Accelerated proton transport in polymer-assisted metal-aminoacid framework

Abstract

Sustainable energy generation employing fuel cells has gained deep research attention in the current energy landscape. Hybrid materials like MOFs are per-excellent candidates than conventional fluoropolymers, having properties like high surface area, tunable structure, and functionalities to incorporate proton carriers. The limitations of pristine MOF membranes are inter-particle resistance and poor mechanical strength that decrease proton conduction and increase activation energy. To address these issues, we employ a Ni-histidine-based MOF, bearing inexpensive, sustainable, and protic aminoacid as ligand. The network is extended through extensive H-bonding between the histidine and solvent water molecules. These protic networks paved the proton conduction in humid conditions (1.8 × 10^− 4 S cm^− 1), which was further enhanced by an order of magnitude (up to 1.5 × 10^− 3 S cm^− 1) through blending with polyvinyl alcohol (PVA). The resulting composite induces mechanical integrity like high flexibility, reduced inner-particle resistance, and a boosted H-bonding network that promotes Ni-His@PVA as an appreciable proton conductor in ambient and non-ambient conditions. Furthermore, decrease in activation energy from the vehicular (0.59 eV for Ni-His) to the Grotthuss regime (0.20 eV for Ni-His@PVA) ensures facile proton transport. This design protocol will encourage sustainable proton-conducting MOF composite membranes for practical fuel cell applications.

Graphical Abstract