Electrocatalytic water splitting is one of the most desirable ways to produce hydrogen, which is a clean and sustainable energy source. Improving the formation and the exposure of active sites is a ...key issue in the design of cost-effective and efficient metal-based electrocatalysts, especially for noble metals, in order to cut down the metal content and improve the mass activity of the metals, while maintaining high catalytic activity. Herein, we report a high-performance Ru-based electrocatalyst consisting of Ru single atoms and Ru nanoclusters encapsulated in highly porous N-doped carbon with abundant hierarchical pores (Ru/p-NC). Remarkably, Ru/p-NC shows excellent HER activity in 1.0 M KOH with a low overpotential of 10 mV at 10 mA cm
−2
, a small Tafel slope of 17 mV dec
−1
as well as good durability for 24 h, outperforming commercial Pt/C and Ru/C catalysts. More importantly, the mass activity and turnover frequency (based on Ru loading) of Ru/p-NC are ultrahigh owing to the low loading of Ru, which are 17 A mg
Ru
−1
and 8.9 H
2
s
−1
, respectively, at a very low overpotential of 25 mV. Experimental results indicate that the porous N-doped carbon support not only leads to exposed active sites but also interacts strongly with the Ru moieties. In addition, it tunes the electronic structure of the catalyst, boosts the stability as well as facilitates mass transport and charge transfer kinetics. This work provides a new route for the synthesis of metal-based porous N-doped carbon hybrid electrocatalysts with abundant exposed active sites and strong metal-support interaction for energy conversion.
Ruthenium single atoms and ruthenium nanoclusters dispersed in hierarchically porous N-doped carbon significantly increase the Ru atom efficiency towards excellent electrocatalytic HER activity in alkaline media.
The roles of soluble Fe and Ni species in the alkaline oxygen evolution reaction (OER) at a Ni anode are reported. The Fe impurities in the electrolyte turn out to be insufficient to directly improve ...the OER activity. The Ni(OH)2/NiOOH film undergoes chemical dissolution to give a stable Ni(ii) species that plays a hindering role in the OER.
Low‐cost and efficient bifunctional catalysts are urgently needed for overall water splitting used in large‐scale energy storage. In this study, we develop a nickel and iron (di)sulfide (Ni−Fe−S) ...composite catalyst that is in situ synthesized and fixed within the intergranular nanopores inside high pure polycrystalline graphite. Two precursor solutions (reactants) may permeate the graphite intergranular pores to a depth of more than 3.5 mm. The nanoscale pores serve as an array of nanoreactors for the synthesis of the Ni−Fe−S nanoparticles under conditions much milder than usual. The prepared catalyst efficiently catalyzes both the hydrogen and oxygen evolution reactions (HER and OER) in 1.0 M KOH. It delivers a current density of 400 mA cm−2 at a full cell voltage of around 2.3 V without considerable activity decay over 24 h electrolysis. The active species of the catalyst are different for the HER and OER and discussed accordingly. The synthesis strategy based on the nanopores in a monolithic conductive substrate proves to be a simple, efficient, and promising way to prepare electrocatalysts that are cheap, abundant, and industrially attractive.
Defect Makes Perfect: The intergranular defects/nanopores inside graphite were used as an array of nanoreactors for in situ synthesizing a bifunctional catalyst. The graphite substrate constitutes a monolithic and rigid conductive medium surrounding and separating the catalyst particles, thereby lowering the electron transfer barrier between them and enhances the robust stability of the catalyst nanoparticles.
Studies on the relationship between osteoporosis and intervertebral disc degeneration (IVDD) are inconsistent. Therefore, we assessed whether IVDD is affected by vertebral osteoporosis in ...ovariectomized mice and investigated the underlying pathogenesis of IVDD related to osteoporosis.
Thirty healthy female C57BL/6 J mice aged 8 weeks were randomly divided into two groups: a control group (sham operation, n = 15) and an ovariectomy group (OVX; bilateral ovariectomy, n = 15). At 12 weeks after surgery, the bone quantity and microstructure in the lumbar vertebra and endplate as well as the volume of the L4/5 disc space were evaluated by microcomputed tomography (micro-CT). The occurrence and characteristic alterations of IVDD were identified via histopathological staining. The osteoclasts were detected using tartrate-resistant acid phosphatase (TRAP) staining. Type II collagen (Col II), osterix (OSX), osteopontin (OPN), and vascular endothelial growth factor (VEGF) expression in the intervertebral disc were detected by immunohistochemical analysis.
OVX significantly increased the body weight and decreased the uterus weight. Micro-CT analysis showed that osteoporosis of the vertebra and osteochondral remodeling of the endplate were accompanied by an increase in the endplate porosity and a decrease in the disc volume in the OVX group. Likewise, histological evaluation revealed that IVDD occurred at 12 weeks after ovariectomy, with features of endochondral ossification of the endplate, loose and broken annulus fibrosus, and degeneration of nucleus pulposus. TRAP staining showed that numerous active osteoclasts appeared in the subchondral bone and cartilaginous endplate of OVX mice, whereas osteoclasts were rarely detected in control mice. Immunohistochemical analysis demonstrated that the expression of osterix was significantly increased, notably in the endplate of OVX mice. In addition, Col II was decreased in the ossification endplate and the degenerative annulus fibrosus, where OPN and VEGF expressions were elevated in OVX mice.
OVX induced vertebral osteoporosis and osteochondral remodeling of the cartilaginous endplate contributing to the angiogenesis and an increase in porosity of the bone-cartilage surface, and also affected the matrix metabolism which consequently had detrimental effects on the intervertebral disc. Our study suggests that preserving the structural integrity and the function of the adjacent structures, including the vertebrae and endplates, may protect the disc against degeneration.
Platinum usually offers the most effective active center for hydrogen evolution reaction (HER), because of the optimal trade‐off between the adsorption and desorption of hydrogeN atoms (H*) on Pt ...atoms. Herein, we report an unusual result regarding the active center of a HER catalyst, which was synthesized by electrodepositing traces of Pt nanoparticles (NPs) into a porous nitrogen‐rich dodecahedron matrix derived from zeolitic imidazolate framework ZIF‐8. With an ultra‐low Pt loading of 2.76 μg cm−2, the N‐Pt‐bonded catalyst can produce a current density of 117 mA cm−2 for the HER in 1.0 m H2SO4 at an overpotential of 50 mV, whereas the commercial Pt/C (300 μg cm−2 Pt) can only reach 50 mA cm−2 under the same conditions. Cyclic voltammetry demonstrates that both the H* adsorption and the Pt oxidation are not allowed to occur on this catalyst, due to a full surface coverage of the trace Pt NPs by imidazole. The results from the specially designed experiments indicate that the imidazole N atoms may act as proton anchor‐sites for the HER due to their electron donor nature. Density functional theory calculations also support a catalytic HER mechanism centered at the Pt‐supported N active center, which needs a Gibbs free energy of H* absorption (ΔGH*) significantly smaller than the absolute value of ΔGH* on the Pt(111) surface. We hope that the results of this study will encourage the research on novel N‐centered catalysts for the HER.
Role reversal: Imidazole N atoms prove to be the real active center of a highly efficient ZIF‐8‐derived electrocatalyst for hydrogen evolution reaction (HER), even in the presence of trace Pt (a well‐known active center). Neither H* adsorption nor Pt oxidation can occur on the nonexposed Pt surface (fully covered by imidazole).
The prognostic value of cytokeratin 19 fragment (CYFRA 21 - 1) and Ki67 in advanced non-small cell lung cancer (NSCLC) patients with wild-type epidermal growth factor receptor (EGFR) remains to be ...explored.
In this study, 983 primary NSCLC patients from January 2016 to December 2019 were retrospectively reviewed. Finally, 117 advanced NSCLC patients with wild-type EGFR and 37 patients with EGFR mutation were included and prognostic value of CYFRA 21 - 1 and Ki67 were also identified.
The patients age, smoking history and the Eastern Corporative Oncology Group (ECOG) performance scores were significantly different between CYFRA21-1 positive and negative groups (p < 0.05), while no significant differences were found in Ki67 high and low groups. The results of over survival (OS) demonstrated that patients with CYFRA21-1 positive had markedly shorter survival time than CYFRA21-1 negative (p < 0.001, For whole cohorts; p = 0.002, For wild-type EGFR). Besides, patients with wild-type EGFR also had shorter survival times than Ki67 high group. Moreover, In CYFRA 21 - 1 positive group, patients with Ki67 high had obviously shorter survival time compared to patients with Ki67 low (median: 24vs23.5 months; p = 0.048). However, Ki67 could not be used as an adverse risk factor for patients with EGFR mutation. Multivariate cox analysis showed that age (HR, 1.031; 95%CI, 1.003 ~ 1.006; p = 0.028), Histopathology (HR, 1.760; 95%CI,1.152 ~ 2.690; p = 0.009), CYFRA 21 - 1 (HR, 2.304; 95%CI,1.224 ~ 4.335; p = 0.01) and Ki67 (HR, 2.130; 95%CI,1.242 ~ 3.652; p = 0.006) served as independent prognostic risk factor for advanced NSCLC patients.
Our finding indicated that CYFRA 21 - 1 was an independent prognostic factor for advanced NSCLC patients and Ki67 status could be a risk stratification marker for CYFRA 21 - 1 positive NSCLC patients with wild-type EGFR.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Ferrate(
vi
), FeO
4
2−
, is a very powerful oxidant that can oxidize a wide variety of inorganic and organic compounds. However, the mechanisms of many of these oxidation reactions have not been ...studied in detail. In this work, we have investigated the kinetics and mechanism of the oxidation of 4-alkylbenzenesulfonates by ferrate in aqueous solutions at pH 7.45-9.63 by UV/Vis spectrophotometry. The reactions are first order with respect to both ferrate and 4-alkylbenzenesulfonate. The second-order rate constants for the oxidation of 4-isopropylbenzenesulfonate by ferrate at 25 °C and
I
= 0.3 M are found to be (5.86 ± 0.08) × 10
−1
M
−1
s
−1
and (4.11 ± 1.50) × 10
−3
M
−1
s
−1
for Fe(O)
3
(OH)
−
and FeO
4
2−
, respectively, indicating that Fe(O)
3
(OH)
−
is two orders of magnitude more reactive than FeO
4
2−
and is the predominant oxidant in neutral and slightly alkaline solutions. This is further supported by the effect of the ionic strength on the rate constant. No solvent kinetic isotope effect (KIE) was found but a moderate primary KIE = 1.6 ± 0.1 was observed in the oxidation of 4-ethylbenzenesulfonate and 4-ethylbenzenesulfonate-d
9
. Alkyl radicals were trapped by CBrCl
3
in the oxidation of alkylarenes by ferrate. Combined with DFT calculations, a hydrogen atom transfer (HAT) mechanism was proposed for the reactions between Fe(O)
3
(OH)
−
and 4-alkylbenzenesulfonates.
Based on the kinetic study and DFT calculations, the mechanism of the oxidation of alkylbenzenesulfonates by ferrate(VI) in aqueous solutions is found to be hydrogen atom transfer (HAT).
Lateral gradient coatings displaying various compositions and microstructures along a single surface are desirable for material screening. Here we report a successful application of bipolar ...electrochemistry to deposit lateral gradient polypyrrole films on a graphite strip substrate. The gradient film shows varying morphologies and a wettability gradient along the length of the bipolar electrode, with superabsorbent property in the middle portion of the film. The film was use as a catalyst matrix for ethanol oxidation in alkaline electrolyte. Aqueous Ni(NO3)2 solution as the catalyst precursor was absorbed into the film. Area-step cyclic voltammetry was used to evaluate the electrocatalytic activity of various local parts along the gradient film to ethanol oxidation. The local surface with the highest catalytic activity was screened out and the excellent catalytic activity is attributed to the outstanding properties of this zone in both water absorption and electrical conductivity. The nickel oxide catalyst can be highly dispersed in the nanoporous network polymer matrix, due to the uniform penetration of the aqueous precursor solution into the superabsorbent film. XPS and EIS analyses support the catalytic mechanism based on the redox transition between NiOOH and Ni(OH)2. This work indicates that loading aqueous catalyst precursors into superabsorbent conducting polymer films may be a promising method for the preparation of electrocatalysts.
Display omitted
•Bipolar electrodeposition of conducting polymer films with a lateral gradient.•Area-step voltammetry for position-resolved characterization of gradient films.•A polypyrrole film with varying morphologies and a wettability gradient.•Superabsorbent part of the film suitable for loading aqueous catalyst precursors.
Stannous sulfate is commonly used as an additive in the positive lead pastes of lead-acid batteries, but its real function and mechanism are still vague and need further study. The present work ...investigates the intrinsic effects of tin additives on the positive electrode performance under well-controlled experimental conditions. The tin additives are added in three ways: the SnSO
4
dissolved in 4.5 M H
2
SO
4
electrolyte, the metal Sn melted in metal Pb substrate, and the SnSO
4
mixed in homemade industrial lead pastes. A series of evolutions are clearly revealed in structure, composition, and redox activity of the positive active materials with the content of Sn. Both the SnSO
4
in the electrolyte and in the positive lead pastes have a significant inhibiting effect on the transformation between PbSO
4
and PbO
2
, leading to a decrease in the charge/discharge capacities with increasing content of SnSO
4
. A similar but weaker inhibiting effect was also found for the Sn melted in the Pb-Sn alloys. The SnSO
4
has a significant enhancement effect on the grain size of PbSO
4
/PbO
2
, which increases the resistance of the solid-phase transformation deep inside the grains during the charge/discharge. All these results do not support the use of SnSO
4
in the positive pastes of lead-acid batteries.
Graphical abstract
A simple electrodeposition approach to grow multi-laminated copper particles on two conductive substrates is presented. Morphological and structural characterization was performed using SEM and XRD. ...The copper crystallites are preferentially oriented with {111} planes parallel to the substrate surfaces, providing an optimum interface for methanol oxidation. There are a large number of edges, corners, and atomic steps around individual multi-laminated nanostructured particles. The excellent electrocatalytic activity of the particles to methanol oxidation in alkaline solutions is demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. The presence of the conductive poly(2-amino-5-mercapto-1,3,4-thiadiazole) interlayer between the Cu particles and the carbon paste substrate results in larger specific surface areas of the particles and smaller charge-transfer resistances of methanol oxidation reaction in the lower potential range. Such an anisotropic laminated structure of non-noble metal nanomaterials deserves further investigation for finding a suitable alternative to noble metal-based anodic catalysts in fuel cells.
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