Microspheres assembled by KMn8O16 nanorods and their catalytic oxygen reduction activity in direct methanol fuel cells

Abstract Microspheres assembled using cryptomelane-type KMn 8 O 16 nanorods are synthesized via a facile template-free, single-step hydrothermal technique. The synthesized KMn 8 O 16 generates nanorods 10–20 nm in diameter and approximately 300–1000 nm long. The rods self-assemble to form microspheres of 2–6 μm in diameters. The electron transfer number for KMn 8 O 16 during the ORR is approximately 3.98 at 0.5 V vs. Hg/HgO, and the H 2 O 2 percentage is 0.66%. Moreover, a direct methanol fuel cell (DMFC) is built using KMn 8 O 16 as cathodic catalyst, PtRu/C alloy as the anodic catalyst and a polymer fiber membrane (PFM) instead of a conventional polymer electrolyte membrane (PEM). The peak power densities (43.3 mW cm −2 and 153.9 mW cm −2 ) have been achieved at 25 °C and 70 °C, respectively. KMn 8 O 16 shows good electrocatalytic activity and stability during oxygen reduction in alkaline solutions and demonstrates tolerance toward methanol poisoning.