Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H2 energy generated via electrolytic water. Engineering favorable defects on the electrocatalysts to ...provide accessible active sites can boost the sluggish reaction thermodynamics or kinetics. Herein, Col_xS nanosheets were designed and grown on reduced graphene oxide （rGO） by controlling the successive two-step hydrothermal reaction. A belt-like cobalt-based precursor was first formed with the assistance of ammonia and rGO, which were then sulfurized into Col_xS by L-cysteine at a higher hydrothermal temperature. Because of the non-stoichiometric defects and ultrathin sheet-like structure, additional cobalt vacancies （V~o） were formed/exposed on the catalyst surface, which expedited the charge diffusion and increased the electroactive surface in contact with the electrolyte. The resulting Col_xS/rGO hybrids exhibited an overpotential as low as 310 mV at 10 mA.cm-2 in an alkaline electrolyte for the oxygen evolution reaction （OER）. Density functional theory calculations indicated that the Vco on the Col_xS/rGO hybrid functioned as catalytic sites for enhanced OER. They also reduced the energy barrier for the transformation of intermediate oxygenated species, promoting the OER thermodynamics.
Gaining insight into the structure evolution of transition-metal phosphides during anodic oxidation is significant to understand their oxygen evolution reaction （OER） mechanism, and then design high- ...efficiency transition metal-based catalysts. Herein, NiCo2Px nanowires （NWs） vertically grown on Ni foam were adopted as the target to explore the insitu morphology and chemical component reconstitution during the anodic oxidation. The major factors causing the transformation from NiCo2Px into the hierarchical NiCo2Px@CoNi（OOH）x NWs are two competing reactions： the dissolution of NiCo2Px NWs and the oxidative re-deposition of dissolved Co^2＋ and Ni^2＋ ions, which is based primarily on the anodic bias applied on NiCo2Px NWs. The well balance of above competing reactions, and local pH on the surface of NiCo2Px NW modulated by the anodic oxidation can serve to control the anodic electrodeposition and rearrangement of metal ions on the surface of NiCo2Px NWs, and the immediate conversion into CoNi（OOH）x. Consequently, the regular hexagonal CoNi（OOH）x nanosheets grew around NiCo2Px NWs. Benefiting from the active catalytic sites on the surface and the sufficient conductivity, the resultant NiCo2Px@CoNi（OOH）x arrays also display good OER activity, in terms of the fast kinetics process, the high energy conversion efficiency, especially the excellent durability. The strategy of in-situ structure reconstitution by electrochemical reaction described here offers a reliable and valid way to construct the highly active systems for various electrocatalvtic applications.
High-temperature nitrogen (N) doping boosts the activity of biochars for peroxymonosulfate (PMS) activation, but the N heat loss causes the unsatisfactory catalytic efficiency. Improving the surface ...area for obtaining the high exposure of N sites is a promising solution. Herein, a soft template-KHCO3 etching strategy is used to synthesize the N-doped porous bowl-like carbon (NPBC) with ultrahigh external surface area (1610.8 m2 g−1). The bowl-like structure eliminates inert bulk interior and allows unobstructed mass transfer of reactants onto both outer and inner surfaces, while the large pore channels by KHCO3 etching further improves the exposure degree of limited N sites. Although NPBC has only 0.43% N content, 93.1% of bisphenol A (BPA) is removed within 1 min through the electron-transfer pathway by fully utilizing the N active centers, and the kinetic rate constant (k) reaches 5.29 min−1, exceeding reported values by 2–270 times. Moreover, the NPBC/PMS system possesses excellent applicability for various organics and conditions, effectively mineralizes BPA and reduces effluent biotoxicity. A quantitative index W representing N exposure degree is first proposed and shows high linearity with the k values of BPA degradation (R2=0.992, 0 <W<3750 m2 g−1%−1), proving the critical role of W in determining catalytic efficiency.
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•Bowl-like structural engineering was used to design N-doped biochar catalyst.•The NPBC900 possessed superhigh external specific surface area of 1610.4 m2 g−1.•BPA degradation rate constant exceeded reported values by 2–270 times.•The catalytic rate of NPBCs was highly linear with the exposure index of N sites.•BPA was mineralized (75.2%) by NPBC/PMS system in an electron-transfer pathway.
•Boron significantly promoted Fe3+/PAA process for SMT removal.•DFT calculation was conducted to confirm the role of boron.•Both •OH and (R-O•) + Fe(IV) contributed important role in SMT removal.•The ...role of •OH, R-O• and Fe(IV) were also confirmed by DFT calculation.•B/Fe3+/PAA process was an efficient approach for removing antibiotic in nature fresh water.
In this work, boron (B) was used to promote Fe3+/peracetic acid (Fe3+/PAA) for the degradation of sulfamethazine (SMT). An SMT degradation efficiency of 9.1% was observed in the Fe3+/PAA system over 60 min, which was significantly increased to 99.3% in the B/Fe3+/PAA system over 10 min. The B/Fe3+/PAA process also exhibited superior resistance to natural substances, excellent adaptability to different harmful substances, and good removal of antibiotics in natural fresh water samples. The mechanism of action of boron for Fe3+ reduction was determined using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, density functional theory (DFT) calculations, and electrochemical tests. The dominant role of •OH was confirmed using quenching experiments, electron spin resonance (EPR) spectroscopy, and quantitative tests. Organic radicals (R-O•) and Fe(IV) also significantly contribute to the removal of SMT. DFT calculations on the reaction between Fe2+ and the PAA were conducted to further determine the contribution from •OH, R-O•, and Fe(IV) from the perspective of thermodynamics and the reaction pathways. Different boron dosages, Fe3+ dosages, and initial pH values were also investigated in the B/Fe3+/PAA system to study their effect of SMT removal and the production of the reactive species. Fe(IV) production determined the kR-O•+Fe(IV) value suggesting that Fe(IV) may play a more important role than R-O•. A comparison of the results with other processes has also proved that the procedure described in this study (B/Fe3+/PAA) is an effective method for the degradation of antibiotics.
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Gaining insight into the structure evolution of transition-metal phosphides during anodic oxidation is significant to understand their oxygen evolution reaction（OER） mechanism, and then design ...highefficiency transition metal-based catalysts. Herein, NiCo2Px nanowires（NWs） vertically grown on Ni foam were adopted as the target to explore the in-situ morphology and chemical component reconstitution during the anodic oxidation. The major factors causing the transformation from NiCo2Px into the hierarchical NiCo2Px@CoNi（OOH）x NWs are two competing reactions: the dissolution of NiCo2Px NWs and the oxidative re-deposition of dissolved Co2+ and Ni2+ ions, which is based primarily on the anodic bias applied on NiCo2 Px NWs. The well balance of above competing reactions, and local pH on the surface of NiCo2Px NW modulated by the anodic oxidation can serve to control the anodic electrodeposition and rearrangement of metal ions on the surface of NiCo2Px NWs, and the immediate conversion into CoNi（OOH）x. Consequently, the regular hexagonal CoNi（OOH）x nanosheets grew around NiCo2Px NWs.Benefiting from the active catalytic sites on the surface and the sufficient conductivity, the resultant NiCo2Px@CoNi（OOH）x arrays also display good OER activity, in terms of the fast kinetics process, the high energy conversion efficiency, especially the excellent durability. The strategy of in-situ structure reconstitution by electrochemical reaction described here offers a reliable and valid way to construct the highly active systems for various electrocatalytic applications.
Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H sub(2) energy generated via electrolytic water. Engineering favorable defects on the electrocatalysts ...to provide accessible active sites can boost the sluggish reaction thermodynamics or kinetics. Herein, Co sub(1-x)S nanosheets were designed and grown on reduced graphene oxide (rGO) by controlling the successive two-step hydrothermal reaction. A belt-like cobalt-based precursor was first formed with the assistance of ammonia and rGO, which were then sulfurized into Co sub(1-x)S by L-cysteine at a higher hydrothermal temperature. Because of the non-stoichiometric defects and ultrathin sheet-like structure, additional cobalt vacancies (V' sub(Co)) were formed/exposed on the catalyst surface, which expedited the charge diffusion and increased the electroactive surface in contact with the electrolyte. The resulting Co sub(1-x)S/rGO hybrids exhibited an overpotential as low as 310 mV at 10 mA.cm super(-2) in an alkaline electrolyte for the oxygen evolution reaction (OER). Density functional theory calculations indicated that the V' sub(Co) on the Co sub(1-x)S/rGO hybrid functioned as catalytic sites for enhanced OER. They also reduced the energy barrier for the transformation of intermediate oxygenated species, promoting the OER thermodynamics. Figure not available: see fulltext.
Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H2 energy generated via electrolytic water. Engineering favorable defects on the electrocatalysts to ...provide accessible active sites can boost the sluggish reaction thermodynamics or kinetics. Herein, Co1–xS nanosheets were designed and grown on reduced graphene oxide (rGO) by controlling the successive two-step hydrothermal reaction. A belt-like cobalt-based precursor was first formed with the assistance of ammonia and rGO, which were then sulfurized into Co1–xS by L-cysteine at a higher hydrothermal temperature. Because of the non-stoichiometric defects and ultrathin sheet-like structure, additional cobalt vacancies (V’Co) were formed/exposed on the catalyst surface, which expedited the charge diffusion and increased the electroactive surface in contact with the electrolyte. The resulting Co1–xS/rGO hybrids exhibited an overpotential as low as 310 mV at 10 mA·cm–2 in an alkaline electrolyte for the oxygen evolution reaction (OER). Density functional theory calculations indicated that the V’Co on the Co1–xS/rGO hybrid functioned as catalytic sites for enhanced OER. They also reduced the energy barrier for the transformation of intermediate oxygenated species, promoting the OER thermodynamics.
A complete understanding of the pharmacokinetics and pharmacodynamics of diclofenac in dental patients, especially in regard to absorption processes, has challenged pharmaceutical scientists during ...the past two decades because of high intra- and inter-subject variabilities and analytical difficulties encountered at low concentrations in biological fluids. A GC-MS method has been developed and validated by the author with a limit of quantitation of 1 ng/ml in human plasma, 97% recovery, 2% to 12% (%CV) precision and 91% to 105% accuracy. The method is suitable for pharmacokinetic studies. Using this method and applying the Wagner-Nelson approach, three models were proposed for the absorption pharmacokinetics of an enteric-coated diclofenac formulation i.e. pure zero-order absorption pharmacokinetics; pure first-order absorption pharmacokinetics; and a combination of zero-order and first-order absorption pharmacokinetics. Study subjects could be fitted into one of these three models, however, the majority of subjects could only be characterized with the combination zero-order and first-order absorption model. Furthermore, the zero-order path dominated the absorption process in general, which could partially explain the highly variable pharmacokinetics of this compound. The analgesic dynamics of diclofenac in dental patients was also studied. The onset time, peak effect, and time to reach peak effect were measured. The plasma diclofenac concentration was not directly related to the analgesic effect, indicating the existence of an effect compartment, which was proposed and characterized with the Hill equation. Misoprostol has been used to prevent the gastric and duodenal ulcer side effect of diclofenac. This study revealed that pharmacokinetically misoprostol did not show an impact on diclofenac, however, pharmacodynamically it prolonged the analgesic effect following third molar extraction. Tramadol is a relatively new analgesic in the United States. Its (+)-O-desmethyl metabolite (+)-M1 has analgesic activity in animal models. The author characterized the population pharmacokinetics of this metabolite in dental patients and proposed that the pharmacokinetics of M1 was nonlinear. The modeling results suggested that the formation and elimination of M1 were trumadol-dose and M1 plasma-concentration dependent respectively.
We have modified and validated a capillary GC-MS method reported by Kadowaki et al. J. Chromatogr., 308 (1984) 329 for the determination of diclofenac in human plasma by using heptane rather than ...benzene as an extraction agent. In addition, acetone was added to the samples as a deproteination agent which increased the recovery of diclofenac. These revised processes allowed clean extraction and near-quantitative recovery of analyte (>95%). Separation was achieved on an HP-1 column with helium as carrier gas. The parent ion peaks of diclofenac (
m
z
277) and the internal standard, 4′-methoxydiclofenac (
m
z
307), were monitored by a mass-selective detector using the selected-ion monitoring mode. The linear range for the routine assay was from 5 to 2000 ng/ml. The detection and lower quantifiable limits were 0.2 and 1 ng/ml, respectively, with no interference from plasma. The within-day and between-day coefficients of variation for high and medium concentrations were less than 5% and were less than 13% for low concentrations (10 ng/ml). This GC-MS assay method has been used for pharmacokinetic and drug interaction studies in humans.
