Ionomer-free electrolysis of DI water enabled by confined in-situ electrolyte generation in Pt nanomesh electrodes

Abstract

This work demonstrates the operation of a non-traditional and completely ionomer-free DI water electrolyzer enabled by our precisely engineered Pt nanomesh electrodes. Nanomesh electrodes developed in our group are composed of inter-connected vertical and horizontal nanowires. The nanowires are 50 nm in diameter with an inter-nanowire spacing of around 50 nm, resulting in billions of nanowires per square cm of footprint. Moreover, the 90x surface enhancement (90 cm2 per geometric cm2) combined with the thin form factor (4 µm) of the nanomesh electrodes brought all the reaction sites extremely close to the membrane allowing the surprising DI water electrolysis at 1 A/cm2 even in the absence of ionomers. Commercial Pt based electrodes could not display this behavior due to the large pore sizes and two orders greater thickness, despite comparable surface area to our nanomesh electrode. This interesting phenomenon taking place in the nanomesh electrodes is facilitated initially by an ‘in-situ electrolyte generation’ step. This is linked to the confinement of electro-generated products such as H+ and OH– within the nano-cages (50 nm wide) of the nanomesh electrode providing the required ionic coupling in the porous electrode. Finally, this phenomenon is demonstrated to also occur in a completely vapor-fed electrolyzer.