Design of the Metal Precursors Molecular Structures in Impregnating Solutions for Preparation of Efficient Ni Mo/Al_2O_3 Hydrodesulfurization Catalysts

The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efficient Ni Mo/Al_2O_3 hydrodesulfurization(HDS) catalysts. At first, five typical impregnating solutions were designed; the existing metal precursors, such as [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species in the solutions were confirmed by laser Raman spectroscopy(LRS). The UV-Vis spectra results indicated that the solutions containing both phosphoric acid and citric acid could change the existing form of nickel species. Five corresponding Ni Mo/Al_2O_3 catalysts were prepared by the incipient wetness impregnation method. The LRS analysis results of dried catalysts showed that the above metal precursors could be partly retained on alumina support after impregnation and drying, although the interface reaction between different metal precursors and alumina support unavoidably took place. Then the catalysts were sulfided and characterized by N2 physisorption, TEM and XPS analyses. The results showed that different metal precursors in impregnating solution could mainly result in the difference in both the morphology of(Ni)Mo S2 slabs and the promoting effect of Ni species. The catalyst prepared mainly with [P2Mo5O23]^(6-)-like species used as precursors exhibited worse dispersion of(Ni)Mo S2 slabs and lower ratio of Ni–Mo–S active phases than the one with [Mo4(citrate)2O11]^(4-)-like species. Promisingly, the catalyst prepared with co-existing [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species showed better hydrodesulfurization activity for 4,6-DMDBT thanks to its more well-dispersed Ni–Mo–S active phases.

Sorption and Diffusion Behavior of Carbon Dioxide into Poly（l-lactic acid） Films at Elevated Pressures

Equilibrium sorption amount, desorption diffusion coefficients and sorption diffusion coefficients of CO2 in poly（l-lactic acid） （PLLA） films at elevated pressures were determined by the gravimetric method, in which the Fick＇s diffusion model was applied to analyze both the desorption and sorption processes. The equilibrium sorption amount of CO2 in PLLA increased with lowering temperature and elevating pressure at the temperature range from 40 to 60 ℃ and pressure from 10^4 to 2x10^4 kPa. Desorption diffusion coefficients were greatly influenced by the equilibrium sorption amount, and they were in the same order of magnitude as the sorption diffusion coefficients. The scan electron microscope （SEM） photos demonstrated that there was no foaming phenomenon of the PLLA film during desorption and sorption processes. The XRD spectra implied that the crystalline degree of PLLA film decreased after CO2 processing. It was concluded that PLLA polymer could be well swollen and plasticized by supercritical CO2.

Boosting carrier dynamics of BiVO_(4) photoanode via heterostructuring with ultrathin BiOI nanosheets for enhanced solar water splitting

Bismuth vanadate(BiVO_(4))has been one of the most promising candidates for solar water splitting while still suffers from poor bulk charge transport that limits its solar to hydrogen conversion efficiency.We demonstrate in this work an efficient strategy for boosting bulk charge transport of BiVO_(4) through the facile impregnation of as-prepared BiVO_(4) photoanode in the precursor solution of ultrathin BiOI nanosheets.Such impregnation creates increased oxygen vacancies in the bulk of BiVO_(4) through the reduction of V^(5+)to V^(4+)by I^(-),which greatly improves bulk separation efficiency for BiVO_(4)-BiOI up to 65.9%at 1.23 V_(RHE) from the original 51.9%of pure BiVO_(4).Moreover,the decoration of the BiOI nanosheets on BiVO_(4) photoanode is also beneficial for addressing the carrier dynamics at surface due to the matched energy levels of BiOI nanosheets and BiVO_(4).The introduced plenty of oxygen vacancies in the bulk of BiVO_(4) and the built-in electric field in BiVO_(4)-BiOI synergistically improve the photocurrent density at 1.23 V_(RHE) up to 3.88 mA cm^(-2).We believe that such facile impregnation strategy will pave an alternative way to the development of highly efficient BiVO_(4) photoanode.