Magnetic-Field-Tuned Spin-Dependent D-Band and Bifunctionality in L1₀-FeCoPt for Enhanced Methanol Oxidation

The spin-dependent electronic structure of transition-metal alloys plays a key role in tuning the magnetic-field-responsive behavior, which plays a critical role in enhancing the electrocatalytic properties under an external magnetic field. This work presents a facile hydrothermal synthesis of L1₀-phase FeCoPt nanoparticles with tunable elemental compositions. The relationship between MOR mass activity and Co content illustrates a volcano shape, and sample FeCoPt-4 possesses the best activity in acidic media, 7.16 times higher than that of commercial Pt/C. In addition to composition, methanol oxidation reaction (MOR) performance can be further enhanced by varying methanol concentration (1 to 10 m) and applying an 8000 Oe magnetic field. First-principles calculations reveal that the d-band center of Pt 5d orbitals and the net spins of Fe/Co can be tuned with increasing Co content, resulting in optimized magnetic field response and enhanced electrocatalytic properties. The combination of experimental and theoretical analysis shows that the MOR process is kinetically governed by the reaction of CO* and OH*, which is affected by the Co content, methanol concentration and acidic/alkaline solution. This research clarifies the multi-factor enhancement mechanism by leveraging spin-dependent electronic structure and bifunctional effect, enabling a novel approach for designing high-performance electrocatalysts for direct methanol fuel cells.