Oxygen Reduction

Recently, it has been reported that mitochondria possess a novel pathway for nitric oxide (NO) synthesis. This pathway is induced when cells experience hypoxia, is nitrite (NO 2 ؊ )-dependent, is independent of NO synthases, and is catalyzed by cytochrome c oxidase (Cco). It has been proposed that this mitochondrially produced NO is a component of hypoxic signaling and the induction of nuclear hypoxic genes. In this study, we examine the NO 2 ؊ -dependent NO production in yeast engineered to contain alternative isoforms, Va or Vb, of Cco subunit V. Previous studies have shown that these isoforms have differential effects on oxygen reduction by Cco, and that their genes (COX5a and COX5b, respectively) are inversely regulated by oxygen. Here, we find that the Vb isozyme has a higher turnover rate for NO production than the Va isozyme and that the Vb isozyme produces NO at much higher oxygen concentrations than the Va isozyme. We have also found that the hypoxic genes CYC7 and OLE1 are induced to higher levels in a strain carrying the Vb isozyme than in a strain carrying the Va isozyme. Together, these results demonstrate that the subunit V isoforms have differential effects on NO 2 ؊ -dependent NO production by Cco and provide further support for a role of Cco in hypoxic signaling. These findings also suggest a positive feedback mechanism in which mitochondrially produced NO induces expression of COX5b, whose protein product then functions to enhance the ability of Cco to produce NO in hypoxic/anoxic cells. hypoxia ͉ mitochondria ͉ reactive oxygen species ͉ nitrite ͉ yeast

The low durability of Pt/C electro-catalysts in polymer electrolyte membrane fuel cells (PEMFC), e.g., as a result of carbon oxidation to CO 2 in an acid medium, has been recognized as one of the most important hindrances to long-term stability. In this work, Pt electrocatalysts supported on TiO 2 -carbon and Vulcan carbon were prepared by the chemical vapor deposition method. The physical and electrochemical properties of Pt/TiO 2 -C and Pt/C electrocatalysts were investigated by the characterization techniques of XRD, TEM, CO stripping and cyclic and linear voltammetry. The prepared materials were electrochemically evaluated in the oxygen reduction reaction (ORR) in an acid medium at room temperature. The XRD results show crystalline fcc platinum formation. The mean particle size is between 2 and 4 nm with a spherical morphology. Pt/TiO 2 -C electrocatalysts showed a higher electrochemical active surface area and better activity results for the ORR compared with the Pt/C samples. The addition of TiO 2 to the conventional Pt/C catalyst modifies the electronic properties affecting the oxygen adsorption and improving the catalytic activity for the oxygen reduction reaction.

Lithium dendrite formation remains the primary failure mode in lithium-based batteries, causing capacity loss, internal short circuits, and thermal runaway. We propose that dendrite nucleation is fundamentally a consequence of periodic, rational-ratio ion-site geometry in conventional electrodes-which creates preferred nucleation points by the same mechanism that produces standing waves in rational-ratio resonators. We introduce the Hurwitz-optimal aperiodic electrode architecture: ion storage sites arranged according to the Three-Distance Theorem at the rotation angle alpha = 360 x (1-1/phi) = 137.508 degrees, where phi = (1+sqrt(5))/2 is the unique number achieving the Hurwitz irrationality bound 1/sqrt(5). This arrangement guarantees: (1) no two sites share a rational-ratio spatial relationship, eliminating preferred nucleation geometry; (2) the minimum inter-site distance remains constant as N increases (proven: min_d = 1.602 for all N up to 500 tested), maximizing site density without clustering; (3) site distribution uniformity of 0.382 = 1/phi^2, the theoretical maximum for aperiodic packings. We predict that electrodes with Hurwitz-optimal microstructure will exhibit suppressed dendrite formation and increased gravimetric capacity compared to hexagonal or random architectures. Experimental validation via laser-patterned anode surfaces is proposed.

Protonic solid oxide fuel cells (P-SOFCs), as a promising power generation technology, have garnered increasing attention due to their advantages of cleanliness, high efficiency, and high reliability. As a critical component of P-SOFCs, proton-conducting electrolytes exhibit high ionic conductivity, enabling high chemical-to-electrical energy conversion efficiency at intermediate temperatures. However, there are still many challenges in further enhancing the proton conductivity and stability of the currently widely used Ba(Zr, Ce)O 3 electrolytes through traditional experimental methods. Herein, this review firstly summarized the current research status of proton-conducting oxides, including ABO 3 perovskite-type oxides and other structural oxides, and highlighted the challenges faced by electrolyte development in terms of proton conductivity, compatibility with other components, and long-term durability. Then, the relevant progress of machine learning (ML) in the research of P-SOFC electrolytes was meticulously discussed and the promising applications of ML in proton-conducting electrolyte performance screening, stability prediction, and morphology analysis were pointed out. More importantly, the challenges and solutions of proton-conducting electrolytes designed by ML were uncovered by considering the reliable database, feature engineering, accurate model, and experimental validation. Overall, this review concluded the advances of ML-assisted P-SOFC electrolytes and addressed the future research directions in the synergy of ML and electrolytes.

Cost-efficient fabrication of cathode catalyst layer having low Pt-loading and high oxygen reduction reaction (ORR) performance is of prime importance towards commercialization of low temperature fuel cells. Here, an attempt has been made to fabricate hierarchically structured and cathode catalyst layer consisting of Pt-nanoparticle clusters supported on defective carbon nanotube (CNT) coated carbon fiber (CNTCF). CNTs are grown on carbon fiber (CF) by chemical vapor deposition (CVD), while electrodeposition is employed to deposit Pt-nanoparticle clusters on the CNTCF. Effect of Pt-loading on oxygen reduction reaction (ORR) performance of the Ptcoated CNTCF (Pt-CNTCF) electrocatalysts is studied by varying the electrodeposition time (ted) between 5 and 30 min, which results a variation of Pt weight fraction in Pt-CNTCF from almost zero to ~0.3. Linear sweep voltammetry using the Pt-CNTCF modified glassy carbon (GC) rotating disc electrode (RDE) is employed to study the ORR performance of the samples. The CNTCF support, owing to the defective structure of CNT, itself exhibits significant ORR activity with an electron transfer number (n) of ~2.6, which leads to a synergistic enhancement of the overall electrocatalytic performance of Pt-CNTCF. For lower Pt-loading on GC (~5 μg cm -2 ), the contribution of CNTCF support dominates, while the Pt-nanoclusters govern the ORR

Six methanol extracts from different parts of plants used in northeast Mexico as general health supplements were examined for their potential as antioxidants. The plants evaluated were: Turnera diffusa Wild. (Turneraceae), Cucurbita foetidissima Kunth (Cucurbitaceae), Flourensia cernua D.C. (Asteraceae), Selaginella pilifera A. Braun (Selaginellaceae), Juglans mollis Engelm. (Juglandaceae) and Centaurea americana Nutt. (Asteraceae alt. Compositae). Antioxidant properties of these extracts were evaluated by means of different assays, including the l,l-diphenyl-2picrylhydrazyl radical test by TLC and spectrophotometry, inhibition of xanthine oxidase (XO) activity, and total phenolics content. Five plants showed high scavenging potential; their total phenolics content was also high. The extracts from four plants inhibited the activity of XO. Two of the most promising plants, T. diffusa and J. mollis, did not show cytotoxicity. Considering that antioxidants prevent lipid peroxidation in foods and help in the treatment and prevention of degenerative illness, these two species are good candidates to be considered and further evaluated as natural additives in foods to provide protection against oxidative degradation.

Reagents: The syntheses were carried out using commercially available reagents. Platinum (II) acetylacetonate [Pt(acac) 2 , Pt 48.0% min] was purchased from Alfa Aesar, Oleylamine (OAm, 80-90%) from Acros Organics, Oleic acid (OLA) from Guangdong Xilong Chemical Co. Ltd. PVP (K30, AR), benzyl alcohol, n-butylamine from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). Carbon nanotubes (CNTs) were purchased from Shenzhen Nanotech Port Co. Ltd (NTP, Shenzhen, China). Cerium dioxide and P25 were purchased from Sigma Aldrich and Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China), respectively. CO (99.99%) was purchased from Linde Gas. All chemicals were used as received without further purification. In a typical synthesis of Pt nanocubes, Platinum(II) acetylacetonate (20 mg), support (e.g., CNTs, CeO 2 or P25) (50 mg) were mixed together with 10 mL benzyl alcohol in a glass pressure vessel. The resulting mixture after stirring at room temperature for 5 min was charged with CO to 1 bar and then heated in oil bath which was preheated to 180°C for 3 h with vigorous stirring. The resulting products were collected by centrifugation, and washed several times with ethanol. In a typical synthesis of the Pt NPs-CNTs-PVP, Platinum(II) acetylacetonate (20 mg), poly(vinylpyrrolidone) (K30, 320.0 mg), Carbon nanotubes (50 mg) were mixed together with 10 mL benzyl alcohol in a glass pressure vessel. The resulting mixture after stirring at room temperature for 5 min was charged with CO to 1 bar and then heated in oil bath which was preheated to 200°C for 1.5 h with vigorous stirring. The resulting products were collected by centrifugation, and washed several times with ethanol and acetone.

Reagents: Pt(II) acetylacetonate (Pt(acac) 2 ) was purchased from Alfa Aesar, oleylamine was purchased from Sigma-Aldrich, Ni(II) acetylacetonate (Ni(acac) 2 ), HAuCl 4 . 4H 2 O, and n-butylamine were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). All other chemicals were of analytical grade or better quality. Ultrapure water (Millipore, ≥18 MΩ cm) was used throughout. Instrumentation: Electrochemical experiments were conducted on a CHI760D electrochemical workstation (CH Instrument Co., USA). A conventional three-electrode system included a glassy carbon RDE (diameter 5 mm, Pine Research Instrumentation) coated with catalysts, a Pt auxiliary electrode and a leak-free saturated calomel reference electrode (SCE). All the potentials are reported with respect to the reversible hydrogen electrode (RHE) and all electrochemical data were obtained at room temperature (25 o C). TEM and HRTEM studies were performed on a TECNAI F-30 high-resolution transmission electron microscopy operating at 300 kV. The samples were prepared by dropping ethanol dispersions of the samples onto 300-mesh carbon-coated copper grids and immediately evaporating the solvent. SEM studies were performed on a Hitachi S4800 scanning electron microscope with a field emission electron gun. The samples were prepared by dropping ethanol dispersions of the samples onto Si substrates and immediately evaporating the solvent. XRD studies were performed on a PANalytical X'pert Pro X-ray diffractometer. Synthesis of Au nanowires: HAuCl 4 . 4H 2 O (0.2 g) in 2 mL hexane and 2 mL oleylamine was added to the mixture of oleic acid (10 mL) and oleylamine (8 mL) at 80 °C under vigorous magnetic

Este trabalho surgiu com o intuito de investigar a infraestrutura nos quesitos "espaço físico e materiais didáticos" como uma adversidade cotidiana do professor de Educação Física da escola pública. Identificando a necessidade de uma atenção maior vinda por partes das políticas educacionais, das secretarias de educação, a fim de fornecerem suportes acerca de uma Educação Física escolar com qualidade, e isto não seria outra coisa que não, materiais específicos com qualidades, espaços físicos como quadras poliesportivas e outros a disposição desta disciplina curricular e de seus alunos. Palavras-chave: Educação física escolar; Infraestrutura; Formação do aluno; Prática pedagógica.

P123 was purchased from J&K Scientific Ltd. (China). Cobalt nitrate hexahydrate (≥ 99.9%, Co(NO 3 ) 2 •6H 2 O), urea (99%, CO(NH 2 ) 2 ) and formaldehyde (37%, CH2O) were purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd. (China). Nafion solution (5%) was purchased from Dupont Co. (USA). 20wt.% Pt/C were purchased from Johnson Matthey Company. Co/N-C was synthesized by a facile method using formaldehyde and urea as carbon and nitrogen sources, cobalt nitrate as cobalt sources. Briefly, 0.65g P123 was dissolved in 40 mL mixture solution, which contained water and ethanol with equal volume ratio, then 10 mmol urea, 0.525 mmol Co(NO 3 ) 2 •6H 2 O and 2 mL formaldehyde were added into the mixture in turn under vigorous stirring. The solution was heated to 75 o C and kept at this temperature for 12 h, followed by heating at 110 o C for further drying. The final dried compound was heated to 800 o C at a rate of 5 o C min -1 under N 2 atmosphere and kept at 800 o C for 2 h. The above as-synthesized Co/N-C was further calcined at 250 o C under air for 3 h, and the final black products were designated as Co@Co 3 O 4 /N-C. X-ray diffractometer with filtered Cu Kα radiation at 40 kV and 40 mA was used for X-ray powder diffraction (XRD) measurements. Transmission electron microscopy (TEM) and highresolution transmission electron microscopy (HRTEM) measurements were completed by using a JEOL JEM-2100 instrument with operating voltage at 200 kV. The X-ray photoelectron spectroscopy (XPS) was with Mg Kα radiation recorded by VG ESCALAB 210 instrument. Raman spectroscopy was recorded using a Renishaw inVia spectrometer (UK). The Co content was analysed by Atomic Absorption Spectrometer (AAS, Thermo S2). The rotating disk electrode (RDE) experiments were performed using MSR electrode rotator (Pine Instrument Co.).

The substitution of oxygen evolution reaction with a thermodynamically favorable small molecule oxidation reaction offers a compelling pathway toward efficient and energy-conserving production of clean hydrogen fuel. Here, we report the rational design and synthesis of ultra-long Pt nanowires (NWs) featuring specific crystal facets, which act as bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR) under alkaline electrolyte. Pt NWs exhibited remarkable performance, requiring only 0.61 V to obtain 10 mA cm-2 when coupling HER with MOR, substantially lower than the 1.76 V demanded for traditional water splitting. The excellent HER and MOR performance could be primarily attributed to the unique one-dimensional structural characteristics, distinctive crystal facets, and increased specific surface area of the Pt NWs. This research underscores the significance of developing bifunctional electrocatalysts, thereby contributing to the ongoing efforts to advance efficient and energy-conserving hydrogen production.

(1) Synthesis of graphite oxides (GOs). GOs were synthesized from natural graphite powder (Wako) by the modified Hummers method. s1 Briefly, 3 g graphite powder was placed into a flask containing a solution of NaNO 3 (3.47 g)/concentrated H 2 SO 4 (138 mL), and 12 g KMnO 4 was then slowly added to the solution in an ice bath. After heating the resulting mixture at 35-40 °C for 1 h with stirring, 240 mL water was added, and the solution was stirred for 30 min while the temperature was held at 90 -100 °C. To terminate the reaction, 600 mL water was added to the flask, followed by 18 mL of a 30 wt% hydrogen peroxide solution. The synthesized GOs were washed once with a HCl solution, followed by distilled water, and was then dialyzed against ultra pure water. The GOs were dried by freeze drying. (2) Synthesis of Fe/N-graphene, Fe-graphene and N-graphene Five hundred and forty milligrams FeCl 3 •6H 2 O (2.0 mmol) and 0.69 ml pentaethylenehexamine (3.0 mmol) were dissolved in 20 ml ethanol to form Fe-Pentaethylenehexamine complexes in solution. Synthesized GO (200 mg) were dispersed in 6.1 mL of the solution containing the complexes using an ultrasonic bath, and the resulting mixture was then dried at 60 °C. The formed residue was placed at the bottom of a half-closed quartz tube, which was then filled with Ar. After filling, the tube was quickly inserted into a muffle furnace preheated to 900 °C and held for 45 s. After heat treatment, the tube was quickly removed from the furnace and cooled under Ar flow to yield Fe/N-graphene. Fe-graphene and N-graphene were prepared in the similar manner to the Fe/N-graphene except that they were obtained in

It has been shown previously that the morphology and subcellular positioning of the Golgi complex is controlled by actin microfilaments. To further characterize the association between actin microfilaments and the Golgi complex, we have used the Clostridium botulinum toxins C2 and C3, which specifically inhibit actin polymerization and cause depolymerization of F-actin in intact cells by the ADP ribosylation of G-actin monomers and the Rho small GTP-binding protein, respectively. Normal rat kidney cells treated with C2 showed that disruption of the actin and the collapse of the Golgi complex occurred concomitantly. However, when cells were treated with C3, the actin disassembly was observed without any change in the organization of the Golgi complex. The absence of the involvement of Rho was further confirmed by the treatment with lysophosphatidic acid or microinjection with the constitutively activated form of RhoA, both of which induced the stress fiber formation without affecting...

Direct ethanol fuel cells are considered indispensable and prospective energy storage devices due to their high volumetric energy density. Platinum (Pt) and Pt-based alloys are regarded as the most effective catalysts for both oxygen reduction reaction (ORR) and ethanol oxidation reaction. To further enhance the catalytic performance of the catalyst, it is necessary to improve the mass activity and utilization efficiency of Pt. In this work, we report a strategy for fabricating ordered mesostructured platinum-palladium alloy nanotubes (MPPNs) with high hierarchical porosity (68%) and abundant exposed active edge sites. MPPNs exhibit excellent catalytic activity and stability for ORR, with a mass activity approximately 7.4 times higher than that of the commercial Pt/C catalyst. After 20 k cycles of accelerated durability test for ORR, MPPNs demonstrate impressive retention of their original mass activity, maintaining a value of 93.9%. Furthermore, they display superior catalytic activity and stability for ethanol oxidation reactions, with a mass activity about 2.4 times higher than that of commercial Pt/C. After the 2,000 scan cycles, the mass activity remains at 84.5% of initial performance. Both experimental and theoretical studies reveal that the synergistic effect of neighboring (111) and (100) facets on the edge sites plays a critical role in enhancing the electrocatalytic selectivity, activity and stability.

Fuel cells are foreseen to have an important role in sustainable energy systems, provided that catalysts with higher activity and stability are developed. In this study, highly active sputtered thin films of platinum alloyed with yttrium (Pt3Y) are deposited on commercial gas diffusion layers and their performance in a proton exchange membrane fuel cell is measured. After acid pretreatment, the alloy is found to have up to 2.5 times higher specific activity than pure platinum. The performance of Pt3Y is much higher than that of pure Pt, even if all of the alloying element was leached out from parts of the thin metal film on the porous support. This indicates that an even higher performance is expected if the structure of the Pt3Y catalyst or the support could be further improved. The results show that platinum alloyed with rare earth metals can be used as highly active cathode catalyst materials, and significantly reduce the amount of platinum needed, in real fuel cells.

Steady-state polarization curves, X-ray photoelectron spectroscopy, and impedance spectroscopy were used to explore the electrochemical properties for carbon steel in alkaline electrolytes. The complex-capacitance representation allowed determination of a capacitance value at high frequency, from which the oxide film thickness could be estimated. These results are in good agreement with values obtained using the power-law model, providing a single mathematical model that is shown to apply in both the anodic and cathodic domains for the characterization of an oxide layer.

A new mechanism of O 2 reduction, which follows different principles than those generally accepted for describing ORR reduction on heteroatom-doped carbons, is suggested. It is based on the ability of oxygen to strongly adsorb in narrow hydrophobic pores. In this respect, a cellular vitreous carbon foamgraphene oxide composite was synthesized. The materials were doped with sulfur and nitrogen and/or heat-treated at 950 o C in order to modify their surface chemistry. The resultant samples presented a macro/microporous nature and were tested as ORR catalysts. To understand the reduction process, their surface was extensively characterized from the texture and chemistry points of view. The treatment applied markedly changed the volumes of small micropores and the surface hydrophilicity/polarity character. The results showed that the electron transfer number was between 3.87-3.96 and onset potential reached 0.879 V for the best performing sample. It is noteworthy that the best performing sample has the highest volume of pores smaller than 0.7 nm while no heteroatom doping. The hydrophobicity and the strong adsorption forces provided by these pores to pull oxygen inside are the possible reasons for the observed excellent performance. A decrease in the volume of these pores resulted in a decrease in the catalytic performance. When the surface was modified with heteroatoms, the performances further worsened because of the induced hydrophilicity.

Mesoporous heteroatom-doped carbon-based nanomaterials are very promising as catalysts for electrochemical energy conversion and storage. We have developed a one-step catalytic chemical vapor deposition method to grow a highly graphitized graphene nanoflake (GF)–carbon nanotube (CNT) hybrid material doped simultaneously with single atoms of N, Co, and Mo (N–Co–Mo–GF/CNT). This high-surface-area material has a mesoporous structure, which facilitates oxygen mass transfer within the catalyst film, and exhibits a high electrocatalytic activity and stability in oxygen reduction and evolution reactions (ORR and OER) in alkaline media. We have shown that in this metal (M)–N–C catalyst, M (Co, Mo)–C centers are the main sites responsible for OER, while, for ORR, both M and N–C centers synergistically serve as the active sites. We systematically investigated tuning of the ORR and OER activity of the porous catalyst depending on the choice of the underlying substrate. The ORR kinetic current ...

The in-plane penetration depth of Sr0.88La0.12CuO2+x thin films at various doping obtained from oxygen reduction has been measured, using AC susceptibility measurements. For the higher doping samples, the superfluid density deviates strongly from the s-wave behavior, suggesting, in analogy with other electron-doped cuprates, a contribution from a nodal hole pocket, or a small gap on the Fermi surface such as an anisotropic s-wave order parameter. The low value of the superfluid densities, likely due to a strong doping-induced disorder, places the superconducting transition of our samples in the phase-fluctuation regime.

www.whxb.pku.edu.cn 符合独立五元环规则的 C 100 (417)Cl 28 形成机理的密度泛函理论研究 尹凡华，谭凯 * 厦门大学化学化工学院，福建省理论与计算重点实验室，福建 厦门 361005 摘要：实验上捕获到 C100(417)Cl28，但其形成机理仍不清楚。本文采用密度泛函理论(DFT)方法研究了生成 C100(417)Cl28 的 反应机理，考虑了可能的经 Stone-Wales (SW)转化、直接氯化和来自于骨架转变等反应路径。结果表明：C100(417)Cl28 形 成的最主要来源是通过 C102(603)骨架转变，即经历氯化、C2 失去和 SW 转变而来。该结果能很好解释实验结果，对富勒烯 氯化物的合成提供了理论依据。 关键词：密度泛函理论；富勒烯氯化物；骨架转变 中图分类号：O641

The bioelectrocatalytic (oxygen reduction reaction, ORR) properties of the multicopper oxidase CueO immobilized on gold electrodes were investigated. Macroscopic electrochemical techniques were combined with in-situ scanning tunneling microscopy (STM) and surface enhanced Raman spectroscopy (SERS) at the ensemble and at the single molecule level. Self-assembled monolayer of mercaptopropionic acid, cysteamine and p-aminothiophenol were chosen as redox mediators. The highest ORR activity was observed for the protein attached to amino terminated adlayers. In-situ STM experiments revealed that the presence of oxygen causes distinct structure and electronic changes in the metallic centers of the enzyme, which determine the rate of intramolecular electron transfer and, consequently, affect the rate of electron tunneling through the protein. Complementary Raman spectroscopy experiments provided access for monitoring structural changes in the redox state of the T1 copper center of the immobilized enzyme during the CueO-catalyzed oxygen reduction cycle. These results unequivocally demonstrate the existence of a direct electronic communication between the electrode substrate and the Type 1 copper center.