Alkaline oxygen evolution: exploring synergy between fcc and hcp cobalt nanoparticles entrapped in N-doped graphene

Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm^–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H⁺ ion transport.     

Fluid‐structure coupling of linear elastic model with compressible flow models

Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure.     

FeCo-based hybrid MOF derived active species for effective oxygen evolution

Metal-organic frameworks(MOFs) have been regarded as promising catalyst materials due to the richness of coordinately unsaturated metal sites on the surface,which can act as catalytic active centres.In this study,a hybrid MOF material composed of Fe-based MOF and Co-based MOF was prepared with the involvement of graphene oxide nanosheets as additive.It was demonstrated that the hybrid MOF materials showed much higher electro-catalytic activity towards oxygen evolution than the single-phase counterparts.To drive current density of 10 mA cm~(-2),the hybrid CoFe-based MOF only needed an over potential of 290 mV in 1 M KOH.The catalytic activity could sustain for a longer time with only slight current density decrease.During oxygen evolution operation,the MOF catalyst evolved into catalytic active species but kept well the microscale sheet-like structure.It is thus believed that this study will provide an avenue for the development of advanced electrocatalysts.     

桂林傩舞现状及问题研究--以秀峰区张家村为例

受神秘的巫文化影响，桂林傩舞有着悠久的历史，曾经盛极一时，但近年来逐渐趋于衰退。通过实地考察张家村傩舞，可以发现桂林傩舞艺术面临着缺乏继承人、观赏性不足、舞蹈造型和手势表达失传、道具不精、基层教育不重视、表演人员经济困难等生存困境。当地政府应该加强宣传力度，加大资金投入，培养傩舞表演的继承人和道具制作的传承人，强化对傩舞的理论与实践研究，不断提炼傩舞的特色内涵，促进桂林傩舞的保护和传承。