PtPd Nanosheets Dominated with (111) Facets Achieving Thermodynamic–Kinetic Synergistic Enhancement of Oxygen Reduction Reaction

Abstract The oxygen reduction reaction (ORR) in fuel cells suffers from an inherent thermodynamic bottleneck. Current research is mostly confined to independent optimization of either its thermodynamic or kinetic properties, failing to break through the catalytic performance limit imposed by classical models. Herein, PtPd alloy nanosheets dominated by the (111) facets, with a thickness of about 1–2 nm, were synthesized under high-pressure conditions using CO as the direct reduction gas. First-principles calculations demonstrate that PtPd alloy nanosheets thermodynamically optimize ORR by lowering the surface O adsorption energy, thereby positively shifting the onset potential to 1.02 V vs RHE. Furthermore, the distinct d-orbital electronic structure of Pd interacting with Pt enables enhanced electron filling into the antibonding orbitals of the OOH intermediate. This electronic modulation reduces the apparent activation energy by approximately 20 kJ mol–1, kinetically accelerating the ORR process. This catalyst simultaneously increases the thermodynamic limiting potential and reduces the kinetic activation energy, ultimately leading to a mass activity of up to 1.275 A mg–1 at 0.95 VRHE, achieving 53.3 times the activity of commercial Pt/C.