As our reliance on renewable energy sources grows, so too does our need to store this energy to mitigate against troughs in supply. Energy storage in batteries or by conversion to chemical fuels are the two most flexible and scalable options, but are normally considered mutually exclusive. Energy storage solutions that can act as both batteries and fuel generation devices (depending on the requirements of the user) could therefore find great utility. In this talk, we shall investigate new device architectures for water splitting and energy storage that use Electron-Coupled-Proton Buffers (ECPBs) as redox mediators (see, for example: Nature Chem. 2013, 5, 403-409; Science, 2014, 345, 1326-1330; Joule, 2018, 2, 1390-1395) allowing high energy-density redox flow batteries and devices for the on-demand generation of hydrogen to be realised based on a common underlying chemistry (Nature Chem. 2018, 10, 1042-1047).