Phosphorylated Graphene Monolith with High Mixed Proton/Electron Conductivity
Abstract
Mixed ionic-electronic conductor (MIEC) plays a crucial role in electrochemistry technologies relevant to energy conversion and storage. The exisiting composite materials often suffered from poor mixed conductive performance due to the distinct phase boundaries and random distributions of the transport channels. Herein, we propose the concept for the fabrication of single-phase MIEC using two-dimensional (2D) building blocks―phosphorylated graphene nanosheets, which are assembled into three-dimensional (3D) interconnected networks with long-range ordered nanochannels. Attributed to the sufficient proton carriers (phosphate groups) confined in electron-conductive nanochannels and the integration of conductive pathways, simultaneously enhanced proton conductivity (0.13 S cm-1) and electron conductivity (0.265 S cm-1) are achieved at 98% RH and 35 oC, surpassing the current performance of all graphene-based MIEC. This approach may pave the way for designing MIEC with high mixed conduction by utilizing the unique properties of 2D materials, beyond the limitations from pure proton-conducting/electron-conducting materials.