Better Organic Semiconductors Through Liquid Purification

Organic semiconducting polymers often contain side products from synthesis that can alter the photophysical and electrochemical properties of polymers. Especially metal traces and organic compounds from synthesis (catalyst and ligands) often remain in the polymer with current purification methods, creating challenges to investigating the real properties of the organic semiconducting polymer. When these impure polymers are employed as the active electrode in heterogeneous electrocatalysis, the remaining metal ion impurities (Pd, Pt, etc.) can result in an overestimation of the electrocatalytic performance (1).<br/>In my talk, I will show how we employ high-performance liquid chromatography (HPLC) to purify polymers by removing metal traces and other organic side products. When comparing the neat polymer to the purified polymers, we observe a clear trend for the electrocatalytic activity for the oxygen reduction reaction (ORR), where a metal-free polymer undergoes the two-electron reaction, forming hydrogen peroxide (H₂O₂) as the main product, while Pd-containing polymers increase the selectivity towards the four-electron process to form water (H₂O). Finally, we fractionate polymers by molecular weight and show that polymers with higher molecular weight achieve higher electrochemical stability during continuous operation.<br/><br/>(1) De La Fuente Durán, A, <i>et. al,</i> Energy Environ. Sci., 2023,16, 5409-5422