Acid-Stable Palladium Catalyst for Low-Loading and High-Power-Density Proton-Exchange-Membrane Fuel Cells

Pd catalysts reach high activity and durability under alkaline conditions but exhibit significantly lower performance and durability compared with platinum under the acidic conditions of proton exchange membrane fuel cells (PEMFCs), which are more representative of practical industrial applications. To address this pragmatic challenge, we developed an acid-stable Pd catalyst with a small size of approximately 5 nm and a robust shell enriched with N defects using a facile method that controls the metal particle size and carbon shell thickness. This was made possible by varying the number of ligands and the oxidation state of Pd. When the catalyst was applied to practical cells, the current density was promoted 2.3 times compared to commercial Pd/C, and the peak power density reached 1009 mW/cm2. Furthermore, after 20,000 cycles, the catalytic activity decreased by only 20%, significantly outperforming previously reported Pd catalysts despite the low loading of 0.15 mg/cm2.