QUANTUM CONFINED WATER IN POLYMERIC NANOCHANNELS: PROTON TRANSPORT AND ELECTROCHEMICAL IMPLICATIONS FOR GREEN HYDROGEN ELECTROLYSIS

Abstract

The confining of water inside sub-nanometer to nanometer-sized polymeric channels introduces novel structural and dynamical characteristics that significantly impact proton transport, with fundamental implications for the development of green hydrogen electrolysis. Within such confinement, water molecules tend to assemble into quasi-one-dimensional chains or ordered hydrogen-bond networks, facilitating proton conduction processes that are deviant from bulk conditions. Molecular simulations and neutron scattering measurements have shown that nuclear quantum effects (NQEs) are instrumental in decreasing the free-energy barrier for proton transfer, typically resulting in nearly barrierless conduction regimes. They result from proton delocalization, zero-point energy contributions, and stabilization of Grotthuss-like hopping mechanisms along aligned water chains. Carbon nanotube and hydrophobic nanochannel studies indicate that confined systems can increase proton mobility by several orders of magnitude over bulk water, a characteristic that can be engineered in polymeric electrolytes like Nafion and customized nanocomposites. In addition, modified hydrogen-bond fluctuations under confinement have been linked to increased ionic conductivity and lower activation energy for electrochemical processes. These results offer a basic template for the engineering of future-generation polymer electrolyte membranes, in which quantum-confined water channels can be tapped to enhance the efficiency and longevities of green hydrogen electrolyzers