Ionomer network of catalyst layers for proton exchange membrane fuel cell

The ionomer binder within catalyst layer (CL) plays a vital role in proton exchange membrane fuel cell (PEMFC). Short-side-chain (SSC) perfluorosulfonic acid (PFSA) ionomers have recently gained considerable attention due to their superior PEMFC performance. However, most studies have focused primarily on SSC ionomer cell performance and seldomly explore the internal mechanism. The intrinsic relationships between catalyst ink and cell performance are still vague. Herein, the structure-property correlations among catalyst ink, CL microstructure, and PEMFC performance with different equivalent weight (EW) ionomers were proposed, especially, the distribution of different EW ionomers in the CL was observed. Our results show that the high ion exchange capacity (IEC) and low ionomer adsorption on Pt/C increase the ease of SSC ionomer to form Pt/C-ionomer connection network in the catalyst ink. Subsequently, a more uniform and continuous ionomer proton conduction network was observed in the CL containing SSC ionomer, which increased the active area, but at the cost of macropore volume. Combined with the high IEC of SSC ionomer, superior proton conductivity and high mass transport resistance for SSC ionomer electrodes are manifested in the ultimate performance. This work also provides an effective way to construct high-performance fuel cells containing SSC PFSA ionomer.