In this work, we have synthesized tetrahexahedral (THH) Pt nanoparticles (NPs) enclosed with {730} high-index facets using a one-step square wave potential procedure. The catalytic activity of the THH NPs toward the oxygen reduction reaction (ORR) is studied under both transient and steady-state conditions. As a benchmark, the ORR activity is compared with those of polycrystalline Pt and a commercial Pt/C catalyst. The results show that, under transient conditions, the catalytic performance of the THH Pt NPs and Pt/C are approximately the same and about 2 times lower than that of polycrystalline Pt. However, under steady-state conditions the THH Pt NPs perform considerably better than Pt/C. Under steady-state conditions THH Pt NPs are even slightly more active than polycrystalline Pt