Improved oxygen reduction activity on silver-modified LaMnO3–graphene via shortens the conduction path of adsorbed oxygen

Abstract

Silver-modified LaMnO₃–reduced graphene oxide (RGO) composites are synthesized via a sol–gel method with citric acid as a chelating agent. The as-prepared nanocomposites are characterized via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The XRD results show that decorating with Ag does not change the perovskite structure and it is metal form. The electrocatalytic activities of the composites for the oxygen reduction reaction are evaluated. The 2 wt% Ag/LaMnO₃–RGO as the air cathode catalyst shows a high voltage plateau. The corresponding oxygen reduction reaction mainly favors a four-electron transfer process, exhibits a maximum cathodic current density of 5.45 mA cm⁻² at 1600 rpm, and displays good stability (i/i₀ = 92.9% at −0.3 V after 30 000 s with a rotation rate of 1600 rpm), which is better than that of the commercial Pt/C (20 wt% Pt on carbon) electrocatalyst at the same testing conditions. Such excellent catalytic activity is attributed to the synergistic effect of Ag, LaMnO₃, and graphene in the composite, which provide numerous reactive sites and the modification of Ag shortens the conduction path of adsorbed oxygen, thus reducing charge transfer resistance and improving cathode performance.