Facile Synthesis of Highly Conductive RuO2-Mn3O4 Composite Nanofibers via Electrospinning and Their Electrochemical Properties

We report on the facile synthesis of highly conductive RuO 2 /Mn 3 O 4 composite nanofiber mats by electrospinning of mixed ruthenium and manganese precurosr solution and their potential suitability as an active electrode in electrochemical capacitors. Electrospun RuO 2 /Mn 3 O 4 fiber mats calcined at 300°C exhibit multiple fiber networks composed of nanoparticles in a size range of 5–10 nm (average ≈ 7.5 nm). Partially crystalline Mn 3 O 4 phases are well mixed with the amorphous RuO x (a-RuO 2 ) phases while pure Mn 3 O 4 fibers exhibit only crystalline phase. Electrochemical capacitors utilizing a-RuO 2 /Mn 3 O 4 fiber mats show a high specific capacitance of 293 Fg −1 at 10 mVs −1 , high rate capability with a capacity loss of only 45% from 10 to 2000 mVs −1 , and superior cycle performance of over 30,000 cycles as compared to those characteristics of Mn 3 O 4 fiber mats (216 Fg −1 at 10 mVs −1 , capacity loss of 94% at 2000 mVs −1 , poor cycle performance of 2000 cycles). These results are correlated with the improved mixed ionic/electronic conductivity of the a-RuO 2 /Mn 3 O 4 fiber mats as well as to its morphological evolution, i.e., highly porous flower-like-fiber networks, during cycling tests.