ZnCo2O4 ultrathin nanosheets towards the high performance of flexible supercapacitors and bifunctional electrocatalysis

With the growing development of portable electronics, extensive research efforts on power sources with flexible feature have been developed. In that field, all-solid-state thin-film flexible supercapacitor (ASSTFS) has been considered as a favorable and competitive candidate owing to its multiple benefits such as ultrathin configuration, good flexibility and high safety against liquid leakage. Currently, the major drawback of ASSTFSs is their relatively low capacitance due to the intrinsic supercapacitive behavior of the electrode materials as well as the limited surface area. In this study, ultrathin structure was introduced into spinel ZnCo2O4 through a topological transformation route. The obtained ZnCo2O4 ultrathin nanosheet serves large specific surface area, and thus shortens the ion diffusion distance, leading to the exposure of more electrochemically active area to achieve a much higher pseudocapacitance as in ASSTFS. When assembled into a flexible supercapacitor, the device exhibits a high specific capacitance of 5100 mu F/cm(2) and a high energy density of 31.8 mWh/cm(3) at power density of 280 mW/cm(3). Furthermore, attributed to the beneficial ultrathin structure, the ZnCo2O4 ultrathin nanosheets also demonstrated the superior oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performances, all of which demonstrating it a promising candidate for energy conversion and storage applications. (C) 2018 Elsevier B.V. All rights reserved.