Rotating-Disk Slurry Electrodeposition of Pt−Fe−Co−Ni−Cu Nanoparticles on Carbon XC-72R Material for the Oxygen Reduction Reaction in Alkaline Media

Abstract The sluggish oxygen reduction reaction (ORR) remains the kinetic bottleneck in alkaline fuel cells and other energy storage devices, demanding highly active and durable cathode catalysts. While elemental platinum (Pt) exhibits exceptional intrinsic activity, its scarcity and high cost necessitate the development of Pt-lean alloys to lower fuel cell production costs without compromising performance. Here, we demonstrate a surfactant-free rotating-disk slurry electrodeposition (RoDSE) approach to co-deposit Pt−Fe−Co−Ni−Cu nanoparticles directly onto Vulcan XC-72R at controlled potentials (−0.80, −1.20, −1.40 V vs RHE). X-ray diffraction confirms single-phase fcc Pt-alloy solid solutions with Vegard-type lattice contraction as 3d-metal content increases, while STEM-EDS shows spatially uniform distributions of all five metals. In O2-saturated 0.1 M KOH at 1600 rpm, Catalyst C achieves E1/2 = 0.89 V vs RHE (cf. 0.87 V for commercial 20 wt % Pt/C) and 2.7−3.1 × higher Pt-normalized mass activity at 0.90 V, with RRDE/Koutecký−Levich analyses indicating n ≈ 3.8−3.9 and low peroxide yields across the diffusion-limited window. Accelerated stress tests (0.60−1.00 V, 100 mV s−1, 20 000 cycles) show that Catalyst B retains its initial E1/2 (≈0 mV shift), while Catalyst C degrades modestly (≈25 mV); Pt/C exhibits substantially larger losses (≈72 mV). Ex situ and in situ X-ray absorption spectroscopy track potential-dependent electronic changes consistent with alloying and reduced surface oxide under ORR conditions. These structure−function correlations establish RoDSE as a high-throughput platform for discovering durable Pt-lean ORR electrocatalysts and pave the way toward high-entropy alloy cathodes and membrane-electrode-assembly integration for practical alkaline fuel cells.