Molybdenum-Pocket Driven Low-Platinum Oxygen Reduction Catalysts for 100-Watt-Scale Fuel Cell Stacks

Developing highly efficient and low-platinum (Pt) proton exchange membrane fuel cell (PEMFC) stacks is imperative for their commercialization. However, ultralow-loading Pt catalysts (<0.10 mg cm^-2) are inherently less active and unstable due to high oxygen resistance, particularly under practical stack operating conditions. Here, we present a molybdenum oxide-pocket-driven Pt₂Co (MoO₃-Pt₂Co) alloy to tackle the aforementioned challenge, where MoO₃ with abundant oxygen vacancies can act as the pivotal "oxygen storage pocket" to boost the oxygen reduction reaction (ORR) activity and minimize the leaching of Co. Consequently, the MoO₃-Pt₂Co/C-based membrane electrode assembly (MEA) enables exceptional peak power densities of 3.20 W cm^-2 and 1.73 W cm^-2 in H₂-O₂ and H₂-air, respectively, with a low Pt loading of 0.10 mg cm^-2, outperforming cutting-edge MEAs. Meanwhile, the MoO₃-Pt₂Co/C-based MEA can retain a record-breaking mass activity of 1.68 A mg^-1 after 30k-cycle accelerated stress tests and can be operated stably at 0.65 V beyond 550 h. Most importantly, we develop a MoO₃-Pt₂Co/C-based fuel cell stack that delivers an excellent rated power of 123 W in H₂-air, which can project Pt utilization of 0.0975 g_Pt kW^-1 for a 100-kW hydrogen fuel cell vehicle, exceeding the US Department of energy (DOE) ultimate target of 0.10 g_Pt kW^-1.