Low-Platinum Alloy Catalysts for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

Abstract

Proton exchange membrane fuel cells offer high energy density and zero emissions, but their reliance on Pt-based catalysts limits commercialization due to high costs and durability concerns. Alloying Pt with transition metals improves catalytic activity, yet stability in acidic environments remains challenging. Ordered intermetallic compounds enhance both activity and stability but often suffer from particle sintering during synthesis, requiring strategies to balance size control and catalytic efficiency. This thesis explores the design of advanced Pt-based electrocatalysts for the oxygen reduction reaction, addressing key aspects such as alloy composition, coordination environment, catalyst supports, and synthesis conditions. A PtMn nanodendrite catalyst is developed to enhance durability, leveraging Mn’s lower electronegativity to suppress metal dissolution and stabilize catalytic performance. Structural analysis confirms that the moderate lattice strain induced by Mn incorporation optimizes the oxygen adsorption energy, further boosting ORR performance. A Cu-induced ordering strategy is employed to transform commercial Pt/C into PtFeCu intermetallic compounds, where Cu diffusion promotes atomic rearrangement and strengthens electronic interactions. Low-surface-energy copper is the key to the boosted atom ordering. Fuel cell testing demonstrates significant performance retention, validating the effectiveness of this approach in achieving high-performance electrocatalysts. To overcome limitations of conventional carbon supports, a mesoporous Co–N–C-supported L10-PtCo catalyst is designed to enhance stability and activity by leveraging CoN4 sites for strong electronic coupling. This prevents nanoparticle aggregation, improves oxygen transport, and optimizes the d-band center. Fuel cells with this catalyst achieve high power density and durability, maintaining performance after 30,000 cycles. Further, a one-dimensional PtNi nanorod catalyst is synthesized to optimize Pt’s local coordination environment. By tuning the morphology—including nanorods, nanodendrites, and nanowires—the electronic structure is precisely adjusted to enhance activity and stability. Lattice contraction and bond length variations correlate with superior ORR performance, while fuel cell tests confirm high efficiency with minimal Pt usage, offering a promising next-generation PEMFC catalyst.