Electrocatalytic activity of LaSr_3Fe_3O_(10) and LaSr_3Fe_3O_(10)-GO towards oxygen reduction reaction in alkaline medium

Oxygen reduction reaction(ORR) plays a critical role in many energy conversion and storage processes.Therein, a comparative study of the electrocatalytic activity for ORR in 0.1 mol/L KOH solution was conducted using layered perovskite-like LaSr_3 Fe_3 O_(10) and LaSr3 Fe_3 O_(10)-graphene oxide(GO) composite as electrodes. Linear sweep voltammetry(LSV) results show that the LaSr3 Fe_3 O_(10)-GO hybrid exhibits higher current density, a more positive onset potential(-0.15 V vs. Hg/HgO) in comparison with LaSr_3 Fe_3 O_(10).The value of the overall transferred electrons for both catalysts implies a dominant two electron process for ORR. Both catalysts under alkalic conditions exhibit a two-step Tafel slope, suggesting a change in the reaction mechanism for ORR. The composite electrode exhibits a higher ORR current density, but inferior durability performances in relative to the LaSr_3 Fe_3 O_(10) electrode.

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.