Synthesis of Ag–decorated vertical graphene nanosheets and their electrocatalytic efficiencies

Herein, we report the successful preparation of Ag–decorated vertical–oriented graphene sheets (Ag/VGs) via helicon wave plasma chemical vapor deposition (HWP–CVD) and radio frequency plasma magnetron sputtering (RF–PMS). VGs were synthesized in a mixture of argon and methane (Ar/CH4) by HWP–CVD, and then the silver nanoparticles on the prepared VGs were modified using the RF-PMS system under different sputtering times and RF power levels. The morphology and structure of the Ag nanoparticles were characterized by scanning electron microscopy (SEM), and the results revealed that Ag nanoparticles were evenly dispersed on the mesoporous wall of the VGs. X-ray diffraction (XRD) results showed that the diameter of the Ag particles increased with the increase of silver loading, and the average size was between 10.49 nm and 25.9 nm, which were consistent with transmission electron microscopy (TEM) results. Ag/VGs were investigated as effective electrocatalysts for use in an alkaline aqueous system. Due to the uniquely ordered and interconnected wall structure of VGs, the area of active sites increased with the Ag loading, which made the Ag/VGs have high oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) performance. The double–layer capacitance (Cdl) of the Ag/VGs under different silver loadings were studied, and the results showed that highest silver content is the best (1.04 mF/cm2). The results showed that, Ag/VGs expected to be a credible electrocatalytic material.

Off-Axis Current Drive with Helicon Waves for CFETR

Off-axis current drive is necessary for Tokamak to maintain and regulate the current profile. Helicon wave is the high order harmonic fast wave and helicon wave current drive (HCD) is one of the key issues in the China Fusion Engineering Test Reactor (CFETR). The theory of HCD is briefly introduced and the simulation results are listed. Helicon waves can realize off-axis current drive under CFETR plasma parameters when the frequency is greater than 1 GHz and drive current is insensitive to the launched value of the parallel index of refraction n||, so wave accessibility issues can be reduced. Travelling Wave Antenna was analyzed by the commercial software package-CST. Near the resonant frequency of the antenna, the Voltage Standing Wave Ratio < 1.2 is obtained for the antenna in the bandwidth of 50 MHz, which means that the antenna does not require a matching system.