Activity In Medium Research Articles

Multi-metal phosphide as bi-functional electrocatalyst for enhanced water splitting performance

Developing cost effective and highly efficient electrocatalyst for water splitting is vital for green hydrogen production. Transition metal phosphides have attracted significant attentions for electrochemical water splitting owing to their desired conductivity, catalytic activity, and stability. Meanwhile, multi-metal compound provides unique tailorable properties as result of its nearly unlimited compositional space. In this study, we have therefore investigated the effect of incorporating a sixth metal of Ti, V, and Zn into a quinary-metal phosphide containing Cr, Mn, Fe, Ni, and Co. We show that the resulting senary-metal phosphides exhibit better oxygen evolution reaction (OER) performances than the quinary-metal phosphide and baseline samples of binary FeCo phosphide and commercial IrO2. We further demonstrate that the addition of Ti into the quinary-metal phosphide (5MT-P) shows the best performance by giving outstanding bi-functional catalytic activity and durability in alkaline media. The 5MT-P catalyst yields a current density of 50 mA cm−2 at overpotentials of 226 and 220 mV for OER and hydrogen evolution reaction (HER), respectively. For overall water splitting, a 5MT-P||5MT-P electrolyzer requires a low cell voltage of 1.69 V to achieve a current density of 100 mA cm−2 and exhibits excellent 100-h durability.

Green synthesis of chicory (Cichorium intybus L.) Chitosan nanoparticles and evaluation of their anti-fungal, anti-hemolytic, and anti-cancer activities

Chicory ( Cichorium intybus L.) is widely consumed as a food plant in many regions of the world and has been involved in traditional medicine due to its unique contents of phytochemicals. We aimed to investigate the anti-fungal, anti-hemolytic, and anti-cancer activities of chicory roots and leaves ethanolic extracts, and their Chitosan nanoparticles (Chit NPs) formulations. The ethanolic extract of chicory roots and leaves were microencapsulated into Chit NPs. The anti-hemolytic, anti-fungal, and anti-cancer activity of chicory extracts and their Chit-NPs were investigated, along with an in vitro toxicological study. Chicory extracts encapsulation into Chit NPs increased their anti-fungal activity against two fungal pathogens, Candida albicans and Aspergillus flavus. Chicory extracts and their Chit NPs appeared strong anti-hemolytic activity in hypotonic media. Due to microencapsulation of roots and leaves extracts into Chit NPs, the IC50 was decreased 2.49 and 2.6-folds in HepG2 and MCF-7 cell lines, and 6.31 and 5.50-folds in HepG2 and MCF-7 cell lines, respectively. The in vitro toxicological study revealed that the IC50 of chicory roots (56.84 ± 6.4 μg/ml) and leaves (45.51 ± 4.2 μg/ml) decreased 8.45 and 6.77-folds in the normal human fibroblasts (WI38) cell line, compared to Doxorubicin (6.72 ± 0.5 μg/ml). Microencapsulation of extracts into Chit NPs increased their toxicity 2.43-folds for Chit-Roots NPs (IC50 = 23.35 ± 2.3 μg/ml) and 1.22-fold for Chit-Leaves NPs (IC50 = 37.29 ± 2.9 μg/ml). Chicory-Chit NPs possess promising anti-cancer and anti-hemolytic activities. It is worth for further testing their efficacy and toxicity in pre-clinical animal models as well as clinical trials.

Metal-organic framework derived ellipse-like NiS2 nanocatalyst for stable electrochemical hydrogen generation in alkaline electrolyte

The development of non-precious and high-efficient electrocatalysts to enhance the activity and stability in alkaline media is impending for massive hydrogen and oxygen production. In this study, NiS2 nanoparticles array with ellipse-like topography was fabricated via simple hydrothermal and sulfurization treatment. The NiS2-400 featured with the unique loose stacking topographic architecture contributes to more exposed active sites, the smaller contact resistance between electrode/electrolyte, faster ion diffusion and electron transfer. As a result, NiS2-400 electrode requires only overpotentials of 116 and 178 mV to drive current densities of 10 and 50 mA cm−2 in 1.0 M KOH towards the hydrogen evolution reaction (HER), coupled with a Tafel slope of 93.0 mV dec−1. Moreover, the resultant NiS2-400 nanoparticles exhibit excellent electrochemical stability for more than 50 h. In addition, the density functional theory (DFT) calculation further confirms that the (200) facet acts as the predominant active site, contributing to the enhanced HER performance.

Phosphorus-Rich Ruthenium Phosphide Embedded on a 3D Porous Dual-Doped Graphitic Carbon for Hydrogen Evolution Reaction.

Metal phosphides have recently emerged as promising electrocatalysts for hydrogen evolution reaction (HER). Herein, we report the synthesis of ruthenium diphosphide embedded on a dual-doped graphitic carbon by pyrolyzing chitosan beads impregnated with ruthenium chloride and phosphorus pentoxide. The as-synthesized RuP2@N-P-C displays a good electrocatalytic activity in acidic, neutral and alkaline media. We show that the HER activity of the electrocatalyst can be tuned by varying the concentration of Li+ cations. Co-diffusion effects on H+ exerted by Li+ on HER in the porous carbon matrix have been observed.

Deactivation Mechanism of Pyridinic Nitrogen-Doped Carbon for ORR in Acidic Media

Nitrogen doped (N-doped) carbons are attracting attention as Pt-free catalysts for oxygen reduction reaction (ORR) in fuel cells. N-doped carbon catalysts exhibit high activity comparable to that of platinum in basic media whereas the activity is significantly reduced in acidic media. To solve the deactivation mechanism based on kinetics, we have investigated the reaction pathway of N-doped carbon catalysts. The active site of pyridinic nitrogen (pyri-N) is protonated to be pyridinium (pyri-NH+) in acidic media due to acid-base equilibrium ofpyri-N + H+ ⇄ pyriNH+ (1)Following to Eq. (1), we recently exhibited thatpyriNH+ + e- + O2⇄ O2a + pyri-NH(2)proceeds using model catalysts with homogenous active sites. In the step, the electrochemical reduction from pyri-NH+ to pyri-NH and thermal O2 adsorption simultaneously occurs wherein the adsorption of O2 promotes the electron transfer into π* orbital of pyri-NH. We proposed that the hydration of pyri-NH+ lowers the redox potential of Eq. (2) decreasing the ORR activity in acidic media. In the present study, we further considered the acid-base equilibrium of pyri-N in Eq. (1) to comprehensively answer why the ORR activity of N-doped carbon catalyst is high in alkaline media and is decreased in acidic media.To investigate the relationship between acid-base equilibrium and the activity, the electrochemical measurements were performed in electrolyte solutions of various pH. Figure 1 shows the onset potential (voltage at -100 μA/cm2) as a function of pH measure with a model catalyst of 1,10-phenanthroline/(carbon black). In the range from pH 5 to 13, the onset potential decreased with a slope of ~59 mV/pH, while at below pH 5, the onset potentials were almost constant. This indicates that the reaction mechanism changes due to the shift of the acid-base equilibrium. In low pH, the reactions determining the onset potential is assumed to be Eq. (2). On the other hand, at high pH, the reaction should start from pyri-N but not from pyri-NH+.We have figured out that pyri-N + H2O +e- + O2⇄ O2a + pyri-NH + OH- (3) takes place in alkaline madia. Figure 2 shows the N1s peak of the model catalyst applied voltage at pH 13 in N2-(left) and O2-(right)saturated electrolyte. A peak at 400.5 eV appeared at higher applied voltage in O2-saturated electrolyte. This means that pyri-N (399.2 eV) is reduced at a higher potential in the presence of O2 to form pyri-NH. In other words, oxygen adsorption and reduction of pyri-N simultaneously occurred in the presence of O2.The redox potentials of Eq. (2) and (3) explain the pH dependences of the onset potentials. The Nernst equations of Eq. (2) and Eq. (3) show pH-independent redox potential vs. RHE and pH-dependent redox potential vs. RHE with the slope of 59 mV/pH, respectively. This also means that the activity depends on the acid-base equilibrium of pyri-N.We also calculated the redox potentials based on DFT as shown in Figure 3. The additional important point is that the redox potentials of Eq. (2) is strongly influenced by the hydration whereas the redox potentials of Eq. (3) is not influenced by the hydration because the stability of pyri-N is not changed by the hydration. Therefore, the ORR activity in alkaline media is high because the redox potential of Eq. (2) vs. RHE is higher for the higher pH and is not influenced by the hydration. On the other hand, the activity in acidic media is lowered by the hydration. This is that the suppression of the hydration by the introduction of the hydrophobicity at the vicinity of the active site can significantly promote the activity in acidic media. Figure 1

(Invited, Digital Presentation) Electrocatalyst and Electrolyte Engineering for Oxygen Evolution in Acidic Media

The slow kinetics of the oxygen evolution reaction (OER) limits the performance of proton exchange membrane (PEM) electrolysers. Only iridium-based oxides are both reasonably active and stable for the OER in acidic electrolytes [1], and high amounts of Ir are needed at the anode of PEM electrolysers. In addition, the lack of stable support materials limits the utilisation of Ir. Designing novel electrocatalysts with enhanced OER activity and stability in acidic media remains a great challenge. In this talk, I will present some recent strategies aiming to understand and engineer the interfacial structure and properties for oxygen evolution electrocatalysis. We have developed self-supported high surface area nanostructured Ir-based networks as highly active electrocatalysts for OER [2]. These networks, prepared by alternating sputtering of Ir and Co, followed by selective Co leaching, show a unique morphology and combine excellent mass activity with promising stability [2]. In addition, our group is working in the development of an easy and affordable method to prepare IrOx catalysts by controlled electrodeposition of Co and Ni in a deep eutectic solvent followed by galvanic displacement [3]. By controlling the conditions during the galvanic displacement, we tune the morphology and thus the electrocatalytic properties for OER. Finally, we have investigated the role of both composition and concentration of the acidic electrolyte (perchloric and sulphuric acid) on the OER electrocatalytic performance of Ir nanoparticles [4]. Our work highlights the key role the electrolyte plays in the performance of Ir-based electrocatalysts during rotating disc electrode measurements.REFERENCES[1] M. Escudero-Escribano et al., Journal of Physical Chemistry B 2018, 122, 947.[2] A.W. Jensen, G.W. Sievers, K.D. Jensen, J. Quinson, J.A. Arminio-Ravelo, V. Brüser, M. Arenz, M. Escudero-Escribano, Journal of Materials Chemistry A 2020, 8, 1066.[3] F.B. Holde, K.N. Dalby, H. Falsig, P. Sebastián-Pascual, M. Escudero-Escribano, in prep., 2022.[4] J.A. Arminio-Ravelo, A.W. Jensen, K.D. Jensen, J. Quinson, M. Escudero-Escribano, ChemPhysChem 2019, 20, 2956.

Crystal Structure-Controlled Electrocatalysis on Iron-Based Oxides Toward Oxygen Evolution in Alkaline Media: Trend and Mechanism

Present energy issues have increasingly stimulated the demand for the development of clean and sustainable energy platforms which can achieve net zero carbon emissions. Renewable energy resources are quite promising candidates for the construction of sustainable decarbonized society. One of examples of harnessing renewable energy-derived electricity is the electrolysis of earth-abundant water into hydrogen, which is a prominent carbon-free chemical fuel with a high weight energy density. Compared with polymer electrolyte water electrolysis in acidic environment, electrochemical alkaline water splitting can employ inexpensive nonprecious metals as electrocatalysts, which can make this technology a large-scale and cost-effective process. However, the anodic oxygen evolution reaction (OER) in the water splitting has a large overpotential, and it is a great bottleneck for widespread use. Thus, highly active and inexpensive electrocatalysts for OER are desired to overcome this concern.Iron (Fe) is a very earth-abundant element that is a quite cheap and non-toxic metal, and thus it is a potential candidate as electrocatalyst for OER. Previous studies have reported several multimetal oxides with Fe and other metallic elements, such as perovskite and brownmillerite types, which have attracted great attentions due to their facile synthesis and easily tunable OER activities by element substitution and doping. However, most of these studies focused on the choice of elements. Contrarily, the effects of crystal structures on OER activity have not yet been sufficiently interpreted, and it can be a crucial aspect to understand the OER electrocatalysis on Fe-based oxides and for the rational design of outstanding OER catalysts.In this study, we aim to comprehensively understand the effects of crystal structures on electrocatalytic OER activities on Fe-based oxides. To obtain versatile insights into OER electrocatalysis, we collected OER performances of Fe-based simple and bimetal oxides from our experiments and literature, and their structural characteristics were obtained from databases for inorganic compounds. Thus, we found that OER efficiencies on the Fe-based oxides were correlated with Fe–O bond lengths in their crystals; i.e., a shorter Fe–O bond length led to a higher OER activity.[1] We then exploited databases to mine potential candidates based on the structure–activity relationship and selected unreported Fe-based bimetal and trimetal oxides with various structures, which can dramatically accelerate our catalyst research. We synthesized these Fe-based multimetal oxides and evaluated their OER activity in alkaline media; remarkably, the OER efficiency on the unreported Fe-based multimetal oxides also exhibited excellent correlation with Fe–O bond lengths, as plotted in Figure 1. It is notable that the trend in the Fe–O bond length and OER activity is applicable to a wide variety of Fe-based simple, bimetal, and trimetal oxides regardless of chemical compositions, crystal categories, and Fe valence states. Furthermore, machine learning analysis proved that Fe–O bond length is the most dominant structural descriptor for OER efficiency compared with other structural parameters.[2] However, it is required to overcome the abovementioned catalytic trend because theoretical Fe–O bond length in Fe-based oxides is limited, and superior OER catalysts cannot be achieved according to this design guideline. Hence, we attempted to switch the OER electrocatalytic mechanism on a Fe-based oxide by the arrangement of crystal structure because different mechanisms should be involved in different descriptors; i.e., the mechanism switch could surpass the abovementioned catalytic trend. Thus, we found post-spinel CaFe2O4 that comprises a large amount of edge-shared FeO6 connectivity in its crystal. DFT calculations unveiled that the structural characteristics induced an unprecedented OER mechanism, multi-iron-site mechanism, where OER process goes through a reaction intermediate with an O–O bridge on multiple Fe sites as depicted in upper side in Figure 1. Consequently, CaFe2O4 exhibited prominent OER activity despite long Fe–O bond length in its crystal.[3] These findings provide a novel insight into the OER electrocatalysis on Fe-based oxides and contribute to the innovation of electrochemical hydrogen production.The part of this paper is based on results obtained from a project, JPNP14021, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Authors acknowledge the PRESTO program (No. JPMJPR15S3) of the JST. The part of DFT calculations was carried out on the supercomputers at NIMS, Hokkaido Univ., Kyushu Univ., and the HPCI systems (project codes: hp180115, hp200131). The part of this work was supported by JSPS KAKENHI Grant Number 20H00314 and 20K15087.

Substituent effects in carbon-nanotube-supported diiron monophosphine complexes for hydrogen evolution reaction

In order to explore substituent effects of PR3-phosphine ligands of diiron dithiolato complexes on the catalytic performances of [FeFe]-hydrogenase mimics for hydrogen evolution reaction (HER) in an aqueous medium, three new diiron monophosphine complexes [{(μ-SCH2)2N(C6H4CH2CH2OH)}Fe2(CO)5{P(C6H4R-4)3}] (labeled as FePR; R = F, H, and Me) were prepared and can be further linked covalently into carbon nanotube (CNT) to construct the target CNT-supported hybrids denoting as CNT-f-FePR. The molecular structures of diiron complexes FePR are well characterized through element analysis, fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and X-ray crystallography, whereas the formations of target hybrids CNT-f-FePR have been confirmed by using X-ray photoelectron spectroscopy (XPS), Raman and FT-IR. Notably, the electrochemical HER performances of target hybrids CNT-f-FePR (R = F, H, and Me) are studied and compared in 0.1 M H2SO4 aqueous solution by means of linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and density functional theory (DFT) calculation. Among these hybrids, the CNT-f-FePF hybrid exhibits a more efficient HER activity in an aqueous media based on their electrochemical observations that the CNT-f-FePF hybrid with F-substituted phosphine has lower applied overpotential, smaller Tafel slope, larger electrochemical active surface area, smaller charge transfer resistance, and lower hydrogen chemisorption free energy relative to its analogues CNT-f-FePH and CNT-f-FePMe with H- or Me-substituted phosphines.

CO2 and Formate Pathway of Methanol Electrooxidation at Rhodium Electrodes in Alkaline Media: An In Situ Electrochemical Attenuated Total Refection Surface-Enhanced Infrared Absorption Spectroscopy and Infrared Reflection Absorption Spectroscopy Investigation.

Rh catalysts exhibit unexpected high activity for the methanol oxidation reaction (MOR) in alkaline conditions, making them potential anodic catalysts for direct methanol fuel cells (DMFCs). Nevertheless, the MOR mechanism on Rh electrodes has not been clarified thus far, which impedes the development of high-efficiency Rh-based MOR catalysts. To investigate it, a combination of in situ electrochemical techniques called attenuated total refection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and infrared reflection absorption spectroscopy (IRAS) is used. Cyclic voltammograms of MOR at Rh electrodes show considerable activity in alkaline media rather than acidic media, although the real-time ATR-SEIRA spectral results demonstrate that methanol can rarely self-decompose on Rh at open-circuit conditions. Meanwhile, in combination of ATR-SEIRAS and IRAS results, CO2 and formate are thought to be MOR products, suggesting a dual-pathway mechanism ("CO2 pathway" and "formate pathway"). Specifically, COad species, which are the major intermediates in the CO2 pathway, can produce at lower potentials and be oxidized into CO2 at a potential of 0.5-0.75 V. Concurrently, the formate can be produced from 0.5 V and diffuse into the bulk electrolyte to become one of the MOR products, while the further electrochemical conversion of formate to CO2 is essentially negligible. More directly, the apparent selectivity (r) of the CO2 pathway is estimated to reach ca. 0.63 at 0.9 V, confirming the potential-dependent selectivity of MOR at Rh surfaces. This study might provide fresh insights into the design and fabrication of effective Rh-based catalysts for MOR.

In Situ S-Doping Strategy of Promoting Iron Coordinated by Nitrogen-Doped Carbon Nanosheets for Efficient Oxygen Reduction Reaction.

Improving transition metal-nitrogen-carbon (M-N-C) as a noble-metal-free catalyst for the oxygen reduction reaction (ORR) is critical to achieve low-cost electrochemical energy conversion. Herein, an in situ S doping strategy of enhancing Fe-N-C activity for ORR was developed by newly designed Fe(II) ion coordinated S-containing bis(imino)-pyridine-based polymers as precursors, which were synthesized through copolymerizing three monomers of 2, 6-diacetylpyridine (DAP), triamterene (TIT), and 2,5-dithiobiurea (DTB) as both N and S sources. All samples derived from various molar ratios of the three monomers possess a self-supporting structure of nanosheets. Additionally, incorporating DTB into the copolymer can not only strongly affect the derived coordinative species of N dopants to Fe atom but also effectively induce the synergistic effect between S dopants and FeNx moieties, resulting a significant improvement for ORR. The S-doped Fe-N-C nansheets with Fe coordinated by 4 pyrrolic N dopants exhibit the highest ORR activity and stability in alkaline media with a higher power output of Zn-air battery than that of the same loading of Pt/C. Theoretical calculation identifies that the thiophenic S dopant adjacent to Fe-pyrrolic N moiety can decrease the d band center of Fe atom, greatly weakening the energy profiles of oxygenated intermediates and thus enhancing ORR. In addition, because of the designability of transition metal coordinated S-containing bis(imino)-pyridine based polymers in the work, therefore, it is believable that this strategy would open a wide space to explore the structural relationship between precursors and MNx active sites with S dopants for the purpose of achieving highly efficient and robust M-N-C catalysts for energy-related electrocatalysis.

A Nanoneedle Ni12P5 Array for Hydrogen Evolution Reaction with High Efficiency over a Wide pH Range

AbstractTransition metal phosphides (TMP) with high conductivity and better H* intermediate adsorption energy have attracted great attention in hydrogen evolution process. Herein, a Ni12P5 nanoneedle array was synthesized by a facile one‐step phosphorization method. As expected, the obtained Ni12P5 nanoneedle arrays exhibits high HER performance, and low overpotentials of 59, 117, and 148 mV are need to drive hydrogen evolution at current densities of 10, 50, and 100 mA cm−2 in 1 mol/L KOH electrolyte, respectively. Meanwhile, the obtained electrode exhibits excellent hydrogen evolution activity in both acidic and neutral media. Excellent electrochemical performances demonstrate that the nickel phosphide could be a candidate for high‐performance water electrolysis over a wide pH range.

Ultrathin metal–organic framework hybrid nanosheets enabled active oxygen evolution electrocatalysis in alkaline media

• Ultrathin MOF hybrid nanosheets with 2.5 nm thickness were synthesized. • They demonstrate excellent OER activity and durability in alkaline media. • Their OER performance is associated to their unique structural and compositional properties. Metal-organic framework (MOF) with unique structural ordering and compositional flexibility has inspired tremendous interest for electrocatalysis. However, it remains elusive as how to adjust its structure and composition for enhanced electrocatalytic performance. In this paper we report the synthesis of 2.5 nm thick MOF hybrid nanosheets and their excellent electrocatalytic performance toward oxygen evolution reaction (OER). These nanosheets were composed of sulfide cluster-doped ultrathin Ni/Fe bimetallic MIL-53 MOF, and show excellent alkaline OER activity and durability; it delivers OER current of 50 and 100 mA cm −2 at 234 and 256 mV overpotential, respectively. Its activity does not fade after 70 h operation at 50 mA cm −2 . The ultrathin nanosheet structure enables exposing of abundant coordinately unsaturated surface active sites, and the doped sulfide clusters optimize the electronic structure and enhance the electrical conductivity of the nanosheets.

Facile and rapid synthesis of ultrafine RuPd alloy anchored in N-doped porous carbon for superior HER electrocatalysis in both alkaline and acidic media

Searching for preeminent electrocatalysts toward hydrogen evolution reaction (HER) is significantly important in transforming renewable electricity to clean hydrogen energy by electrochemical water splitting. Herein, ultrafine RuPd alloy nanoparticles anchored in MOFs-derived N-doped porous carbon dodecahedrons (Ru x Pd 1−x @NPC) were synthesized by microwave-assisted ethylene glycol reduction method. Due to the synergistic promotion by modulating the composition and structure, excellent HER catalytic performance was achieved in both alkaline and acidic media for the as-prepared Ru x Pd 1−x @NPC electrocatalysts with low noble metal loading. In which, Ru 0.7 Pd 0.3 @NPC exhibited significantly enhanced alkaline HER activity with a low overpotential of only 20 mV to reach a current density of 10 mA cm −2 . Meanwhile, Ru 0.3 Pd 0.7 @NPC showed admirable HER activity in acidic media, which delivered an overpotential of 36 mV at 10 mA cm −2 . Additionally, the proposed catalysts demonstrated high mass activity and good long-term stability in both alkaline and acidic condition, remarkably surpassing the commercial Pt/C catalyst. The superior activity of the Ru x Pd 1−x @NPC catalysts is attributed to improved intrinsic activity, fast charge transfer kinetics and distinct electrochemical active surface areas after alloying. This work provides a rapid and facile synthesis of highly efficient, durable and affordable alloy electrocatalysts for hydrogen evolution. With low noble metal loading, the alloying Ru x Pd 1−x @NPC electrocatalysts synthesized by facile and rapid microwave-assisted reduction method exhibit dramatically enhanced performance for sustainable hydrogen evolution. • Series of ultrafine alloying RuPd nanoparticles are dispersedly encapsulated in N-doped porous carbon dodecahedrons. • A facile and rapid microwave-assisted reduction method is proposed to synthesize RuPd alloy catalysts. • Enhanced HER electrocatalytic performance is realized in both alkaline and acidic media .

(Digital Presentation) Effect of Iron Doping on Oxygen Reduction Activity of Zirconium Oxides Containing Carbon and Nitrogen Using Pyrazine Carboxylic Acid As Platinum Alternative Cathodes for PEFC

Fe-added zirconium oxide catalysts were synthesized by using pyrazine carboxylic acid to enhance oxygen reduction reaction (ORR) activity in acidic media. Fe-added zirconium oxide with a Fe/Zr atomic ratio of 0.1 showed highest ORR onset potential, 0.917 V vs. reversible hydrogen electrode among other zirconium oxide-based catalysts including the previous study. High quality active sites for ORR might be created by substitution of Zr4+ by Fe3+ in ZrO2 monoclinic structure. Although no use of carbon support caused a large particle size of zirconium oxides approximately 20~200 nm, the ORR activity drastically increased because of the creation of high quality active sites. We found that a positive correlation between a ratio of ZrO2 monoclinic structure and ORR activity. As a result, the use of pyrazine carboxylic acid was useful to create high quality active sites and a suitable electron conduction path.

What is the Real Origin of the Activity of Fe-N-C Electrocatalysts in the O2 Reduction Reaction? Critical Roles of Coordinating Pyrrolic N and Axially Adsorbing Species.

Fe-N-C electrocatalysts have emerged as promising substitutes for Pt-based catalysts for the oxygen reduction reaction (ORR). However, their real catalytic active site is still under debate. The underlying roles of different types of coordinating N including pyridinic and pyrrolic N in catalytic performance require thorough clarification. In addition, how to understand the pH-dependent activity of Fe-N-C catalysts is another urgent issue. Herein, we comprehensively studied 13 different N-coordinated FeNxC configurations and their corresponding ORR activity through simulations which mimic the realistic electrocatalytic environment on the basis of constant-potential implicit solvent models. We demonstrate that coordinating pyrrolic N contributes to a higher activity than pyridinic N, and pyrrolic FeN4C exhibits the highest activity in acidic media. Meanwhile, the in situ active site transformation to *O-FeN4C and *OH-FeN4C clarifies the origin of the higher activity of Fe-N-C in alkaline media. These findings can provide indispensable guidelines for rational design of better durable Fe-N-C catalysts.

Pt Atomic Layers Boosted Hydrogen Evolution Reaction in Nonacidic Media

AbstractPt‐based electrocatalysts exhibit high performance toward hydrogen evolution reaction (HER) since they can boost sluggish kinetics of water dissociation. To develop efficient Pt catalysts in nonacidic media, Pt electrocatalysts with a Rh core and a shell of a few Pt atomic layers (Rh@PtnL, n = 1, 2, 2.6) are designed. Ultrathin Pt atomic layers on a Rh core modulate electronic structures of Rh@PtnL electrocatalysts, generating a combined effect of ligand, compressive strain, and electron transfer. The Rh@PtnL electrocatalysts thus offer significantly higher HER activity in alkaline and neutral media than the RhPt alloy, Rh/C, and commercial Pt/C catalysts. The overpotential of a Rh@Pt2L electrocatalyst is only 5 mV at 10 mA cm−2 in 1.0 M KOH. The density functional theory calculations confirm that the excellent HER activity of this Rh@Pt2L electrocatalyst in nonacidic media is attributed to an enhanced hydrogen desorption and a decreased energetic barrier during the hydrogen generating process. These Rh@PtnL electrocatalysts shed the light on the design of advanced catalysts to efficiently produce green hydrogen in nonacidic media.

Robust and highly conductive Ti4O7/MXene nanocomposites as high-performance and long cyclic stability oxygen reduction electrocatalysts

Electrocatalysts play an important role in the cathodic Oxygen Reduction Reaction (ORR) of fuel cells. Because of the high cost, poor cycle stability and methanol tolerance, the commercial Pt/C catalysts have been seriously restricted during large-scale application and development in electrochemical devices. The development of non-noble metal ORR catalysts is one of the effective ways to achieve fuel cell cost reduction and performance improvement at the same time. In this work, Ti4O7/MXene nanocomposites were synthesized through hydrothermal followed by carbothermal reduction reactions. Such catalysts exhibit large electrochemical active surface area (ECSA = 215.74 cm2) and excellent ORR catalytic activity in alkaline media. The initial potential and half-wave potential were confirmed to be 0.91 V and 0.72 V with the electron transfer number of 3.3. In addition, the Ti4O7/MXene catalysts have better cyclic stability and methanol tolerance than commercial Pt/C catalyst. This study provides a new idea and method for the innovative preparation of MXene-based composite electrocatalysts.

Differential proMMP-2 and proMMP-9 secretion in human pre-implantation embryos at day 5 of development.

Morphological development is the most common non-invasive criterion used to select in vitro human embryos for implantation. With this criterion, however, embryos in cellular arrest go unnoticed. A more accurate criterion is needed to improve the success rate of implantation. Extracellular matrix metalloproteases type 2 (MMP-2) and MMP-9 are key markers of embryonic development and the implantation process, according to various animal studies. The first objective of this study was to examine proMMP-2 and proMMP-9 activity in the culture media of human embryos with good morphological development. Secondly, the results of proMMP-2 and proMMP-9 activity in the culture medium were compared between pregnant and non-pregnant. Forty-two patients were approved by the Ethics and Research Committees of the Instituto Nacional de Perinatología in México City hospital, based on institutional inclusion criteria for in vitro fertilization. On day 5 of development, embryos were transferred to patients, and the culture media secretion profile of proMMP-2 and proMMP-9 activity was determined by substrate gel zymography. After analysis of embryo sac development, each patient was assigned to the pregnant (n=17) or non-pregnant (n=25) group. Our results demonstrate that proMMP-2 was active in the culture media corresponding to all 17 women achieving full-term pregnancy and proMMP-9 in the media corresponding to 11 of these women. Contrarily proMMP-2 and proMMP-9 were active in the culture media corresponding to 3 and 11 of the 25 non-pregnant patients, respectively. The clinical implications of this study suggest the activity evaluation of proMMP-2 and proMMP-9 in embryonic culture media on day 5 of development appears to be a reliable indicator of the quality of embryos and their capacity to establish a pregnancy.

Channel‐Rich Pt 0.23 Mn 0.42 Ni 0.35 Ternary Alloy Nanocatalysts for Efficient Hydrogen Evolution

The development of highly active and durable electrocatalysts with low Pt content for key reactions (hydrogen evolution reactions) in acidic electrolyte environments is desirable but remains an open challenge for clean and efficient energy conversion. Here, homogeneous, and unique Pt0.23Mn0.42Ni0.35 flower-like nanostructure were firstly synthesized by a simple low-temperature oil-phase strategy. These Pt0.23Mn0.42Ni0.35 catalysts exhibit a significantly increased electrochemically active surface area and excellent electrical conductivity due to their alloy nature, uniform, and unique channel-rich morphological characteristics. The new-type catalyst shows an ultra-small overpotential of 23 mV at a current density of 10 mA cm−2, high mass activity (7.61 A mg−1 Pt at −0.07 V) and excellent stability in acidic media.

The activities of the ukrainian media during the russian-ukrainian war

The purpose of the article. The research is related to the analysis of the activities of the Ukrainian mass media during the Russian occupation and the coverage of their role in the information struggle from the beginning of the war until now. The research methodology includes the use of a descriptive method, the method of analysis and synthesis to identify the importance of mass media functioning in society. Scientific novelty. The scientific novelty is in the fact that the article clarifies the main aspects of the activity of the Ukrainian mass media since the beginning of the full-scale Russian invasion of the territory of our country. In addition, it emphasizes the change in their information content, substantiates the strengthening of its patriotic direction, аnalyses the emergence of new means of expression that fill the language media practice with topical content. Conclusions. A detailed analysis of the activities of the Ukrainian media during the Russian occupation revealed the importance of media communication, which significantly increased during this period, which enables the increase of the information product as well as contributes to the increase in awareness of society in general. The topics and contents of the content have changed: the main focus is now on information about the course of war events, the reaction of the world community to them, the creation of new forms of television and radio broadcasts, the publication of patriotic works, changes in the content of advertising products, etc. The modifications, observed in the Ukrainian language, are also noted and perceived as a reaction to the terrible events of today: regrouping of vocabulary, emergence of new means of expression, consolidation of new language norms, etc. Modern mass media, performing informational and social functions, transform the traditional system of spiritual values of Ukrainian society into the global information space. Keywords: mass media, social networks, information content, neologisms, idiom, obscene language.