Tungsten oxide and carbide composite synthesized by hot filament chemical deposition as electrodes in aqueous-based electrochemical capacitors
By Soares, Davi M.; Vicentini, Rafael; Peterlevitz, Alfredo C.; Rodella, Cristiane B.; Silva, Leonardo M. da; Zanin, Hudson
Published in Journal of Energy Storage
2019
Abstract
Developing more sustainable, low cost and feasible energy storage devices is a keystone of aerospace, automobile, and electronics industries. In research new materials and techniques that allow their production in large scale are studied by researchers around the world. Regarding materials, supercapacitors, for instance, may have carbon based materials on electrodes, owing to their chemical stability, low cost, and safety; however, their specific capacitance is lower when compared to other materials. Additionally, materials that may provide higher capacitance–due to faradaic or redox reactions – are also studied. Within this group, transition metal oxides are potential candidates for that, once faradaic behavior may provide higher capacitance values; however, not cyclability in most cases. Thus, this work presents a composite material with tungsten carbide (W2C) and tungsten oxide species (WxOy), which showed both faradaic behavior and cyclability. This composite material was synthesized by deposition of tungsten using a technique known as hot filament chemical vapor deposition (HFCVD). In this process, sublimation of tungsten occurred under H2 constant flow; thus, reducing the metallic tungsten; while oxide species were formed by spontaneous passivation. Experimental results indicate that the efficiency improved from 59% to 85% for first and 10, 000th cycles, respectively, with boost of specific capacitance of 160%. In sum, the material reported herein presents the unique aspect of improving its properties during cyclability. Therefore, such feature and synthesis process may enable its use as renewable energy storage devices.