Ionomer engineering for optimized water channels in industry-scale water electrolysis using non-noble metal catalyst.

The application of non-noble metal catalysts to replace high-cost iridium plays a critical role in the industrialization of proton exchange membrane water electrolysis (PEMWE). However, the activity and stability of non-noble metal catalysts are unsatisfactory especially at high current densities. This can partially be attributed to the limited water channels of Nafion ionomer in the catalyst layer which impede proton hydrate transport, resulting in a low local pH and accelerating non-noble metal dissolution. We propose that introducing an amphiphilic-like CF3CF2CF2CH2OH molecule into Nafion ionomer (FOH-Nafion) via molecular engineering, optimizes the mass transfer of proton hydrates and therefore increase the stability of Co-based catalysts under high current densities. More dispersed and interleaved hydrophilic and hydrophobic regions of Nafion lead to efficient channels for proton hydrate transport. Such molecular engineering kept Co3O4 catalyst running over 270 h at 830 mA cm-2, about 4 times that of the pristine Nafion ionomer. The molecular engineering strategy for the water channel in catalyst layer provides a pathway to improve the performance of non-noble metal catalysts in PEMWE.