In-situ preparation of low Pt loading multi rhombic-pyramidal Pt–Pd catalyst layer for high-performance proton exchange membrane fuel cells

The catalyst layer (CL) is the only electrochemical reaction site in proton exchange membrane fuel cells (PEMFCs), decisive in their performance. Herein, a mild and simplified strategy is implemented into the in-situ growth of Pt–Pd alloy catalysts on the gas diffusion layer (GDL) as the CLs for PEMFCs. Pt/C is used as the nucleation site to assist the in-situ growth of the Pt–Pd CL. The as-prepared Pt–Pd CL behaves as a multi rhombic-pyramidal structure, which are evenly distributed on the GDL surface. The effect of the Pt/Pd atomic ratio on the electrocatalytic activity is investigated through a single-cell performance test, and the optimal atomic ratio is determined to be 1/2, which exhibits excellent cell performance and low activation polarization loss. Meanwhile, the single-cell test results reveal that Pt₁Pd₂ CL reaches optimal performance at a loading of 0.122 mg cm⁻² (∼0.06 mg_Pt cm⁻²), with a peak Pt-specific power density of 14.23 W mg⁻¹ (6.81 W mg⁻¹ in PtPd), approximately 3.96 times that of a commercial Pt/C CL (0.2 mg_Pt cm⁻²). Furthermore, Pt₁Pd₂ CL shows significantly better stability than the commercial Pt/C CL, indicating that the in-situ preparation of the Pt-based CL has an excellent prospect for the commercial development of PEMFCs.