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 Pt 2 Co (MoO 3 ‐Pt 2 Co) alloy to tackle the aforementioned challenge, where MoO 3 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 MoO 3 ‐Pt 2 Co/C‐based membrane electrode assembly (MEA) enables exceptional peak power densities of 3.20 W cm −2 and 1.73 W cm −2 in H 2 ‐O 2 and H 2 ‐air, respectively, with a low Pt loading of 0.10 mg cm −2 , outperforming cutting‐edge MEAs. Meanwhile, the MoO 3 ‐Pt 2 Co/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 MoO 3 ‐Pt 2 Co/C‐based fuel cell stack that delivers an excellent rated power of 123 W in H 2 ‐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 .