LaSr_2Mn_2O_7 Ruddlesden-Popper manganites for oxygen reduction and electrochemical capacitors

LaSr2 Mn2 O7,a Ruddlesden-Popper type bilayered perovskite,was investigated as oxygen catalyst for oxygen reduction reaction(ORR) and active electrode material for electrochemical capacitors in KOH solutions.XPS results show that Mn takes a mixed Mn2+,Mn3+and Mn4+valence state with an average valence of 3.4.As catalyst towards ORR,LaSr2 Mn2 O7 and LaSr2 Mn2 O7/acetylene black composite favor four electron pathways for ORR.LaSr2 Mn2 O7/C composite shows a comparable onset potential for ORR to that of Pt/C electrode.The improved ORR activity of LaSr2 Mn2 O7/acetylene black composite is attributed to the synergy between catalytic LaSr2 Mn2 O7 and conductive acetylene black.As electrode material for electrochemical capacitors,LaSr2 Mn2 O7 exhibits a maximum specific capacitance of 167.2 F/g with 62%faradic contribution at a scan rate of 1 mV/s in cyclic voltammetry test.