Oxygen reduction reaction and PEM fuel cell performance of pulse electrodeposited Pt–Ni and Pt–Ni–Mo(O) nanoparticles

Proton exchange membrane fuel cells (PEMFCs) are an important alternative to fossil fuels and a complement to batteries for the electrification of vehicles. However, their high cost obstructs commercialisation, and the catalyst material, including its synthesis, constitutes one of the major cost components. In this work, Pt–Ni and Pt–Ni–Mo(O) nanoparticles (NPs) of varying composition have been synthesised in a single step by pulse electrodeposition onto a PEMFC’s gas diffusion layer. The proposed synthesis route combines NP synthesis and their fixation onto the microporous carbon layer in a single step. Both Pt–Ni and Pt–Ni–Mo(O) catalysts exhibit extremely high mass activities at oxygen reduction reaction (ORR) with very low Pt loadings of around 4 μg/cm 2 due to the favourable distribution of NPs in contact with the proton exchange membrane. Particle sizes of 40–50 nm and 40–80 nm were obtained for Pt–Ni and Pt–Ni–Mo(O) systems, respectively. The highest ORR mass activities were found for Pt 67 Ni 33 and Pt 66 Ni 32 –MoO x NPs. The feasibility of a single-step electrodeposition of Pt–Ni–Mo(O) NPs was successfully demonstrated, however, the ternary NPs are of more amorphous nature in contrast to the crystalline, binary Pt–Ni particles, due to the oxidised state of Mo. Nevertheless, despite their heterogeneous nature, the ternary NPs show homogeneous behaviour even on a microscopic scale. • Synthesis, fixation and distribution of Pt alloy nanoparticles in a single step. • Ultrahigh ORR mass activities up to 10 mA/μg Pt in half-cell tests. • Best ORR and PEMFC performance for Pt 67 Ni 33 and Pt 66 Ni 32 -MoOx.