Synthesis Of Vertically-oriented Graphene At Atmospheric Pressure With Application To Energy Storage

Plasma enhanced chemical vapor deposition (PECVD) technique is the main method of synthesizing vertically-oriented graphene nanosheets currently. Comparing with other PECVD techniques at low pressure, the normal glow discharge PECVD at atmospheric pressure holds more advantages and greater potential for the industrial and continuous preparation of vertically-oriented graphene nanosheets. However, conventional single-pin-to-plate electrode arrangement in the normal glow discharge PECVD at atmospheric pressure owns the obvious drawback of producing a non-uniform electric field, subsequently leading to a fairly poor uniformity of the as-grown vertically-oriented graphene nanosheets and its application to energy storage. Aiming at this problem, this article built a novel multi-pin normal glow discharge PECVD system at atmospheric pressure, demonstrated its effective improvement on the uniformity of electric fields and plasma through mutual compensation of uniform electric fields, by numerical simulation and experiment, and analyzed the morphology and structure of the as-produced samples.The uniform and rapid synthesis of vertically-oriented graphene at atmospheric pressure was achieved by the multi-pin normal glow discharge PECVD system. The morphology, structure, components and physical, chemical properties of as-produced vertically oriented graphene were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and the time-dependent growth rules of vertically oriented graphene nanosheets were analyzed and obtained. The performance of application to energy storage of vertically-oriented graphene in supercapacitors was researched fundamentally by electrochemical test methods, such as cyclic voltammograms, galvanostatic charge-discharge and ac impedance spectroscopy. The research demonstrated that supercapacitors based on vertically-oriented graphene as the active material had excellent electrochemical performance. The specific capacitance of vertically oriented graphene supercapacitors at scan rate of voltage as high as1000mV/s and2000mV/s still holded to be132.4F/g and132.4F/g, with only9.0%and10.8%loss, and it is able to charge and discharge stably at the ultra-high current density of50A/g or even1000A/g. Compared with other carbon materials such as graphene papers, carbon nanotubes and activated carbon as the active material in supercapacitors, vertically-oriented graphene owns great advantages of huge specific surface area, high charge and discharge rate, low internal impedance, environmental protection and prospect of industrial preparation.