Strong Metal‐Support Interactions Regulate Interfacial Water for Active and Durable Low‐Pt Bifunctional Hydrogen Oxidation/Oxygen Reduction Catalysis

The development of highly active and stable low‐Pt alkaline hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) catalysts is crucial for reducing the cost of hydroxide exchange membrane fuel cells (HEMFCs). Here, it is realized by a HOR/ORR bifunctional Pt@MoO x /C catalyst featuring strong metal‐support interaction (SMSI). The partially covered MoO x species exhibit strong interactions with Pt, which stabilize the Pt nanoparticles under both HOR and ORR conditions. The modulated electronic structure arising from SMSI optimizes the binding of hydrogen and hydroxyl species on Pt sites. In addition to the conventional electronic effect of SMSI, the catalyst–electrolyte interfacial water structure is also regulated, resulting in a more interconnected hydrogen‐bond network. Consequently, Pt@MoO x /C exhibits outstanding activity and stability toward both the HOR and ORR. It delivers an HOR exchange current density of 3.55 mA cm Pt −2 , which is 4.4 times that of commercial Pt/C, and a ORR mass activity of 1.08 A mg Pt −1 at 0.9 V versus RHE, 2.3 times that of commercial Pt/C. Furthermore, an HEMFC employing Pt@MoO x /C as both the anode and cathode catalysts, with an ultralow total Pt loading of 0.1 mg Pt cm −2 , delivers a peak power density of 920 mW cm −2 and operates stably for over 250 h.