The water-soluble cationic nickel(II) complex of meso-tetrakis(4-N-methylpyridyl)porphyrin (1) can electrocatalyze water oxidation to O2 in neutral aqueous solution (pH 7.0) with the onset of the catalytic wave appearing at ∼1.0 V (vs NHE). The homogeneous catalysis with 1 was verified. Catalyst 1 exhibited water oxidation activity in a pH range 2.0-8.0 and had a strict linear dependence of catalytic current on its concentration. After 10 h of constant potential electrolysis at 1.32 V (vs NHE), a negligible difference of the solution was observed by UV-vis. In addition, inspection of the working electrode by electrochemistry, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDX) showed no sign of deposition of NiOx films. These results strongly argued that 1 is a real molecular electrocatalyst for water oxidation. The turnover frequency (TOF) for this process was 0.67 s(-1) at 20 °C. On the basis of results from the kinetic isotope effect (KIE) and inhibition experiments, electrochemical studies in various buffer solutions with different anions and pHs, and DFT calculations, a catalytic cycle of 1 for water oxidation via a formally Ni(IV) species was proposed.

Water oxidation is the key step in natural and artificial photosynthesis for solar-energy conversion. As this process is thermodynamically unfavorable and is challenging from a kinetic point of view, the development of highly efficient catalysts with low energy cost is a subject of fundamental significance. Herein, we report on iron-based films as highly efficient water-oxidation catalysts. The films can be quickly deposited onto electrodes from Fe(II) ions in acetate buffer at pH 7.0 by simple cyclic voltammetry. The extremely low iron loading on the electrodes is critical for improved atom efficiency for catalysis. Our results showed that this film could catalyze water oxidation in neutral phosphate solution with a turnover frequency (TOF) of 756 h(-1) at an applied overpotential of 530 mV. The significance of this approach includes the use of earth-abundant iron, the fast and simple method for catalyst preparation, the low catalyst loading, and the large TOF for O2 evolution in neutral aqueous media.

Multivariate metal-organic frameworks with active Fe/Ni building blocks that are spatially arranged in an open structure are synthesized and explored for oxygen evolution reaction. The heterogeneity and porosity of this system prove to show synergy effect and give low onset overpotential at 170 mV. These MOFs are further fabricated into thin films over nickel foam by controlled electrochemical deposition to improve the surface conductivity and the overall stability. The Fe/Ni metal-organic framework film exhibits outstanding electrocatalytic activity with low overpotential of 270 mV at 10 mA cm(-2), small Tafel slope, high Faradaic efficiency, high turnover frequency, and great stability.

due to their different redox behaviors and/or diverse solubility product constants of these metal ions with hydroxide ions. Herein, we report a stepwise electrodeposition strategy to make an ultrathin NiFe film, whose catalytic activity for water oxidation is significantly improved as compared to the NiFe film formed by a typical cathodic electrolysis method. By using the stepwise strategy, that is first deposition of Ni-based film via cathodic electrolysis followed by the integration of Fe species via anodic CV (Figure 1), the amounts of Ni/Fe-based materials loaded on electrodes can be controlled. In addition, the interconnected reticular film structure resulted from stepwise deposition is favorable to electrocatalytic water oxidation by assisting both mass and charge transportation. This work should therefore be very valuable to film preparation that is interesting in electrocatalysis and other electrochemical studies.Typically, a layer of Ni-based film was first deposited on an electrode by cathodic electrolysis of an Ni(NO 3 ) 2 aqueous solution at an applied potential of −0.80 V versus normal hydrogen electrode (NHE) for 300 s. The electrode was then rinsed and immersed in a freshly prepared FeSO 4 acetate buffer (0.1 m, pH 7.0) under argon for CV incorporation of Fe into the previously formed Ni-based film. The CV deposition was conducted in one cycle of 0.20-1.35 V versus NHE. It is worth noting that prior to the dissolution of FeSO 4 , the acetate buffer is vigorously bubbled with argon for at least 30 min to remove the dissolved O 2 in the solution. Argon protection is essential to prevent the oxidation of Fe II to Fe III by O 2 , a step aimed at well-controlled Fe deposition. [21,22] This NiFe film from stepwise electrodeposition is denoted hereafter as NiFe-SW. The film evolution is illustrated in Figure 1 showing the optical images of the film on indium tin oxide (ITO) electrodes and scanning electron microscopy (SEM) images of the film on glassy carbon (GC) electrodes. The transparent nature of this ultrathin film permits its potential uses in photoactive devices. [21,31,32] The morphologies of electrodeposited films were analyzed by SEM and transmission electron microscopy (TEM). As shown in Figure 2A, Ni-based film from cathodic electrolysis was composed of isolated nanoplates with legible boundaries. Such isolated domains have been commonly observed for films that are electrodeposited using the electrolysis method. [18,23,26] After CV incorporation of Fe into the aforementioned Ni-based film, the resulting NiFe-SW film consisted of uniformly interconnected nanoribbons with porous structures (Figure 2B-D). TEM image of Ni-based film showed nanoplates with a layered morphology and edge steps, which was consistent with typical metal hydroxide structures ( Figure 2E). [45] On the contrary, NiFe-SW film evolved into curly and contorted nanosheets Increasing energy demands and environmental issues related to the use of fossil fuels have forced people to exploit sustainable and carbon-free energy resour...

An ultrathin Fe-based film was prepared by electrodeposition from an Fe(II) solution through a fast and simple cyclic voltammetry method. The extremely low Fe loading of 12.3 nmol cm(-2) on indium tin oxide electrodes is crucial for high atom efficiency and transparence of the resulted film. This Fe-based film was shown to be a very efficient electrocatalyst for oxygen evolution from neutral aqueous solution with remarkable activity and stability. In a 34 h controlled potential electrolysis at 1.45 V (vs NHE) and pH 7.0, impressive turnover number of 5.2 × 10(4) and turnover frequency of 1528 h(-1) were obtained. To the best of our knowledge, these values represent one of the highest among electrodeposited catalyst films for water oxidation under comparable conditions. The morphology and the composition of the catalyst film was determined by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy, which all confirmed the deposition of Fe-based materials with Fe(III) oxidation state on the electrode. This study is significant because of the use of iron, the fast and simple cyclic voltammetry electrodeposition, the extremely low catalyst loading and thus the transparency of the catalyst film, the remarkable activity and stability, and the oxygen evolution in neutral aqueous media.

Alzheimer’s disease (AD) is one of the most prevalent neurodegenerative diseases, yet current therapeutic treatments are inadequate due to a complex disease pathogenesis. The plant polyphenol apigenin has been shown to have anti-inflammatory and neuroprotective properties in a number of cell and animal models; however a comprehensive assessment has not been performed in a human model of AD. Here we have used a human induced pluripotent stem cell (iPSC) model of familial and sporadic AD, in addition to healthy controls, to assess the neuroprotective activity of apigenin. The iPSC-derived AD neurons demonstrated a hyper-excitable calcium signalling phenotype, elevated levels of nitrite, increased cytotoxicity and apoptosis, reduced neurite length and increased susceptibility to inflammatory stress challenge from activated murine microglia, in comparison to control neurons. We identified that apigenin has potent anti-inflammatory properties with the ability to protect neurites and cell viability by promoting a global down-regulation of cytokine and nitric oxide (NO) release in inflammatory cells. In addition, we show that apigenin is able to protect iPSC-derived AD neurons via multiple means by reducing the frequency of spontaneous Ca2+ signals and significantly reducing caspase-3/7 mediated apoptosis. These data demonstrate the broad neuroprotective action of apigenin against AD pathogenesis in a human disease model.

A low-grade pro-inflammatory state is at the pathogenic core of obesity and type 2 diabetes. We tested the hypothesis that the plant terpenoid compound ginsenoside Rb1 (Rb1), known to exert anti-inflammatory effects, would ameliorate obesity, obesity-associated inflammation and glucose intolerance in the high-fat diet-induced obese mouse model. Furthermore, we examined the effect of Rb1 treatment on central leptin sensitivity and the leptin signaling pathway in the hypothalamus. We found that intraperitoneal injections of Rb1 (14 mg/kg, daily) for 21 days significantly reduced body weight gain, fat mass accumulation, and improved glucose tolerance in obese mice on a HF diet compared to vehicle treatment. Importantly, Rb1 treatment also reduced levels of pro-inflammatory cytokines (TNF-α, IL-6 and/or IL-1β) and NF-κB pathway molecules (p-IKK and p-IκBα) in adipose tissue and liver. In the hypothalamus, Rb1 treatment decreased the expression of inflammatory markers (IL-6, IL-1β and p-IKK) and negative regulators of leptin signaling (SOCS3 and PTP1B). Furthermore, Rb1 treatment also restored the anorexic effect of leptin in high-fat fed mice as well as leptin pSTAT3 signaling in the hypothalamus. Ginsenoside Rb1 has potential for use as an anti-obesity therapeutic agent that modulates obesity-induced inflammation and improves central leptin sensitivity in HF diet-induced obesity.

Chronic inflammation is involved in the pathogenesis of obesity and type 2 diabetes. Recently teasaponin, an extract from tea, has been shown to have antiinflammatory effects. We examined the effect of teasaponin on obesity, inflammation, glucose metabolism, and central leptin sensitivity in obese mice fed a high-fat (HF) diet for 16 weeks. Intraperitoneal injections of teasaponin (10 mg/kg, daily) for 21 days significantly decreased the food intake and body weight of HF diet-induced obese mice. Teasaponin treatment also reduced the protein levels of proinflammatory cytokines (TNF-α, IL-6, and/or IL-1β) and nuclear factor-κB signaling (phosphorylated inhibitory-κB kinase and phosphorylated inhibitory-κBα) in adipose tissue and the liver. The antiinflammatory effects of teasaponin were associated with improved glycemic status in the treated animals, evidenced by improved glucose tolerance, homeostasis model assessment, and fasting plasma insulin. In the hypothalamus, teasaponin decreased both proinflammatory cytokines and inflammatory signaling in the mediobasal hypothalamus. Teasaponin treatment also enhanced the anorexigenic effect of central leptin administration, restored leptin phosphorylated signal transducer and activator of transcription-3 (p-STAT3) signaling in the arcuate nucleus, and increased hypothalamic expression of the anorexigenic peptide proopiomelanocortin. These results identify a potential novel application for teasaponin as an antiobesity and antiinflammatory agent.