Oxygen reduction activity of Pd-Mn3O4 nanoparticles and performance enhancement by voltammetrically accelerated degradation.

Electrochemical properties of Pd-Mn3O4 nanoparticles toward oxygen reduction reaction (ORR) in acidic media were investigated. The catalysts were prepared by polyol reduction of Pd(acac)2 and thermal decomposition of Mn2(CO)10. Surface composition and structure of the particles vary depending on the injection temperature of Mn2(CO)10 and are closely related to the electrochemical properties. The presence of Mn3O4 promotes the performance towards ORR by facilitating oxygen transfer to the active sites of Pd. Through an accelerated degradation test (ADT), nanoparticles with a Pd-rich shell are obtained by dissolution of surface exposed Mn3O4 and at 0.57 V (vs. Ag/AgCl) this catalyst shows the highest activity towards ORR, 149% in mass activity and 142% in specific activity compared to that of Pd/C.