SiO2-Fe/N/C catalyst with enhanced mass transport in PEM fuel cells

Today’s high-loading non-platinum group metal (non-PGM, e.g., Fe/N/C) catalyst layer has presented a comparable performance to commercial Pt/C catalyst layer in the kinetic region. However, if the non-PGM catalyst layer is too thick (i.e. high loading), it will inevitably result in a severe performance loss in the mass-transport region. Herein, we employed SiO2 nanoparticle chains to adjust the mesoporous structure and wettability (i.e., making the catalyst surface more hydrophobic), in order to enhance the mass-transport properties of the catalyst layer with high-loading of Fe/N/C (labeled as SiO2-Fe/N/C). Simultaneously, SiO2-Fe/N/C catalyst shows more pyridinic-N and defects in the carbon matrix, which may create more active sites and thus compensate the decreased mass activity of oxygen reduction reaction (ORR) caused by the incorporation of inactive SiO2. Further, SiO2-Fe/N/C catalyst exhibits more than 25 % performance increase (e.g., at 0.4 V) than the pristine Fe/N/C in H2/Air proton exchange membrane fuel cells (PEMFCs). This work provides a new and effective strategy to improve the mass-transport properties of the Fe/N/C catalysts.