Development of Nanosized Mn 3 O 4 -Co 3 O 4 on Multiwalled Carbon Nanotubes for Cathode Catalyst in Urea Fuel Cell

Double-oxide Mn 3 O 4 -Co 3 O 4 nanoparticles were synthesized and anchored on multiwalled carbon nanotubes (MWCNTs) via a single-step solvothermal method. The largest specific area (99.82 m 2 g −1 ) of the catalyst was confirmed via a nitrogen adsorption isotherm. Furthermore, the uniform coating of the Mn 3 O 4 -Co 3 O 4 nanoparticles on the surface of the MWCNTs was observed via scanning electron microscopy and transmission electron microscopy; the uniform coating provided an effective transport pathway during the electrocatalytic activities. The rotating disk electrode and rotating ring disk electrode measurements indicated that the electron transfer number was 3.96 and the evolution of H 2 O 2 was 2%. In addition, the Mn 3 O 4 -Co 3 O 4 /MWCNT catalyst did not undergo urea poisoning and remained stable in an alkaline solution. Conversely, commercial Pt/C could not withstand urea poisoning for long. The performance cell achieved a power density of 0.4226 mW cm −2 at 50 °C. Therefore, Mn 3 O 4 -Co 3 O 4 /MWCNT is an efficient and inexpensive noble-metal-free cathodic catalyst for direct urea fuel cells.