Fabrication and characterization of polyoxometalate/2D graphene-based flexible supercapacitors for wearable electronic pulse-beat application

Nowadays, low-dimensional graphene nanomaterials, such as two dimensional (2D) graphene nanosheets (2D GNs), have been widely reported and suggested for, e.g., catalysts, solar cells, and photovoltaic devices, but previous works still do not pay much attention to the flexible electronics sensor that base on the 2D graphene nanomaterials. Here we report on using a highly conductive polyoxometalate (POM) and 2D GNs foam to fabricate the 2D GNs-based supercapacitors capable of detecting the pulse beat rate. Characterization techniques, such as the X-ray diffraction, energy dispersive X-ray spectra, transmission electron microscopy, galvanostatic charge–discharge and cyclic voltammetry, are used to illustrate the structural and electrochemical properties. Our results reveal that the POM can disperse into 2D GNs to form the POM/2D GNs nanocomposites. In the meanwhile, we find the specific cycling stability of POM/2D GNs can be significantly enhanced as compared to bulk 2D GNs foam. Moreover, we design a flexible pulse sensor device, which is based on depositing the POM/2D GNs foam on a conductive adhesive substrate. Our results reveal that the POM/2D GNs-based sensor is sensitive to the external pulse beat, which can linearly detect a bending area within the range of 0.483 mm². This work indicates that the POM/2D GNs can act as a type of sensor material to monitor the human body health.