Ionic Liquid-Modified Microporous ZnCoNC-Based Electrocatalysts for Polymer Electrolyte Fuel Cells

Non-platinum group metal (non-PGM) oxygen reduction reaction (ORR) catalysts have been widely reported, but their application in proton exchange membrane fuel cells (PEMFCs) is challenging because of their poor performance in acidic environments. Here, [BMIM] [NTf2] ionic liquid (IL) modification of microporous ZnCoNC catalysts (derived from ZIF-ZnCo) is investigated to study their behavior in PEMFCs and to elucidate the catalytic mechanisms in practical operation. The high O-2 solubility of ILs enhances the utilization of active sites with porous ZnCoNC, and their hydrophobic nature facilitates the water transport during fuel cell operation. The half-cell measurement in aqueous HClO4 shows that with the 20 wt % IL modification, the electron-transfer number increases from 2.58 to 3.88, approaching the desired 4-electron-transfer ORR. The power density obtained shows 140% improvement in single-cell PEMFC tests. The catalyst also yields an interesting performance in alkaline anion-exchange membrane fuel cells.