Selective Area Growth and Characterization of GaN Nanorods Fabricated by Adjusting the Hydrogen Flow Rate and Growth Temperature with Metal Organic Chemical Vapor Deposition

CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposition （MOCVD）. The SAG template is obtained by nanospherical-lens photolithography. It is found that increasing the flow rate of 1-12 will change the CaN crystal shape from pyramid to vertical rod, while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale. Finally the CaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H2：N2 ratio is 1：1 and the growth temperature is 1030℃. The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy. The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.

Advanced heterolytic H_(2) adsorption of K-added Ru/MgO catalysts for accelerating hydrogen storage into aromatic benzyltoluenes

Herein,we report a highly active K-added Ru/MgO catalyst for hydrogen storage into aromatic benzyltoluenes at low temperatures to advance liquid organic hydrogen carrier technology.The hydrogenation activity of Ru/K/MgO catalysts exhibits a volcano-shaped dependence on the K content at the maximum with 0.02 wt%.This is in good agreement with the strength and capacity of H_(2) adsorption derived from basicity,despite a gradual decrease in the textural property and the corresponding increase in the Ru particle size with increasing the K content.Density functional theory calculations show that heterolytic hydrogen adsorption properties(strength and polarization)are facilitated up to a specific density of K on the Ru–MgO interface and excessive K suppresses heterolytic H_(2) adsorption by direct interaction between K and hydrogen,assuring the hydrogenation activity and H_(2) adsorption capability of Ru/K/MgO catalysts.Hence,the Ru/K/MgO catalyst,when K is added in an optimal amount,is highly effective to accelerate hydrogen storage kinetics at low temperatures owing to the enhanced heterolytic H_(2) adsorption.

Numerical Study on the Process of Chemical Looping Hydrogen Production with Multiple Circulating Fluidized Bed Reactors

Hydrogen is an attractive energy carrier due to the high conversion efficiency and low pollutant emission.Chemical looping hydrogen production(CLHP)is an available way for producing high purity hydrogen with relatively low penalty energy and CO_(2)is captured simultaneously.Three reactors are usually contained for CLHP system including air reactor(AR),fuel reactor(FR)and steam reactor(SR).In current work,we focus on the performance of CLHP system,which is the basement for operation and design.Numerical simulations are carried out for analyzing the flow behavior and the numerical structure is built according to the experimental unit constructed at Southeast University,China.Results show that the operation of L-valve influences most the solid circulating rate of system and particles pass L-valve easily with large aeration rate.Mass distribution results indicate that fuel reactor has the capacity for particles storage.Increase of gas inlet rate of steam reactor leads to more particles leave steam reactor and accumulate into fuel reactor.L-valve can prevent the gas leakage between reactors and it will be adopted for reactive unit.Combining the operation of fuel reactor and L-valve,the system can reach steady state and get the regulating ability.

3D CFD modeling of acetone hydrogenation in fixed bed reactor with spherical particles

Acetone hydrogenation in a fixed bed reactor packed with spherical catalyst particles was simulated to study the effects of inlet gas velocity and particle diameter on hydrogenation reaction. Computational results show that the catalyst particles in the reactor are almost isothermal, and the high isopropanol concentration appears at the lee of the particles. With the increase of inlet velocity, the outlet isopropanol mole fraction decreases, and the total pressure drop increases drastically. Small diameter catalyst particles are favorable for acetone hydrogenation, but result in large pressure drop.