) to form 3-(1,2-dihydrox-yethyl) furo[3,4-b]quinoxaline-1-one (DFQ) with strong fluorescence emission. Moreover, Cu3(HITP)2 is able to catalyze the chemiluminescence (CL) reaction of ABEI-H2O2 to generate a strong and glow-type emission based on its POD activity. Inspired by the multienzyme mimicry activity of Cu3(HITP)2, the simple and sensitive fluorescence and chemiluminescence sensing platforms are successfully constructed and applied for the detection of AA. The sensors show high sensitivity and excellent selectivity. We believe that this multienzyme mimicry activity nanomaterial not only can be used to construct the multiple-mode biosensing platform, but also enables the extensive applications in the fields of biomedicine, energy, and environment.

Temperature-Dependent Oxidation Behavior of Silicon Carbide Surface: Reactive Molecular Dynamics Simulations.

The high-temperature oxidation mechanism of silicon carbide (SiC) is crucial for designing thermal protection systems in aircraft. This study explored the oxidative chemical reaction processes and mechanism on SiC surface and interfaces within the temperature range of 300-2300 K by using reactive molecular dynamics simulation. The oxygen impact on the silica (SiOx) growth of the SiC surface was analyzed, which shows a progressive increase of silica thickness. The simulation results indicated that the oxidation process of SiC was a typical passive oxidation mechanism. With the environmental temperature rising and oxygen impact, the increase of oxidation thickness on the SiC surface undergoes three oxidizing reaction processes: little chemical adsorption of oxygen molecules on the initial surface, rapid oxidation of silicon and carbon, and dramatic oxidation of the interface between the oxidation layer and SiC. Additionally, this work studied the mechanism of oxidation thickness growth and chemical diffusion of oxygen. The oxidation rate is weakened according to the oxygen atom diffusion barrier effect of silica repulsion. Moreover, the kinetic parameters were statistically calculated by fitting the growth of Si-O bonds and their reaction rate constants. Subsequently, the activation energy and pre-exponential factors were derived by using the Arrhenius equation to model the chemical reaction kinetics of the thermal oxidation process. The chemical reaction behaviors of the two stages could be concluded as follows: (i) in stage I, the initial oxidation is reaction rate limiting; (ii) in stage II, SiC oxidation is limited by both the oxidation reaction rate and the oxygen diffusion coefficient of the oxidation layer. The activation energy of stage II increased compared with stage I due to the oxygen atoms diffusion barrier between the oxidation layers. This study on the oxidation and ablation mechanism of the SiC surface at the atomic scale would provide insight into understanding thermal oxidation behavior and the design of ceramic materials.

High-Entropy Engineering in Hollow Layered Hydroxide Arrays to Boost 5-Hydroxymethylfurfural Electrooxidation by Suppressing Oxygen Evolution.

The electricity-driven 5-hydroxymethylfurfural (HMF) oxidation reaction has exhibited increasing potential to produce high-value-added 2,5-furandicarboxylic acid (FDCA). Unfortunately, the competitive oxygen evolution reaction (OER) can decrease the yield and Faradaic efficiency (FE) of FDCA under high potentials. Here, we report a general MOF-templated strategy to construct a new class of hollow high-entropy layered hydroxide array (HE-LHA) electrocatalysts including quinary, senary, and septenary phases composed of CoNiMnCuZn with Cd and Mg on carbon cloth (CC) for boosting the HMF oxidation reaction (HMFOR) by suppressing the OER. Impressively, the septenary CC@CoNiMnCuZnCdMg-LHA exhibits a low potential of 1.42 VRHE for the HMFOR but a high potential of 1.68 VRHE for the OER to achieve 100 mA cm-2, ranking it among one of the best electrocatalysts for the HMFOR. Finite element simulations show its hollow array morphology can induce a strong local electric field over all of the shell, thus favoring the electrocatalytic process. In situ electrochemical impedance spectroscopy and theoretical calculations further reveal that the Co, Ni, Cu, Zn, Mn, Cd, and Mg metals in high-entropy LHAs can accelerate the HMFOR but suppress the OER by optimizing the adsorption energy of the HMF* and OH*. This work sheds light on the rational design and construction of high-entropy nanoarchitectures for advanced electrocatalysis.

NiCo2O4-based wool-ball as an electrocatalyst for methanol assisted water splitting, an alternative to water splitting

Hydrogen energy is considered a potential solution to the energy crisis and environmental pollution concerns. Pure hydrogen can be produced from electrochemical water splitting, however, the oxygen evolution reaction (OER) is the primary obstacle due to its sluggish reaction kinetics. Introducing methanol oxidation is one possible solution to replace OER for water splitting to produce hydrogen as an energy source. In this article, a NiCo₂O₄-based wool-ball electrocatalyst was prepared via a solvothermal process followed by annealing. The catalyst showed high purity and a wool-ball structure, where the threads are arranged in different patterns and composed of sub-nano-sized spheres. The catalyst exhibited an excellent response to oxidation reactions and reduced severely the potential for 250 mV, when 1.17 mM of methanol was introduced into a 1 M KOH solution. The catalyst also demonstrated good performance for the hydrogen evolution reaction (HER), however, there was a reduction in performance in the presence of methanol. This might be due to the formation of a methanol layer that inhibits the HER in the KOH solution, as methanol does not participate in HER. This resistance was confirmed with electrochemical impedance spectroscopy (EIS) and electrochemical surface area (ECSA) measurements, where the ECSA value in KOH was 4.10, which reduced to 2.63 in the presence of methanol. The catalyst exhibited excellent stability for both HER and methanol oxidation reaction (MOR) over a long duration of 3600 s.

Selective Reduction of NO into N2 Catalyzed by the RhM2O3- Clusters (M = Ta, V, and Al): Importance of the Triatomic Lewis Acid-Base-Acid Mδ+-Rhδ--Mδ+ Site.

Catalytic NO reduction by CO into N2 and CO2 is imperative owing to the increasingly rigorous emission regulation. Identifying the nature of active sites that govern the reactivity and selectivity of NO reduction is pivotal to tailor catalysts, while it is extremely challenging because of the complexity of real-life systems. Guided by our newly discovered triatomic Lewis acid-base-acid (LABA, Ceδ+-Rhδ--Ceδ+) site that accounts for the selective reduction of NO into N2 catalyzed by the RhCe2O3- cluster in gas-phase experiments, the reactivity of the RhM2O3- (M = Ta, V, and Al) clusters in catalytic NO reduction by CO was explored. We determined theoretically that the LABA site still prevails to reduce NO to N2 mediated by RhTa2O3- and RhV2O3-, and the strong M-oxygen affinity was emphasized to construct the LABA site. An overall assessment highlights that RhV2O3- functions as a more promising catalyst because the well-fitting V-O bonding strength facilitates both elementary reactions of NO reduction and CO oxidation.

Pt-decorated binary transition metal oxides (MnO-NiO, MnO-TiO2) for enhanced electrocatalysis of oxygen reduction and borohydride oxidation

Integrating transition metal oxides with precious metals is a strategic approach to designing cost-effective electrocatalysts with enhanced stability. Herein, platinum (Pt) nanoparticles (NPs) were prepared by microwave irradiation and anchored onto MnO and two binary metal oxides, MnO-NiO and MnO-TiO2, obtained by solid-state dispersion. Voltammetric and electrochemical impedance spectroscopy techniques evaluated their performance for oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) in alkaline media. Tafel slope and the number of exchanged electrons, n, were determined to compare the three electrocatalysts’ performance for fuel cell applications. Pt/MnO-NiO revealed a Tafel slope of 177 mV dec–1 for ORR and an n value of ca. 4 and 3 e- for ORR and BOR, respectively. These findings demonstrate that Pt NPs supported on binary metal oxide supports, particularly Pt/MnO-NiO, are promising electrocatalysts for ORR and BOR in alkaline media, thus recommending their use in direct borohydride fuel cells.

Rational phosphorization of ferrocene-based metal organic framework for enhanced oxygen evolution and urea oxidation performance

Developing high-performance and inexpensive water-splitting electrocatalysts is crucial for addressing current energy and environmental issues. In this work, a ferrocene (Fc)-based metal organic framework (MOF) was rationally phosphorized to construct a CoFeP/MOF composite electrocatalyst. Thanks to the excellent conductivity, high specific surface area, and rich heterojunction interfaces, the prepared catalyst exhibits outstanding catalytic activity and long-term endurance, which can realize 50 mA cm−2 at an overpotential of 246 mV for oxygen evolution reaction (OER) in 1.0 M KOH and a cell potential of 1.441 V (vs. RHE) for urea oxidation reaction (UOR) in 1.0 M KOH and 0.5 M urea. The electrolyzer assembled from the prepared electrode and Pt/C electrode can drive 50 mA cm−2 at 1.605 V and 1.524 V (vs. RHE) in the overall/urea-assisted water splitting tests, demonstrating great application prospects. This work provides valuable reference for improving the performance of MOF type bifunctional water electrolysis catalysts.

Controlling Chlorine-Doped Nickel Diselenide Ultrathin Nanosheets through Steric Effects: An Electrocatalyst for Oxygen Evolution Reaction and Urea Oxidation Reaction.

Exploration of electrocatalysts suitable for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is essential for electrocatalytic hydrogen production. In this work, a ligand substitution strategy is used to synthesize ultrathin-nanosheet electrocatalysts of Cl-doped NiSe2 (NiSe2-a and NiSe2-b), which exhibit high-electrocatalytic activity during OER and UOR. NiSe2-a and NiSe2-b only need an overpotential of 227 and 268 mV, respectively, to achieve a current density of 10 mA cm-2 during OER. Furthermore, NiSe2-a with its smaller steric effects exhibits excellent catalytic performance for UOR, requiring an ultralow potential of 1.360 V to deliver a current density of 100 mA cm-2. This excellent performance can be attributed to the nonmetallic elements (Se and Cl) modulating and optimizing the charge state of the metal sites, thereby increasing the electrocatalytic activity. Overall, this work provides an unparalleled example of tuning space structures to design efficient electrocatalysts and has promising industrial applications.

B-137 Sepsis risk prediction using machine learning (ML) and routine blood markers up to 1 week before emergency admission

Abstract Background Sepsis is a major global health concern, responsible for approximately 50 million cases and 11 million deaths annually, representing 20% of global mortality. It is the leading cause of hospital readmissions and deaths, with associated costs exceeding $38 billion per year. Alarmingly, 80% of sepsis cases occur outside the hospital, and 70% of patients visit an outpatient facility within a week of admission. Early diagnosis and appropriate treatment could prevent 80% of sepsis-related deaths. Our study demonstrates that machine learning models hold significant promise in identifying sepsis risks using routine blood tests up to 1 week before admission. Methods For our study, we utilized a dataset of over 25,000 patient records, including both sepsis and non-sepsis cases, sourced from MIMIC-IV (version 2.2), a comprehensive electronic health record dataset from Beth Israel Deaconess Medical Center, Boston, MA. We employed a gradient boosted model with 300 trees, a maximal depth of 30 layers, and gain ratio as the criterion for attribute selection. The model's performance was evaluated using 10-fold cross-validation, demonstrating optimal performance. Input parameters included age, gender, and results of routine blood markers such as complete blood counts, differential counts, comprehensive metabolic panels, and lipid panels recorded up to 1 week before sepsis diagnosis. Results Our model achieved remarkable predictive accuracy for sepsis risk, with an area under the receiver operating characteristic curve (AUC) of 0.99 and accuracy of 0.99. Notably, the model achieved 1.0 sensitivity, 0.99 specificity, 0.99 positive predictive value, 1.0 negative predictive value, 0.99 F measure, and 0.99 Youden index. Calcium, protein, liver enzymes, hematocrit, white blood cells, and cholesterol were identified as key contributors to sepsis risk prediction. Importantly, prediction accuracy remained consistent up to 1 week prior to diagnosis. Conclusions In conclusion, dysregulated intracellular calcium handling during sepsis is associated with an intensified inflammatory response, cellular death, and subsequent organ dysfunction. Low serum protein levels, particularly albumin, are linked to poor outcomes in sepsis. Recent studies have identified liver dysfunction as an early event in sepsis, underscoring its significance in the disease process. Elevated bilirubin levels are associated with an increased risk of mortality. Low hematocrit (HCT) levels are linked to higher 30-day mortality and serve as an independent prognostic biomarker in sepsis. Monocytes play a significant role in sepsis pathophysiology, undergoing various changes including preserved phagocytic activity, increased reactive oxygen species and nitric oxide generation, and decreased production of inflammatory cytokines such as IL-6 and TNF-alpha. Septic patients often exhibit lymphopenia, affecting CD4 and CD8 T cells, B cells, and natural killer (NK) cells. Hypocholesterolemia is common in sepsis and serves as an important early prognostic factor, with low plasma concentrations associated with poor outcomes. Since every hour of delayed treatment increases the risk of death by 4%-9%, changes in routine blood markers detected by machine learning models can provide early indications of impending sepsis up to 1 week before diagnosis.

Selenate-based heterojunction with cobalt–nickel paired site for electrocatalytic oxidation of 5-hydroxymethylfurfural coupling water splitting to produce hydrogen

It is very appealing that 5-hydroxymethylfurfural (HMF) is electrocatalytical oxidized as 2,5-furandicarboxylic acid (FDCA) linking to non-classical cathodic hydrogen (H2) production. However, the electrocatalysts for electrocatalytic HMF oxidative reaction (e-HMFOR) have been facing low Faradaic efficiency (FE) and high water splitting voltage. Herein, we propose a strategy of the NiSeO3@(CoSeO3)4 heterojunction by constructing a Co-Ni paired site, where the Co site is in charge of adsorbing for HMF while the electrons are transferred to the Ni site, thus giving the NiSeO3@(CoSeO3)4 heterojunction superior electrocatalytic performances for e-HMFOR and water splitting. By optimizing conditions, the NiSeO3@(CoSeO3)4 heterojunction has high conversion of 99.7%, high selectivity of 99.9%, and high FE of 98.4% at 1.3 V, as well as low cell voltage of 1.31 V at 10 mA cm−2 in 1 M KOH + 0.1 M HMF. This study offers a potential insight for e-HMFOR to high value-added FDCA coupling water splitting to produce H2 in an economical manner.

Water oxidation through electrocatalytic process using cobalt and nickel complexes of thiazole Schiff-base ligands

Ni(OAc)2.4H2O and CoCl2.6H2O reacted with thiazole ligands, HL and HL' (where HL= (E)-2-(((4-phenylthiazol-2-yl)imino)methyl)phenol and HL'= (Z)-2-(2-benzylidenehydrazinyl)-4-phenylthiazole, in ethanol to create new mononuclear Co(II) and Ni(II) complexes, CoL2, NiL2, CoL'2, and NiL'2 (1-4). X-ray diffraction analysis, spectroscopic, and electrochemical methods were used to study the complexes. A carbon paste electrode that had been modified by complexes 1-4 was used as the working electrode in a three-electrode setup to test the complexes' ability in water oxidation reaction at pH 13. The linear sweep voltammetry (LSV) curves showed that complexes 3 and 2 have much greater activity and only require the overpotential of 570 and 690 mV ʋs. RHE at a current density of 10 mA/cm2 with Tafel slopes of 86.92 and 94.19 mVdec−1 respectively in an alkaline solution. In addition, the amperometry tests exhibited brilliant stability for water oxidation by CPE-complex 3 and CPE-complex 2 under electrochemical conditions at pH 13. Although X-ray diffraction patterns did not display a crystalline structure, the scanning electron microscopy images displayed that cobalt oxide and nickel oxide in an alkaline condition are proper catalysts for water oxidation reaction on the surface of the modified electrode.

PtCu-a-SnO2 interface engineering on PtCu-SnO2 aerogels for ethanol oxidation electrocatalysis

Designing catalysts with high activity and stability to boost their ethanol oxidation reaction (EOR) performance is one of the central targets in the development of direct ethanol fuel cells (DEFCs). However, how to design the EOR catalysts in a rational way is still challenging, needing more efforts put in. Herein, we have synthesized a catalyst of PtCu-SnO2 aerogel via ingeniously introducing Cu into Pt-SnO2 system, resulting in the formation of a main phase of alloy (PtCu)-amorphous oxide (a-SnO2) interface. Benefiting from the optimized structures, the PtCu-SnO2 aerogel displays excellent acidic EOR performance with 4.5 times promotion in activity compared to pure Pt aerogel. In-depth investigations through electrochemical in-situ Fourier transform infrared spectroscopy and density functional theory calculations have shown that the absorbed OH on a-SnO2 surface together with the greatly-modified electronic structure of the alloy surface atoms can facilitate the C1 pathway and the oxidation of *CO intermediates for ethanol oxidation reaction. The resulting affinity of surface OH and the modification of reaction energies both in turn contribute to the improvement of EOR performance with high activity, stability, and anti-poisoning ability, proving interfacial engineering an effective strategy for the rational design of EOR catalyst.

Photothermal Synergistic Effect Induces Bimetallic Cooperation to Modulate Product Selectivity of CO2 Reduction on Different CeO2 Crystal Facets

AbstractProduct selectivity of solar‐driven CO2 reduction and H2O oxidation reactions has been successfully controlled by tuning the spatial distance between Pt/Au bimetallic active sites on different crystal facets of CeO2 catalysts. The replacement depth of Ce atoms by monatomic Pt determines the distance between bimetallic sites, while Au clusters are deposited on the surface. This space configuration creates a favourable microenvironment for the migration of active hydrogen species (*H). The *H is generated via the activation of H2O on monatomic Pt sites and migrate towards Au clusters with a strong capacity for CO2 adsorption. Under concentrated solar irradiation, selectivity of the (100) facet towards CO is 100 %, and the selectivity of the (110) and (111) facets towards CH4 is 33.5 % and 97.6 %, respectively. Notably, the CH4 yield on the (111) facet is as high as 369.4 μmol/g/h, and the solar‐to‐chemical energy efficiency of 0.23 % is 33.8 times higher than that under non‐concentrated solar irradiation. The impacts of high‐density flux photon and thermal effects on carriers and *H migration at the microscale are comprehensively discussed. This study provides a new avenue for tuning the spatial distance between active sites to achieve optimal product selectivity.

Balanced adsorption and oxidation in a porous P, N-doped carbon prepared by melt-salt-mediated strategy for enhanced fenton-like reaction

The activation of persulfate oxidation processes using carbon-based catalysts is attractive for eliminating persistent aromatic organic pollutants in wastewater treatment. Herein, N and P co-doped carbonaceous (NPC) catalysts with an ultrahigh surface area were synthesized using a melt-salt-mediated strategy, employing Zeolitic Imidazolate Framework-8 as a self-sacrificing template. The NPC(1:1) carbon, prepared under optimized conditions, exhibited the highest surface area of 2001.5 m2/g, characterized by the highest number of defects and a high dispersion of N (1.89 %) and P (0.30 %) atoms on the carbon. This carbon catalyst exhibited a high capacity for adsorption and potential for activating persulfates in the removal of p-Nitrophenol (p-NP). Experimental data indicate a balance between adsorption and oxidation in the NPC(1:1)/PDS/p-NP system, with the highest catalytic removal rate achieved through moderate pre-adsorption of p-NP. Evidence from quenching, electron paramagnetic resonance (EPR), and amperometric i-t experiments suggests that the NPC(1:1)/PDS system primarily degrades p-NP through an electron transfer pathway. Defects in carbon and graphitic N were identified as catalytic sites. These defects resulted in an electron-deficient state, which leads to the activation of PDS and graphitic N was more reactive than both pyridinic and pyrrolic N in the adsorption of PDS molecules. Additionally, P-containing groups such as C-P-O, C-O-P, and C3-P were pinpointed as active sites on the carbons through DFT calculations. The intermediates during p-NP degradation were identified, and possible degradation pathways were proposed. A toxicity analysis indicated a significant reduction in overall toxicity following the oxidation treatment. This study provides innovative insights into the balance between adsorption and catalytic activity in porous carbon-activated persulfate oxidation reactions, thereby aiding in the development of enhanced oxidation catalysts for environmental remediation.

Effects of particle size, binder wettability, and sintering atmosphere on the microstructural and mechanical properties of binder jetted 18Ni300 alloy

A fully dense 18Ni300 mold steel was firstly prepared by the binder jetting (BJ) process. We developed a water-based binder characterized by its low viscosity, which significantly enhanced the penetration of binder into the fine powder layer. This process resulted in a deep, narrow cross-section due to reduced flow resistance, leading to strong inter-layer bonding and high surface quality of the green part. The densification behavior of 18Ni300 BJ green parts with different particle sizes was meticulously analyzed. A remarkable tensile property of YS = 783 MPa, UTS = 1012 MPa and EL = 8.8% were obtained in sintered 18Ni300 alloy with fine powder under 1460 °C and 50 mTorr vacuum. Building on thermodynamic theory, we introduced a novel criterion to assess the oxidation reactions in 18Ni300 parts fabricated by the BJ method during sintering under different atmospheric conditions.

Efficient catalysis for acidic methanol oxidation: Exploration of a Low-Platinum quaternary alloy catalyst via a Two-Step method

The quest for platinum-based catalysts with enhanced catalytic efficacy and durability during the methanol oxidation reaction (MOR) has been a focal point in energy conversion science. Traditional platinum-based catalysts are often constrained by their high platinum content, which escalates economic costs and complicates experimental protocols. In this study, we introduce a low-platinum-loaded catalyst synthesized via a two-step method, which incorporates a four-component alloy. This innovative approach significantly reduces platinum content while maintaining superior catalytic performance through precise control over the alloy’s composition and structure. The two-step synthesis methodology streamlines the conventional multi-step processes, enhancing the catalyst preparation’s efficiency and reproducibility. The resulting PtCoSnCu/N-C alloy catalyst exhibits remarkable catalytic activity in methanol solution, with mass activity and specific activity that are 9.73 and 9.75 times higher, respectively, than those of commercial platinum on carbon (Pt/C) catalysts. Notably, the optimized PtCoSnCu/N-C alloy catalyst demonstrates exceptional long-term stability, outperforming Pt/C in aging and extended stability tests. Density functional theory (DFT) calculations elucidate the optimization of the electronic structure and the synergistic effect of surface atoms in the PtCoSnCu/N-C catalyst, which mitigates the adsorption energy of CO molecules and enhances the utilization rate of active sites during the oxidation process. This research presents a paradigm-shifting low-platinum catalyst strategy for methanol fuel cells, establishing a theoretical foundation for catalyst design and optimization.

Bimetallic MnZn-MOF-74 with enhanced percentage of MnIII: Efficiently catalytic activity for direct oxidative carboxylation of olefins to cyclic carbonates under mild and solvent-free condition

Multi-functional MOF catalyst with oxidative- and acid- centers showed potential in olefins oxidative carboxylation to cyclic carbonates directly. In this work, a series of bimetallic MnZn-MOF-74 with different molar ratios of Mn and Zn were synthesized successfully through a one-pot facile method. Thoroughly characterization indicated that the existence of Zn regulated the valance state distribution of Mn in the obtained MnZn-MOF-74. Mn99.3Zn0.7-MOF-74 with the highest ratio of MnIII (61.3 %) performed the most efficient activity for olefin direct tandem oxidative carboxylation reaction using aqueous tert-butyl hydroperoxide oxidant under solvent-free condition of 90 °C, 1.0 MPa CO2 and 4 h. Mn99.3Zn0.7-MOF-74 also showed satisfactory versatility and recyclability. Based on the experiments, a feasible mechanism was presented. Thanks to the high ratio of active MnIII as main oxidative center, the coordination unsaturated bimetal Mn and Zn as Lewis-acid sites, O2– of metal − O as Lewis-base sites and combined effect with Bu4NBr cocatalyst, Mn99.3Zn0.7-MOF-74 presented efficient performance for the direct synthesis of cyclic carbonates from olefins. The metal Zn in MOF can regulate the valance state distribution of Mn and result in efficient catalytic property, presenting a potential avenue for direct oxidative carboxylation reaction of olefins to cyclic carbonates synthesis.

Long-time oxidation resistance of KD-SiC fibers with different composition and structure in air atmosphere

Continuous silicon carbide (SiC) fibers, as reinforcement of ceramic matrix composites, have broad application prospects in the fields of aviation, aerospace and nuclear energy. Three typical KD-SiC fibers were adopted to explore the relationship of the composition and structure with their long-term oxidation (1–100 h) resistance in air environment. The mechanical strength retention of the nearly stoichiometric polycrystalline SiC fiber (C-1) was generally higher than that of the SiC fiber (C-3) with excess carbon and low oxygen, also higher than the nearly stoichiometric SiC fiber (C-2), especially under oxidation conditions of higher temperature and longer holding time. By comparing the high-temperature resistance with oxidation resistance at 1200–1600 °C, it was found that the oxidation reaction was the dominant factor affecting the mechanical properties. This work could provide theoretical and practical references for improvement of oxidation resistance of SiC fibers and their composites.