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To reduce the platinum group metal (PGM) loading in anion exchange membrane fuel cells (AEMFCs), it is important to transition to catalysts with very low PGM content, and eventually to catalysts that are completely PGM-free. In this work, four supported low-PGM Pt and PtRu catalysts were prepared using a new, simple, scalable technique: Controlled Surface Tension (CST) method. CST allows for a high density of very small multi-atom clusters. Catalysts were physically characterized using a wide array of techniques and tested for their ORR and HOR activity both ex-situ and integrated into operating AEMFCs. The PGM loading was reduced by a factor of 14 while achieving comparable performance to commercial catalysts. AEMFCs were also assembled with ultralow PGM loading (0.05 mgPGM cm-2), where PtRu anodes were paired with Fe–N–C cathodes to achieve a specific power of 25 W/mg PGM (40 W/mg Pt). [Display omitted] • Simple synthesis of multi-atom clusters of supported Pt and PtRu. • Quantified the ex-situ and in-situ activity of the catalysts. • AEMFCs with record-high specific peak power density. • Demonstrated very high performance with only 0.05mgPGM/cm2 loading. • Exceeded DOE 2022 target for initial AEMFC performance. [ABSTRACT FROM AUTHOR]