Lanthanum-Induced Quasi-Covalent Bonding and Chemical Potential Bridging in Pt ₃ Co Intermetallic Catalysts for Durable Fuel Cells

Pt-based intermetallic compounds represent the most promising catalysts for oxygen reduction reaction (ORR). However, they still face stability challenges, primarily due to component segregation and oxidation/dissolution of both transition metal and Pt atoms under harsh electrochemical conditions. Herein, we strategically incorporate electron-donating La into the L1₂-Pt₃Co intermetallic catalyst to steer a quasi-covalent Pt-M interaction and bridge the core-shell chemical potential gradient, enhancing ORR durability. Combined experimental and theoretical analyses elucidate that the transition from metallic to quasi-covalent bonding strengthens Pt-Co/La interactions, which effectively suppresses Pt leaching. Furthermore, La-mediated electronic modulation reduces the core-shell chemical potential difference, thus inhibiting Co migration from the core to the outermost surface and the subsequent oxidative dissolution. Due to these properties, the as-developed catalyst demonstrates high ORR activity under H₂-air conditions, achieving a peak power density of 1.27 W cm^-2 and high mass activity (MA) of 1.29 A mg_Pt^-1. More importantly, it exhibits exceptional stability with 87% MA retention and only 12 mV voltage loss at 0.8 A cm^-2 after 30k accelerated durability cycles, outperforming DOE 2026 targets (60% MA retention and voltage loss <30 mV). This study proposes a new structural engineering strategy for enhancing catalytic robustness in harsh electrochemical environments.