Integration of two-dimensional graphene and one-dimensional carbon nanotubes (CNTs) to create potentially useful 3D mesoscopic carbon structures with enhanced properties relative to the original materials is very desirable.

The effects of both graphene nanoplatelets and reduced graphene oxide as additives to the negative active material in valve-regulated lead–acid batteries for electric bikes were investigated. Low-temperature performance, charge acceptance, cycle performance, and water loss were investigated. The test results show that the low-temperature performance, charge acceptance, and large-current discharge performance of the batteries with graphene additives were significantly improved compared to the control battery, and the cycle life under 100% depth of discharge condition was extended by more than 52% from 250 to 380 cycles. Meanwhile, the amount of water loss from the batteries with graphene changed only slightly compared with the control cells. The excellent performance of the batteries can be ascribed to the graphene promoting the negative-plate charge and discharge processes and suppressing the growth of lead sulfate crystals.

Controlled growth of circular single-crystalline graphene domains has been achieved by atmospheric pressure chemical vapor deposition (APCVD) using solid copper as substrate, thereby demonstrating that the shape of the graphene grains can potentially be precisely tuned by optimizing growth parameters. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that the round domains have smooth, clean edges that permit seamless merging of adjacent graphene. Transmission electron microscopy (TEM) and Raman spectra together indicate that the graphene film is mostly monolayer, and electron diffraction reveals that these domains are single crystals. The growth and merging of these circular graphene domains to yield single-crystal graphene films enable us to elucidate the nucleation and growth mechanism of graphene on solid copper foil substrates.

No abstract