​​Proton exchange membrane fuel cells have the potential for widespread use in a hydrogen-based economy. Crucial to their design is the presence of a material to act as the membrane that efficiently transfers protons from one side of the cell to the other. The polymer Nafion is currently the most widespread membrane material but, in recent years, hybrid metal organic framework (MOF) materials have been made that show efficient proton transfer.

In this study, the group of researchers designed and synthesised three organic linkers, which they used to build three new MOFs. By measuring their proton conductivity, and comparing it to the structure, they were able to show that, by incorporating free and accessible carboxylic acid groups into the MOFs, proton conductivity can be increased.

Looking to further analyse their findings, and to understand the mechanism behind this increase in conduction, they measured one of their new MOFs, MFM-512, on IRIS using quasi-elastic neutron scattering. Using neutrons, they were able to study the movement of the hydrogen atoms, and determine that the proton conduction is mediated by the model of “free diffusion inside a sphere” rather than “jump diffusion between sites”.

Instrument: IRIS

Related publication: “Modulating proton diffusion and conductivity in metal–organic frameworks by incorporation of accessible free carboxylic acid groups​” Chem. Sci., 2019, 10, 1492-1499 

DOI: 10.1039/C8SC03022G

Funding: EPSRC, ERC, Royal Society and University of Manchester

Authors: P Rought, C Marsh, S Pili (University of Manchester), IP Silverwood, V Garcia Sakai (ISIS), M Li (University of Nottingham), MS Brown (University of Manchester), SP Argent (University of Warwick), I Vitorica-Yrezabal, G Whitehead (University of Manchester), MR Warren (Diamond Light Source), S Yang, M Schröder (University of Manchester) ​