A Single Energy Conversion and Storage Device of Cobalt Oxide Nanosheets and N-Doped Reduced Graphene Oxide Aerogel

Abstract

The hybridization between energy conversion and energy storage materials in a single cell (HECS) is proposed in this work. The HECS cell consists of photoactive cobalt oxide (Co3O4) positive electrode as the energy conversion material and N-doped reduced graphene oxide aerogel (N-rGOAE) as the energy storage material. The photoactive Co3O4 nanosheets were prepared by using various calcination temperatures for which the in situ electrochemical XAS suggests that the Co3O4 nanosheets calcined at 300oC exhibit the highest change in oxidation state compared to other conditions. The HECS cell using photoactive Co3O4 film calcined at 300oC and N-rGOAE exhibits 1.7-fold higher specific capacitance under LED light illumination than that of the dark condition. Under white LED light illumination, the photovoltaic effect can be generated in the Co3O4 electrode with electron-hole pairs, while the N-rGOAE can balance all the charges generated from the Co3O4 via both electrochemical double-layer and pseudocapacitive behaviours.