RESUMO
Ruthenium (Ru) is an ideal substitute to commercial Pt/C for the acidic hydrogen evolution reaction (HER), but it still suffers from undesirable activity due to the strong adsorption free energy of H* (ΔGH*). Herein, we propose crystalline phase engineering by loading Ru clusters on precisely prepared cubic and hexagonal molybdenum carbide (α-MoC/ß-Mo2C) supports to modulate the interfacial interactions and achieve high HER activity. Advanced spectroscopies demonstrate that Ru on ß-Mo2C shows a lower valence state and withdraws more electrons from the support than that of Ru on α-MoC, indicative of a strong interfacial interaction. Density functional theory reveals that the ΔGH* of Ru/ß-Mo2C approaches 0 eV, illuminating an enhancement mechanism at the Ru/ß-Mo2C interface. The resultant Ru/ß-Mo2C exhibits an encouraging performance in a proton exchange membrane water electrolyzer with a low cell voltage (1.58 V@ 1.0 A cm-2) and long stability (500 h@ 1.0 A cm-2).
RESUMO
A simple, specific, and accurate high-performance liquid chromatographic method, using UV detection for the determination of penciclovir in human plasma, is described. Chromatographic separation is performed on a BDS-C(18) column using a mixture of phosphate buffer (20mM, pH adjusted to 7.5 with phosphoric acid), methanol, and acetonitrile (94:3:3, v/v/v) as mobile phase. The wavelength of the UV detector is set at 254 nm. The flow-rate is 1.0 mL/min. The assay is linear over the concentration range of 0.1-5.0 microg/mL for penciclovir (r > 0.9996). The limit of quantitation for penciclovir in human plasma is 0.1 microg/mL. The relative standard deviation is less than 7.0% for all the analytes. The method is successfully applied to a randomized crossover bioequivalence study of two different famciclovir capsules in 20 healthy volunteers.
